A comparative study of various chemical modifiers for the determination of molybdenum in milk by electrothermal atomisation atomic absorption spectrometry was carried out. Methods with nitric acid or barium difluoride as the chemical modifier and in the absence of a chemical modifier were studied by introducing the milk samples directly into the graphite furnace with octyl alcohol. The graphite furnace programme, amount of modifier and the calibration and additions graphs were studied in all instances. The characteristic masses were 17.82, 18.64 and 12.08 pg of molybdenum in the absence of a chemical modifier and with nitric acid or barium difluoride as the chemical modifier, respectively. The precision, accuracy and interferences of the method were also investigated. (Hide)

A sensitive method for the determination of vanadium in water by atomic absorption spectrometry with electrothermal atomization and using hot injection and preconcentration on the graphite tube is described. The water sample (200µL) is added to the heated graphite tube in four portions over 200s. Magnesium nitrate is used as matrix modifier. The precision, accuracy and interferences of the method were investigated. The method allows vanadium down to 0.27µg1-1 to be detected. (Hide)

A method for the determination of molybdenum in infant formula and human milk by electrothermal atomic absorption spectrometry was developed and optimized. Samples were injected directly in the graphite tube with barium difluoride as the matrix modifier. The detection limit was 0.89µg Mo l-1. The molybdenum levels found in infant formula and human milk were 0.09-2.23 µg Mo g-1 and 2.32-8.38 µg Mo 1-1, respectively. (Hide)

A simple and rapid method is described for the spectrophotometric determination of iron in samples of bread and flour. The sample was digested with sulphuric acid and nitric acid. Ammonium thiocyanate was added to digestion solution. The resulting red complex was extracted with methyl isobutyl ketone and the absorbance of the organic fraction was measured ( at room temperature) at 500 nm.The absorption properties of the complex formed between iron and thiocyanate, its stability over several minutes and the reproducibility of the method were considered. The sensitivity of the method is 0.0002µg/cm2. Iron concentrations for samples analysed lay between 47.5 and 154.95 µg/g. (Hide)

A sensitive me thod for the determination of vanadium in water by electrothermal atomisation atomic absorption spectrometry (ETAAS) is described. The vanadium is chelated with 8-hydroxyquinoline in isobutyl methyl ketone and determined by ETAAS after pre-heating the pyrolitic graphite coated graphite tube of a graphite furnace atomiser before injection. The effects of the pH and amount of reagent required for the extraction were studied. The precision, accuracy and interferences of the method were also investigated. The proposed method allows concentrations of vanadium of 0.16 µg L-1 to be detected. (Hide)

The chelating poly(dithiocarbamate) resin with macroreticular support is shown to be effective for the preconcentration of cadmium and lead from non-saline waters. The retained ions can be eluted efficiently in 5 ml of 8 mol dm-3 nitric acid from 1-20 cm columns of resin. Poly(dithiocarbamate) resin used for preconcentration in the determination of cadmium and lead by flame atomic absorption spectrometry. The common ions present in non-saline waters do not interfere. The sensitivity was 0.10 µg L-1 of Cd and 0.73µg L-1 of Pb. The detection limits were 0.03 and 0.34 µg L-1 for Cd and Pb, respectively. The cadmium and lead concentration ranges, determined in mineral and tap waters, were between 0.1 and 0.8 µg L-1 and between 0.7 and 16.9 µg L-1, respectively. (Hide)

Various modifiers were investigated for the molybdenum determination in human serum samples by electrothermal atomization atomic absorption spectrometry. Methods with magnesium nitrate, barium difluoride, nitric acid, palladium-magnesium nitrate and palladium-hydroxylamine were studied by introducing the serum samples directly into the graphite furnace with 0.2% triton X-100. The mineralisation and atomization curves, the amount of modifier and the calibration and addition graphs were studied in all instances. The characteristic masses were 18, 22, 17, 12 and 13 pg of molybdenum for magnesium nitrate, barium difluoride, nitric acid, palladium-magnesium nitrate and palladium-hydroxylamine, respectively. The precision, accuracy and interferences of the methods were also investigated. (Hide)

Sample preparation is a very important stage in the determination of heavy metals. In this paper a comparison was made of three digestion procedures: conventional acid digestion, calcination and microwave acid digestion. Conventional procedures (acid digestion and calcination) are very tedious and take a lot of time, while microwave acid digestion is a very rapid procedure and the results obtained in Zn, Fe and Cu determinations are comparable with those obtained with the conventional methods. (Hide)

Vanadium determination was carried out in petroleum samples by atomic absorption spectrometry with electrothermal atomization. Three procedures of sample preparation were studied : xylene solution, dry calcination and wet digestion with sulphuric acid and hydrogen peroxide. The xylene dissolution and dry calcination were the optimum procedures. (Hide)

This article describes a spectrophotometric procedure for the determination of phosphorous in samples of fruits and vegetables grown in Galicia. The sample was digested with sulphuric and nitric acids and was evaporated to dryness. The residue was dissolved in water. Amonium molybdate solution and stannous chloride were added to the aqueous solution.The absorbance of the resulting blue complex was measured ( at room temperature) at 696 nm. The absorption properties of the complex, its stability over several minutes and the reproducibility of the method were considered. Phosphorous concentrations for the samples analysed lay between 2597 and 240 µg/g. (Hide)

This method describes the direct determination of lead in beer. The determination was performed using ETAAS. The sensitivity, detection limit, quatification limit and percent recovery were: 0.67 µg/l, 0.7µg/l,2.7µg/l y 100.7%, respectively. Different brands of beer from Spain and other European countries were analyzed by this method, and all were well below the maximum levels permitted in international legislation. Lead concentration for samples analysed lay between 3.0 and 14.8 µg/l. (Hide)

Traces of copper ions are sorbed on a cation-exchange resin ( amberlite IR-120). The pH of the sample is not critical within the range 2-4. The collected copper can be eluted efficiently in 25 ml of 3M hydrochloric acid. After elution copper is determined by flame atomic absorption spectrophotometry at 324.8 nm.The detection limit was 2.84 µg L-1. Relative Standard deviations were 26.42-8.00 at µg L-1 levels and recovery was about 100.01-98.95%. Commons cations present in natural waters do not interfere. In this work was realized an approach to speciation. (Hide)

This article describes a spectrophotometric procedure for the determination of phosphorous in samples of fruits and vegetables grown in Galicia. The sample was digested with sulphuric and nitric acids and was evaporated to dryness. The residue was dissolved in water. Amonium molybdate solution and stannous chloride were added to the aqueous solution.The absorbance of the resulting blue complex was measured ( at room temperature) at 696 nm. The absorption properties of the complex, its stability over several minutes and the reproducibility of the method were considered. Phosphorous concentrations for the samples analysed lay between 2597 and 240 µg/g. (Hide)

A chelating poly(dithiocarbamate) resin (PDTC) with macroreticular support in characterized as effective collector for traces of manganese from natural waters. Using small PDTC columns preconcentration of manganese can be achieved even at high flow-rates (5-6 ml/min) and sample volume (1500ml). Accordingly, PDTC resin is used for the preconcentration of manganese from water samples prior to its determination by flame atomic-absorption spectrometry. A series of ions abundant in natural waters do not interfere. The sensitivity and detection limit were 2.5 and 0.5 µg/L, respectively. The relative Standard deviations of the results for a manganese concentration of 40-400 µg/l are in the range 1.1-6.2%. In mineral and tap waters analysed, the manganese concentration range was between 2.9 and 30.8 µg/l. (Hide)

A chelating poly( dithiocarbamate) resin with macroreticular support is shown to be effective for the preconcentration of copper, iron and zinc in natural waters. The retained ions can be eluted efficiently in 5ml of 8 M nitric acid from 1-20 cm columns of resin.This poly(dithiocarbamate) resin is used for the preconcentration and determination of copper, iron and zinc by flame atomic absorption spectrophotometry. Common ions present in natural waters do not interfere. The detection limits were 0.50, 0.21 and 0.04µg L-1 for Cu, Fe and Zn respectively. (Hide)

A method for the direct determination of molybdenum in human serum by electrothermal atomic absorption spectrometry was developed and optimized. Samples were injected directly in the graphite tube with magnesium nitrate as the matrix modifiers in the presence of 0.05% triton X-100. The characteristic mass was 18pg. The detection and quantification limits were 0.3 y 1.0 µg L-1 respectively. The molybdenum levels found in hemodialisis patients were 1.0-8.3 µg Mo L-1 and in healthy individuals were lowest than 1 µg Mo L-1. (Hide)

The effect of palladium as matrix modifier for direct molybdenum determination in waters by electrothermal atomisation atomic absorption spectrometry is tested by using Pd-Mg(NO3)2 and Pd-hydroxylamine hydrochloride. The use of these matrix modifiers provide a more high temperature stabilisation for the molybdenum, thus losses during the ashing step are not produced at temperature of 1800º C. Ashing is more favorable in two step (the first step at 600ºC). The optimum atomization temperatures were 2800 and 2700ºC for Pd-Mg(NO3)2 and Pd- hydroxylamine hydrochloride respectively. Data on sensitivity, calibration, accuracy, precision and interferences are given. (Hide)

Preparation and preliminary investigations on application of a poly –styrene macroreticular , crosslinked poly(dithiocarbamate) resin for the concentration of trace metals from waters is reported. The pH dependence of metal-resin chelation has been determined for Fe (III), Cr(III), Ni(II), Cu(II), Pb(II), Co(II), Cd(II), Zn (II) and Mn(II). The resin exhibits no affinity for alcali and alkaline earth metals. Cr(III) is not retained quantitatively in the pH range 4-12. The resin selectivity and capacity has been determined at pH 6. Metals were recovered by elution with 8 M nitric acid and determined in the eluate by flame atomic absorption spectrophotometry. (Hide)

A method for the determination of chromium(III) and (VI) species has been studied and applied to mineral water samples. The chromium (III) was chelated with 0.1 mil/l 8-hydroxyquinoline in methyl alcohol, extracted in isobutyl methyl ketone and determined by ETA-AAS. The effects of the pH, extraction and heating time and amounts of the reagents required for the extraction were studied. A method for the determination of total chromium was optimized too, and the chromium (VI) can be calculated. The precision , sensibility, accuracy, graphite furnace program and interferences for both methods were also investigated. (Hide)

In this paper a review about the analytical methods used in the sample preparation and in the determination of different metal species in biological samples is described. (Hide)

Preliminary investigations on the application of a polystyrene macroreticular, cross-linked poly ( aminophosphonic acid) resin for the concentration of trace metals from aqueous solutions are reported. The pH dependence of metal-resin chelation was determined for Mg(II), Ca(II),Fe(III), Cr(III), Ni(II),Cu(II), Pb(II), Zn (II) and Mn(II). The resin exhibits no affinity for the alcali metals tested over the pH range 1-14. The resin selectivity and capacity were determined at pH 5. Metals were easily recovered by elution with 3 M hydrochloric acid and determined in the eluate by flame atomic absorption spectrometry. (Hide)

A flame atomic-absorption spectrophotometric method for determining strontium in natural waters is described. The use of ethylenediamine tetraacetic acid (EDTA) to suppress interferences was studied, and ion-exchange with Amberlite IR-120 (H+) to concentrate the metal was used; strontium being eluted with 3% EDTA. The precision and reproducibility of the method were also investigated, and optimum results were obtained. Strontium concentrations for samples analyzed were between 4 and 147 µg/L. The detection limit was 1.6 µg/L, and the sensitivity was 3.2µg/L for strontium. (Hide)

A method for the determination of aluminium in water by electrothermal atomization atomic absorption spectrometry using palladium-magnesium nitrate as matrix modifier is described. The charring and atomization temperatures and times and the amount of modifier were optimized. The calibration and addition graphs, detection limit, cuantification limit, precision, accuracy , interferences, and characteristic mass were also investigated. The method was applied to the determination of aluminium in water samples. (Hide)

The acid digestion of mussel samples was studied by microwave heating in high-pressure teflon bombs, followed by determination of Zn, Fe and Cu by flame atomic absorption spectrometry (FAAS). The digestion time , the power of the microwaves and the amount of nitric acid were varied using the certified reference material DOLT-1 (NRCC). Using 3 min of digestion time and 2ml of nitric acid, the complete dissolution of 0.2g of freeze-dried samples is possible. This procedure was applied to the determination of these metals in 46 mussel samples from estuaries in Galicia, Spain. (Hide)

A method for the determination of lead in mussel slurries by atomic absorption spectrometry with electrothermal atomization using Pd-Mg(NO3)2 as a chemical modifier is proposed. The drying, ashing and atomization temperatures were optimized. Calibration and Standard additions graphs, sensitivity, precision, accuracy and the effects of different slurry stabilization agents were also studied. The method was applied to the determination of lead in mussel samples from the Galicia coast and the results obtained were compared with those achieved by means of a wet digestion procedure. (Hide)

A method for the determination of chromium (III) and total chromium was studied. Chromium(III) was chelated with 0.1 mol l-1 quinolin-8-ol in methanol, extracted with isobutyl methyl ketone and determined by electrothermal atomic absorption spectrometry. The effects of the pH, extraction and heating time and amounts of reagents required for the extraction were studied. The detection limit of this method was 12 ng l-1. Different modifiers (nitric acid, magnesium nitrate and sodium tungstate) for the determination of total chromium were also investigated and a method for preconcentration on a graphite tube with hot injection using magnesium nitrate was optimized. The detection limit for the determination of total chromium using this procedure was 29 ng l-1. The precision obtained for different amounts of chromium(III) and total chromium were 2.8-6.2 and 2.2-4.3%, respectively. The graphite furnace programmes, the accuracy and the interferences for the both procedures were also studied. (Hide)

A method is described for the direct determination of tin in tap waters by electrothermal atomization atomic absorption spectrometry (ETA-AAS), using magnesium-nitric acid and palladium-magnesium as chemical modifiers. The charring and atomization temperatures and times, and the amount of modifier were optimized. The calibration and addition graphs, detection limit, quantitation limit, precision, accuracy, interferences and characteristic mass were also investigated. The method was applied to the determination of tin in tap water samples. (Hide)

A method for the determination of arsenic in slurries of mussel tissue using palladium-magnesium nitrate as modifier was optimized. The slurry was stabilized by a 0.015 % (v/v) of Triton X-100. To achieve complete mineralization the slurries were ashed at 480 ºC for 10s in an air flow (50 ml/min) and at 1200ºC for 15s in an argon flow (300 ml /min) in the presence of Pd-Mg (NO3)2 as modifier. The optimum atomization temperature was 2200 ªC. The precision and accuracy of the method were studied using the Reference Material BCR nº 278 Mussel Tissue (Mytilus edulis). The determination limit (LOD) of the final slurry solution was 1 μg/L of arsenic corresponding to an arsenic level in the mussel of 1.3 μg/g, for a 0.5 %(m/v) slurry. Results of calibration using aqueous standards and the standard additions method were compared. The method was applied to the determination of arsenic in mussels from the Galician coast. The levels found lie between 2 and 9.3 μg/g of arsenic. (Hide)

A method for the determination of Mercury in marine sediment slurries by electrothermal atomization atomic absorption spectrometry was optimized. It was found that a particle size <20μm is sufficient to achieve total atomization of the mercury content in the solid particles of the slurry. This particle size was achieved with simple mechanical grinding, using zirconia beads. The use of different thickening agents, viz, Triton X-100, Viscalex HV30 and glycerol, during the slurry preparation was studied. In addition, an acid predigestion was applied to verify the efficiency of the slurry sampling. The use of palladium at a concentration of 15 mg l-1 was found satisfactory for stabilizing mercury at 200 ºC. Three charring steps, two involving an oxidative process, were studied. The optimum atomization temperature was 1450ºC. A limit of detection of 70μg kg -1 was achieved. The standard additions method was used for the determination of mercury in marine sediment samples from the Galician coast, the levels being between 2.2 and 3.2 mg kg-1. (Hide)

Graphite tubes with L`vov platform coated with zirconium have been tested as atomization surface for tin determination in tap water by Electrothermal Atomization Atomic Absorption Spectrometry (ETAAS). The pyrolisis and atomization temperatures and times were optimized. The calibration and addition graphs were made. Sensitivity and common interferences were investigated and the behaviour of these tubes was compared with standard total pyrolytic graphite tubes using palladium-magnesium nitrate as chemical modifier. (Hide)

A method for the indirect determination of trace amounts of iodide by electrothermal atomic absorption spectrometry through the measurement of the mercury signal generated when small amounts of iodide and mercury are heated in a graphite furnace is described. The measured absorbances are related to the values of the signals from an iodide-mercury complex. The pH required for the formation of the Hgxly complex as well as other parameters involved in measurement of the signals are also determined. The limits of detection and quantification obtained were 3.0 and 10.1 μg l-1 of iodide, respectively , and the characteristic mass was 38.8 pg of iodide. The relative standard deviations obtained were from 5.1-8.9% (n=7), depending on concentration. In the range 5-20 μg l-1 recoveries were 94.8-104.4%. The method has been applied to a range of tap waters. (Hide)

A method of the determination of lead in slurries of marine sediment using palladium-magnesium nitrate as a chemical modifier has been optimized. To stabilize the marine sediment slurry, different thickening agents were studied. The grinding time and the particle size were also studied. To achieve complete pyrolysis of the slurry sample, two charring steps were used: the first one at a low temperature, 480ºC, and the second at 900ºC. The precision of the method was studied as within-batch precision; the relative standard deviations obtained in both cases were less than 3%. The relative standard deviation for the repeatability of the over-all procedure was 5.0%. The accuracy of the method was studied using a Certified Reference Material PACS-1 (marine sediment) from the National Research Council of Canada, which has a certified lead content of 404±20 mg kg-1; the result obtained was 418±11 mg kg-1. The detection limit for lead was 0.22µg l-1. Calibrations using aqueous standards and the reference material were compared. This method has been applied to the determination of lead in marine sediment samples from the Galicia coast and the results were compared with a sample digestion method using nitric and hydrochloric acids in a high pressure poly(tetrafluoroethylene) bomb and microwave energy. No significant differences were found between the two procedures. (Hide)

Treating cow milk samples with ultrasound or with any of three surfactants (sodium tetrapropylenebenzosulphonate (A), saponin (B) and sodium dodecylbenzosulphonate (C) allowed reproducible measurement of zinc content by direct flame atomic absorption spectrometry, with coefficients of deviation less than 2.30% in all cases. Sodium tetrapropylenebenzosulphonate, with which the limit of detection was 10 mg/l, is preferred to the other treatments because it achieve greatest reduction in matrix effect. The results obtained with sodium tetrapropylenebenzosulphonate for nine commercial cow milks and fifteen formula milks are reported. (Hide)

A comparison of the copper determination in cocaine and heroin by electrothermal atomic absorption spectrometry by using palladium-magnesium nitrate and nitric acid as chemical modifiers was carried out. Cocaine samples were dissolved in 2 ml of nitric acid 35.0%, diluting to 10 ml with ultrapure water. It was found and optimum charring temperature of 1300ºC when nitric acid and palladium-magnesium nitrate were used as chemical modifiers. The optimum atomization temperature achieved was 2400 ºC for the use of both chemical modifiers. Calibration and standard addition graphs were performed and it was obtained that aqueous calibration is a real possibility for the use of both chemical modifiers. The LOD reached was 3.9µg kg-1 and 7.4 µg kg-1 for the use of palladium-magnesium nitrate and nitric acid, respectively. The within-bath precision (n=11) oscillated between 0.6 and 1.6% and 0.7 and 3.2% for 20 and 0 µg l-1 of Cu spiked samples for palladium-magnesium nitrate and nitric acid respectively. The analytical recovery was close to 100% for all concentration levels and for both chemical modifiers. A study of the effect of several species on the determination of copper, and a study of the precision and analytical recovery with the variation of the amount of sample, were finally carried out for the use of palladium-magnesium nitrate as more adequate chemical modifier. Copper concentrations found in heroin samples oscillated between 1.59 and 3.83 mg kg-1, being the copper concentration interval in cocaine 0.06-0.32 mg kg-1. (Hide)

A comparative study of the use of nitric acid and magnesium nitrate as chemical modifiers, using a deuterium are background corrector, in the direct determination of nickel in cocaine and heroin was developed. Cocaine samples were dissolved in 2 ml of 35.0% nitric acid where as heroin was dissolved in water. Pyrolysis temperatures of 1500 and 1600 ºC were obtained for nitric acid and magnesium nitrate, respectively, for cocaine and heroin solutions, a deuterium lamp being adequate to correct the background signals obtained. The sensitivity was better with the use of magnesium nitrate, the limit of detection being 32.1 µg kg-1 compared with 34.3 µg kg-1 with nitric acid. The within-batch precision (n=11) and the analytical recovery were adequate with the use of both chemical modifiers. The introduction of a cooling step was studied through the within-run precision, resulting in an optimum temperature of 200ºC. Howewer, the sensitivity obtained by using cooling was poorer than that given by programmes without a cooling step. Similarly, the omission of the pyrolisis step did not give satisfactory results. Studies on interferences and on the variation of the analytical performance with the amount is sample were also carried out with the use of magnesium nitrate as the most suitable chemical modifier. Finally, the method was applied to determine nickel in heroin and cocaine samples confiscated by the Spanish Police, the concentrations found in heroin being between 0.50 and 1.35 mg kg-1 and in cocaine between 0.07 and 0.34 mg kg-1. (Hide)

Various matrix modifiers were investigated for the determination of molybdenum in human urine samples by electrothermal atomization atomic absorption spectrometry. Methods with nitric acid, barium difluoride, magnesium nitrate, palladium-magnesium nitrate and palladium-hydroxylamine were studied by introducing the urine samples directly into the graphite furnace with 0.3% Triton X-100. The charring and atomization curves, the amount modifier and the calibration and addition graphs were studied in all instances. The precision, accuracy and chemical interferences of the methods were also investigated. The matrix interferences have been removed with the modifiers barium difluoride, palladium-magnesium nitrate and palladium-hydroxylamine. The limits of detection and quantification were 0.2 and 0.7 µg l-1, respectively, for these modifiers. The characteristic masses were 14.1, 18.0 and 14.9 pg of Mo for palladium-magnesium nitrate, palladium-hydroxylamine hydrochloride and barium difluoride, respectively. The method with palladium-magnesium nitrate has been applied to the study of the amount of molybdenum in human urine samples. The molybdenum levels found lie between 4.8-205.6 µg l-1. (Hide)

A method for the determination of lead in illicit heavy drugs by electrothermal atomic absorption spectrometry using palladium as a chemical modifier was developed. A sample of drug, 0.5 g, was dissolved in 2 ml of HNO3 35.0%(v/v), diluting to 10 ml with ultrapure water. First, a comparative study of palladium, magnesium and palladium-magnesium used as chemical modifiers was carried out, and it was found that palladium alone is adequate to stabilize lead at a charring temperature of 1000ºC. The optimum atomization temperature was 2400ºC. A study on the insertion of a cool-down step before the atomization step and a study on the omission of the charring step were made. Neither approach was advantageous. A limit of detection of 31.4 µg kg-1 and a characteristic mass of 24.4 pg were obtained, with analytical recoveries between 98.0 and 105.0% for a 2.5-40 µg l-1 concentration range. The within-batch precision (n=11) was oscillated between 6.4 and 0.2% for a drug solution spiked with 0 and 40µg l-1, respectively. Finally a study of some interferences, and study of the precision and analytical recovery on the amount of sample were also carried out. (Hide)

An on-line column preconcentration technique for flow-injection flame atomic absorption spectrometry has been developed for the determination of trace metals in natural waters. A minicolumn (20 mm X 2 mm i.d.) filled with a poly(aminophosphonic acid) chelating resin (PAPhA, 20-30 mesh) was used for the preconcentration procedure. For 2 ml samples, detection limits of 0.5,5.0, 1.5, 1.6,3.5, 0.6,3.2,3.1 and 0.4 µg l-1 for Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, respectively were achieved. The precision (coefficient of variation) obtained was in the range between 1.1 (Cd and Cu) and 3.3% (Co). Accuracy was also investigated and results agreed with the certified values of the reference material. The sampling rate was 48 h-1. The method was applied to the determination of trace metals in natural water samples from Galicia (Spain). (Hide)

Preliminary studies addressed to the determination of iodine, as iodine, by indirect ETAAS and applying solvent extraction are described. The work was carried out to achieved a selective quantification of the iodide contained in the complex formed with mercury(II) in acid medium, but selectivity problems were found. The formation of an ion association complex between mercury(II), iodide and 2.2´dipyridyl was studied. Several parameters were optimized related to the extraction process: the optimal pH interval, 6.8-7.6; volume of extractant, 2 ml; and shaking time 30s are proposed. Regarding the performance of the measurements, the optimized graphite furnace temperature programme was also studied, yielding 200 and 1000 ºC as the best temperatures for the mineralization and atomization steps, respectively. The standard calibration and the standard additions methods were performed. The RSDs of the procedure were between 4.9 and 8.0%, for the standard calibration and from 3.2 to 15.6% for the standard additions method. (Hide)

A ethod for the determination of arsenic (III) and total arsenic was studied. Arsenic (III) was chelated with 2% sodium diethyldithiocarbamate in water, extracted with isobutyl methyl ketone and determined by electrothermal atomic absorption spectrometry, using palladium as chemical modifier. The effects of pH, extraction time and amounts of reagents required for the extraction were studied. The detection limit of this method was 25µg kg-1. Different modifiers [LaCl3-HNO3, Pd-Mg(NO3)2] for the total arsenic determination in slurries of marine sediment samples were also investigated; LaCl3-HNO3 was avoided because a double peak was observed. The detection limit for the determination of total arsenic using Pd-Mg(NO3)2 as modifier was 44µg kg-1. The precisions obtained for the different amounts of arsenic(III) and total arsenic were 0.57-2.99 and 0.83-0.45%, respectively. The graphite furnace programmes, accuracy and interferences for both procedures were also studied. The method has been applied to the determination of arsenic (III) and total arsenic in sediment samples from Galicia (North West of Spain). (Hide)

Methods for the determination of As, Cd, Pb, Hg and Sn by electrothermal atomic absorption spectrometry in marine sediment slurry samples were developed. Triton X-100 was used as surfactant to stabilize the marine sediment slurry. Palladium or a mixture of palladium and magnesium nitrates was used as a chemical modifier. With the use of these modifiers it was possible to stabilize As, Cd, Pb, Hg and Sn to temperatures of 1200,700,900,200 and 1300ºC respectively, and the optimum atomization temperatures were 2300, 2500, 2500, 1450 and 1900 ºC. Precision and accuracy of the method were investigated using the marine sediment reference material PACS-1 (National Research Council Canada). The detection limits were 44,0.008,60,70 and 57 µg kg-1 for As, Cd, Pb, Hg and Sn respectively. (Hide)

A simple method for the determination of chromium (III) and total chromium in a flow injection system comprising chelating ion-exchange and flame atomic absorption spectrometry (FAAS) was described. A minicolumn (85 mm X 1.6 mm i.d.) filled with a poly(aminophosphonic acid) chelating resin (PAPhA, 20-30 mesh) was used for speciation and preconcentration of chromium because this resin is selective for Cr(III) ions. The flow injection manifold employed allows a high rate of introduction of the sample and retention of Cr(III) on the minicolumn. Total chromium was obtained by an efficient reduction of Cr(VI) to Cr(III) by ascorbic acid as reducing reagent. Elution was performed by using a small volume of 0.5M hydrochloric acid. For 6.6 ml samples, the detection limit for the total chromium and Cr(III) was 0.2 µg l-1. The precision (coefficient of variation) obtained for different amounts of Cr(III) and total Cr were 1.2-5.9% and 1.2-5.7%, respectively. Chemicals and flow variables, interferences and other figures or merit of the proposed methodology were studied. The method has been applied to the determination of total Cr, Cr(III) and by difference between these two species the Cr(VI) concentration in natural water samples: tap, mineral and river waters. (Hide)

Two liquid-liquid extraction procedures have been optimized for analysis of sea water samples. Tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) compounds were extracted with tropolone in chloroform from samples acidified to 1 M with HCL. The extracts were evaporated to dryness and redissolved in methanol, prior to separation of the alkytin compounds by liquid chromatography. Total tin was extracted from samples at pH 2 using oxine in isobutylmethylketone (IBMK). The optimized extraction procedure for alkyltin compounds was used as a pre-treatment of the samples when the speciation of tin was being performed. The IBMK solutions obtained from the extraction of total tin were directly subjected to electrothermal atomic absorption spectrometry, using zirconium-coated graphite tubes with L`vov plataforms. (Hide)

An optimized procedure is described for the separation of tributyltin(TBT) and dibutyltin(DBT) by high performance liquid chromatography(HPLC) using atomic absorption spectrometry (AAS) as a detection system. An on-line coupling between HPLC and electrothermal atomic absorption spectrometry(ETAAS) has been developed; the interface uses a 6-way valve between the outlet of the chromatographic column and the capillary of the autosampler arm. With this system 98mL of the chromatographic stream were injected into the graphite furnace which was preheated at 120ºC; the conditions of its design and working are described. With this interface only one fraction of the chromatographic peak is isolated and its absorbance determined, so the reconstruccion of this peak is not needed; this fact makes the procedure quicker and easier to carry out. The proposed procedure is applied to the determination of TBT and DBT in marine water samples with a previous liquid-liquid extraction, and the limits of detection (LOD) obtained for TBT and DBT are 31 and 28 ng L-1, respectively. (Hide)

Butyltin compounds were extracted and preconcentrated from sea water samples with a liquid-liquid extraction procedure using 0.03% tropolone in chloroform, the extracts were evaporated until dry and redissolved in methanol. The determination of these compounds was performed with high performance liquid chromatography (HPLC) directly coupled with electrothermal atomic absorption spectrometry (ETAAS). The sensitivity obtained with this procedure was 31 ng l-1 and 28 ng l-1, for TBT and DBT, respectively. Total tin was extracted and preconcentrated with a solution of 0.5% oxine in isobutylmethylketone (IBMK) and the extracts were directly subjected to ETAAS. The sensitivity obtained for total tin was 0.9 mg l-1. These two procedures were applied to the determination of butyltin compounds and total tin in sea water samples of estuaries in Galicia (Nothwest of Spain). (Hide)

A comparative study of different chemical modifiers in graphite furnace atomic absorption spectrometry for the direct determination of mercury in sea water samples in synthetic sea water samples of high (72.8‰ and low 34.2‰) salinity and in aqueous solutions, was carried out. The use of reduced palladium produces better results. The mixture of palladium nitrate and ascorbic acid, gives the best limit of detection (1.9μgl-1). The use of reduced palladium and magnesium nitrate produced excellent recoveries (close to 100%) in the whole salinity range for all mercury concentration tested. The use of palladium nitrate alone or combined with magnesium nitrate gave good recoveries with respect to a real sea water sample for low salinities. The interference from the major components of sea water were completely removed by using reduced palladium and magnesium nitrate modifiers. Thus, a single calibration curve with synthetic sea water may be applied to the analysis of sea water samples of widely differing salinities. (Hide)

A comparative study of different chemical modifiers for the direct determination of arsenic in real and in synthetic sea water samples of high (72.8‰) and low (34.2‰) salinity was carried out. The use of lanthanum chloride and magnesium nitrate (LOD= 3.0μgl-1) offers good recoveries for low salinities, while for high salinities an enhancement higher than 200% was obtained, rendering this method unsuitable for sea water samples. The use of silver nitrate (LOD=2.0μgl-1) produces unfavourable analytical recoveries, around 150 and 300% for synthetic sea water of low and high salinity. Zirconium oxychloride (LOD=1.8μgl-1) and palladium nitrate alone or combined with magnesium nitrate and reducing agents (LOD=1.1-1.3μgl-1) produce analytical recoveries close to 100% for all arsenic concentration tried over all salinities; thus, a single calibration curve using aqueous standard solutions may be applied to the analysis of sea water samples over all salinities. Finally, the addition of reducing agents and magnesium nitrate to palladium does not improve the sensitivity (Hide)

Methods for the direct determination of silver in sea water samples by ETA-AAS using different chemical modifiers were studied. The effect of salinity was studied using synthetic sea water of high (72.8‰) and low (34.2‰) salinity, and the results were compared with aqueous standard solutions. The charring temperatures achieved were 800 and 900ºC for magnesium nitrate and ammonium dihydrogen phosphate respectively, being 1100ºC for palladium nitrate and their mixtures. The best sensitivity obtained in the peak-height measurement mode was achieved by using reduced palladium (limit of detection between 0.5 and 1.1 μgl-1 for an injection volume of 20μl) with analytical recoveries close to 100% for synthetic and real sea water samples. The use of ammonium dihydrogen phosphate (LOD of 1.3 μgl-1 for an injection volume of 20 μl) produced good recoveries for low salinity; at high salinity an increase of around 25% was obtained, the method being unsuitable for sea water analysis. Finally, an interference study of the major components of sea water was carried out and applied to the analysis of surface sea water from the Galicia coast. (Hide)

In this paper the cadmium determination in human scalp hair was performed using the slurry sampling technique in Eelectrothermal Atomic Absorption Spectrometry. The detection and quantification limits were 22.5 and 74.9 µg/ Kg respectively. The within-run precision, CVs, for low, normal and above-normal concentrations were, 6.9 ; 4.2 and 2.5 % respectively. No intereferences of different ions were found. The cadmium concentrations found were 0.02 – 0.19µg/g. (Hide)

A method for the determination of total chromium in cocaine and heroin by flameless atomic absorption spectrometry is presented. Cocaine samples were dissolved in 2ml of HNO3 35.0% (v/v) to dissolve inert species, and also diluted to 10 ml Mg(NO3)2 and HNO3 as chemical modifiers, were compared in terms of sensitivity, precision and accuracy, a lower detection limit being obtained for the use of Mg(NO3)2, 5.77 μg kg-1 (7.23μg kg-1 for HNO3). Within-batch precision was found to be 6.19% and 1.48% for drug solution spiked with 0 and 10 μg l-1 of Cr3+, respectively, when using Mg(NO3)2, and 7.45 and 1.19% for the same respective concentration levels when using HNO3. Similar results on analytical recovery were obtained for both Mg(NO3)2 and HNO3.Mg(NO3)2 was selected as the more adequate of the two chemical modifiers. A study of the introduction of a cooling-down step, but no advantage was observed. Studies on the variation in precision and analytical recovery with the amount of sample, and interferent effects of different species on chromium determination were developed. Finally, chromium concentrations obtained in cocaine samples varied between 0.02 and 0.14 mg kg-1, the levels in the heroin samples being in the 0.05-0.59 mg kg-1 range. (Hide)

A method for the determination of lead in human hair slurries by electrothermal atomic absorption spectrometry was optimized. Particle size reduction was achieved with a vibrational mill ball equipped with zirconia cups, 20 min being sufficient grinding time to achieve an adequate particle diameter (<1µm). The use of different thickening agents, namely glycerol, Triton X-100 and Viscalex HV30, was studied and glycerol was found to be the best. The use of Pd and Mg(NO3)2 at optimum concentrations of 20 and 25 mg l-1 respectively was found to be satisfactory for stabilizing lead at 1100ºC. A limit of detection of 0.21 mg kg-1 was obtained. The limit of detection can be reduced to 0.05 mg kg-1 without loss of analytical performance by increasing four-fold the amount of hair sample. Accuracy was studied by analysis of a CRM 397 human hair reference material with a certified lead content of 33.0 ±1.2 mg Pb kg-1. The standard addition method was used for the determination of lead in hair samples from healthy people, the levels being between 2.3 and 35.5 mg kg-1. (Hide)

Methods for the determination of aluminium and strontium in illicit drugs by electrothermal atomic absorption spectrometry using magnesium nitrate and palladium-magnesium nitrate as chemical modifiers were developed. 0.5 g samples of cocaine were dissolved in 2 ml of HNO3 35%(m/v) and diluted to 10 ml with ultrapure water. Determinations can be performed in the linear range of 1.2-30µg L-1 Al3+ and 0.5-10 µg L-1 Sr2+. Limits of detection of 48.0µg Al kg-1 and 16.6µg Sr kg-1, and characteristic masses of 15.1 pg for aluminium and 3.8 pg for strontium were obtained. The analytical recoveries were between 97.3 and 101.2% for aluminium and between 97.3 and 101.2% for strontium. The within-batch precision (n=11) oscillated between 1.9 and 2.6% for aluminium and 2.5 and 5.1% for strontium. Studied on interference precision and analytical recovery were also carried out. (Hide)

Methods were developed for the determination of ultratrace amounts of cadmium in sea-water by cold vapour/trapping and atomization in a graphite furnace. Iridium-, tungsten- and zirconium-coated graphite tubes were investigated for the in situ preconcentration of cadmium cold vapour. Hydrochloric acid(0.25 mol l-1) and sodium tetrahydroborate (2%) were used as carrier and reducing solutions, respectively. Cobalt, gallium and silicon were used as catalysts for cadmium species generation. By using iridium-coated graphite tubes and gallium as a catalyst, a characteristic mass of 3 pg and a detection limit of 4 ng l-1 were obtained for a 500µl sample volume. The precision was between 0.2 (for unspiked sea-water) and 1.3% (for sea-water spiked with 0.5µg l-1 of cadmium). The proposed method was applied to the determination of cadmium in several certified water reference materials and sea-water samples. (Hide)

A comparative study of different chemical modifiers for the direct determination of chromium and nickel in polluted sea water by ETAAS was carried out. The effect of salinity was studied using synthetic sea water of high and low salinity on comparison with aqueous standard solutions. Calcium chloride and palladium nitrate were found the most adequate chemical modifiers for chromium and nickel determination, respectively. The optimum pyrolysis temperatures achieved by using these modifiers were 1600 for chromium and 1700ºC for nickel. The atomization temperature was 2600ºC in both cases. Detection limits (defined as 3 SD/m) of 0.2 and 1.0 µg L-1, with and injection volume of 20 µL were obtained for chromium and nickel respectively. The precision was 1.3-5.7% for chromium and 2.2-5.8% for nickel. The analyte recovery and interferences from NaCl and K2SO4 were studied. (Hide)

Butyltin compounds are extractd and preconcentrated from the marine water samples with a liquid-liquid extraction procedure using 0.03% tropolone in chloroform, the extracts are evaporated to dryness and redissolved in methanol. The determination of these compounds is performed with HPLC directy coupled with ETAAS. The sensitivity obtained is 31 ng l-1 and 28 ng l-1, for TBT and DBT, respectively. Total tin is extracted and preconcentrated with a solution of 0.5% oxine in IBMK and the extracts are directly subjected to ETAAS. The sensitivity obtained for total tin is 0.9µg l-1. These two procedures are applied to the determination of butyltin compounds and total tin in marine water samples of estuarines from Galicia ( Northwest of Spain).A statistical study was made with the data obtained, to prove if there is a correlation among the data obtained. (Hide)

A method for the determination of cadmium in slurries of marine sediment using palladium and phosphate as chemical modifier has been optimized. To stabilize the marine sediment slurry, Triton X-100 at 0.1% was used. To obtain a complete pyrolisis of the slurry sample two mineralization steps were used, the first at 480ºC and the second at 600ºC and 700ºC for phosphate and palladium, respectively. The precision and accuracy of the method have been studied by analyzing the Reference Material PACS-1 (marine sediment) of National Research Council Canada. The detection limits (LOD) were 11.9µg kg-1 for phosphate and 42.0µg kg-1 when palladium was used. These methods have been applied to the determination of cadmium in marine sediment samples from the Galicia coast and the results of both methods were compared; no significant differences were found between the two procedures. (Hide)

Methods for the direct determination of silver and manganese in cocaine and heroin by electrothermal atomic absorption spectrometry using palladium as chemical modifier have been developed. Cocaine samples, 0.5 g, were dissolved in 2 ml of 35.0% (m/v), HNO3 diluting to 10 ml with ultrapure water. A comparative study of palladium, magnesium nitrate, palladium-magnesium nitrate and nitric acid used as chemical modifiers was carried out, and it was found that palladium alone is adequate to stabilize silver and manganese at charring temperatures of 1000 and 1300 degrees C respectively. A study was made on the insertion of a cooling step before the atomization step, and this approach was not advantageous. Limits of detection of 2.3 and 6.9 mu g kg(-1) were obtained for silver and manganese respectively. The analytical recovery oscillated between 95.9 and 103.6% for silver and between 99.7 and 103.0% for manganese. Finally, a study of some interferences and a study of the precision and analytical recovery of the amount of sample were also carried out. (Hide)

Electrothermal atomic absorption spectrometry using Zeeman effect background corrector was applied to the determination of traces of cadmium in cocaine and heroin samples. (NH4)2HPO4 at an optimum concentration of 0.2% (m/v) was used as chemical modifier. The charring temperature reached was 800ºC. The absolute limit of detection (for cocaine sample concentration of 20.0% (m/v) was 0.6 μg kg-1. Cadmium recoveries oscillated between 99.8±3.2 and 103.1±2.7%. Matrix effect was important and thus the standard addition method was used to analyze the cocaine and heroin samples. Cadmium levels in cocaine were in the 5.0-45.6 μg kg-1 range, the levels in heroin samples between 10.2 and 192.0 μg kg-1. (Hide)

Rapid methods were developed for the direct determination of Ag, Al, Cd and Mn in cocaine and heroin by ETAAS using programmes omitting the charring step. Sample pretreatment was simple: dissolution in ultrapure water or in 35.0% (v/v) HNO3 for heroin or cocaine, respectively. Optimum drying temperatures were 250ºC for Ag, Al and Mn, and 300ºC for Cd. The run cycles were 35 and 37s, for Ag and Al respectively, and 36s for Cd and Mn. The best results were obtained with Pd, Mg(NO3)2 and (NH4)2HPO4, as chemical modifiers. The limits of detection were 8.6, 55.9,2.2 and 12.4 μg kg-1 for Ag, Al, Cd and Mn, respectively. (Hide)

A method for the direct determination of copper in samples of whole milk, non-fat milk and whey milk by electrothermal atomic spectrometry (ETAAS) was studied. The fat separation by centrifugation at 3200 rpm and the separation of casein mycelles to obtain the whey milk by ultracentrifugation at 31000g were investigated. In all cases Mg(NO3)2 was used as chemical modifier and Triton X-100 (0.2w/v) as emulsifying agent. The optimum pyrolisis temperature was 1500ºC. The detection limit was 0.4μg/l of copper. The precision was studied for the whole milk and the coefficients of variation (CV) were 5.7, 4.0, 2.4, and 2.8% for 0, 5, 10 and 20μg/l of copper added. The accuracy was determined by using the Reference Material Milk A-11 (IAEA) with a certified content of 378.4±24 n Cu/g; 359±16 ng/g were found. The method was applied to ten cow milk samples, the levels of copper being determined for whole milk, non-fat milk and whey milk. A statistical study was applied and it was concluded that the majority of copper is in the non-fat milk. (Hide)

A method was optimized for the determination of tin in slurries of marine sediment samples using palladium-magnesium nitrate as chemical modifier and Triton X-100 (0.1%) surfactant as stabilizer. To obtain a complete pyrolisis of the slurry sample, two charring steps were used, the first at 480ºC and the second at 1300ºC. The precision and accuracy of the method were studied using the Reference Material PACS-1 (marine sediment) from National Research Council Canada. The detection limit (LOD) was 57.6 μg kg-1. The method was applied to the determination of tin in marine sediment samples from the Galicia coast. (Hide)

Method have been developed for the trace determination of total and inorganic mercury in natural waters by cold vapour generation-trapping and atomization in a graphite furnace by selective reduction with NaBH4 and SnCl2. Iridium, tungstate and zirconium coated graphite tubes were investigated for the preconcentration of the mercury vapour. The carrier solution was 0.4 M of HCl, and 0.2% NaBH4 and 1.0% SnCl2 were used as reducing solutions for total and inorganic mercury, respectively. Using iridium coated graphite tubes characteristic masses of 300 and 240 pg for total and inorganic mercury, respectively, and detection limits of 90 and 60 ng l-1 for total and inorganic mercury were obtained for a 1500μl sample volume. The precision was between 0.7 and 2.1%. Accuracy of method was confirmed by the analysis of IAEA/W-4 fresh water reference material. (Hide)

Methods for the direct determination of iron and zinc in different components of cow milk (whole milk, non fat milk and whey milk) by flame atomic absorption spectrometry (FAAS) were performed using two nebulizers (nebulizer of platinum with a glass impact bead and a high performance nebulizer). The non fat milk and the whey milk were obtained by physical procedures (centrifugation and ultracentrifugation) in absence of chemical treatment. A limit of detection of 0.024 and 0.007 μg ml-1 for iron and zinc, respectively, were obtained by using a high performance nebulizer. The precision obtained varied between 1.4-4.0% and 0.4-1.9% for iron and zinc, respectively. The accuracy of the methods was studied with the analysis of SRM-1549 and A-11 non fat milk reference materials. The methods were applied to ten cow milk samples. Dates about the distribution of iron and zinc into the different components of cow milk were present. (Hide)

Rapid methods for the determination of lead, cadmium and manganese in human scalp hair by ETAAS using rapid atomizer programs and deuterium arc background correction have been developed. Samples were powdered by means of a zirconia vibrating ball mill over a period of 20 min (mean particle size less than 1 m). Then 0.1 g of the powder was suspended in a few ml of water and diluted to 25 ml. An optimum drying temperature of 250 °C was found for lead, cadmium and manganese. Optimum atomization temperatures of 2200 and 1900 °C were found for cadmium and manganese, and for lead, respectively. The program cycles were 38 s for cadmium and lead, and 37 s for manganese. Glycerol, at an optimum concentration of 0.4% m/v, was used as a stabilizing agent. Simple aqueous calibration was used for all analytes. The limits of detection were 0.03, 0.05 and 0.04 mg kg-1 for cadmium, lead and manganese, respectively. Accuracy was studied by analysing CRM 397 human hair, and the cadmium and lead levels were found to be in accordance with the certified accuracy values. The levels of metals obtained were in agreement with those previously reported for healthy people in Europe, i.e., less than 3.0 and 0.3 mg kg-1 for lead and cadmium, respectively. (Hide)

A continuous-flow procedure is proposed for the indirect determination of ascorbic acid, based on its reducing properties because of the oxidation of its 1,2-enediol group. Iron(III) was injected into a 1,10-phenanthroline stream, which was mixed with a sample carrier and then with a sodium picrate solution stream. In these conditions the iron(III) was reduced to iron(II) by the ascorbic acid. Thus, the iron(II) formed reacts with 1,10-phenanthroline to form a charged red complex, which with picrate ion forms a stable red-orange uncharged ion-association complex that is adsorbed “on-line” on a non-ionic polymeric adsorbent (Amberlite XAD-4), proportionally to the ascorbic acid in the sample. The unadsorbed iron was determined by flame atomic absorption spectrometry. The proposed method allows the determination of ascorbic acid in the range 0.5–25 μg ml–1 with a relative standard deviation of 2.9% at a rate of ca. 90 samples h–1. This method has been applied to the determination of ascorbic acid in pharmaceutical preparations, fruit juices and sweets. The results obtained in the analysis are compared with those provided by the 2,6-dichloroindophenol method. (Hide)

A highly sensitive and simple procedure was developed for the direct determination of total As in sea-water samples by hydride generation atomic fluorescence spectrometry. The method involves the generation of arsenic hydride from sea-water samples, diluted with HCl to a final HCl concentration of 2 mol l–1, which were merged with a reducing solution, viz., 3% m/v NaBH4. The sample and NaBH4 were pumped at flow rates of 6.0 and 1.3 ml min-1, respectively, and allowed to react in a 200 cm×0.8 mm id reaction coil. The evolved arsenic hydride was removed using an argon flow rate of 400 ml min–1 and passed to a hydrogen diffusion flame where the atomic fluorescence of As was measured at 193.7 nm. With the proposed procedure a detection limit of 5.0 ng l–1 was achieved. The repeatability of the determination varied between 1.5 and 4.0%. The accuracy was confirmed by the analysis of two sea-water reference materials (NASS-4 and CRM-403) and by recovery studies on natural samples spiked with known concentrations of As(III) and As(V). The proposed method was successfully applied to the determination of As in several sea-water samples. The number of samples that can be analysed is 40 per hour. (Hide)

Se desarrollan métodos para la determinación de metales traza, As, Cd, Hg y Pb, mediante generación de vapor haciendo uso de sistemas automáticos por inyección en flujo, atrapamiento y atomización en un horno de grafito. Se estudio la eficiencia de distintos recubrimientos (tubos de grafito recubiertos con Ir, Zr, y W) para la preconcentración de los distintos vapores generados. Los resultados obtenidos se comparan con los proporcionados por la técnica generación de vapor- EAA. (Hide)

Se desarrollan métodos para la determinación directa de Ag, As, Cd, Cr, Hg, Ni y Pb en muestras de agua de mar usando EAA con atomización electrotérmica. Con este objetivo se utilizan dos equipos de diferente diseño: el primero de los cuales se encuentra equipado con una lámpara de D2 como corrector de fondo y un atomizador convencional y el otro se encuentra equipado con un corrector de fondo basado en el efecto Zeeman y un atomizador de calentamiento transversal. (Hide)

Se realiza la determinación de galio e indio en diferentes muestras : mineral de cobre, alunita, polvo de una planta de acero y cenizas de carbón por Espectroscopía de Absorción Atómica con Atomización Electrotérmica , previa preconcentración de la muestra y separación de interferencias usando la resina Amberlita XAD-2 modificada con 1-(2-piridilazo)-2-naftol(PAN). (Hide)

Arsenic in sea water was determined directly by graphite furnace atomic absorption spectrometry (GFAAS) using palladium nitrate as Chemicals modifier, at an optimum concentration of 15 mg l-1. Deuterium and Zeeman effect background correction were compared and gave detection limits of 0.6 and 0.8 μg l-1, respectively. Precisions between 8 and 2%, for both correctors, were obtained with an injection volume of 40μl. The accuracy obtained with different reference materials: CRM-403 (1.461 μg kg-1), NASS-4 (1.26±0.09μg l-1) and IAEA/W-4 (24-31μg l-1) was studied for large injection volumes for both background correction systems. Interferences by chloride, sodium, potassium, calcium and silicon were removed by Zeeman correction, where as deuterium correction was much less effective and was insufficiently accurate for sea water samples. (Hide)

Methods were developed for the trace determination of total arsenic, ‘As(III)', ‘As(V)', dimethylarsonic acid (DMAA) and monomethylarsonic acid (MMAA) in sea and hot-spring waters by hydride generation/trapping and atomization in a graphite furnace using coated graphite tubes. Selective medium reactions were used to generate selectively hydrides of each arsenic species: 1. reduction with NaBH4 in thioglycollic acid medium (total arsenic); 2. reduction with NaBH4 in hydrochloric acid medium (inorganic arsenic, ‘As(III)' and ‘As(V)'); 3. reduction with NaBH4 in citric acid/sodium hydroxide buffer (‘As(III)'); and 4. reduction with NaBH4 in acetic acid (‘As(III)' and DMAA). The ‘As(V)' and MMAA can be evaluated by difference. Iridium, tungsten and zirconium-coated graphite tubes were investigated for the in situ preconcentration of arsenic hydrides. Trapping onto Zr-coated graphite tubes offers the best analytical performances, with detection limits of 56 ng l−1 for total arsenic (first selective medium reaction); 50 ng l−1 for inorganic arsenic and ‘As(III)' and DMAA (second and fourth selective medium reaction), and 80ngl−1 for ‘As(III)' (third selective medium reaction). (Hide)

A method for the determination of total organic tin from marine water samples by electrothermal atomization absorption spectrometry (ETAAS) is described. Samples are previously preconcentrated with a chelating molecule (tropolone) impregnated on a macroporous polymer (Amberlite XAD-2). The graphite furnace programme and preconcentration parameters were optimized. Calibration and addition graphs were performed. Sensitivity obtained with this procedure was 13 ng l−1. Relative standard deviation was always >10% and analytical recovery were satisfactory, ~100%. Some possible interferences were investigated, having no problems with this factor. This procedure allows the distinction between organotin compounds and inorganic tin IV, since the latter is not retained on the column. (Hide)

Electrothermal atomic absorption spectrometry (ETAAS) applying a Zeeman effect background correction system (ZEBC) and a tranverse heated atomizer was used to directly determine chromium in sea water. Calcium chloride (at a concentration of 20 mg L-1) was applied as chemical modifier with optimum charring and atomization temperatures of 1600°C and 2000°C, respectively. The detection limit was 0.2 μg L-1, by injecting 20 μL aliquot of sea water sample. This detection limit could be reduced further to 0.05 μg L-1, using multiple injections (injection of five 20 μL aliquot of sea water). The accuracy of the methods developed were confirmed by analyses of different certified reference materials. Finally, interferences from major and minor components of sea water are studied. (Hide)

Methods for the direct determination of Ni in sea water samples by ETAAS were developed using Zeeman effect background correction system (ZEBC) and a multi-injection technique. A mass of palladium nitrate of 2.5 μg (for an injection volume of 100 μl) was used as chemical modifier. The optimum pyrolysis and atomization temperatures were 1700 and 2100°C, respectively. The characteristic mass m0) and characteristic concentration (C0), precision and accuracy were studied for different injection volumes (20, 100 and 200 μl). For an injection volume of 100 μl (five 20 μl aliquot) of sample the accuracy analysis of different certified materials (saline and non saline water) was agreeable. The total time of the proposed procedure is 6 min. A m0 and C0 of 34.5 pg and 0.3 μg l−1, respectively were obtained for this injection volume (100 μl). Finally, interferences from major and minor components of sea water was studied. (Hide)

Methods for the determination of aluminium and manganese in human scalp hair samples by electrothermal atomic absorption spectrometry using the slurry sampling technique were developed. Palladium and magnesium nitrate were used as chemical modifiers. Hair samples were pulverized using a zirconia vibrational mill ball, and were prepared as aqueous slurries. Determinations can be performed in the linear ranges of 1.9–150 μg l−1 Al3+ and 0.03–10.0 μg l−1 Mn2+. Limits of detection of 0.9 mg kg−1 and 27.6 μg kg−1 were obtained for aluminium and manganese, respectively. The analytical recoveries were between 99.6 and 101.8% for aluminium and in the 98.3–101.3% range for manganese. The repeatability of the methods (n=11), slurry preparation procedure and ETAAS measurement, was 16.0 and 7.9% for aluminium and manganese, respectively. The methods were finally applied to the aluminium and manganese determination in 25 scalp hair samples from healthy adults. The levels for aluminium were between 8.21 and 74.08 mg kg−1, while concentrations between 0.03 and 1.20 mg kg−1 were found for manganese. (Hide)

A comparison was carried out between the use of wetting agents, Viscalex HV30 or glycerol, and an acid predigestion of the slurry for the determination of major metals (Ca, Cu, K, Mg, Na and Zn) in human scalp hair by FAAS/FAES with a high-performance nebulizer. Human scalp hair was pulverized in a Zr vibrating ball mill over a period of 20 min (mean particle size about 0.8 wm measured by laser diffraction). The use of wetting agents was only found adequate for dilute slurries; thus, Viscalex HV30 can be proposed for the determination of Zn in scalp hair slurries (relative atomization efficiency close to unit). For all cases, the use of acidified slurries with nitric acid at a concentration of 1.0% offers adequate analytical performance: LODs of 5.0, 3.5, 3.1 and 20.0 mg kg-1 for Ca, Cu, Fe and K, respectively, and 1.7, 0.6 and 3.5 μg kg-1 for Mg, Na and Zn. The repeatability of the overall method (n = 11), acid predigestion-slurry pretreatment and FAAS/FAES determination expressed as RSD (%), was between 8.7 for Zn and 18.6 for K. The developed methods were applied to 25 human scalp hair samples from healthy adults (Hide)

The use of Ir, W and Zr-coated graphite tubes, as permanent chemical modifiers, was studied for the determination of chromium in human scalp hair by ETAAS using the slurry sampling technique. The use of Mg(NO3)2 and Pd, as aqueous chemical modifiers, was also investigated and compared to the use of the permanent chemical modifiers. Scalp hair samples were pulverized using a Zr vibrational ball mill, (mean particle diameter of 0.8 μm) and suspended in ultrapure water. The lowest limit of detection, 44.5 μg kg-1,was achieved for the use of W-coated graphite tubes. The repeatability of the overall procedures (slurry preparation and ETAAS determination) were 15.7, 14.5 and 16.7% for W- and Zr-coated graphite tubes and Mg(NO3)2, respectively. The methods were applied to several reference materials, CRM 397 (human hair), DOLT-1 (dogfish liver) and DORM-1 (dogfish muscle), and the results obtained were in agreement to the certified values. Finally, the methods were applied to several human scalp hair samples from healthy adults. (Hide)

Methods for the direct trace determination of lead in sea water involving hydride generation, trapping and the atomization of the hydride generated in a graphite furnace has been developed. Different permanent coated graphite tubes: iridium, tungstate and zirconium coated graphite tubes were investigated for the in situ preconcentration of lead hydride. The results obtained were compared with the ones achieved by the conventional HG-AAS. Trapping on Ir-coated graphite tubes offers the best analytical performances, with detection limits of 60ng l−1. The accuracy was studied using IAEA/W-4 and SLRS-2 reference materials, and the method was applied to several sea water samples. The number of samples analyzed in an hour was 40. (Hide)

A simple and rapid method for the determination of traces of silver in human hair by slurry sampling and electrothermal atomic absorption spectrometry was optimized. Hair pulverization and the particle size reduction were achieved using a vibrational zirconia mill ball for 20 min. Palladium nitrate, magnesium nitrate and palladium-magnesium nitrate were investigated as chemical modifiers to thermally stabilize silver. Glycerol was used as wetting agent to stabilize the hair slurries. A limit of detection of 21.6 μg kg–1 was obtained for the use of palladium nitrate as best chemical modifier. The repeteability of the overall procedure (slurry preparation and atomic absorption spectrometric determination) corresponding to eleven measurements was 14.3%. Matrix effect was significant and so, the standard addition method was used to determine silver in hair samples from healthy people. The levels found varied between 0.10 and 1.62 mg kg–1. (Hide)

Methods were developed for the trace determination of As, Cd, Hg and Pb in seawater by vapour generation, trapping and atomization in a graphite furnace. Iridium-coated graphite tubes were investigated for the in situ preconcentration of vapors. Hydrochloric acid ( 4.0, 0.25, 0.4 and 0.15 M) was used for As, Cd, Hg and Pb, respectively, and sodium-tetrahydroborate concentrations of 2.0, 2.0, 0.2 and 4.0% for As, Cd, Hg and Pb, respectively, as the carrier and reductant solutions. Using iridium-coated graphite tubes, characteristic masses (m0) of 44.5 and 70 pg ( for As, Cd and Pb) were obtained for a 500 ml sample volume. For Hg, the m0 was 300 pg for a 1500μL sample volume. The precision was longer than 5% for all cases. The proposed methods were applied to several certified saline and non-saline water reference materials and seawater samples. (Hide)

A critical study of the use of chemical modification and background correction systems was carried out for the direct determination of several high and medium volatility and refractory metals (Ag, As, Cd, Cr, Hg, Ni and Pb) in sea-water samples by ETAAS. The influence of increasing sea-water inorganic matrix on the atomic signals, by the introduction of a large injection volume, was evaluated for different chemical modifiers [mainly Pd(NO3)2 , Mg(NO3)2 and also reduced palladium, which was done by using different reducing agents, viz., ascorbic acid, hydroxylamine hydrochloride and citric acid] and with two background correction systems [deuterium arc background correction (DABC) and Zeeman effect background correction (ZEBC)]. The influence of the salt matrix from sea-water was found to be very important for medium volatility metals such as Ag, As and Pb (charring temperatures between 1100 and 1400 °C), whereas for refractory (Cr and Ni, with charring temperatures of 1500 and 1600 °C, respectively) and high volatility metals such as Cd and Hg (charring temperature of 500 and 300 °C, respectively) this influence was insignificant. By using chemical modification and background correction, the interferences from the saline matrix were lowered for all metals studied (except Pb) and their direct determination in sea-water samples became possible. For high and medium volatility metals the use of reduced palladium offers better analytical performance than the use of palladium nitrate, while the addition of reducing agents does not improve the analytical performance for refractory metals. (Hide)

A flow injection preconcentration system with a chelating resin was developed to determine trace and ultratrace amounts of cadmium in mussels by flame atomic absorption spectrometry. The metal was preconcentrated on a minicolumn packed with poly(aminophosphonic acid) resin and eluted with dilute hydrochloric acid into the nebuliser–burner system of an atomic absorption spectrometer. A preconcentration factor of 16–47, equivalent to 3.4–10 ml of sample, was achieved by using a time-based technique. The detection limit (3σ) in the sample digest was 0.56 µg l–1 for a sample volume of 3.4 ml. The precision (relative standard deviation) obtained for different amounts of cadmium was in the range 1.4–6.6% at the 1–20 µg l–1 level. Chemical and flow variables, and other figures of merit of the proposed methodology, were studied. The method demonstrates high tolerance to interferences, and the analytical results obtained for a certified reference material were in good agreement with the certified value. The method was successfully applied to the determination of trace amounts of cadmium in mussel samples from estuaries in Galicia (Spain). (Hide)

The content of four trace elements, Selenium, Iodine, Chromium and Molybdenum have been measured in formulas and human milks, and the levels of serum Selenium, erythrocyte glutathione peroxidasa were determined to assess their status in newborns and infants. The content of milks and the intakes of the four elements are below the RDA of USA and Nutrition European Committees. Regarding Selenium status, serum levels are low, quite similar to countries with low selenium in soil and milks. Many newborns and infants in Spain actually, are in a risk situation of “marginal deficiency”. This is relevant, especially at early life periods, when nutritional demand, requirements for growth and development and vulnerability of central nervous system and thyroid, are both higher. It would be advisable to urge the producers of formulas to comply with the actual recommendations about the content of these essential elements. (Hide)

A new method to determination of Zn and Fe in different components of human milk and several types of milk has been developed. The separation technique used was the ultracentrifugation, with this technique is possible the complete separation of fat, milk whey and caseins. The Zn and Fe were determined in the three milk fractions. (Hide)

The copper speciation in milks used in lactation of human infants has been carried out by HPLC-ETAAS using Gel filtration chromatography after the fat and casein separation by ultracentrifugation. The proposed procedure has been applied to ten cow milk, fourteen human milk and ten infant formula samples. There are important differences between the milk samples. In the cow milk the Cu is principally found in the fraction of /764 kDa, for the infant formulas the higher amount is in the 910 kDa fraction. In the human milk the Cu is more distributed between all fractions, being the more significant the 21 and 81 kDa fractions. (Hide)

A procedure using the gel filtration chromatography to separate proteins, the fraction collection and the FAAS to determine Zn is developed and applied to samples of the human milk, infant formula and cow milk. In the human milk the Zn is distributed between the different proteins, the protein of low molecular weight 21 kDa is the protein with a higher precentage of Zn. In the infant formulas the more important is the protein of 877 kDa. For the cow milk it was not possible to detect the Zn levels in the protein fractions because in this milk the zinc is principally in the fat and in the casein and in proteins of high molecular weight.(Hide)

The use of the hydride generation with trapping on Ir-coated graphite tubes offers better sensivity than the HG-AAS in the lead determination. The introduction of a preheating step in order to break the hydrides before their atomization was found unnecessary. The method could be used for the direct determination of lead in estuarine water avoiding the matrix effect and with a sensitivity in the range of ng/l that can be improved by increasing the sample volume. The use of Ga as a catalyst improves the efficiency of Cd cold vapour generation, and with the Ir-coated graphite tubes for trapping the cold vapour of Cd a better sensitivity than for CVAAS is obtained, thus making possible the direct determination of ultratrace amounts of cadmium in sea waters, avoiding the laborious preconcentration procedures. The number of samples that can be analysed is 45 by hour. Could vapour mercury can be effectively adsorbed onto the surface of Ir, Zr and W coated graphite tubes at room temperature. The Ir gives the best analytical performance. Thus, this permanent chemical modifier could be used for the vapour mercury preconcentration avoiding the problems related to the use of palladium. The inorganic and total mercury concentration of 15 samples can be determined per hour. (Hide)

A continuous-flow procedure is proposed for the indirect determination of sodium cyclamate by an atomic absorption spectrometric method in artificial sweeteners mixtures and soft drinks. Sulfamic group is oxidized to sulfate and it is continuously precipited with lead ion in a flow manifold. The lead sulfate formed is retained on a filter, washed with diluted ethanol and dissolved in ammonium acetate for on-line atomic absorption determination of lead, the amount of which in the precipitate is proportional to that of cyclamate in the sample. The proposed method allows the determination of sodium cyclamate in the range 1-90 µg ml-1 with a relative standard deviation of 3.1% at a rate of ca. 35 samples per h. The 3 sigma detection limit is 0.25 µg ml-1. The method is very selective, no compounds normally found in the analysed samples and other artificial sweeteners had any effect on the determination of cyclamate (Hide)

Capillary electrophoresis with indirect UV detection was used to det. simultaneously arsenic, selenium, antimony and tellurium compds. The sepn. was achieved in a fused silica capillary filled with an electrolyte soln. contg. sodium chromate and an electroosmotic flow modifier, trimethyltetradecylammonium hydroxide (TTAOH). The effect of the TTAOH concn. and electrolyte soln. pH on the electrophoretic mobility of the species was studied. The best simultaneous sepn. of these species was achieved with 0.5 mM TTAOH and an electrolyte pH of 11.2 within 5 min. Detection limits range from 13 µg L-1 for SeVI to 509 µg L-1 for TeIV with electromigrative injection. The reproducibility was <10% and linearity was verified in the 0-100 mg L-1 range for all species. Interferences by other inorg. ions were studied. This method was applied to the detn. of metalloids in a spiked drinking water. Water exts. of industrial soils were analyzed and results were compared with those of ICP-MS measurements. (Hide)

The subantarctic frontal zone surveyed during the Apr.-May 1991 SUZIL cruise in the Crozet-Kerguelen-Amsterdam area showed a strong horizontal (north to south) gradient of dissolved silicates, increasing with depth, from 5 to 10 µmol Si/kg at 100 m, and 10-70 µmol Si/kg at 600 m. The northern limit of this frontal zone, formed by the confluence of the Subtropical and Subantarctic Fronts, was delimited at the surface by the 2 µmol Si/kg silicate isoline. Silicate-salinity diagrams also allow different water regimes to be positioned relative to the frontal zone. This sloping interface is between 2 water bodies, one to the north with more saline subtropical water of less concd. silicate than the southern one, corresponding to subantarctic water which is less saline and richer in silicate. It was concluded that dissolved silicate can be used as a useful tracer of frontal zone water masses in the Indian sector of the Southern Ocean, providing a sound complement to other hydrog. data. (Hide)

Fifteen Metallic species, silver (Ag), aluminium (Al), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), , manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), strontium (Sr) and zinc (Zn), were determined in 46 cocaine samples confiscated by the Spanish police in Galicia (northwest Spain). Classification of these cocaine samples according to their geographic origin (Colombia and Venezuela) was achieved by the application of pattern recognition techniques to the metallic content data. Cocaine samples, around 0.5 g were directly dissolved in 2 mL of 35.0% (v/v) HNO3, diluted to 10 mL with ultrapure water. The metals were quantified by means of electrothermal atomic absorption spectrometry (Ag, Al, Cd, Cr, Cu, Mn, Ni, Pb and Sr), flame atomic emission spectrometry (K and Na). Results show that two geographic origins can be established through the presence of trace and major elements. (Hide)

A method for the trace determination of tin in seawater samples by a hydride generation technique using a flow injection system coupled with AAS was investigated. Tin hydride was generated using 0.4% NaBH4 in 0.2% NaOH as the reductant. The carrier solution was 5.6.10-2 M HCl. The tin hydride generated was carried to the quartz cell by an argon stream flow of 100 ml/min, where it was atomized at 900ºC. Peak height was used for measurement of the analytical signal. A detection limit of 130 ng/L was obtained for a 500μL sample volume. The precision was between 2.0 and 9.0% and analytical recovery was close to 100%. (Hide)

A study was carried out about the use of different surfactants such as glycerol, saponin, sodium dodecylbenzenesulphonate (NaDBS), Triton X-100, and viscalex, in the emulsion preparation of milk fat. NaDBS was selected as the most suitable agent at 1.1 and 0.01% (w/v) for fat in cow`s milk and infant formula, respectively. For calibration, the method of standard additions was used. The limit of detection obtained for the cow`s milk and infant formula fat were 2.3 and 2.9μg/L, respectively. The coefficient of variations was 3.6 and 4.5% and the recovery obtained was between 98-108 and 93-102% for cow`s milk fat and infant formula fat, respectively. The method was applied to the Zn determination in whole milk and milk fat for different cow milks and infant formulas by flame atomic absorption spectrometry (FAAS). (Hide)

Several minor (Cu, Fe, Mg and Zn) and trace (Ag, As, Cd and Pb) elements were extracted from biological materials, such as human hair and mussel, using an enzymatic hydrolysis procedure based on pronase E. The reaction conditions, viz., pH and temperature, were fixed at optimum values of 7.4 and 37u°C, respectively. Other variables affecting the enzymatic hydrolysis procedure, such as enzymatic hydrolysis time, enzyme concentration, volume of enzyme solution and sample mass, were studied and optimized. The pH value was adjusted with a TRIS–HCl solution as buffer system. The minor elements were measured by FAAS while trace elements were determined by ETAAS under optimum conditions. In order to determine the total element concentration in samples, a microwave-induced acid digestion procedure in laboratory-made low pressure PTFE bombs was optimized. The enzymatic hydrolysis was effective for mussel samples (recoveries of about 100% were obtained for As, Cd, Cu and Mg); however, it was poor for human hair (recoveries were lower than 70%). (Hide)

The use of the slurry sampling technique was applied for the determination of total mercury in human hair by electrothermal atomic absorption spectrometry (ETAAS). In addition, an acid leaching procedure with hydrochloric acid was developed in order to determine Me–Hg+ in human hair with ETAAS. Palladium reduced by ascorbic acid was found to be adequate as a chemical modifier for both total mercury determination in hair slurries and methyl-mercury determination in hydrochloric acid solutions, at concentrations of 20 and 50 mg l−1 for palladium and ascorbic acid, respectively. The acid leaching procedure was carried out by mechanical stirring with hydrochloric acid at 4%, and a leaching time of 2 min was selected. The limits of detection were 0.04 and 0.10 μg g−1 for methyl-mercury and total mercury determination, respectively. The within-batch precision was between 1.8 and 8.8% for total mercury determination, and between 1.5 and 6.5% for methyl-mercury. The method was applied to 20 human hair samples from healthy people, and it was also applied to the CRM 397 human hair reference material, finding results that agree with the certified ones. (Hide)

A method to determine iodide is developed, based on the formation of an ion pair between 1, 10-phenanthroline, mercury(II) and iodide that can be selectively extracted into IBMK. When the IBMK layer is analyzed by electrothermal atomic absorption spectrometry (ETAAS) for mercury, iodide can be quantified too. Parameters related to the preparation of the ion pair and to the measuring process are studied. Thus, 7.2-7.4 reveals to be the best pH interval to carry out the extraction, and 250 and 1000 °C, respectively, the mineralization and atomization temperatures for mercury determination by ETAAS. The procedure is applied to drinking tap water and commercial infant formulae milk samples. The accuracy of the method has been investigated by means of the analytical recovery for water samples (mean analytical recovery obtained at different concentration levels 98.1%) and by using the certified reference material BCR CRM No 151 Skim Milk Powder (Spiked) for the infant formulae (results within certification interval). The repeatability of the measurements at different concentration levels gave a RSD lower than 10% for both types of samples and the repeatability of the whole procedure for infant formulae shows a RSD of 1.33%. In addition, the limits of detection and quantification were 2.5 µg/L and 8.5 µg/L, respectively, for drinking water and 1.1 µg/g and 3.8 µg/g, respectively, for infant formulae. (Hide)

A review with 50 references about the use of the Atomic Absorption Spectrometry as an alternative technique for iodine determination was developed (Hide)

The subantarctic frontal zone surveyed during the Apr.-May 1991 SUZIL cruise in the Crozet-Kerguelen-Amsterdam area showed a strong horizontal (north to south) gradient of dissolved silicates, increasing with depth, from 5 to 10 µmol Si/kg at 100 m, and 10-70 µmol Si/kg at 600 m. The northern limit of this frontal zone, formed by the confluence of the Subtropical and Subantarctic Fronts, was delimited at the surface by the 2 µmol Si/kg silicate isoline. Silicate-salinity diagrams also allow different water regimes to be positioned relative to the frontal zone. This sloping interface is between 2 water bodies, one to the north with more saline subtropical water of less concd. silicate than the southern one, corresponding to subantarctic water which is less saline and richer in silicate. It was concluded that dissolved silicate can be used as a useful tracer of frontal zone water masses in the Indian sector of the Southern Ocean, providing a sound complement to other hydrog. data. (Hide)

em>The Rias of Galicia are commonly divided into the Rias Altas and the Rias Bajas, the former being north, and the latter south of Cape Finisterre (NW Iberian Peninsula). The difference in their sediments and biological characteristics justifies a chemical study of the influence of nutrients in the Galician coastal zone. Data from 1977 to 1992, obtained from research cruises on the continental shelf and in the Rias are considered. The sources of nutrient salts, such as from land, remineralization, oceanic fluxes, and winter mixing have been taken into account. It is concluded that the Rias Bajas are richer in nutrient salts than the Rias Altas. This difference is not due to the river input since this is low and similar in both groups of Rias. Neither is it due to winter mixing, which is comparatively more beneficial to spring blooms in the Rias Altas than in the Rias Bajas. Instead, it is caused by summer processes, when nutrient salt remineralize and new nutrient salts become available in the euphotic zone, due to upwelling: these processes exert a far greater influence in the Rias Bajas than in the Rias Altas. Also the presence of depleted, nutrient-poor coastal waters in front of the Rias Altas impedes the penetration of upwelled seawater into these Rias, whereas south of Cape Finisterre, upwelled seawater can penetrate directly into the Rias Bajas. Hence the Rias Bajas receives more new nutrients in summer than the Rias Altas. (Hide)

A method for the selenium determination in a mother and her child’s hair using palladium as a chemical modifier was optimized. The sample was digested with nitric acid and hydrogen peroxide and diluted to 5 ml. To achieve complete mineralization the samples were ashed at 1200°C in the presence of palladium as a chemical modifier. The optimun atomization temperature was 1900°C. The precision and accuracy of the method were studied using the reference material CRM 397. Results of calibration using aqueous standards and the standard addition method were compared. The method was applied to the selenium determination in 30 samples of the mother’s and child’s hair. The levels found were 0.54±0.34 μg/g for mother’s hair and 0.77±0.25 μg/g for child’s hair. (Hide)

A Plackett–Burman 27×3/32 design for seven factors (nitric acid concentration, hydrochloride acid concentration, hydrogen peroxide concentration, acid solution volume, particle size, microwave power, and exposure time to microwave energy) was carried out in order to find the significant variables affecting the metals acid leaching after a pseudo-digestion procedure by microwave energy from mussel. Nitric acid concentration, hydrochloride concentration or hydrogen peroxide, and exposure time to microwave energy were the most significant variables, and a 23+star central composite design was used for their optimization. Nitric and hydrochloric acid concentrations between 4.1 and 5.3 M, and between 2.8 and 3.8 M, respectively, were found as optimum for many elements (Ca, Cd, Cr, Cu, Fe, Mg, Mn, Pb and Zn) yielding the acid leaching process for times in the 1.2–2.2 min range. However, As was quantitatively leached with hydrochloric acid concentrations between 4.8 and 5.3 M and an exposure time of 2.0 min, while Co and Se were extracted using nitric acid (1.0 and 5.0 M, respectively) and hydrogen peroxide (5.0 M) solution and an exposure time of 2.0 min. Finally, Hg was extracted using a hydrochloric acid/hydrogen peroxide solution at 3.5:2.0 M, and also for an optimum time of microwave radiation of 1.75 min. Trace metals were determined using flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry and cold vapor — atomic absorption spectrometry. The methods were finally applied to several reference materials (DORM-1, DOLT-1 and TORT-1), achieving good accuracy. (Hide)

Experimental designs were used for the optimisation of acid-leaching procedures assisted by ultrasonic energy for the extraction of Ca, Cu, Fe, Mg, Mn and Zn from human hair samples. A Plackett–Burman 27×3/32 design for seven factors ([HNO3], [HCl], [H2O2], acid/oxidant solution volume, exposure time to ultrasounds, temperature of the ultrasonic bath and hair particle size) was used in order to choose the variables affecting the acid-leaching process. The variables [HNO3], [HCl] and temperature of the ultrasonic bath were found to be the most important parameters for the acid-leaching procedure, and these variables were optimised by a response surface design (central composite design 23+star) which involved 16 experiments. Optimum values in the 3.7–4.2 M range were found for [HNO3], while optimum values between 3.0 and 3.5 M were found for [HCl]. The optimum temperature of the ultrasonic bath was between 80 and 90°C. An acid digestion induced by microwave energy (details given) was used to obtain the total metal concentration and also for comparative purposes. Ca, Cu, Fe, Mg and Zn were measured by flame atomic absorption spectrometry (FAAS) using a conventional air/acetylene flame, while Mn was determined by electrothermal atomic absorption spectrometry (ETAAS) under optimised conditions. Two different reference materials, IAEA-085 International Atomic Energy Agency, Monaco) and NIES No. 13 (National Institute for Environmental Studies, Japan), with certified metal contents for some of the elements investigated, were used in order to verify the accuracy of the methods. (Hide)

The slurry sampling approach including platform atomization; matrix modification, by using (NH4)2HPO4; and slurry stabilization by adding Triton X-100 as a dispersant agent, was used for cadmium determination in seafood products, tuna and shell-fish (mussels, clams and cockles) slurries, and several seafood products reference materials (DORM-1, DOLT-1 and CRM-278) slurries by ETAAS. A pyrolisis temperature of 600ºC was obtained by using (NH4)2HPO4 at a concentration of 50 mg L-1. The use of oxygen as the purge gas during the pyrolisis step was not necessary. The optimum atomization temperature obtained was 1200ºC. Aqueous calibration was possible for the determination of cadmium in tuna, clam and cockle slurries; however, it was not considered adequate for mussel slurries. It was found that calibration using the standard addition method is better. The good precision and accuracy of the procedure is illustrated by the results obtained for the reference materials, tuna and mussel samples. (Hide)

Speciation of iron in milk was carried out by high performance liquid chromatography (HPLC) and electrothermal atomic absorption spectrometry (ETAAS). Milk whey was obtained and low molecular weight protein separation was performed by size exclusion chromatography (SEC) with a TSK Gel SW glass guard (Waters) pre-column and a TSK-Gel G2000 glass (Toso Haas) column. After studying water as a possible mobile phase, this mobile phase was carefully selected in order to avoid alterations of the sample and to make subsequent iron determination in the protein fractions easier by ETAAS. The proposed method is sensitive (limit of detection [LOD] and LOQ 1.4 and 4.7 μg l−1, respectively) and precise (relative standard deviation [RSD]<10%). Iron is principally found in the proteins of 3 and 76 kDa in breast milk, and it is irregularly distributed in infant formulas. (Hide)

A sensitive method for vanadium determination in milk by atomic absorption spectrometry with electrothermal atomisation using hot injection and preconcentration in the graphite tube was developed. Three 30µl portions of milk sample were injected into the heated graphite tube, inserting a drying and mineralisation step between each injection. Barium difluoride was used as a chemical modifier at a concentration of 100rmgrlm1; with this modifier, vanadium was stable up to 2000u°C. The precision and accuracy of the method were investigated. The detection limit was 0.5, 0.7 and 0.6rµgrlm1 for cows' milk, human milk and infant formulae, respectively. The method was applied to vanadium determination in 17 infant formulae samples, 13 human milk samples and 10 cows' milk samples. (Hide)

An acid leaching procedure, for use as a sample pre-treatment, was developed for Cd, Cr, Hg, Pb and Se determination in human hair. A Plackett–Burman experimental design was used as a multivariate strategy for the evaluation of the effects of varying several variables at once. The effects on acid leaching of metals of nitric acid, hydrochloric acid and hydrogen peroxide concentrations, acid solution volume, exposure time to ultrasound, temperature of the ultrasonic bath, and hair particle size, have been investigated. From these studies, certain variables showed up as significant, and they were optimised by a 23 + star central composite design, which involved 16 experiments. Optimum values of the variables were selected for the development of acid leaching procedures to extract trace metals from human hair. Electrothermal atomic absorption spectrometry (ETAAS) was used to determine Cd, Cr, Pb and Se, while cold vapour-atomic absorption spectrometry (CVAAS) was used for Hg measurements. An acid digestion induced by microwave energy was used to obtain the total metal concentration and also for comparative purposes. IAEA-085 and NIES No.13 certified reference materials, which offer certified values for some elements, were used in order to verify the accuracy of the methods (Hide)

Capillary electrophoresis with an indirect UV detection was used in this study to analyse silicate, simultaneously with other nutrients (nitrite, nitrate, phosphate). The separation was achieved in a fused silica capillary filled with an electrolyte solution containing sodium chromate and an electroosmotic flow modifier, trimethyltetradecylammonium bromure (TTAB). The effect of the TTAB concentration and electrolyte solution pH on the electrophoretic mobility of the species is being discussed. The best simultaneous separation of these species is achieved with 0.2 mM TTAB and an electrolyte pH of 11 within 10 min. Detection limits were 0.73, 1.13, 0.60 and 1.32 μM for nitrite, nitrate, phosphate and silicate, respectively. Reproducibility is below 10% whatever the species. This method was applied to determine these species in different samples of river water and the results were compared with those of conventional colorimetric method measurements. The two methods do not give significantly different values for the mean concentration of these anions. (Hide)

The wind effect on water circulation was described by means of hydrodynamical and thermohaline measurements carried out in the ria of Pontevedra (NW Spain) from February to July 1998. The samples were measured both at an anchored station situated in the inner part of the ria and at other stations located in the main channel. In this way, temporal and spatial events were related. Thermohaline variables (salinity and temperature) were used to clarify the current patterns measured at the anchored station. It has been observed that there is a clear predominance of wind in the main estuary axis direction. The wind direction is strongly dependent on topography. Wind speeds higher than 4 ms-1are able to dominate the current at surface layers, even against tidal effect. Easterly winds force water to leave the estuary at surface layers while westerly winds force water to enter it. Diurnal breezes associated with westerly winds were rarely recorded. Bottom layers were controlled by tide, except during an upwelling event. (Hide)

Speciation analysis of copper and lead in Tubarao river sediment using the Tessier sequential extraction procedure. The sequential extraction procedure proposed by Tessier and total digestion were applied for the analysis of sediment samples from Tubarao river. The recoveries were between 93.5 and 102.5% for Cu and 99.2 and 111% for Pb. The precision was tipically better than 6% for Cu and 3% for Pb. Comparison of the values obtained for the total digest with the sum of the extracted fractions showed that there were no significant losses in the extraction steps so that the method can be used for the monitoring availability and mobility of these analytes. According to ten points of sampling, was possible to determined the average of labiles phases (fractions 1 and 4) for Pb and Cu: 33.70% and 18.18%, respectively; and the inert phases (fraction 5-residual): 66.30% for Pb and 81.82% for Cu. (Hide)

Methods were developed for the determination of Ga in complex ores by electrothermal atomization atomic absorption spectrometry using matrix modification after its separation with Amberlite XAD-2 coated with 1-(2-piridylazo)-2-naphtol. Nickel, magnesium, and aluminium nitrates were used as the matrix modifiers, which were then compared in terms of maximum pyrolysis temperature, sensitivity, and background signal. The results show that the absorption signals for Ga were enhanced and the matrix interferences eliminated. The standard additions method was applied. The recommended method was also applied to the determination of Ga in real samples. The relative standard deviations for six replicate determinations were in the range 1..5 to 2.9% for Ga in different ore samples with Ga concentrations of 6.6-42μg g-1. (Hide)

A method to determine iodide in infant formula samples by indirect atomic absorption spectrometry (IAAS) was developed. The iodide in solution resulting from an alkaline digestion (Na2CO3–NaOH) of the sample is precipitated with silver; the precipitate is redissolved by adding cyanide solution, and this solution is subjected to GF-AAS. Temperatures of 1000 and 2100°C were selected for the ashing and atomization steps, respectively, using a mixture of Pd and Mg(NO3)2 as a matrix modifier (at concentrations of 36 and 16 μg ml−1, respectively). The sensitivity, LOD, LOQ and characteristic mass obtained were, respectively, 1.12×10−2 l μg−1, 3.1 μg g−1 and 10.4 μg g−1 and 7.3 pg, referred to sample. The linear interval of concentrations extends up to 10 μg l−1 of iodide, with no need to use the standard addition method; the mean R.S.D. of data within this range is 3.4%, with 2.9% over the whole procedure. No interfering effects were observed among the foreign ions studied, and 100.0% was the mean analytical recovery achieved within the linear range of concentrations. The application of the method to seven real samples gave a mean content of 12.8 μg g−1 of iodide, as well as less than 3.1 μg g−1 in eight other samples. (Hide)

The effects of several variables on the As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Pb, Se and Zn ultrasonic bath induced-acid leaching from lyophilised seafood samples have been studied by experimental designs. The determinations were carried out by electrothermal atomic absorption spectrometry (As, Cd, Co, Cr, Mn, Pb and Se), flame atomic absorption spectrometry (Ca, Cu, Fe, Mg and Zn) and by cold vapour-atomic absorption spectrometry (Hg). A Plackett–Burman experimental design was used to select the most significant variables that affect to the acid leaching process, while central composite designs were used to found optimum values for the variables involved in the acid leaching. The optimum conditions found for each variable and each element were tabulated. Accurate results were obtained by measuring DORM-1, DOLT-1 and TORT-1 certified reference materials, and the procedure was finally applied to mussel, clam and tuna samples. (Hide)

To complete these microwave distillation studies, a method for iodide determination in milk ¬type samples is proposed. The iodide contained in the sample is oxidized to iodine, which is distilled by means of microwave energy and reduced back to iodide. This iodide is combined with Hg(II) and 2,2'¬dipyridyl to give an ion pair, which is selectively extracted into IBMK. Mercury is determined in the extract by ETAAS in order to determine iodide. The yield of the distillation process (100%) was evaluated using the Sandell–Kolthoff reaction. In addition, for the solvent extraction, no buffer was needed; 3/5 was the best phase ratio (organic/aqueous); 30rs was the shaking time and the extracts were stable for 24rh, at least. The yield of the extraction procedure (studied also using the Sandell–Kolthoff reaction) was 87.5 and 87.1%, for standards and samples, respectively. Regarding the ETAAS measurements, the ashing temperature selected for both samples and standards was 150u°C; 800 and 1000u°C were the atomization temperatures chosen for samples and standards, respectively. Palladium in IBMK was the chemical modifier at a concentration of 3.0rµgrmlm1, both for samples and standards. The sensitivity was 3.50.10-3lµg-1 (standard additions); the LOD and LOQ were 0.2 and 0.6 µgml-1, referred to sample; the mean characteristic mass within the linear range of concentrations (0–17.5µgl-1) was 27.3pg; the mean analytical recovery within that range was 97.5% for a liquid whole milk sample and 100.6% for a CRM, which also gave results within certification. The method was applied to liquid whole milk, milk powder and infant formulae samples. (Hide)

A method to determine the selenium distribution in milk whey fractions was developed. After milk whey preconcentration by ultrafiltration, selenium in the protein fractions was separated by size exclusion chromatography (SEC) and determined by electrothermal atomic absorption spectroscopy (ETAAS) using a sampling procedure based on fraction collection, fraction preconcentration by ultrafiltration and introduction into the furnace after digestion, hydride generation and hydride preconcentration. The digestion and reduction conditions of the milk whey fractions obtained by SEC were studied. The hydride generation parameters and preconcentration into an iridium coated graphite tube using ETAAS with a Zeeman background correction were optimised. The method was applied to six infant formula milks and selenium was found in three fractions of cow¬based infant formulas: 40kDa, >160kDa and mostly in the <10kDa fraction. (Hide)

This method will allow the determination of bound copper to low relative molecular mass compounds in milk. The milk whey obtained by ultracentrifugation was submitted to fractionation by size exclusion chromatography (SEC) on a TSK-Gel2000 (Toso Haas) column with a mobile phase of 0.2 M NH4NO3 + NH3, pH 6.7. Fractions of effluent corresponding to the protein peaks were collected and the copper content was determined by ETAAS. The method was sensitive (LOD 0.4 μg l-1 and LOQ 1.5 μg l-1 in the fraction; LOQ 7.5–22.5 μg l-1 referred to the milk sample and depended on fraction volume) and precise (RSD - 10%). Media sample recoveries from the column were 101.2%. Cu was predominantly present in fractions corresponding to relative molecular mass 76 and 15 kDa of breast milk while copper was mostly found in fractions corresponding to 14 and 38 kDa of cow’s milk-based infant formulae; moreover, copper was eluted in the relative molecular mass region <6 kDa (Hide)

A chelating sorbent obtained by adsorption of 1-(2-pyridylazo)-2-naphthol (PAN) on Amberlite XAD-2 was used for the preconcentration of Ga and In. The analytical characteristics of the chelating sorbent were investigated and optimun sorption conditions for these metals under dynamic conditions were established. A peristaltic pump is used to adjust the flow rate of the solution. Elements are collected from the column by using a mixture adjusted to a pH range of 4-7 and 6-12 by ammonia or ammonium chloride for Ga and In, respectively. The procedure developed was applied to the analysis of different ores. (Hide)

Size exclusion chromatography (SEC) and flame atomic absorption spectroscopy (FAAS) were used for the separation of metal-containing species in milk whey. After milk ultracentrifugation, the sample was injected into a TSK-Gel G2000 glass column and eluted with 0.2M NH4NO3-NH3, pH 6.7. Low molecular weight proteins were fractionated, and the fractions were characterized by molecular weight. Zinc distributions were obtained by FAAS using a high performance nebulizer. The method was very sensitive (limit of detection= 2.6.10-3μg/mL; limit of quantitation = 8.9.10-3μg/mL) and precise (RDS≤10%). This method was applied to the determination of Zn in binding compounds in breast milk whey and in commercial cow`s milk-based formulas. Distribution patterns were different. The presence of Zn in most fractions in breast milk was most significant, where as in infant formulas Zn was detected only in fractions of molecular weight<5kDa and in the highest molecular weight peak. (Hide)

Systematic errors obsd.when using inductively coupled plasma at. emission spectrometry (ICP-AES) and mass spectrometry (ICP-MS) for the multi-element detn. in acid digests of environmental samples (tea leaves) were evaluated. Two chemometric approaches, exptl. design and principal component anal., were used in order to establish the errors assocd. with each stage of the anal. method: sample digestion (effect of the "no. of acid digestions") and measurement step (effect of the "no. of replicates" and the "calibration"). The elements under study were Co, Cr, Cs, Cu, Ni, Pb, Rb and Ti by ICP-MS, and Ba, Ca, Fe, Mg, Mn, Sr and Zn by ICP-MS and ICP-AES. Flame at. absorption spectrometry was used for comparative purposes. A Chinese tea certified ref. material with certified concn. for most of the elements was employed as the sample matrix. Variance estn. was made from ANOVA outputs from a full factorial design (FFD) 41 × 41 × 21. (Hide)

A simple transformation that uses the half-range and central value has been used as a data pre-treatment procedure for principal component analisis (PCA) and pattern recognition techniques. The results obtained have been compared with the results from classical normalisation of data, autoscaling and the minimun-maximum transformation. Three data sets were used in the study. The first was formed by determining 17 elements in 53 tea samples. The second and third data sets arose from two long-term drift studies performed to examine instrumental stability at standard and robust conditions. The instruments used were an ICP-OES and ICP-MS. The study revealed that the half-range and central value transformation resulted in a better classification of the tea samples that that achieved using the classical normalisation.. The loadings in the PCA for the long-term stability study, under both standard and robust conditions, were found to be similar to the drift trends only when the minimum-maximum transformation and the mean or maximum normalisation were used s data pre-treatments. (Hide)

Se estudió la determinación del contenido de hiero en las fracciones proteicas de la lece humana y de formulas infantiles Se observó una diferencia importante en la distribución del hierro en las diferentes proteínas. En el caso de la leche humana hay una variación en el perfil según el tipo de muestra, estando el mayor porcentaje en la fracción de menor peso molecular ( 1-5 KDa). En las formulas infantiles el hierro se encuentra distribuido en 3 fracciones proteicas, entre 1-5, 10-50 y > 100KDa. (Hide)

Se estudio en primer lugar el contenido total de hierro en las leches de formula empleadas en la alimentación infantil, encontrandose los resultados obtenidos entre lo límites 2,8 a 16,2 mg/ml. Posteriormente se realizó la separación de la leche en sus componentes: suero, grasa y caseína y se determinó el contenido de hierro en cada fracción. En la mayoría de las muestras estudiadas el mayor porcentaje de hierro se encuentra en el suero y ligado también al precipitado obtenido por ultracentrifugación. (Hide)

This paper describes the application of a trilinear parallel factor anal. (PARAFAC) to study systematic error during the multi-element detn. of a range of analytes in acid digests of solid samples (tea leaves) by ICP-AES and ICP-MS. The three variables studied were the "no. of digestions", in order to assess the systematic error assocd. with the sample pre-treatment, and the "no. of replicates" and "calibration", to provide information on the systematic error assocd. with the anal. detn. itself. The elements under study were Co, Cr, Cu, Ni, Pb, Rb and Ti by ICP-MS, and Ba, Ca, Fe, Mg, Mn, Sr and Zn by both ICP-MS and ICP-AES. For some elements flame at. absorption spectrometry was used for comparative purposes. A Chinese tea certified ref. material contg. many of the metals above was used in the study. The results obtained were compared to results from ANOVA. It was found that the systematic error, expressed as the sum of squares after PARAFAC, was quite different from the results obtained using ANOVA due to the very different way in which the models are built. The PARAFAC approach is shown to be straightforward to implement and robust. (Hide)

In this work, tetramethylammonium hydroxide (TMAH) was used to solubilize the DORM-1 dogfish muscle certified reference material as a model substance for the determination of As, Cd, Pb and Se by electrothermal atomic absorption spectrometry (ETAAS). The sample was mixed with a small amount of TMAH and heated to 60 °C for 10 min in a water bath. After dissolution, As and Se were determined using palladium and magnesium nitrates as a chemical modifier added in solution. For Cd and Pb, best results were obtained with a mixture of 250 μg of each of iridium and rhodium as permanent modifiers. In both cases, the calibration was performed with aqueous solutions in 0.2% v/v HNO3. The temperature program for each analyte was optimized using pyrolysis and atomization curves established with the fish reference material. The detection limits in dry samples and the characteristic mass values were: Cd 0.005 μg g−1 and 0.9 pg; Pb 0.04 μg g−1 and 7.6 pg; As 0.4 μg g−1 and 13 pg and Se 0.6 μg g−1 and 20 pg, respectively. Results from the determination of these elements in the DORM-1 certified fish reference material were within the 95% confidence interval of the certified values. (Hide)

A procedure for simultaneous solvent extreaction of Cu(II) and Fe(III) from river surface waters as diethyldithiocarbamates (DDC) 1,1,1-trifluoroacetylacetonates into iso-Bu Me ketone (IBMK) was developed prior to their determination by flame atomic absorption spectrometry. Exptl. design approaches were used to obtain the best compromise conditions for simultaneous solvent extraction Variables such as pH, Na DDC or 1,1,1-trifluoro-2,4-pentanodione (H(TFA)) concentrations, reaction time, IBMK vol. and extraction time were optimized. First, Plackett-Burman designs involving 13 experiments. and 2 replicates were used as screening designs to det. which variables were significant. DDC or H(TFA) concentration, as well as pH and IBMK vol. were found statistically significant and they were finally optimized by applying a central composite design (15 experiments and 2 replicates). Optimum values for these variables were selected for compromise extraction conditions of Cu(II) and Fe(III) species. An optimum pH of 5.3 was chosen for Cu-H(TFA) and Fe-H(TFA) formation with an optimum H(TFA) concentration of 0.20% (m/v). The optimum IBMK vol. for extraction was 8 mL, allowing a pre-concentration factor of 10. A microwave-assisted peroxydisulfate oxidn. was used to break down the metal-org. matter complexes in river surface waters to assess the total Cu and Fe contents. Applying the exptl. design approach, optimum conditions was an irradation. for 5.0 min at a microwave power of 500 W using 0.5 g of ammonium peroxydisulfate. The method was applied to det. total Cu and Fe contents and also labile Cu(II) and Fe(III) contents in several river surface H2O samples. (Hide)

A direct method for Si determination in milk samples by electrothermal atomic absorption spectrometry was developed. Pd was used as chem. modifier at a concentration of 610 mg L-1; with this modifier, Si was stable up to 1800° C. The precision and accuracy of the method were investigated. The detection limit was 16.2, 2.7 and 7.2 mg L-1 for cows' milk, human milk, and infant formula, resp. The method was applied to Si determination in 17 infant formula samples, 13 human milk samples and 12 cows' milk samples. (Hide)

Different sample pre-treatments for seafood products were compared for determination of trace elements (As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se and Zn) by flame atomic absorption spectrometry (FAAS) and electrothermal atomic absorption spectrometry (ETAAS). Classic pre-treatments such as microwave assisted-acid digestion and the slurry sampling technique were compared with new procedures such as microwave energy or ultrasound energy assisted-acid leaching process and enzymatic hydrolysis methodologies based on the use of pronase E. The methods were applied to DORM-1 and DOLT-1 ref. materials with certified contents for the studied elements. The Student-Newman-Keuls (SNK) method was used to compare element concentration means obtained with each sample pre-treatment and also the certified concentrations means in both reference materials. Multivariate techniques such as principal components analysis (PCA) were also applied for comparative purposes. (Hide)

A rapid and simple method for separation and determination of tributyltin (TBT) in mineral and tap H2O is described. The procedure is based on the selective retention of TBT by a chelating resin, Amberlite XAD-2 impregnated with tropolone. The addition of 0.8% H2SO4 to the H2O sample leads to the retention of TBT by the resin while monobutyltin (MBT), dibutyltin (DBT) and inorganic Sn remain in solution TBT is eluted with Me iso-Bu ketone (MIBK) obtaining a preconcentration factor of 80. Sn concentration is determined by ETAAS using Zr coated tubes. Multi-injection and hot injection techniques were used to enhance the sensitivity of the method. A detection limit of 14.4 ng L-1 is achieved with recoveries near to 100%. The procedure was successfully applied to TBT determination in various fresh H2O samples. (Hide)

Human scalp hair samples of drug-free subjects and drug abusers (heroin and cocaine-heroin abusers) were analyzed for trace metals by flame atomic absorption spectrometry (FAAS), flame atomic emission spectrometry (FAES) and electrothermal atomic absorption spectrometry (ETAAS). The classification of drug-free subjects and drug abuses groups with four multivariate methods using the metal contents in hair samples as discriminant variables has been discussed. Principal component anal. (PCA), cluster anal. (CA), linear discriminant anal. (LDA) and soft independent modeling of class analogy (SIMCA) allow distinguishing the two groups correctly. However, predictions by SIMCA are less satisfactory. Thirteen elements (Ag, Al, Ca, Cd, Cr, Cu, K, Mg, Mn, Na, Ni, Pb, and Zn) were determined by FAAS/FAES/ETAAS in 53 hair samples (16 samples of drug-free people and 37 samples of drug abusers). Human hair samples were prepd. as aq. slurries as sample pre-treatment and they were analyzed using the slurry sampling technique. The half-range central value transformation was novelty used as data pre-treatment to homogenize the data. Grouping in the samples (drug-free people and drug abusers) were obsd. by using PCA and CA (squared Euclidean distance between objects and Ward method as clustering procedure). The application of LDA gave a correct recognition assignation percentage of 91.7 and 100.0% for the drug-free people and drug abusers, resp., at a significance of 5%, while SIMCA offered recognition percentages of 83.3 and 91.3% for drug-free people and drug abusers, resp., also at 5%. Finally, some studies were developed to classify heroin abusers and polidrug abusers (cocaine-heroin abusers) by the cited multivariate statistical methods. Recognition percentages of 90.9 and 100.0% were reached for heroin abusers and polidrug abusers groups, resp., after LDA, while these percentages decreased to percentages lower than 90.0% when SIMCA was applied. (Hide)

The use of ammonium molybdate to minimize the phosphate interference when measuring selenium by electrothermal at. absorption spectrometry (ETAAS) with deuterium background correction was evaluated. Ammonium molybdate did not produce a selenium thermal stabilization; however, the presence of ammonium molybdate decreased the phosphate interference. The study was carried out with mussel acid digests and mussel slurries. Pd-Mg(NO3)2 was used as a chem. modifier at optimum concentrations of 300 and 250 mg l-1, resp., yielding optimum pyrolysis and atomization temps. of 1200 and 2100°, resp. A yellow solid (ammonium molybdophosphate) was obtained when adding ammonium molybdate to mussel acid digest solutions. This precipitate can be removed after centrifugation prior to ETAAS determination. Addnl., studies on the sampling of the solid ammonium molybdophosphate (AMP) together with the liq. phase, as a slurry, were also developed. The volatilization of the solid AMP was not reached at temperatures lower than 2500°. By this way, phosphate, as AMP, is not present in the vapour phase at the atomization temp. (2100°), yielding a reduction of the spectral interference by phosphate. The proposed method was validated analyzing three ref. materials of marine origin (DORM-1, DOLT-1 and TORT-1). Good agreement with the certified selenium contents was reached for all cases (Hide)

The development of an in vitro method to simulate new-born digestion and to study iron and zinc bioavailability from human milk and cow's milk based infant formulas was carried out. Enzyme treatment was conducted in two stages involving (1) pepsin at pH 5.0 followed by (2) pancreatin at neutral pH, where the incubation times were kept short to mimic the fast transit in the infant's gastrointestinal tract. Solubility of trace elements was used to express bioavailability, and so analytes were determined in the fractions obtained after centrifugation by flame atomic absorption spectrometry (FAAS) using a high performance nebulizer. The results were compared to those obtained by performing gastric digestion at pH 2.0 for an adult, using various incubators to treat the sample and centrifugation or ultracentrifugation to sep. sol. fractions. No differences in iron bioavailability from breast milk and infant formulas at different pHs could be detected due to the variability of the infant formulas analyzed. However, zinc bioavailability from breast milk samples was higher than those obtained from infant formulas at the new born gastric pH. (Hide)

The optimisation of a simple multielement extraction method employing an experimental design approach is described. The method uses centrifugation to pass one extractant solution at varying pH through a contaminated soil sample. The nature and concentration of the acid, rate of centrifugation and time, number of sequential leachates and the ratio of extractant volume : sample weight have been studied in order to obtain the optimum conditions for extraction. A fractional factorial experimental design was performed, and the results were used to identify significance which was then evaluated by carrying out a central composite experimental approach. Once optimum conditions had been obtained, sequential leaches were analysed by ICP-AES and chemometrics were employed to identify the composition of each component. Comparisons have been made with previous studies and tentative assignments, based on well defined separated fractions and percentage compositions for individual elements, used to identify the different physico-chemical components in the sample. (Hide)

The analysis of solvent residues trapped into crystals of illicit drugs provides useful evidence for monitoring current use trend in the chemical underground, and is also a suitable tool to achieve the complete chemical characterisation of street drugs for comparative examination of separate specimens. This paper describes a method developed in order to perform simultaneous qualitative and quantitative analysis of solvent residues in cocaine samples. The method is based on GC–MS analysis of solvents after their extraction/concentration from drug matrices accomplished by solid-phase microextraction (SPME) in static head space. The proposed method has been used to detect residues of solvents in 47 illicit street cocaine samples. Quantitative analyses were carried out only for the solvents identified at concentration values higher than 1 ppm. Statistical evaluation of our results allowed us to group the illicit samples into various classes according to different kinds of residual solvent, in connection with different clandestine manufacturing processes used to prepare illicit cocaine. (Hide)

A procedure for separation and preconcentration of trace amts. of copper(II), cadmium(II), and lead(II) in river water samples is proposed. The procedure is based on the adsorption of Cu2+, Cd2+, and Pb2+ ions on a column of Amberlite XAD-2 resin loaded with 1-(2-pyridylazo)-2-naphthol (PAN) reagent prior to their detn. by flame at. absorption spectrometry (FAAS). Sorption is quant. in the pH range of 6.0-8.5 for Cu, 7.5-8.5 for Cd and 8.0-11.0 for Pb; the optimum pH for simultaneous retention was 8.5. Quant. desorption for Cu2+ occurs in a 2-3 M HCl or 2-3 M HNO3 medium, for Cd2+ in a 2-4 M HCl or 0.5-3 M HNO3 medium, and only with 3 M HNO3 for Pb2+. The sorption capacity of the resin was 0.1081, 0.0228, and 0.0065 m-mole g-1 of the dry Amberlite-PAN for Cu2+, Cd2+ and Pb2+, resp. The simultaneous detn. of three cations is possible using 3 M HNO3 as an eluent. The limit of tolerance of some electrolytes were also studied. The highest preconcn. factor obtained was 50. The precision of the method, evaluated as the relative std. deviation obtained by analyzing a series of seven replicates, was below 5% for all three elements. The std. addn. technique was used, and anal. results achieved for Simulated Fresh Water IAEA W-4, a std. ref. material, were in good agreement with certified values. The proposed procedure was applied to the anal. of different river water samples using flame AAS. (Hide)

A new method was developed for the speciation of chromium by electrothermal at. absorption spectrometry. The 1,1,1-trifluoro-2,4-pentadione (TFA) reacts selectively with Cr(III) to form a volatile complex. Then, the Cr(III)-TFA complex is volatilized in the graphite furnace before atomization of Cr(VI). The conditions for the complex formation were studied using acetic acid/sodium acetate as the buffer soln. at pH 6 and TFA at a conc. of 4% (vol./vol.), with subsequent heating in a microwave oven for 2 min at 100 W. The optimum charring and atomization temps. for the Cr(VI) detn. were 1500 and 2200°, resp. The volatilization temp. of the Cr(III)-TFA complex was 140°, where Cr(III) was completely removed. The method described for the detn. of Cr(VI) is sensitive (with detection and quantification limits of 0.15 and 0.52 mg L-1, resp.), accurate, and precise. The Cr(III) concn. was established by calcg. the difference between total chromium and Cr(VI) concn. (Hide)

A new method for the direct detn. of Cr(VI) by electrothermal at. absorption spectrometry was developed. The formation of a volatile complex between Cr(III) and thenoyltrifluoroacetonate was used to sep. both species. The optimum conditions for complex formation were: pH range 5-6 (using HOAc/NaOAc as a buffer soln.), sonication time of 5 s at 40° with a reaction time of 3 h and 30 min before measurement. At temps. 700° the complex formed was completely volatilized, making Cr(VI) detn. possible, independent from Cr(III). The optimum temp. program for Cr(VI) detn. was 1600 and 2400 for pyrolysis and atomization, resp. Better sepn. of the species was obtained when 5 mg L-1 of Pd was added as a modifier. The developed method was precise (with relative std. deviation <10%), with a detection limit of 0.7 mg L-1 Cr. CRM 544 (lyophilized Cr) was used to demonstrate the accuracy of the method. (Hide)

A method for the determination of Se in human placenta slurries was developed using ETAAS with Zeeman-effect background correction. Particle size reduction was achieved by pulverizing the sample in a vibrating ball mill and diluting with ultrapure water to obtain an aqueous slurry. To achieve a particle diameter of 20µm, a grinding time of 20 minutes was sufficient. The use of two matrix modifiers, such as palladium and ammonium molybdate, was studied. A palladium concentration of 750 mg/L and ammonium molybdate concentration of 2000 mg/L was necessary to stabilize the selenium. The limit of detection was lower for the first modifier. Accuracy was studied by analysis of four reference materials with certified Se content. The method was applied to 21 samples of human placenta using the standard addition procedure, with levels between 0.58-0.90 µg/g (mean: 0.7± 0.10 µg/g). (Hide)

This article discuss, using sediment samples from the Ria of Ferrol, the need for a better understanding of the biogeochemical cycle of lead in the Galician rias which, until now, was based on differing methodologies mainly applied to the biota in only few areas of the most important rias from a socio-economic point of view. Thirty-five samples of superficial sediment were analysed for lead (IN THE 63 µm and total fractions) and opal percentage and organic carbon in the total. An analytical method is proposed employing ETAAS, whereby the sediment is introduced directly as a slurry together with the optimised amount of chemical modifiers. The accuracy of the method was checked by means of a certified reference material, obtaining a sensitivity of 2.72µ g¯¹ Pb with an RSD of 5.9%. Values of lead in the superficial sediment of the Ria of Ferrol ranged from 13.5 to 159.1 µg g ¯¹ for the fraction < 63 µm, and from 12.1 to 142.5 µg g¯¹ for the total fraction. The distribution does not follow a decreasing trend from the innermost part of the ria, as may have been expected, but rather maximum values were found in the vicinity of the harbour area in the middle ria, indicating that rias behave as a lead deposition barrier avoiding the export of the metal to the open sea. Lead dispersion is mainly controlled by the tidal currents, given its lowest concentrations in the zones of strongest current, and also by the plankton, following the relationship obtained [Pb]= 48 [opal] + 16. A baseline lead concentration of 18.2 µg g-¹ was obtained for the fraction <63 µm using core samples dated al 3745 ± 70 years before present. Applying this background values, the lead enrichment in the Ria of Ferrol is classified from moderate to considerable. (Hide)

Trace metals in tea originating from various Asian and African countries were determined by using inductively coupled plasma-atomic emission spectrometry and inductively coupled plasma-mass spectrometry. Pattern recognition techniques were then used to classify the tea according to its geographical origin. Principal component analysis (PCA) and cluster analysis (CA), as exploratory techniques, and linear discriminant analysis (LDA) and soft independent modelling of class analogy (SIMCA), were used as classification procedures. In total, 17 elements (Al, Ba, Ca, Cd, Co, Cr, Cu, Cs, Mg, Mn, Ni, Pb, Rb, Sr, Ti, V, Zn) were determined in a range of 85 tea samples (36 samples from Asian countries, 18 samples from African countries, 24 commercial blends and seven samples of unknown origin). Natural groupings of the samples (Asian and African teas) were observed using PCA and CA (squared Euclidean distance between objects and Ward's method as clustering procedure). The application of LDA gave correct assignation percentages of 100.0% and 94.4% for the African and Asian teas, respectively, at a significance level of 5%. SIMCA offered percentages of 100.0% and 91.7% for African and Asian groups, respectively, at the same significance level. LDA, also at a significance level of 5%, allowed a 100% of correct case identification for the three classes China, India and Sri Lanka. However, a satisfactory classification using SIMCA was only obtained for the Chinese teas (100% of cases correctly classified), while teas from India and Sri Lanka appear to form the same class. (Hide)

A method for the determination of nickel and cobalt in slurries of marine sediment samples by Electrothermal Atomic Absorption Spectrometry (ETAAS) with Zeeman background correction, using palladium as chemical modifier has been developed. With this modifier is possible to determine both elements simultaneously using 1200 ºC and 2500 ºC as ashing and atomisation temperatures respectively as compromise conditions. The accuracy of the method was studied using a marine sediment Certified Reference Material (PACS-2 from the NRCC) and the detection limits were 0.28 and 0.43 µg g-1 for Ni and Co respectively. This method has been applied to the nickel and cobalt determination in marine sediment samples from the Ria Ferrol (Galicia, NW Spain). The concentrations obtained were between 11.3 and 67.2 µg g-1 and 5.0 and 21.0 µg g-1 for Co, with an average ria concentration of 32 µg g-1 for Ni and 10 µg g-1 for Co. The background levels of 11.6 and 4.6 µg g-1 were obtained for Ni and Co respectively, thus the sediment contamination factor is calculated indicating moderate contamination of both heavy metals in general, with severe contamination in the innermost part of the ria. (Hide)

En este trabajo se realiza un estudio acerca de la especiación de selenio en leche, para ello se separan la grasa, suero y caseinas por ultacentrifugacion. Se preconcentra el suero por ultrafiltración y se realiza la separación de las proteinas del suero por Cromatografía de Exclusión y la determinación de selenio se realiza por Generación de hidruros - Espectroscopía de Absorción Atomica con Atomización Electrotérmica. El selenio se encontro básicamente en tres fracciones, la de 40KDa, en la de 160 KDa y principalmente en la de 10 kDa.(Hide)

The physico-chemistry forms in which the heavy metals occur in the environment, particularly in biol. samples, may strongly condition their bioavailability and toxicity. Hence, the distinction between different fractions of the total metal is of interest. Today, the challenge facing the scientific community and regulatory agencies is to assess health risks and/or benefits of low-level exposure to metals and metalloids in the environment, esp. in foods. Accordingly, new anal. procedures to enable detn. of trace and ultratrace levels of metals/metalloids and their species are needed so that the steps of extn. and sepn. must be mild enough to liberate the species from the matrix while maintaining their chem. integrity. The combination of enzymic digestions plus ultrasonication, by either bath or probe, has recently emerged as a promising methodol. for metal/metalloid speciation with environmentally acceptable performance. We critically review the state-of-the art of enzymic digestion in sample treatment for total metal detn. and speciation by at. spectrometry. In addn., we comment on new trends based on the capability of novel sample treatments using enzymes and ultrasonication. We also provide guidelines to implement this analytical methodology in the laboratory. (Hide)

The study attempts to measure the total Cr content in sediments of all the Ria de Arousa (Galicia, NW Spain). The method was developed by analyzing slurries by electrothermal atomic absorption spectrometry. The metal determination was carried out optimizing the electrothermal program and the concentration of Mg nitrate as a chem. modifier. What was aimed to be achieved is a general explanation of the Cr content along the estuary because there could be a Cr sink in this marine environment. Results obtained were between 43.4 ± 1.7 mg g-1 and 184.6 ± 26.9 mg g-1 from the end of the Ulla river to the Atlantic Ocean, most of them higher than the background ref. levels. (Hide)

A study of the Cd, Pb and Sn content in marine surface sediment from the Ria de Arousa was realized. For this, 21 sediment samples were taken in triplicate, lyophilized and sieved, and the fraction 63 mm was taken for anal. The samples were prepared in a form of slurries and analyzed by electrothermal atomic absorption spectrometry. The concentration ranges obtained were 90-990 mg kg-1 Cd, 26.5-91.3 mg g-1 Pb and 5.0-20.8 mg g-1 Sn. The highest concentrations of these metals are in the inner part of the Ria, near to the port and urban nucleus such as Vilagarcia or Rianxo, and decrease toward the mouth of the Ria. (Hide)

A fast ultrasound energy and moderate temperature method was developed to extract humic substances from marine sediment. The extractive process was optimized using a Plackett-Burman design as a multi-variate optimization approach. Temp. and the no. of repeated extns. were the most significant variables (P = 95%) affecting extn. of fulvic and humic acids from marine sediment. These 2 variables had optimum values of 65º and 3 repeated extns. The combination of ultrasound energy and moderate temperature was also studied to optimize an acid treatment prior NaOH extraction. Results from the Plackett-Burman design showed all factors, except ultrasound power for humic acids extn. and temp. and no. of repeated acid treatments for fulvic acids extn., were statistically significant (P = 95%). Thus, some factors were optimized using a central composite design. Optimized acid treatment consisted in 1 sonication step at room temp. at 17 kHz ultrasound power with 10 mL of 6.0 M HCl for 15 min. This method was precise (relative std. deviations were 8.7% for HA and 11.4% for FA, for 11 detns.) and results were comparable (in terms of humic and fulvic acid concns. and in terms of elemental [C, H, N] composition) to those obtained after applying methods based on mech. stirring. The method was used with marine sediment from the Ria de Arousa Estuary, Spain. (Hide)

A systematic evaluation of different variables affecting the enzymatic hydrolysis of mussel soft tissue by five enzymes, three proteases (pepsin, pancreatin and trypsin), lipase and amylase, has been carried out for the detn. of trace elements (As, Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) by inductively coupled plasma-at. emission spectrometry (ICP-AES). Enzymatic hydrolysis methods offers advantages such as a less species alteration, safer lab. conditions and a less contaminant wastes. The enzymatic hydrolysis was performed in an incubation camera Boxcult with orbital and horizontal shaker. Variables affecting the enzymatic hydrolysis process were simultaneously studied by applying a Plackett-Burman design (PBD). For a confidence interval of 95%, the significant factors for all enzymes and for most of the elements were the pH, the incubation temp. and the ionic strength. These significant factors were optimized later by using a central composite design (CCD), which gave optimum conditions at pH of 1, incubation temp. of 37º and ionic strength fixed by sodium chloride at 0.2 M when using pepsin. For pancreatin, trypsin, lipase and amylase there were found two different optimum condition sets. The first one involves the use of a 0.5 M phosphate buffer (ionic strength), at a pH of 6 and at an incubation temp. of 37º, which allows the quant. extn. of Al, Cr, Mn, Pb and Zn. The second conditions set employees a 0.1 M phosphate buffer (ionic strength), a pH of 9 and an incubation temp. at 37º, and it results adequate to ext. As, Cd, Cu, Fe and Ni. Anal. performances, repeatability of the over-all procedure and accuracy, by analyzing DORM-1, DORM-2 and TORT-1 certified ref. materials, were finally assessed for each enzyme. Good agreement with certified values has been assessed for most of the elements (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) when using trypsin, pepsin and/or pancreatin, except for Cd and Pb in DORM-1 and DORM-2 because of the certified contents in such certified reference materials are lower than the limit of detection (0.10 and 0.16 mg g-1 for Cd and Pb, resp., for the use of trypsin). (Hide)

The purpose of the present paper is to develop an easy and quick in vitro method to compare copper availability from breast milk and infant formulas. This study focuses on the differences caused by the use of pH 2.0 (adult gastric pH) or pH 5.0 (newborn gastric pH) in the first stage of the enzymolysis. pH affects Cu soly., a possible estimator of the availability. Selection of a digestor, times of enzymolysis, centrifugation parameters, and Cu determination by ETAAS were discussed as well. Percentage of Cu soly. was larger from breast milk (gastric pH 2.0, 65.3±14.0 vs 40.0±13.9%; gastric pH 5.0, 61.2±16.5 vs 26.6±10.3%), but the sol. content was larger from infant formulas for both pHs (gastric pH 2.0, 245.3±82.1 vs 113.0±103.4 ng mL-1; gastric pH 2.0, 169.3±76.9 vs 75.3±21.9 vs ng mL-1). (Hide)

Ultrasound energy has been applied to speed up enzymatic hydrolysis processes of mussel tissue in order to determine trace and ultratrace elements (As, Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn). The element releases, by action of three proteases (pepsin, pancreatin, trypsin), lipase, and a-amylase, have been evaluated by inductively coupled plasma at. emission spectrometry. Different variables such as pH, sonication temp., ionic strength, hydrolysis time, ultrasound frequency, extg. vol., and enzyme mass were simultaneously studied by applying an exptl. design approach (Plackett-Burman design and central composite design). Results showed that the hydrolysis time was statistically nonsignificant (confidence interval of 95%) for most of the elements and enzymes, meaning that the hydrolysis procedure can be finished within a 30-60-min range. These hydrolysis times are far shorter than those obtained when using thermostatic cameras, between 12 and 24 h. Statistically significant factors were the ultrasound frequency (the highest metals releasing at high-ultrasound frequency), pH, sonication temp., and ionic strength. All metals can be extd. using the same operating conditions (pH of 1.0 and sodium chloride at 1.0% for pepsin; pH of 7.5, temp. at 37º, and 0.4 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for amylase; pH of 8.0 and 0.5 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for pancreatin; pH of 5.0 and 0.5 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for lipase; pH of 8.0 and 0.2 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for trypsin). Anal. performances, such as limits of detection and quantification, repeatability of the overall procedure, and accuracy, by analyzing DORM-1, DORM-2, and TORT-1 certified ref. materials, were finally assessed for each enzyme. (Hide)

A multivariate optimization of a MeOH extn. of total As species from marine seaweed was performed using ultrasound energy to speed up the anal. process. Variables such as MeOH concn., ultrasound power, sonication time, water bath temp., and the no. of repeated extns. were studied. As the screening method, a Plackett-Burman 26 ´ 3/32 design for six variables was applied to establish the variables that significantly affect the extn. process. After statistical evaluation (confidence level of 95.0%), the MeOH concn., no. of repeated extns., and water bath temp. are significant factors and were optimized using a central composite design. Electrothermal at. absorption spectrometry (ETAAS) was used to det. total As, while total inorg. As was assessed by hydride generation at. absorption spectrometry (HG-AAS). Pyrolysis and atomization temps. of 250 and 2100º, resp., are optimum to perform the total As detn. by ETAAS. HCl and Na borohydride concns. of 0.2% (m/v) and 3.0M, resp., and a cell temp. of 900º were used to det. total inorg. As by HG-AAS. The methods were validated by analyzing two certified ref. materials, P-ACHK and IAEA-140 /TM. (Hide)

Simple methods for the detn. Of Cd, Cr, Cu, Pb, and Zn fractions bound to low mol. wt. compds. (presumably metallothionein-like proteins) in mussels (Mytilus edulis) have been developed. The methods involve the novel application of using a blending (Stomacher) rather than a cutting mixer device to perform the homogenization between the fresh mussel tissue and the extractant soln. [10 mM TRIS-HCl buffer at pH 7.4 with 5 mM 2-mercaptoethanol (2-MCE), 0.01 mM phenylmethylsulfonyl fluoride (PMSF), and 25 mM sodium chloride]. Optimum conditions for the cytosolic prepn. (after an exptl. design approach) were a ratio of sample wt.: extg. vol. of 0.2 g/mL and a blending time of 5 min. The Cu and Zn concns. bound to low mol. wt. compds. (LMW proteins) were measured by flame at. absorption spectrometry using a high performance nebulizer, while Cd, Cr, and Pb levels in the cytosolic solns. were assessed by electrothermal at. absorption spectrometry. A microwave-assisted acid digestion procedure was also applied to det. the total metal concn. The limits of detection (LOD) for Cd, Cr, and Pb were 0.7, 3.0, and 6.6 ng g-1, resp., and for Cu and Zn they were 0.05 and 0.01 mg g-1, resp. The methods were applied to 16 mussel samples from the Ria de Arousa estuary. (Hide)

Five different iron salts—sulphate, lactate, diphosphate, encapsulated sulphate, and EDTA-Fe(III)—were used to fortify an infant formula to study possible differences in iron bioavailability. The effect of iron fortification at two levels (0.5 mg Fe 100 kcal−1 and 1.5 mg Fe 100 kcal−1) on the bioavailability of other important trace elements such as copper and zinc were also evaluated. An in vitro method based on element dialysability (i.e., the fraction available by absorption) to simulate newborn digestion was applied to study iron, copper and zinc bioavailability. Enzyme treatment was carried out in two stages involving pepsin at pH 5.0 followed by pancreatin at pH 7.0. The incubation times were short to mimic the transit of meal in an infant's gastrointestinal tract. Iron, copper and zinc were determined using inductively coupled plasma atomic emission spectrometry using an axially configured device. The percentages of Fe, Cu and Zn dialysable at both iron fortification levels are discussed. From these results, EDTA-Fe (III) appears to be the most adequate salt for iron fortification of infant formulas. (Hide)

In a research of chromium availability, the three-stage sequential extraction procedure, proposed by European Community Bureau of Reference (BCR), has been applied for the metal fractionation in marine sediment samples. The procedure has been modified, evaluating the effect of microwave energy to perform the sequential method. Results achieved a substantial reduction in time in comparison to the traditional shaking technique. The time of the first and the second extractions were reduced to 30 s in both steps using microwave heating and working at 66 W of power. To the third extraction, higher power was necessary so it was chosen to work at 198 W. In the last step investigated, time was reduced to 1 min, being a great improvement respect to the conventional BCR sequential extraction protocol. Chromium determinations in these extracts were carried out by Electrothermal Atomic Absorption Spectrometry (ETAAS). The developed method was applied for chromium determination in marine sediment samples from Ria de Arousa (Galicia, NW of Spain). The values obtained by our laboratory ranged from 0.10 to 1.02 µg g-1 for soluble and reducible fractions, and from 5.5 to 60.0 µg g-1 for the oxidisable fraction. The higher concentrations obtained were the chromium associated with the organic fraction of the marine sediments. (Hide)

An ETAAS method was developed for the detn. Of Sb in seawater using ammonium nitrate as the matrix modifier plus Zeeman-effect background correction. The concn. selected for the modifier was 35.2 mg/mL, and the temp. program selected for the graphite furnace for a spiked sample was 1200º and 1900º for mineralization and atomization, resp. The use of the std. addns. method was mandatory due to the matrix effects obsd. The LOD and LOQ achieved were 2.7 and 9.0 mg/L, resp.; 9.6 pg was the mean characteristic mass obtained within the linear range of concns. (0-20 mg/L Sb). The method was applied to spiked coastal seawater samples from the Mediterranean Sea. (Hide)

A sensitive method was developed for the detn. of V in seawater by ETAAS using hot injection and preconcn. in the graphite tube. Five portions of seawater samples were injected into a heated graphite tube using a drying and charring step between each injection. The influence of ammonium nitrate as the chem. modifier was studied. The charring temps. were 1700º in the presence and absence of this modifier. The precision and accuracy of the method were also studied. The detection limit was 0.8 mg L-1. The proposed method was applied to the detn. of V in seawater samples; the detection levels found were between 1.5-4.2 mg L-1. (Hide)

Six different designs of silica-slotted tube atom traps (STATs), which are positioned on a conventional burner head from a flame at. absorption spectrometer, were used and compared in terms of sensitivity in the detn. of cadmium in mussel samples. Different parameters affecting the design of STATs, such as the length of the tube, the outer and inner diams., the length of the base and exit slots, the angle between the base and exit slots, and the use of exit holes instead exit slots, were evaluated. The STATs showing low outer and inner diams. and a disposition of 120º between the base and exit slots have led to a sensitivity enhancement of around 3.9-fold. Matrix effect was minimized with all proposed STATs and cadmium detn. by STAT-FAAS can be carried out with aq. calibrations. Finally, good repeatability and accuracy, assessed after analyzing DOLT-3, TORT-1, and GBW 08571 certified ref. materials, were achieved for all STATs. (Hide)

The level of As and Sb was detd. in sea-water by axial ICP-OES with continuous hydride generation after performing pre-redn. with thiourea and carrying out a pre-concn. by co-pptn. with La in a PTFE knotted reactor (KR). Optimization of the whole system was performed using exptl. design and with online pre-concn. and ultimate hydride generation. Using a pre-concn. time of two minutes and consuming 16 mL of sample, the LOD and LOQ were 0.17 and 0.56 mg L-1, resp., for As, and 0.27 and 0.88 mg L-1 for Sb. Pre-concn. was carried out off-line in the KR to decrease the LOD and LOQ to 0.031 and 0.10 mg L-1 (As 188.979 nm) and 0.043 and 0.15 mg L-1 (Sb 217.582 nm) (sample vol. 83 mL). The method was precise, with RSDs (n = 11) of 5.7% for As and 9.4% for Sb. The method was accurate, with a recovery of 108.5% for As and 106.0% for Sb. Also, values of 3.0 ± 0.5 mg As L-1 and 14.7 ± 1.5 mg Sb L-1 were obtained for a ref. material with certified content of 2.7 ± 1.0 mg As L-1 and 13.7 ± 8.5 mg Sb L-1. The method can be applied to element detn. in unpolluted sea-water samples. (Hide)

The effect of 2 sources of Se, selenized yeast (Se-Y) and sodium selenite, added to total mixed rations (TMR) fed to cows on Se milk content and distribution in milk components was studied on 3 farms for 6 wk. The maximal increase in milk Se was attained with Se-Y supplemented at 0.3 mg/g. The effect was immediate, with an increase of 9 mg/L being obsd. after only 5 days, and remained steady until the last sample at day 40 of Se supplementation. Se distribution in milk components was const., 53.6, 42.6, and 9.3% in whey, casein, and fat, resp., and was unaffected by the form of supplementation. The effect of the level of Se-Y supplementation on milk Se was studied on 2 farms. Increasing dietary Se-Y from 0 to 0.5 mg/g elevated milk Se content from 20 to 39 mg/L. Se-enriched cow's milk at different levels can be produced by varying dietary Se supplementation in the form of selenized yeast. (Hide)

Fe, Cu and Zn detn. By AAS was performed in 35 infant formula samples from different manufacturers. The trace element content was studied in whole, fat and whey milk, and different chemometric tools have been used in order to observe differences or correlations between infant formulas fortified with inorg. salts (iron, copper and zinc sulfates) or with org. and inorg. salts (iron and copper gluconates, or zinc and iron lactates and zinc oxides). Principal-components anal. (PCA) achieved a redn. from 9 variables to 3 (accounting for 80.8% of the total variability), and some differences between infant formula from the 2 groups were obsd. Cluster anal. gave similar results as PCA. Linear discriminant anal. (LDA) allowed the classification of infant formulas in two categories or classes: the 1st class formed by samples fortified with inorg. salts (category A) and the 2nd one by samples fortified with org. and inorg. salts (category B). The percentages of samples correctly classified were 96.1 and 100.0 for the categories A and B, resp. After the application of the soft independent modeling of class analogy (SIMCA) approach, percentages of cases correctly assigned of 87.5 and 12.5 were achieved for the categories A and B, resp. However, it must be said that the application of SIMCA led to bad results because of the small no. of sample used, mainly in category B. (Hide)

A novel accelerated enzymatic hydrolysis by mean of ultrasonication has been developed and applied as sample pre-treatment for edible seaweed in order to det. total levels of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Three enzymes, a-amylase, pepsin and trypsin, have been evaluated and the released metals from seaweed have been measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). Variables such as pH, sonication temp., ultrasound frequency, ionic strength, hydrolysis time, extg. vol. and enzyme mass were simultaneously studied by a Plackett-Burman design (PBD). Results have showed that there had not been any significant variable (confidence interval of 95%) affecting the conventional or the ultrasound-assisted enzymatic hydrolysis processes. This fact is attributed to the high salt content in seaweed, which generates a soln. with a high ionic strength. The ultrasound-assisted enzymic hydrolysis can be completed in 30 min when using an ultrasound frequency at 35 kHz. Quant. recoveries were only reached when using pepsin, while recoveries close to 80% were obtained for the use of a-amylase and trypsin. The methods were validated by analyzing IAEA-140/TM, Fucus - Sea Plant Homogenate - and NIES-09, Sargasso, certified ref. materials. (Hide)

A flow injection online sorption preconcn. system using a polytetrafluoroethylene (PTFE) knotted reactor was coupled with electrothermal at. absorption spectrometry (ETAAS) to det. selectively As(iii) in sea-water samples. Sepn. of As inorg. species was achieved by the online formation of As(iii)-pyrrolidine dithiocarbamate (PDC) complex in an acid medium, its sorption onto the inner walls of the knotted reactor (KR) and elution with 40 mL of EtOH. An enhancement factor (EF) of 44 was obtained compared with the slope of the linear portion of the calibration curve before and after preconcn. The detection limit (3 s) was 0.008 mg L-1 As(III). The precision (relative std. deviation n = 11) was 4.5% at 0.1 mg L-1 As(III). The accuracy was demonstrated by total As detn. in certified ref. material, NASS-4, after pre-redn. of As(v) with L-cysteine 0.25% (m/v). (Hide)

Microwave energy has been novelty applied to speed up a tetramethylammonium hydroxide (TMAH) alkaline digestion of seaweed samples and to assist distn. of iodine from seaweed alk. digests. Iodide in the alk. digests from seaweed and distd. iodine, reduced back to iodine in a hydroxylamine hydrochloride soln., was detd. by a catalytic spectrophotometric method based on the catalytic effect of iodide on the oxidn. of As(III) by Ce(IV) in H2SO4/HCl medium (Sandell-Kolthoff reaction). The detn. of iodide was directly performed in the alk. digests, while total iodine was assessed by analyzing the hydroxylamine hydrochloride soln. after the distn. process. Microwave-assisted alk. digestion was performed using 7.5 mL of TMAH and irradiating samples at 670 W for two 5.5 min steps. Microwave-assisted distn. was carried out using 4.0 mL of the alk. digest and 3 mL of a 2.2 M hydrochloric acid and 0.05% (m/v) sodium nitrite soln., with a microwave power at 670 W for two 90 s steps. The distillate (iodine vapor) was bubbled in 10 mL of a 500 mg/mL hydroxylamine hydrochloride soln. (accepting soln.). The linear calibration ranges were 0.30-20.0 and 0.40-20.0 mg/L for iodide detn. and total iodine detn., resp. The limit of detection was 9.2 mg/g for iodide and 28.5 mg/g for total iodine. Repeatability of the overall procedures, expressed as R.S.D. for 11 detns., was 2.6% for 196.3 mg/g of iodide measured after microwave-assisted alk. digestion, and 5.8% for 954.3 mg/g of total iodine by microwave-assisted alk. digestion followed by microwave-assisted distn. Finally, accuracy of the methods was assessed by analyzing the NIST-09 (Sargasso) certified ref. material and the methods were applied to the detn. of iodide and total iodine in different Atlantic edible seaweed samples with satisfactory results. (Hide)

A new method using diluted reagents (nitric and hydrochloric acids and oxygen peroxide) and ultrasound energy to assist metals acid leaching with from edible seaweed was optimized. The method uses a 1st sonication at high temp. with hydrochloric acid as a previous stage to an ultrasound-assisted acid leaching with 7 mL of an acid soln. contg. nitric acid, hydrochloric acid and hydrogen peroxide at 3.7, 3.0 and 3.0 M, resp. Optimum conditions for the 1st sonication step were ultrasound energy at 17 kHz, sonication temp. at 65 ºC, an acid vol. of 2 mL, an hydrochloric acid concn. of 6.0 M and a sonication time of 10 min. It has been found that the 1st sonication stage at high temp. with hydrochloric acid is necessary to obtain quant. recoveries for As, Ba, Fe and V. O. Otherwise quant. recoveries were reached for the other elements investigated (Ca, K, Na, Mg, Cd, Cr, Cu, Mn, Ni, Pb and Zn). The repeatability of the ultrasound-assisted acid leaching method was around 10% for all elements. Adequate limit of detection and limit of quantification were reached by using inductively coupled plasma-optical emission spectrometry (ICP-OES) for measurements. The method resulted accurate after analyzing several seaweed certified ref. materials (IAEA-140/TM, NIES-03 and NIES-09). The method was finally applied to the multi-element detn. in edible seaweed samples. (Hide)

An ultrasound-assisted solvent extn. Procedure has been optimized to speed up total polycyclic arom. hydrocarbons (T-PAHs) extn. from mussel soft tissue. The T-PAHs releases have been evaluated by spectrofluorimetry (excitation and fluorescence emission wavelengths of 300 and 382 nm, resp., and using chrysene as calibrant). Variables such as sonication time, ultrasound frequency, n-hexane vol., dichloromethane vol., no. of repeated extns. with n-hexane and no. of repeated extn. with dichloromethane were simultaneously studied by applying a Plackett-Burman design (PBD) approach. Results showed that ultrasound frequency and n-hexane and dichloromethane vols. were statistically significant variables (confidence interval of 95%). These last two variables were finally optimized by using central composite designs (CCD), yielding optimum n-hexane and dichloromethane vols. of 2.5 and 6.5 mL, resp. The lowest T-PAHs releasing at high ultrasound frequency (35 kHz) led to choice the lowest ultrasound frequency (17 kHz) to perform the extn. Variables such as sonication time and no. of repeated extn. with n-hexane or dichloromethane were statistically non-significant and they were fixed at 10 min and the extn. with n-hexane and dichloromethane were performed once. The limit of detection was 0.021 mg g-1 (referred to dried mass), the repeatability of the overall method was 4.7% (n = 9) and the anal. recoveries were between 98 and 105%. The proposed method was finally applied to 16 mussel samples (Mytilus galloprovincialis) from Ria de Arousa estuary (Galicia, northwest Spain). (Hide)

A sample pretreatment method based on an ultrasound-assisted acid leaching process with dild. reagents (nitric and hydrochloric acids and hydrogen peroxide) has been developed to det. major (Ca, K, Na, and Mg) and trace (Cu, Fe, Mn, and Zn) elements in edible seaweeds. Optimization has been carried out using a Plackett-Burman design (PBD) as the screening method to select the most significant factors affecting the ultrasound-assisted acid leaching procedure. The results showed that the water bath temp., ultrasound frequency, nitric acid concn., sonication time, and extg. vol. are the most statistically significant variables (P = 95%). These significant factors were optimized by a central composite design (CCD), and the optimum compromise conditions were as follows: extn. vol. 7 mL, nitric acid concn. 3.7 M, sonication time 35 min, ultrasound frequency 17 kHz, and waterbath temp. 65ºC. The repeatability of the ultrasound-assisted acid leaching method was lower than 5% for the elements. The method was found to be accurate after analyzing different certified ref. materials (IAEA-140/TM, NIES-CRM-03 NIES-CRM-09, and BCR-61). Finally, the method was applied to different edible Atlantic seaweeds. (Hide)

Possibilities of the use of com. C18 cartridges to sep. and preconc. trace elements from seawater were evaluated. Trace elements (Al, Cd, Cu, Fe, Mn, Ni, Pb, Sn, V and Zn) were previously complexed with 8-hydroxyquinoline, 8-HQ (5 ´10-4 M as final concn.) at alk. pH (8.0 ± 0.1) and then they were eluted with 2.5 mL of 2.0M HNO3. Metals eluted from cartridges were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). Variables affecting the metal-8-HQ complexation such as pH and 8-HQ concn., and affecting the metal-8-HQ complexes solid phase adsorption and elution (load and elution flow rates and concn. and vol. of eluting soln.) were studied to find compromise operating conditions for the simultaneous metals complexation, adsorption and elution. After studies of contamination of com. C18 cartridges for trace metals, high reagent blanks were reached for Ti so that they are useless for the detn. of this element. Com. C18 cartridges can be used at least seven times without loss of adsorption properties. Working with a seawater sample vol. of 100 mL and using an optimum HNO3 vol. of 2.5 mL for elution, a preconcn. factor of 40 was achieved, factor high enough to det. trace elements in unpolluted surface seawater samples by ICP-OES. Anal. performances, such as limits of detection and quantification, repeatability of the overall procedure and accuracy, by analyzing saline (CASS-3 and SLEW-3) and nonsaline (TM-24) certified ref. materials, were finally assessed. (Hide)

The sampling procedure currently applied in a feedstuff factory for incoming raw materials was compared with another sampling method (designed by the authors). The commodities considered were maize, soya and barley, and the sampling protocols were evaluated on the basis of the results obtained when samples taken by both methods were analyzed for moisture and sp. gr. The differences obsd. in the results obtained from samples collected by both sampling procedures were not statistically significant (two-sided t-test, a=0.05) and hence the validity of the current method was confirmed. However, the results showed that the raw materials become stratified during travel from origin to factory, and this must be taken into account. To improve the current sampling protocol, the points where samples have to be taken must be specified. (Hide)

A procedure was developed for detg. the Se in cow's milk using hydride generation-at. absorption spectrometry (HG-AAS) following microwave-assisted acid digestion. The Se distributions in milk whey, fat and micellar casein phases were studied after sepg. the different phases by ultracentrifugation and detg. the Se in all of them. The detection limits obtained by HG-AAS for the whole milk, milk whey and micellar casein were 0.074, 0.065 and 0.075 mg l-1, resp. The accuracy for the whole milk was checked by using a Certified Ref. Material CRM 8435 whole milk powder from NIST, and the anal. recoveries for the milk whey and casein micelles were 100.9 and 96.9%, resp. A mass balance study of the detn. of Se in the different milk phases was carried out, obtaining values of 95.5-100.8%. The total content of Se was detd. in 37 milk samples from 15 different manufacturers, 19 whole milk samples and 18 skimmed milk samples. The Se levels found were within the 8.5-21 mg l-1 range. The Se distributions in the different milk phases were studied in 14 whole milk samples, and the highest Se levels were found in milk whey (47.2-73.6%), while the lowest level was found for the fat phase (4.8-16.2%). A strong correlation was found between the Se levels in whole milk and the Se levels in the milk components. (Hide)

In a research of chromium availability, the three-stage sequential extn. procedure, proposed by European Community Bureau of Ref. (BCR), has been applied for the metal fractionation in marine sediment samples. The procedure has been modified, evaluating the effect of microwave energy to perform the sequential method. Results achieved a substantial redn. in time in comparison to the traditional shaking technique. The time of the first and the second extns. were reduced to 30 s in both steps using microwave heating and working at 66 W of power. To the third extn., higher power was necessary so it was chosen to work at 198 W. In the last step investigated, time was reduced to 1 min, being a great improvement respect to the conventional BCR sequential extn. protocol. Chromium detns. in these exts. were carried out by Electrothermal At. Absorption Spectrometry (ETAAS). The developed method was applied for chromium detn. in marine sediment samples from Ria de Arousa (Galicia, NW of Spain). The values obtained by our lab. ranged from 0.10 to 1.02 mg g-1 for sol. and reducible fractions, and from 5.5 to 60.0 mg g-1 for the oxidizable fraction. The higher concns. obtained were the chromium assocd. with the org. fraction of the marine sediments. (Hide)

A study on selenium levels has been carried out in human placenta, maternal and umbilical cord blood, hair and nails of a group of 50 mothers and in the hair of the newborns. The determinations were perfomed by electrothermal atomic absorption spectrometry. The selenium concentration obtained for each sample type was as follows: For the human placenta the values obtained were between 0.56 and 1.06 μg/g (mean±standard deviation: 0.81±0.02 μg/g). The levels for the umbilical cord blood were 51.1–104.2 μg/l (76.3±6.5 μg/l). For the maternal blood the values measured were between 57.3 and 117.9 μg/l (90.0±15.2 μg/l), and for hair and nails were 0.22–1.5 μg/g (0.60±0.37 μg/g) and 0.46–1.57 μg/g (0.90±0.27 μg/g), respectively. For the hair of the newborns the values obtained were between 0.40 and 2.53 μg/g (1.04±0.48 μg/g). The effect of different variables as age, habitat, nutritional index or gestation age of the mothers on the selenium concentration in the samples was studied. The influence of the habitat is significant with a confidence level of 95% for the selenium concentration in maternal blood and umbilical cord blood samples. The influence of the mothers’ age is significant with a confidence level of 95% for the selenium concentration in the umbilical cord blood samples. For the placenta samples, the effect of the nutritional index is significant with a confidence level of 95%. There is a positive correlation between samples of umbilical cord blood and the newborns’ hair, between placenta and umbilical cord, and between cord blood and maternal blood. (Hide)

Methods were developed for indium (In) determination in complex ores by electrothermal atomization atomic absorption spectrometry using matrix modification after its separation with Amberlite XAD-2 coated with 1-(2-pyridylazo)-2-naphthol (PAN). Palladium–magnesium, nickel, and zinc nitrates were used as matrix modifiers and were compared in terms of maximum pyrolysis temperature, sensitivity and background signal. They have enhanced the absorption signals for indium, respectively eliminating the matrix interferences. The standard additions method was applied. The relative standard deviations for six replicate determinations were in the range 0.3–4.0% for indium in different ores samples for indium concentrations 7.6–209 μg g−1. The recommended method was applied to the indium determination in real samples. The data obtained by this method were in good agreement with those obtained by ICP-AES. (Hide)

Rapid leaching procedures by Pressurized Liquid Extraction (PLE) were developed for As, Cd, Cr, Ni and Pb leaching from environmental matrixes (marine sediment and soil samples). The Pressurized Liq. Extn. is completed after 16 min. The released elements by HOAc Pressurized Liq. Extn. were evaluated by inductively coupled plasma-optical emission spectrometry. The optimum multi-element leaching conditions when using 5.0 mL stainless steel extn. cells, were: HOAc concn. 8.0M, extn. temp. 100º, pressure 1500 psi, static time 5 min, flush solvent 60%, two extn. steps and 0.50 g of diatomaceous earth as dispersing agent (diatomaceous earth mass/sample mass ratio of 2). High HOAc concns. and high extn. temps. increase the metal leaching efficiency. Limits of detection (between 0.12 and 0.5 mg g-1) and repeatability of the over-all procedure (around 6.0%) were assessed. Finally, accuracy was studied by analyzing PACS-2 (marine sediment), GBW-07409 (soil), IRANT-12-1-07 (cambisol soil) and IRANT-12-1-08 (luvisol soil) certified ref. materials (CRMs). These certified ref. materials offer certified concns. ranges between 2.9 and 26.2 mg g-1 for As, from 0.068 to 2.85 mg g- 1 for Cd, between 26.4 and 90.7 mg g-1 for Cr, from 9.3 to 40.0 mg g-1 for Ni and between 16.3 and 183.0 mg g-1 for Pb. Recoveries after anal. were 95.7-105.1% for As, 96.2% for Cd, 95.2 and 100.6% for Cr, 95.7 and 103% for Ni and 94.2 and 105.5% for Pb. (Hide)

Many of the most recent developments in analytical and environmental chemistry involve metal speciation studies. For chromium it is possible to distinguish between the toxic hexavalent species and the non-toxic trivalent species. The purpose was to develop a method for the quantification of Cr using an online system for the sepn. and preconcn. of both species. The research builds on previous publications using an alumina column and eluent solns. of ammonia for Cr(VI) and nitric acid for Cr(III). However, this approach facilitates either the detn. of Cr(VI) or Cr(III), but not both from the same sample injection. Using stds. contg. both Cr(III) and Cr(VI) in Na2CO3 /NaOH media at pH 7.5±0.5, both species are retained on the column simultaneously, and are then eluted selectively and sequentially using ammonia soln. and nitric acid. Similar results were obtained with sample contg. Cr(VI). The optimum conditions obtained were 2M ammonia, 1.5M nitric acid, with a flow rate of 2 mL/min. Two types of samples, marine sediments and cements, were analyzed. The LODs were 0.45 mgCrVI/g (alk. extn.)/0.38 mgCrVI/g (water extn.), and 2.9 mgCrIII/g (alk. extn.)/1.2 mgCrIII/g (water extn.). Speciation recoveries were 102±4, and 101±5%, and the percent relative std. deviation of peak area was 7.1 and 8.7% for Cr(VI) and Cr(III), resp. The overall recovery of the procedure of alk. extn./speciation for Cr(VI) was 99±3% (75 mgCrVI/gcement); and linear ranges extended to 150 mg/L for Cr(III) and 200 mg/L for Cr(VI). (Hide)

Pressurized liquid extraction (PLE), commonly used for org. compds. extn., has been applied for trace element leaching from marine biol. material to det. major and trace elements (Al, As, Cd, Co, Cu, Fe, Hg, Li, Mn, Pb, Se, Sr, V and Zn). The released elements by formic acid PLE have been evaluated by inductively coupled plasma-optical emission spectrometry (ICP-OES). Different variables, such as formic acid concn., extn. temp., static time, extn. steps, pressure, mean particle size and diatomaceous earth (DE) mass/sample mass ratio were simultaneously studied by applying an exptl. design approach (Plackett-Burman design (PBD) and central composite design (CCD)). Results showed that the extn. temp. was statistically significant (confidence interval of 95%) for most of the elements (high metal releasing was achieved at high temps.). In addn., formic acid concn. was also statistically significant (confidence interval of 95%) for metals such as Cd and Cu. Most of the metals can be extd. using the same PLE operating conditions (formic acid concn. of 1.0 M, extn. temp. at 125º, static time of 5 min, one extn. step, extn. pressure at 500 psi and DE mass/sample mass ratio of 2). Taking in mind PLE requirements at the optimized operating conditions (125º), a time of 6 min is needed to pre-heat the cell. Therefore, the PLE assisted multi-element leaching is completed after 12 min. Anal. performances, such as limits of detection and quantification, repeatability of the over-all procedure and accuracy, by analyzing GBW-08571, DORM-2, DOLT-3 and TORT-2 certified ref. materials, were finally assessed. (Hide)

Surface marine sediments from Ria de Arousa estuary were analyzed for humic and fulvic acids by UV-visible spectrometry and were characterized using elemental anal. (carbon, hydrogen and nitrogen elemental compn.) and spectrometric data (A2/A4 ratio, absorbancies at 270 and 407 nm and E4/E6 ratio, absorbancies at 465 and 665 nm). These variables were used as discriminating factors to distinguish of marine and terrestrial origin of humic and fulvic acids in Ria de Arousa surface marine sediments. Principal component anal., PCA, and cluster anal., CA, were used as unsupervised pattern recognition procedures. The half-range central value transformation was used as data pre-treatment to homogenize data. After a Varimax rotation, PCA applied to humic acid data has reveled that spectrometric A2/A4 and E4/E6 ratios are the main dominating features in the 1st principal component (48.6% of total variance), the humic acid content is the feature with the highest wt. in the 2nd principal component (22.9% of the total variability) and the carbon elemental compn. domain in the 3rd principal component (13.3% of total variance). Results from PCA revealed that surface sediments collected at inner-left part of the estuary and at the mouth of the river Ulla belong to the same group. Similarly, PCA showed that surface sediments from the right mouth of the estuary form a compact group. Taking in account the water circulation in Ria de Arousa estuary, these findings mean that the org. matter in surface sediments from the inner-left part of the estuary derived mainly from terrestrial org. matter while the org. matter in surface sediments from the right mouth of the estuary is mainly derived from marine sources. Finally, it must be noticed that any classification of surface sediments was assessed when applying of PCA and CA from fulvic acids data. (Hide)

As and Sb behavior in the Ria de Arousa, Galicia, northwestern Spain, and their response to the Prestige oil spill accident in the estuary was evaluated. As and Sb were simultaneously detd. by hydride generation-inductively coupled plasma-optical emission spectroscopy in seawater following pre-concn. with La in a knotted reactor. Highest As concns. were in the inner and middle portions of the ria where current is weaker and adjacent to the main area ports; largest Sb concns. were in the bay of the ria. Linear variation of concn. vs. salinity for As and As:Sb ratios indicated there was no pollution in Arousa water. The Prestige oil spill had no serious effect and As concns. (most <1.5 mg/L) were similar to av. oceanic concns.; Sb concns. (most <0.15 mg/L) were less than oceanic concns. (Hide)

A review. An overview of pressurized liq. extn. (PLE) applied to organometal compds. for speciation studies is given. Also it is dealt with the feasibility of this technique for simultaneous metal extn. To verify the potential applicability of PLE for total metal extn., two certified ref. materials (GBW-08751 Mussel Tissue and PACS-2 Marine Sediment) were subjected to pressurized carboxylic acids. Acetic acid and formic acid under pressurized conditions appear to ext. metals from environmental materials. Exploiting the rapidity and the automation of PLE could be a new trend in pre-treating samples for total metal extn. (Hide)

The purpose of the work described in this paper was to develop an easy and quick in-vitro method for comparing the bioavailability of Se in cows' milk after different cow feed. The study focuses on bioavailability differences resulting from the use of different Se species (org. Se as selenised yeast and sodium selenite) for supplementation of forage. A procedure for detn. of Se in cows' milk and dialyzates, by hydride-generation at.-fluorescence spectrometry (HG-AFS) after microwave-assisted acid digestion, was optimized. The results show it is possible to obtain cows' milk enriched with Se at different concn. without altering the original compn. of the milk. The bioavailability was statistically greater for cows' milk obtained after supplementation of forage with org. Se at levels of 0.4 and 0.5 mg Se g-1 than for that obtained after supplementation with inorg. and org. Se at levels of 0.2 and 0.3 mg Se g-1 (Hide)

Systematic errors obsd. When using flame at. absorption spectrometry (FAAS) and electrothermal at. spectrometry (ETAAS) for the anal. of biol. solid materials (seafood products) were evaluated. The effect of the sample pre-treatment method (microwave-assisted acid digestion, ultrasound-assisted acid leaching and slurry sampling) as well as the no. of times that a certain pre-treatment process is repeated, were two factors evaluated. They give information about the effect of the sample pre-treatment on the uncertainty in the anal. In addn., the no. of measurements (i.e., no. of times that an acid digest, an acid leachate or aq. slurry are analyzed) and the calibration technique used (aq. calibration method or std. addn. technique) were other two variables taken into account. This last factor gives information about the effect of the calibration on the results, while the replicate measurements showed the repeatability. A fifth variable named as sample matrix tests the influence of the matrix sample on the systematic error through the use of different ref. materials. This variable allows the study of the effect of the trace element concns. on the uncertainty because the trace elements contents are different in each ref. material. Exptl. design and principal component anal. approaches were used as chemometric tools. It has been found that the use of the slurry sampling technique in ETAAS and FAAS and the detn. of high element concns. by ETAAS have led to poor precision. (Hide)

The possibilities of pressurized liquid extraction (PLE) have been novelty tested to assist the cytosol prepn. from wet mussel soft tissue before the detn. of metals bound to metallothionein-like proteins (MLPs). Results obtained after PLE were compared with those obtained after a classical blending procedure for mussel cytosolic prepn. Isoforms MLP-1 (retention time of 4.1 min) and MLP-2 (retention time of 7.4 min) were sepd. by anion exchange high-performance liq. chromatog. (HPLC) and the concns. of Ba, Cu, Mn, Sr and Zn bound to MLP isoforms were directly measured by inductively coupled plasma-at. emission spectrometry (ICP-OES) as a multi-element detector. The optimized PLE-assisted mussel cytosol prepn. has consisted of one extn. cycle at room temp. and 1500 psi for 2 min. Since sepn. between the solid mussel residue and the ext. (cytosol) is performed by the PLE system, the cytosol prepn. method is faster than conventional cytosol prepn. methods by cutting/blending using Ultraturrax or Stomacher devices. (Hide)

The use of ultrasound energy for accelerating the pronase E enzymic hydrolysis of human hair for extg. illicit drugs was novelty tested. The enzymic exts. obtained after 30 min of sonication in an ultrasonic water bath were subjected to an optimized solid-phase extn. process, which involved a soln. of 2.0% (vol./vol.) acetic acid in methanol as eluting soln. and concn. by N2 stream evapn. A gas chromatog./mass spectrometry method was used to sep. and det. cocaine, benzoylecgonine, codeine, morphine, and 6-monoacethylmorphine in 20 min. Variables affecting ultrasound-assisted pronase E hydrolysis such as hydrolysis temp., hydrolysis time, enzyme concn., catalyzer (1,4-dithiothreitol) concn., ionic strength, pH, and ultrasound frequency were simultaneously evaluated by a Plackett-Burman design 28 PBD of resoln. III. The most statistically significant variables were ionic strength and pH, which means that analyte extn. is mainly attributed to pronase E activity. The optimization or evaluation of all the factors has led to an accelerated pronase E hydrolysis of human hair, which can be completed in 30 min. Results were found to be statistically similar to those obtained with conventional pronase E hydrolysis. The accelerated method was finally applied to several human hair samples from multidrug abusers. (Hide)

The feasibility of microwave energy to speed up the alk. extn. of humic substances (humic acid, HA, and fulvic acid, FA) from marine sediments has been checked. Extns. were performed by using 20 mL of sodium hydroxide at 0.1 M (two repeated extns.) after an ultrasound-assisted acid pre-treatment of samples to remove the carbonate fraction (ultrasound power at 17 kHz, 10 mL of 6.0 M hydrochloric acid for 15 min). After sepn. of HA and FA fractions by acidifying with 6 M HCl, the FA fraction (supernatant) was purified by passing the soln. through a column of Amberlite XAD-8. Both HA and FA exts. were measured by UV-visible spectrophotometry. All variables affecting the extn. process (sodium hydroxide concn. and vol., ramp and hold times, temp. and no. of repeated extns.) have been screened by using a Plackett-Burman design (PBD) as multivariate approach. The variables temp. and no. of repeated extns. were the most significant factors (P = 95%) affecting the extn. of both FA and HA from marine sediments. These two variables have led optimum values of 150 ºC and two repeated extns. The developed method has been found precise (R.S.D.s of 9% for HA and 12% for FA, for 11 detns.) and its results were comparable in terms of elemental (C, H and N) compn. to those obtained after applying methods based on mech. stirring and ultrasounds assisting. However, higher HA and FA concns. than those obtained after conventional stirring and ultrasound irradn. were obtained when applying microwave energy. This means a higher efficiency of microwave energy than ultrasounds or mech. stirring to ext. HA and FA fractions from marine sediments. The method was finally applied to different surface marine sediments from the Ria de Arousa estuary. (Hide)

A method for antimony detn. in mussel tissue by ETAAS, using palladium-magnesium nitrate as a chem. modifier, was optimized. Before spectrometric anal., the samples were mineralized by microwave heating using a mixt. of nitric and sulfuric acid as the digesting agents. The optimum pyrolysis and atomization temps. were 1100 and 1800 ºC, resp. The method was precise (with %RSD <10%), accurate (with recoveries between 90-104%), and sensitive (LOD 0.02 mg g-1). The method was applied to the detn. of antimony in cultivated mussel samples from the Ria de Arousa, an estuary situated in Galicia (NW Spain). (Hide)

The feasibility of pressurized chelating solvents [ethylenediaminetetracetic acid (EDTA) dipotassium salt, 1,10-ortho-phenanthroline (PHEN), 8-hydroxyquinoline (8HQ), chloramine-T (CT), 1,1,1-trifluoro-2,4-pentanedione (H(fta)), 2,2'-azobis-(2-methylpropionamidine) dihydrochloride (AMPAHC) and 1,5-diphenylcarbazone (DFC)] has been investigated from a novel aspect to speed up metals leaching from atm. particulate matter (PM10). The target elements (Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn) have been evaluated by inductively coupled plasma-optical emission spectrometry (ICP-OES). The highest metal recoveries (within the 85-100% range) were found when using EDTA. Variables inherent to pressurized liq. extn. (temp., chelating solvent concn., static time, pressure, no. of cycles, dispersing agent mass, flush vol. and purge time) were simultaneously studied by applying a Plackett-Burman design (PBD) as the screening method. Results showed statistical significance for some factors such as extn. temp. and EDTA concn. The static time and the no. of cycles were statistically non-significant for most of the elements, meaning that the pressurized leaching procedure can be finished after 12 min (5 min for pre-heating the extn. cell at 100º plus 5 min of static time plus 1 min of purge time plus 1 min of end relief time). In addn., the presence of dispersing agent was not necessary, which reduces the time for filling of the cells. Quant. recoveries for all metals were reached under the following extn. conditions: 40 mM EDTA, extn. temp. of 100º, pressure of 1000 psi, static time of 5 min and one extn. cycle. Anal. performances, such as limits of detection and quantification and repeatability of the over-all procedure, have been established. Finally, results obtained by EDTA-based pressurized liq. extn. have been found to be statistically comparable with those obtained after conventional acid digestion with nitric, hydrofluoric and perchloric acids. (Hide)

A new, simple, fast and automated method based on acetic acid-pressurized liq. extn. (PLE) was developed for the simultaneous extn. of major and trace elements (As, Ca, Cd, Co, Cr, K, Mg, Mn, Na, Pb, Sr, and Zn) from edible seaweeds. The target elements were simultaneously detd. by inductively coupled plasma-optical emission spectrometry (ICP-OES). The influence of several extn. parameters (e.g. acetic acid concn., extn. temp., extn. time, pressure, no. of cycles, particle size and diatomaceous earth (DE) mass/sample mass ratio) on the efficiency of metal leaching was evaluated. The results showed that metal extn. efficiency depends on the mass ratio of the dispersing agent mass and the sample. The optimized procedure consisted of the following conditions: acetic acid (0.75 M) as an extg. soln., 5 min of extn. time, one extn. cycle at room temp. at a pressure of 10.3 MPa and addn. of a dispersing agent (at a ratio of 5:1 over the sample mass). The leaching procedure was completed after 7 min (5 min extn. time plus 1 min purge time plus 1 min end relief time). Limits of detection and quantification and repeatability of the over all procedure were assessed. Method validation was performed analyzing 2 seaweed ref. materials (NIES-03 Chlorella Kessleri and NIES-09 Sargasso). The developed extn. method was applied to red (Dulse and Nori), green (Sea Lettuce) and brown (Kombu, Wakame and Sea Spaghetti) edible seaweeds. (Hide)

A method for the detn. Of antimony in a slurry of marine sediment samples was developed. The temps. of the graphite furnance program were optimized using a mixed chem. modifier consisting of palladium and magnesium nitrate and a wavelength of 217.6 nm. Under these conditions, the background levels were very high and the atomization profile showed a pronounced baseline rendering quantification impossible; this effect can be due to the presence of silicon in the sample. The expts. were repeated using the 206.8-nm antimony line at which no neg. baseline was obsd. and the background levels decreased. Therefore, this absorbance line was selected for the detn. of antimony in this work. The graphite furnace program was optimized using the mineralization and atomization temps. of 1400º and 1700º, resp. The concn. of the matrix modifier was also investigated and best results were obtained with 40-30 mg L-1 of palladium and magnesium nitrate, resp. The anal. characteristics were 0.8 and 2.8 mg g-1 for the detection and quantification limits, resp., with a characteristic mass of 18.8 pg and 95.6% of recovery percentage. The method was applied to the detn. of antimony in different surface marine sediment samples obtained from Ria de Arousa (NW Spain) (Hide)

Possibilities for the use of an inexpensive sulfydryl cotton fiber (SCF) adsorbent to sep. and preconc. traces of Hg from acid digests from edible seaweed were evaluated. Com. empty cartridges were filled with around 0.75 g of lab.-made adsorbent and they were incorporated in the 5-way valve of an automatic flow injection anal. system. Traces of Hg in acid digests were pumped through the cartridges for 45 s (flow rate of 8.8 mL min-1) and then eluted from cartridges with 0.5 M hydrochloric acid and 1.0 M sodium chloride soln. for 45 s at a flow rate of 5.8 mL min-1. At the same time that Hg is eluted from the cartridges, the eluate is mixed with a 0.05% (m/v) sodium tetrahydroborate soln. and the Hg cold vapor is swept through the atomization cell with an argon flow of 50 mL min-1. The overall procedure (Hg sepn./preconcn. and Hg cold vapor generation/atomization) is completed after around 90 s. The developed method implies an enrichment factor of 10.2 with a limit of detection of 5.23 ng g-1. Repeatability of the overall procedure and accuracy were successfully assessed. (Hide)

We developed a rapid and feasible method to det. total iodine and iodide in edible seaweeds by an inexpensive anal. technique, catalytic spectrophotometry. Seaweed samples were solubilized by applying a microwave-assisted alk. digestion with tetramethylammonium hydroxide (TMAH). The percentage of iodide was measured directly in the alk. digests by observing the catalytic effect of iodide on the oxidn. of As(III) by Ce(IV) in H2SO4/HCl medium. In order to det. total iodine, a microwave-assisted sodium tetrahydroborate (NaBH4) redn. was optimized. After this treatment, all iodine species present in the alk. digests were reduced to iodide. Microwave-assisted alk. digestion was performed using 7.5 mL of TMAH and irradiating samples at 670 W for two 5.5 min steps. Microwave-assisted NaBH4 redn. was carried out using 2.5 mL of the alk. digest, 3.0 mL of a 10% (m/v) NaBH4 soln. and 2.0 mL of 5.0 M hydrochloric acid, at a microwave power of 360 W for 3.5 min. The linear calibration ranges were 0.30-20.0 and 0.43-20.0 mg l-1 for iodide detn. and total iodine detn., resp. The limit of detection was 9.2 mg g-1 for iodide and 54.0 mg g-1 for total iodine. Repeatability of the overall procedures, expressed as RSD for eleven detns., was 10.4% (microwave-assisted alk. digestion followed by microwave-assisted NaBH4 redn. for the detn. of total iodine). Accuracy of the method was assessed by analyzing the NIES-09 (Sargasso) certified ref. material. Edible seaweed anal. has shown that most of the iodine is present as iodide in brown seaweed samples (90% of the total iodine), while red seaweeds have iodide percentages lower than 30% and green seaweeds lower than 80%. (Hide)

A multivariate optimization of the main parameters which might affect Ag, Au, Cd, Cu, Ni and Zn vapor generation and detection using inductively coupled plasma optical emission spectrometry was carried out. Na tetrahydroborate was used as reducing agent and const. concns. of 8-hydroxyquinoline and Co were added to all the stds. to increase the efficiency of the reaction. A home-made gas-liq. separator was used and vapor was carried directly to the plasma using an Ar flow. A 26-2 factorial design plus two addnl. points in the center of the exptl. domain was run to select influential factors in the detn.; afterwards, an orthogonal composite design 24 + star was performed to select optimum values for the factors. Desirability was the parameter used to select optimum conditions to carry out simultaneous detn. of all the elements. Optimum values of studied factors were: [Co], 1 mg L-1; [HNO3], 0.43M; [8-hydroxyquinoline], 38 mg L-1; [NaBH4], 2.24%; and Ar nebulizer flow rate (injection Ar flow rate), 0.74 L min-1. Detection limits were under 10 mg L-1 for all the elements except for Ag (Ag vapor formation increased using HCl). Relative std. deviations were under 10% (n = 11) and an interference study was carried out. Ni and Cu are the most serious interferents that drastically reduce responses for most of the elements. It must be pointed out that using the developed method, vapors of Co, Cr, Mo and Fe were obtained as well. The limit of detection for Fe was 7.4 mg L-1 and the relative std. deviation (%) was 7.7 (Fe 238.204 nm). (Hide)

Studies on the application of a short microwave irradn. cycle and the use of dild. acids to ext. trace elements from raft mussel samples were developed. Multi-element detns. (Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb, Sn, V and Zn) were carried out by inductively coupled plasma-optical emission spectrometry (ICP-OES). Parameters such as acid/oxidizing reagents (dild. nitric acid, hydrochloric acid and hydrogen peroxide) concns., acid/oxidizing soln. vol., temp., ramp time and hold time for the microwave heating were simultaneously studied by using an exptl. design approach. The optimum conditions have showed the sample pre-treatment of 10 mussel samples to less than 3.0 min when a microwave power of 600 W and a controlled temp. of 65 ºC were used. This time (hold time plus ramp time) is quite shorter than those reported for conventional microwave-assisted acid digestion procedures. Since temp. inside the reactor is not high, the venting time can be shorted to 15 min. In addn., the concn. of acid/oxidizing reagents needed to complete the acid leaching (2.5 M, 3.0 M and 0.5 % (m/v) for nitric acid, hydrochloric acid and hydrogen peroxide, resp.) is lower than the required concn. for a conventional microwave-assisted acid digestion (concd. acids). The proposed method has showed a good repeatability of the overall method, and relative std. deviations between 11 and 2% were reached for 12 replicate microwave-assisted acid leaching and ICP-OES measurements. The method was finally validated by analyzing TORT-1 and GBW-08571 certified ref. materials and it was successfully applied to fast multi-element detns. in several raft mussel samples. (Hide)

An analytical method was developed for detn. of major (Ca, K, Mg, and Na) and trace elements (As, Cd, Co, Li, Ni, and Sr) in human scalp hair. The proposed method includes a novel, simple, rapid, highly efficient, and automated metal-leaching procedure, by pressurized-liq. extn. (PLE), combined with a rapid simultaneous detection system-inductively coupled plasma-optical-emission spectrometry (ICP-OES). PLE is one of the most promising recently introduced sample-prepn. techniques, with the advantages of reducing solvent consumption and enabling automated sample handling. The operating conditions for PLE, including concn. of the extn. solvent, extn. temp., static time, no. of extn. steps, pressure, mean particle size, diatomaceous earth (DE) mass/sample mass ratio, and flush vol. were studied using an exptl. design (Plackett-Burman design, PBD). The optimum conditions were use of 0.75 mol L-1 acetic acid as extg. soln. and powd. hair samples thoroughly mixed with DE, as a dispersing agent, at a DE mass/sample mass ratio of 4. Extn. was performed at room temp. and an extn. pressure of 140 atm for 5 min in one extn. step. The flush vol. was fixed at 60%. The PLE-assisted multi-element leaching proposed is complete after 7 min (5 min static time plus 1 min purge time plus 1 min end relief time). Under the optimized conditions the figures of merit, for example limits of detection and quantification, repeatability of the over-all procedure, and accuracy, were evaluated. Anal. of GBW-07601 (human hair) certified ref. material revealed accuracy was good for the target elements. The optimized method was finally applied to several human scalp-hair samples. (Hide)

The purpose of this paper is to develop an easy and quick online selenium speciation method (LC-UV-HG-AFS) in cow milk obtained after different supplementation to cow feed. This study focuses on selenium speciation in cow milk after the use of different selenium species (org. selenium as selenised yeast and inorg. selenium as sodium selenite) in the supplementation of forages. Sepn. was carried out on a mBondapack C18 column with the pos. charged ion-pairing agent tetraethylammonium chloride in the mobile phase. The optimization of pre-redn. conditions was carried out; this step was done with UV irradn. and a heating block to improve the redn. of the different Se-compds. Variables such as exposure time, hydrochloric acid concn. and temp. were studied. The detection limits for SeCyst2, Se(IV), SeMet and Se(VI) were 0.4, 0.5, 0.9 and 1.0 mg l-1, resp. The proposed method was applied to cow milk samples. The milk samples obtained after an org. supplementation of feeding as selenised yeast present three species of selenium, SeCyst2, Se(IV) and SeMet, while only SeCyst2 and Se(IV) are present in milk samples obtained after an inorg. supplementation of feeding. (Hide)

A rapid method for the detn. Of Al, Ba, Cu, Fe, Mn, Sr and Zn binding metallothionein-like proteins (MLPs) in mussels (Mytilus galloprovincialis) by inductively coupled plasma-optical emission spectrometry was developed. The method uses a short column (8 mm ´75 mm) anion exchange HPLC with inductively coupled plasma-optical emission spectrometric (ICP-OES) detection. Working in isocratic mode (75 mM Tris-HCl at pH 7.4, flow rate at 0.8 mL min-1), two major MLPs isoforms (MLP-1 and MLP-2) can be sepd. in ten minutes. The distribution of basal metals binding MLPs was assessed by on line HPLC and ICP-OES, while the basal contents of metals binding MLPs were obtained after off line HPLC and ICP-OES (collection of the two major fractions and multi-element detn. by ICP-OES). The calcd. LODs were 81, 6, 10, 13, 30, 9 and 123 ng g-1 for Al, Ba, Cu, Fe, Mn, Sr and Zn binding MLP-1 and MLP-2, resp. The repeatability of the over-all method (five different mussel cytosols prepd. from the same mussel sample and subjected to the off line HPLC-ICP-OES procedure twice) was from 11.2 for Cu to 16.2% for Zn. The method was finally applied to different raft mussels from Ria de Arousa estuary to know basal levels of elements binding MLPs. (Hide)

The feasibility of pressurized solvents (liqs. at a high pressure and/or high temp. without the subcrit. point being reached) has been newly investigated to accelerate enzymic hydrolysis processes of mussel tissue for multielement detns. The target elements (Al, As, Cd, Co, Cu, Fe, Hg, Li, Mn, Pb, Se, Sr, V, and Zn) were released from dried mussel tissue by action of two proteases (pepsin and pancreatin), and they have been evaluated by inductively coupled plasma optical emission spectrometry (ICP-OES). Variables inherent to the enzymic activity (pH, ionic strength, temp., and enzyme mass) and factors affecting pressurization (static time, pressure, and no. of cycles) were simultaneously studied by applying a Plackett-Burman design (PBD) as the screening method. Results showed that pH, ionic strength, and temp. were the most statistically significant factors (confidence interval of 95%) under pressurized conditions for pepsin, while pH and ionic strength affected pancreatin activity. This means that metal extn. is mostly attributed to enzymic activity. The static time (enzymic hydrolysis time) was found statistically nonsignificant for most of the elements, meaning that the hydrolysis procedure can be finished within a 2-15 min range. For pepsin, optimized conditions (pH 1.0, temp. 40º, pressure 1500 psi, static time 2 min, and no. of cycles 3) gave quant. extns. for As, Cd, Co, Cu, Hg, Li, Mn, Pb, Se, Sr, V, and Zn. The pepsin mass was 0.05 g, and the soln. was Milli-Q water at pH 1.0 (adjusted with hydrochloric acid). For pancreatin, quant. recoveries were only reached for As, Cd, Cu, Li, Pb, and Sr at room temp., at a pressure of 1500 psi, for a static time of 2 min and a no. of cycles of 3. The extn. soln. was a 0.3 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer at a pH of 7.5 working at room temp. Around 0.5 g of diatomaceous earth was used as dispersing agent for hydrolyzes with either enzyme. Anal. Performances, such as limits of detection and quantification and repeatability of the overall procedure, have been established. Finally, accuracy of the methods was assessed by analyzing seafood certified ref. materials (GBW-08571, DORM-2, DOLT-3, TORT-2), fatty tissues certified ref. materials (BCR 185, NIST 1577b), and fibrous certified ref. materials (BCR 62, GBW-08501). (Hide)

Direct determination of cooper, lead and cadmium by electrothermal atomic absorption spectrometry in aniseed spirits was proposed. The methods were validated by studying quality parameters surch as trueness, precision, linearity and sensitivity. Recoveries ranging between 96% and 104% were obtained from spiked samples at several concentration levels. Repeatability was less than 5% and intermediate precision was less than 8%. The procedure is fast and shows limits of detection of 0.6, 0.7 and 0.004 µg1-1 for Cu, Pb and Cd, respectively. Samples were just diluted in a water/ethanol/nitric acid mixture. Cu was present at higher concentrations, with values in the range 6-473 µg 1-1. Minor levels of Pb and Cd were present with concentrations of less than 6 and 1.4 µg 1-1, respectively. (Hide)

A method for Selenocystine and Selenomethionine determination by LC-ES-MS was developed in this work. The mass spectrometer was used in a positive mode and the m/z used for the identification of Selenomethionine and Selenocystine were 198.35 and 337.15 respectively. The selenium species were separated using a LC system. A silica chromatographic column (ZORBAX Eclipse XDB-C8 of 50 mm length and 2.1 mm internal diameter (particle size 3.5 µm)) was used. The separation was realised in isocratic mode, using methanol:water (1:1) with 1% of acetic acid and a flow rate of 200 µl/min. The developed method was precise (RSD of 4.5% and 3.9% for Selenomethionine and Selenocystine respectively) and sensible (limit of detection (LOD) 0.06 and 0.99 mg L-1 for selenomethionine and selenocystine respectively). (Hide)

The aim of this study was to develop a method to determine iodine in human milk and infant formulas using the ICP-MS. The milk samples were digested using an alkaline digestion (5% NH3, 45 W, 2 min 30 s), and the method was validated using a certified reference material BCR CRM151. On the other hand the milk was separated in three fractions, whey, fat and caseins using ultracentrifugation (15min, 4ºC, 50000rpm) and the iodine was determined in the different fractions. 27 samples of different infant formulas and 14 samples of human milk has been studied. In the human milk the values found were between 144 ± 93,2 µg/Kg, whereas in the infant formulas the values were 53.3 ±19.5. For both types of samples the bigger amount of iodine is in the whey fraction, between 80-90 %, whereas in the fat there is about a 2% of the total iodine and in the casein fraction the levels are between 5-10% depending on the type of sample. (Hide)

In the present work, accumulation and distribution of aluminium in the rat brain following both intraperitoneal and oral administration were studied. Electrothermal atomic absorption spectrometry was used to determine aluminium concentration in different brain areas (cerebellum, ventral midbrain, cortex, hippocampus, and striatum). The most of the brain areas showed accumulation of aluminium, but a greater and more significant increase was noted in the group receiving aluminium via intraperitoneal administration. Aluminium distribution was also dependent on the administration route used. (Hide)

Matrix solid-phase dispersion (MSPD) has been applied to extract arsenical species (arsenite, As(III); arsenate, As(V); monomethylarsonic acid; dimethylarsinic acid, DMA; arsenobetaine, AsB; and arsenocholine) from seafood products. High-performance liquid chromatography coupled to inductively coupled plasma-mass spectrometry was used to separate and detect all arsenic species. Variables affecting MSPD, such as the solid support material (dispersing agent), solid support mass/sample mass ratio, elution solvent composition, and elution solvent volume, have been fully evaluated. Quantitative recoveries for inorganic and organic arsenic species have been obtained when using diatomaceous earth or octadecyl-functionalized silica gel (C18) as a solid support material, with a solid support mass/sample mass ratio of 7.0. Elution of arsenical compounds has been assessed using 10 mL of 50/50 methanol/ultrapure water as an elution solvent. The MSPD method has been found precise, with RSDs of ∼9% for As(III), DMA, and As(V) and 3% for AsB. The developed procedure has been tested by analyzing different certified reference materials of marine origin such as DORM-2 and BCR 627, which offer certified contents for some arsenic species. The method has been also applied to assess arsenic speciation in different mollusks, cold water fishes, and white fishes. (Hide)

Diffuse reflectance near-infrared spectroscopy (NIR) combined with partial least squares (PLS) data treatment has been employed for the rapid and nondestructive determination of sedimentary humic substances. Forty one samples of surface estuarine sediments, taken during distinct seasonal periods from different locations across Ria de Arousa (northwest of Spain), were scanned at wavelengths from 833 to 2,976 nm (12,000 to 3,360 cm-1). Twenty four samples were randomly selected, from previous hierarchical cluster analysis of their NIR spectra, for the calibration set, and the 17 remaining samples were assigned to the validation set. NIR spectra of calibration samples were correlated to measured values of humic acids (HAs) and fulvic acids (FAs), which ranged from 1.53 to 28.17 mg/g and from 0.37 to 2.45 mg/g, respectively, using PLS regression and multiplicative scattering correction on the raw and first-derivative NIR spectra, respectively. Low root mean square error of prediction values of 4.3 mg HA/g sediment and 0.25 mg FA/g sediment were obtained. Good residual prediction deviation values of 1.16 and 1.2 were obtained for HA and FA, respectively, allowing the PLS models built to be considered as appropriate tools for screening purposes. (Hide)

A multivariate optimization of the main parameters which might affect Ag, Au, Cd, Cu, Ni and Zn vapour generation and detection using inductively coupled plasma optical emission spectrometry has been carried out. Sodium tetrahydroborate was used as reducing agent and constant concentrations of 8-hydroxyquinoline and cobalt were added to all the standards in order to increase the efficiency of the reaction. A home-made gas-liquid separator was used and vapour was carried directly to the plasma using an Ar flow. A 2 6-2 factorial design plus two additional points in the centre of the experimental domain was run to select influential factors in the determination; afterwards, an orthogonal composite design 24 + star was performed to select optimum values for the factors. Desirability was the parameter used to select optimum conditions to carry out simultaneous determination of all the elements. Optimum values of studied factors were: [Co], 1 mg L-1; [HNO3], 0.43 M; [8-hydroxyquinoline], 38 mg L-1; [NaBH4], 2.24%; and Ar nebulizer flow rate (injection Ar flow rate), 0.74 L min-1. Detection limits were under 10 μg L-1 for all the elements except for Ag (silver vapour formation increased using hydrochloric acid). Relative standard deviations were under 10% (n = 11) and an interference study was carried out. Ni and Cu are the most serious interferents that drastically reduce responses for most of the elements. It must be pointed out that using the developed method, vapours of cobalt, chromium, molybdenum and iron were obtained as well. The limit of detection for iron was 7.4 μg L-1 and the RSD (%) was 7.7 (Fe 238.204 nm). (Hide)

Preliminary results of development of a direct and fast method of determination of antimony in samples of tap water using GFAAS are presented. The found levels of antimony were lower than permitted for human consumption. A mixture of Pd and Mg(NO3)2 (concentrations in the injected solution: 8.6 μg mL-1 and 5.8 μg mL-1 respectively) was used as the chemical modifier. The pyrolysis and atomization temperatures were 1000 and 1700°C, respectively and the mean analytical recovery 98.2%. (Hide)

Several nickel ion imprinted polymers were prepared via precipitation polymerization using 4-vinylpyridine or 2-(diethylamino) ethyl methacrylate as monomers (vinylated reagents) and a cross-linking agent divinylbenzene in the presence of nickel(II) alone or nickel(II) and 8-hydroxyquinoline (non-vinylated reagent). For all cases, 2,2′-azobisisobutyronitrile (AIBN) was used as an initiator and an acetonitrile/toluene (3:1) mixture was chosen as a porogen. After packing the polymer particles into empty SPE cartridges, nickel(II) ions were removed by washing with 50 mL of 2.0 M nitric acid. Characterization of the polymer particles has been carried out by scanning electron microscopy, energy dispersive X-ray fluorescence and elemental analysis. The best nickel imprinting properties were given by polymers synthesized in the presence of 8-hydroxyquinoline and 2-(diethylamino) ethyl methacrylate as a monomer. The optimum pH for quantitative nickel retention was 8.5 ± 0.5, while elution was completed with 2.5 mL of 2.0 M nitric acid. When using polymer masses of 300 mg, sample volumes until 250 mL can be passed through the cartridges without reaching the breakthrough volume. Therefore, a pre-concentration factor of 100 has been reached when eluting with 2.5 mL of the elution solution. Electrothermal atomic absorption spectrometry has been used as a detector for nickel determination. The limit of detection of the method was 0.050 μg L-1 (pre-concentration factor of 100), while the relative standard deviation for eleven replicates was 6%. Accuracy of the method was assessed by analyzing different certified reference materials: SLEW-3 (estuarine water) and TM-23.3 and TM-24 (lake water). (Hide)

Arsenic determination in mussel tissue was performed by electrothermal atomic absorption spectrometry (ETAAS) with Zeeman background correction and using iridium as a chemical modifier. Samples were digested by microwave heating using a mixture of nitric and sulphuric acids. This mixture makes possible the destruction of organoarsenic compounds, specifically arsenobetaine, prior to the graphite furnace determination. Optimum pyrolysis and atomization temperatures were 1,100 and 1,800 °C, respectively. The method was precise (with RSD% 10), accurate (study of a certified reference material: 18.4 ± 1.4 μg As g-1 vs. a certified content: 18.0 ± 1.1 μg As g-1; recoveries between 90 and 104%) and sensitive (LOD 0.21 μg g-1 on a dry weight basis). The method was applied to the determination of arsenic in aquaculture mussels collected in four sampling campaigns from the productive Ría de Arousa (estuary sited in Galicia, NW of Spain). (Hide)

The Spanish norm UNE 66020-1:2001 is equivalent to the international norm ISO 2859-1:1999 and deals with inspection by attributes of lots of material. In order to implement such a norm in a canned marine food factory (which manufactures mainly bluefin tuna in vegetal oil), some preliminary work was carried out. First, a careful study of the production process led to three possible sources of variation in the final weight of the cans produced, namely the canning machine, the cans used and the balance utilized for weighing. Afterward, each of these sources of variation was studied, which resulted in a value of the process average. This average shall enable the responsible authority of the company to set an acceptance quality limit, which should allow the application of the cited norm (Hide)

Phthalates are a group of chemical compounds with increasing interest from the analytical point of view. The risks for human health associated with some of these compounds have unleashed the necessity to develop analytical methods with great sensitivity that allow us to detect their presence at trace levels in order to assure protection for the population. A simple and rapid method for determining a group of phthalate esters in aqueous samples was developed. The method was based on highperformance liquid chromatography–(electrospray)-mass spectrometry (HPLC–ES-MS), working in positive ionisation (PI) mode. A gradient elution was performed with acetonitrile–ultrapure water starting from 5 to 75% acetonitrile in 5 min followed by isocratic elution during 5 min. Standard calibration curves were linear for all the analytes over the concentration range 10–500 ngmL−1 .The LOD values found for DMP, DEP, BBP and DBP were 0.8, 3.4, 0.6 and 1.2 ngmL−1 respectively. The relative standard deviation ranged from 0.8 to 1.7%, which indicated good method precision. The proposed analytical method has been applied to the analysis of commercial physiological saline solutions in order to check the presence of phthalates and to determine their concentration. (Hide)

Its has been developed a partial least squares near infrared (PLS-NIR) method for the determination of estuarine sediment physicochemical parameters. The method was based on the chemometric treatment of first order derivative reflectance spectra obtained from samples previously lyophilized and sieved through a lower than 63 µm grid. Spectra were scanned from 833 to 2976 nm, averaging 36 scans per spectrum at a resolution of 8cm -1, using chromatographic glass vials of 9.5 mm internal diameter as measurement cells. Models were built using reference data of 31 samples selected through the use of a hierarchical cluster analysis of NI spectra of sediments obtained from the Ria de Arousa estuary and prediction parameters were established from a validation set of 50 samples of the same area, pH, redox potential (Eh), carbon (c) , nitrogen (N) and hydrogen (H) content together with Sn, Pb, Cd, As, Sb and toral Cr and also acid soluble, reducible and oxidable Cr fractions were employed as characteristic parameters of the studied sediments. Standard error of prediction values for C and N content were of the order of 4 and 1.3 mg g-1 for H. Prediction errors for pH and Eh were 0.15 units and 37 mV, respectively, this indicating the good prediction capabilities of the method. Regarding trace metal concentrations PLS-NIR provided prediction error levels for unknow samples around 20% for Sn, Pb, As and Sb and root mean square errors of prediction around 40% for concentration levels of 400ng g-1 Cd and 100 µg g-1 Cr. For the different extractable fractions of Cr the residual prediction deviation varied from 1.3 to 1.7 but relative errors found for samples of the validation set were only useful for screening purposes. (Hide)

Nickel (II) and lead (II) ionic imprinted 8- hydroxyquinoline polymers were synthesized by a precipitation polymerization technique and were used as selective solid phase extraction suppors for the determination of nickel and lead in seawater by flow injection solid phase extraction on-line inductively coupled plasma-optical emission spectrometry. An optimum loading flow rate of 2.25 mL min -1 for 2 min and an elution flow rate of 2.25 mL min -1 for 1 min gave an enrichment factor of 15 for nickel. However, a low dynamic capacity and/or rate for adsorption and desorption was found for lead ionic imprinted polymer and a flow rate of 3.00 mL min -1 for 4 min loading and a flow rate of 2.25 mL min -1 for 1min elution gave a enrichment factor of 5. The limit of detection was 0.33 µg L -1 for nickel and 1.88 µg L -1 for lead, with a precision (n=11) of 8% (2.37 µg Ni L-1) for nickel and 11% (8.38 µg Pb L-1) for lead. Accuracy was also assessed by analyzing SLEW-3 (estuarine water) and TM-24 (lake water) certified reference materials, and the values determined were in good agreement with the certified concentrations. (Hide)

A new ionic imprinted polymer (IIP) for Ni(II) recognition/pre-concentration was prepared via precipitation polymerization using 2-(diethylamino) ethyl methacrylate (DEM) and divinylbenzene (DVB) as a crosslinking agent in the presence of nickel (II) and 5-vynil-8-hydroxyquinoline (5- VHQ) as a bi-fncionalized ligand. An important increase on the selectivity of the synthesised IIP for nickel (II) ions was obtained when comparing to the use of 8-hydroxyquinoline (8-HQ) as a ligand. The synthesised IIP was used as a new support for solid phase extraction (SPE) of nickel (II) from seawater before inductively coupled plasma optical emission spectrometry (ICP-OES) detection. Variables affecting the SPE process, such as pH, load and elution flow rates, and concentration and volume of the eluting solution, were fully evaluated. The optimised procedure consists of a sample loading (100 mL of seawater al a pH of 9.0 ± 0.1) through IIP-SPE cartridges containing 300 mg of the synthesised IIP at a flow rate of 3.0 mL min -1. Elution was performed by passing 2.5 mL of 2.0 M nitric acid at a flow rate of 1.5 mL min -1, which gave a pre-concentration factor of 40. The limit of detection (LOD) of the method was 0.26 µg L-1, while the relative standard derivation (RSD) for eleven replicated measurements was 3%. Accuracy of the method was assessed by analyzing SLEW-3 (estuarine water) and TM-23.3 (lake water) certified reference materials. In addition to the selectivity of the synthesised material for nickel (II) ions against other transition metal ions and major alkaline and alkaline-earth metals (Na+, K+, Mg+2 and Ca+2) in seawater, it can be stated that the salt matrix is efficiently removed by using the proposed IIP-SPE procedure. (Hide)

La expocision al pomo y al cadmio es un problema de salud publica debido a la amplia exposición a estos toxicos en la población general. El objetivo del estudio es determinar la concentración de plomo y cadmio en sangre en una población laboral procedente de 4 centros hospitalarios universitarios de Madrid, Getafe, Cartagena y Santiago de Compostela e identificar los factores asociados. En el estudio participaron 252 sujetos a los q se les administró el cuestionario estandarizado PESA de exposición al plomo y cadmio. La concentración de plomo y cadmio en sangre se midió por espectrometría de absorción atómica con atomización electrotérmica y correción de fondo por efecto Zeeman en espectrómetros Perkin-Elmer; se garantizó la transferibilidad de los resultados. La mediana de la concentración global de plomo en sangre fue de 2.0 µg/ dl (rango intercuartílico [RIC]: 1.2-3.1) y la de cadmio fue de 0.2 µg/L (RIC: 0.1-0.4). La mediana de plomo en mujeres menopausicas fue superior (2.9 µg/dl) a las mujeres premenopausicas (1.3 µg/dl) (0.001). La mediana de cadmio de los sujetos fumadores (0.54 µg/L) fue mayor que la de los sujetos no fumadores (0.21 µg/L) (0.001). Se observa un descenso en las concentraciones de plomo y cadmio en sangre respecto a estudios previos realizados en España. Sin embargo, los resultados sugieren que existen factores de mayor riesgo, como la edad, la menopausia, la antigüedad de la vivienda y la exposición al humo de tabaco. (Hide)

In the current work, samples of Mytilus galloprovincialis collected in different sites from Ria de Arousa estuary (Galicia, north-western Spain) were analysed for total Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn and for Ba, Cu, Mn and Zn bound to metallothionein-like proteins isoforms I (MLP-I) contents. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to assess total metal contents in raft mussels, while high performance liquid chromatographic (HPLC) with an on-line metal detection with ICP-OES was used to measure metals bound to MLP-I. A microwave-assisted acid digestion procedure was used as a sample pre-treatment for total metal contents, while a cytosolic preparation method based on a blending procedure with TRIS-HCL (pH 7,4) as an extracting solution was used to isolate MLP-I. Concentrations of total metals and metals bound to MLP-I were used as discriminanting factors to establish different regions in the Ria de Arousa estuary. Principal component analysis (PCA) and cluster analysis (CA) were used as unsupervised pattern recognition procedures, and the half-range central value transformation was used as a data pre-treatment to homogenizate data sets. Results have revealed a separation of raft mussels in good agreement with water circulation pattern and oceanographic processes in the estuary only when concentrations of metals to bound MLP-I are used as discriminanting factors. Otherwise, raft mussels are classified as samples harvested in the inner or outer sides of the Ría. (Hide)

Matrix solid-phase dispersión (MSPD) has been designed and classically used for organic compound purification and extraction. It offers fast, efficient sample pre-treatment for solid, semi-solid, viscous and liquid samples, when compared to traditional extraction methods. Its main advantages are flexibility, selectivity, and the possibility of performing extraction and clean up in one step, resulting in rapid pre-treatment and low solvent consumption. We give an overview of MSPD applied to extracting organic compounds, and assess the feasibility of MSPD for extracting organometallic compounds [arsenobetaine (AsB) and dimethylarsonic acid (DMA)], inorganic antimony species [Sb(III) and Sb (V)] and bromide and iodide. We subjected several Certified Reference Materials (CRMs) (e.g., DORM-2 Dogfish Muscle, BCR-627 Tuna Fish Tissue, and PACS-2 Marine Sediment) and an edible seaweed sample (Kombu, Laminaria ochroleuca) to MSPD by testing different solid supports and eluting solutions. Inductively coupled plasma mas spectrometry (ICP-MS), high performance liquid chromatography combined with ICP-MS (HPLC-ICP-MS) and HPLC combined with hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS) have been used for bromide and iodide, arsenic organometallic compounds, and inorganic antimony, respectively. We found that MSPD can extract total arsenic and certain arsenic compounds (AsB and DMA) from seafood, halides from seaweed and antimony from marine sediments. (Hide)

The capabilities of synthesized ionic imprinted polymer (IIP), originally prepared for Ni recognition/preconcentration from seawater, have been evaluated for other trace elements pre-concentration. The polymer has been synthesized by the precipitation polymerization technique using a ternary pre-polymerization complex formed by the template (Ni), the monomer (2-(diethylamino)ethylmethacrylate, DEM) and a non-vinylated chelating agent (8-hydroxyquinoline, 8-HQ). Since the complexing agent (8-HQ) is trapped into the polymeric matrix, but is not linked to the polymer chains, specific interactions between the functional groups (present in the monomer and the complexing agent) and other trace elements rather than Ni may occur. Results have shown that IIP offers imprinting properties for the template (Ni(II)) and also for Cu(II), Pb(II), Zn(II), AS(V) and Cd(II), with analytical recoveries close to 100% for all elements except for As(V) and Cd(II) (around 70%), whereas the non-imprinted polymer (NIP) did not show affinity for any trace element. In addition, the polymer does not interact with alkaline or alkaline-earth metals, so Na, K, Mg, and Ca from the seawater salt matrix could be effectively removed. Variables affecting the IIP-solid phase extraction (SPE) process (pH, load flow rate and concentration and volume of the eluting solution) were completely studied. Inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) have been used as multielement detectors. Acidified seawater samples must only be trated to fix an alkaline pH (8.5 ± 05) and passed through IIP-SPE cartridges. After seawater sample loading (250 mL), analytes were eluted with 2.5 mL of 2.0 M nitric acid, offering a pre-concentration factor of 100. Therefore, the limits of detection (LODs) of the method were 0.14, 0.15, 0.18 and 0.03 μgL-1, for Ni, Cu, Pb and Zn, respectively, for ICP-MS detection. Accuracy of the method was assessed by analyzing SLEW-3 (estuarine water), and TM-23.3 and TM-24 (lake water) certified reference materials. (Hide)

A review of recent literatura utilizing alternative simple pretreatment methods for solid enviromental and biological materials analysis to assess total metals content by atomic spectrometry is provided. All the selected treatments coincide with all or some of the fundamentals of Green Chemistry policy suchg as prevention of waste generation; safer and less toxic solvents and reagents; and designs for energy efficiency. The review covers the classic slurry sampling technique, mainly, its current trends, as well as developments based on the use of diluted acids, chelating agents solutions, or even water for leaching (extraction) methods assisted by ultrasounds, microwave energy, or pressurization. In addition, the use of conventional or assisted enzymatic hydrolysis procedures is also discussed. (Hide)

The feasibility of microwave energy to assist the solubilisation of edible seaweed samples by tetramethylammonium hydroxide (TMAH) has been investigated to extract iodine and bromine. Inductively coupled plasma-mass spectrometry (ICP-MS) has been used as a multi-elemnt detector. Variables affecting the microwave assisted exaction/solubilisation (temperature, Tmah volume, ramp time and hold time) were firstly screened by applying a fractional factorial design (25-1+2), resolution V and 2 centre points. When extracting both halogens, results shwed stastical significance (confidence interval of 95%) for TMAH volume and temperature, and also for the two order interaction between both variables. Therefore, these two variables were finally optimized by a 22+starorthogonal central composite design with 5 centre points and 2 replicates, and optimuvalues of 200ºC and 10 mL for temperature and TMAH volume, respectively, were found. The extraction time (ramp and hold times) was found statiscally non-significant, and values of 10 and 5 min were chosen for the ramp time and the hold time, respectively. This means a fast microwave heating cycle. Repeteability of the over-all procedure has been found to be 6% for both elements, while iodine and bromine concentrations of 24.6 and 19.9 ng g-1, respectively, were established for the limit of detection. Accuracy of the method was assessed by analyzing the NIES-09 (Sargasso, Sargassum fullvellum) certified reference material (CRM) and the iodine and bromine concentrations found have been in good agreement with the indicative values for this CRM. Finally, the method was applied to several edible dried and canned seaweed samples.(Hide)

Vapor generation and atomization conditions in a heated quartz tuve to detect Ag, Cd, Co, Cu, Ni, and Zn using High Resolution Continuum Source AAS (HRCSAAS), were optimized. Vapors were generated after mixing acidified solutions containing 8-hydroxiquinoline (oxine) with sodium tetrahydroborate. Afterwards, they were swept to the heated quartz cell by an argon flow. Reaction loop size and temperature of the quartz cell were optimized for each element. A temperature of 960 ºC was selected as a compromise value to detect most of the metals. Afterwards, a Plackett-Burmann design was proposed to select which parameters were most important. Type of acid and its concentration were the most statistical significant variables. Optimum conditions for sequential detection of Cd, Cu, Ni, and Zn were: 1 mgL-1 Co as catalyst, 250 mgL-1 oxine, 0.6M nitric acid, 1.75% (w/w) sodium tetrahydroborate (prepared in 0.4 (w/v)% NaOH), a reaction loop of 250 μL, and a 25 Lh-1 carrier Ar flow. Ag and Co were each detected in their own optimized conditions. Analytical performance of the system was evaluated in connection with a selected pixel number, and spectral correction was used to eliminate NO absortion bands interference in Zn detection. Detection limits were in the range of 1.5-18 μgL-1 for Ag, Cu, Cd and Zn, whereas sensitivity was worst for Co (169 μgL-1) and Ni (586 μgL-1). Atomization in a quartza cell of Co and Ni volatile species, generated by an addition of sodium tetrahydroborate to an acidified solution of the analytes, was reported for the first time in this paper. Precision expressed as RSD (%) had values lower than 10% except for Ni. (Hide)

Three microalgal species (Dictyosphaerium chlorelloides (D.c.), Scenedesmus intermedius (S.i.) and Scenedesmus sp. (S.s.)) were encapsulated in silicate sol-gel matrices and the increase in the amount of chlorophyll fluorescence signal was used to quantify simazine. Influence of several parameters on the preparation of the sensing layers has been evaluated: effect of pH on sol-gel gelation time; effect of algae density on sensor response; influence of glycerol (%) on the membrane stability. Long term stability was also tested and the fluorescence signal from biosensors remained stable for at least 3 weeks. D.c. biosensor presented the lowest detection limits for simazine (3.6 microg L-1) and the broadest dynamic calibration range (19-860 microg L-1) with IC(50) 125+/-14 microg L-1. Biosensor was validated by HPLC with UV/DAD detection. The biosensor showed response to those herbicides that inhibit the photosynthesis at photosystem II (triazines: simazine, atrazine, propazine, terbuthylazine; urea based herbicides: linuron). However, no significant increases of fluorescence response was obtained for similar concentrations of 2,4-D (hormonal herbicide) or Cu(II). The combined use of two biosensors that use two different genotypes, sensitive and resistant to simazine, jointly allowed improving microalgae biosensor specificity. (Hide)

The capabilities of synthesized ionic imprinted polymer (IIP), originally prepared for Ni recognition/preconcentration from seawater, have been evaluated for other trace elements pre-concentration. The polymer has been synthesized by the precipitation polymerization technique using a ternary pre-polymerization complex formed by the template (Ni), the monomer (2-(diethylamino)ethylmethacrylate, DEM) and a non-vinylated chelating agent (8-hydroxyquinoline, 8-HQ). Since the complexing agent (8-HQ) is trapped into the polymeric matrix, but is not linked to the polymer chains, specific interactions between the functional groups (present in the monomer and the complexing agent) and other trace elements rather than Ni may occur. Results have shown that IIP offers imprinting properties for the template (Ni(II)) and also for Cu(II), Pb(II), Zn(II), AS(V) and Cd(II), with analytical recoveries close to 100% for all elements except for As(V) and Cd(II) (around 70%), whereas the non-imprinted polymer (NIP) did not show affinity for any trace element. In addition, the polymer does not interact with alkaline or alkaline-earth metals, so Na, K, Mg, and Ca from the seawater salt matrix could be effectively removed. Variables affecting the IIP-solid phase extraction (SPE) process (pH, load flow rate and concentration and volume of the eluting solution) were completely studied. Inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) have been used as multielement detectors. Acidified seawater samples must only be trated to fix an alkaline pH (8.5 ± 05) and passed through IIP-SPE cartridges. After seawater sample loading (250 mL), analytes were eluted with 2.5 mL of 2.0 M nitric acid, offering a pre-concentration factor of 100. Therefore, the limits of detection (LODs) of the method were 0.14, 0.15, 0.18 and 0.03 µgL-1, for Ni, Cu, Pb and Zn, respectively, for ICP-MS detection. Accuracy of the method was assessed by analyzing SLEW-3 (estuarine water), and TM-23.3 and TM-24 (lake water) certified reference materials. (Hide)

Raw edible seaweed harvested in the Galician coast (Northwestern Spain), including two red seaweed types (Dulse and Nori), three brown seaweed (Kombu, Wakame and Sea Spaghetti), one green seaweed (Sea Lettuce) and one microalgae (Spirulina platensis) were studied to assess trace elements bioavailability using an in vitro method (simulated gastric and intestinal digestion/dialysis). Similarly, a cooked seaweed sample (canned in brine) consisting of a mixture of two brown seaweed (Sea Spaghetti and Furbelows) and a derived product (Agar-Agar) from the red seaweed Gelidiumm sesquipedale, were also included in the study. The total trace element content as well as the non-dialyzable fractions was carried out after a microwave acid digestion of the seaweed samples by inductively coupled plasma-mass spectrometry (ICP-MS). The dialyzable fraction was determined without any pre-treatment by ICP-MS. PIPES buffer solution at a pH of 7.0 and dialysis membranes of 10kDa molecular weight cut off (MWCO) were used for intestinal digestion. Accuracy of the method was assessed by analyzing a NIES-09 certified reference material (Sargasso seaweed). The accuracy of the in vitro procedure was established by a mass balance study which led to good accuracy of the whole in vitro process, after statistical evaluation (95% confidence interval). The highest dialyzability percentages (100±0.2%) were obtained for Dulse in Mn and V. (Hide)

A method for determining a group of phtalate esters in pharmaceutical formulae used id parentenal nutrition samples (with and without vitamins) has been developed. The phthalic acis esters (PAEs) studied were dimethyl phthalate, diethyl phthalate, butyl benzyl phthalate, dibutyl phthalate, di-(2-ethylhexyl) phthalate, and dioctyl phthalate. This group of phthalates was determined by high performance liquid chromatography (HPLC) electrospray ionization-mass spectrometry, working in positive ion mode. The phthalates analyzed were extracted from the samples using hexane and sodium hydroxide. The hexane was then evaporated, and the compounds were redissolved in acetonitrile. The compounds were separated by HPLC working in gradient mode with acetonitrile-ultrapure water starting from 5% to 75% acetonitrile in 5min, followed by isocratic elution for 27 min. Standard calibration curves were linear for all the analytes over the concentration range 10-250 ųg L-1. The method was precise(with RSD from 3.3% to 12.9%) and sensitive . The proposed analytical method has been applied to the analysis of these compounds in different pharmaceutical formulae (with different composition) for parenteral nutritional samples in order to check the presence of phthalates and determine their concentration. (Hide)

A method was developed for total arsenic determination in seaweed samples by hydride generation (HG) coupled with atomic fluorescence spectrometry (AFS). Seaweed samples were digested by microwave heating using a mixture of nitric acid and hydrogen peroxide. The parameters relating to the hydride-generation were optimized, selecting as optimum concentration 1.25% (w/v) for NaBH4, and 0.75 M and 0.1 M for HCl used as a carrier and sample dilution solution respectively. The method was precise (with RSD% 10%), accurate (study of a certified reference material: 103.4 ±4.9 µg As g-1 vs a certified content: 115 ± 9 µg As g-1; recoveries between 104.6 and 105.0%) and sensitive (LOD 2. µg g-1 on a dry weight basis) The method was applied for total arsenic determination in several red seaweed (Nori and Dulse), brown seaweed (Wakame, Sea Spaghetti and Kombu), and green seaweed (Sea Lettuce). (Hide)

Major and trace elements in North Atlantic seaweed originating from Galicia (northwestern Spain) were detd. by using inductively coupled plasma-optical emission spectrometry (ICP-OES) (Ba, Ca, Cu, K, Mg, Mn, Na, Sr, and Zn), inductively coupled plasma-mass spectrometry (ICP-MS) (Br and I) and hydride generation-at. fluorescence spectrometry (HG-AFS) (As). Pattern recognition techniques were then used to classify the edible seaweed according to their type (red, brown, and green seaweed) and also their variety (Wakame, Fucus, Sea Spaghetti, Kombu, Dulse, Nori, and Sea Lettuce). Principal component anal. (PCA) and cluster anal. (CA) were used as exploratory techniques, and linear discriminant anal. (LDA) and soft independent modeling of class analogy (SIMCA) were used as classification procedures. In total, 12 elements were detd. in a range of 35 edible seaweed samples (20 brown seaweed, 10 red seaweed, 4 green seaweed, and 1 canned seaweed). Natural groupings of the samples (brown, red, and green types) were obsd. using PCA and CA (squared Euclidean distance between objects and Ward method as clustering procedure). The application of LDA gave correct assignation percentages of 100% for brown, red, and green types at a significance level of 5%. However, a satisfactory classification (recognition and prediction) using SIMCA was obtained only for red seaweed (100% of cases correctly classified), whereas percentages of 89 and 80% were obtained for brown seaweed for recognition (training set) and prediction (testing set), respectively. (Hide)

Partial least squares Fourier-transform IR (PLS-FTIR) models were developed for the quality assessment of estuarine sediments through the evaluation of several physico-chem. parameters. Models were based on the chemometric treatment of attenuated total reflection (ATR) spectra directly obtained from samples previously lyophilized and sieved through a lower than 63 μm grid. Spectra were scanned from 3997 to 523 cm-1, averaging 36 scans per spectrum with a nominal resoln. of 8 cm-1. Models were built using ref. data obtained for sediment samples collected from Ria de Arousa estuary. Hierarchical cluster classification of sediment ATR spectra was employed for the establishment of the independent calibration and validation sample sets. Several parameters, like trace element content (Sn, Pb, Cd, As, Sb and total Cr and also acid sol., reducible and oxidizable Cr fractions), elemental compn. (carbon (C), nitrogen (N) and hydrogen (H) content), pH, redox potential (Eh), together with the amt. of fulvic and humic acids, were evaluated. Residual predictive deviation (RPD) values ranging from 1.79 to 2.28 were obtained for all trace elements with the exception of Pb, which exhibited a RPD value of 1.5, similar to those obtained for the different extractable fractions of Cr. Regarding the elemental anal., excellent RPD values were also obtained for C and N, but for H only adequate values for screening purposes were achieved. Prediction errors for pH and Eh were 0.13 units and 30 mV, resp., thus indicating the good prediction capabilities of the method. For humic substances, excellent results were obtained for humic acids when compared with fulvic ones. In short, direct ART-FTIR measurements on solid sediments allow a rapid screening of many components of sediments and quant. data of the main physico-chem. parameters. (Hide)

Chromium is an estuarine contaminant due to its industrial applications like leather tanning, dyeing or chromium plating. The most common explanation about the presence of this metal is the frequent estuarine spill, particularly in ecosystems like rivers, estuaries and coasts near anthropogenic activities. The purpose of this study is the investigation of the distribution and evolution of chromium in sediments of the surface layer of an estuary, detg. directly the total content by electrothermal at. absorption spectroscopy (ETAAS) using slurries. Results were correlated with the environmental conditions and the chem. of the metal to have a partial overview of the potential risk of chromium presence in the water column and the biota of the estuary. The pH values, oxidn.-redn. potential (ORP), elemental anal. (carbon, nitrogen and hydrogen content), and changes of total chromium with time were analyzed. This information was used to establish the environmental conditions where chromium appeared, was transported and was accumulated in the marine sediments collected following a time evolution of two years. (Hide)

A simple and fast sample pre-treatment method based on matrix solid-phase dispersion (MSPD) for isolating cocaine, benzoylecgonine (BZE), codeine, morphine and 6-monoacetylmorphine (6-MAM) from human hair was developed. The MSPD approach consisted of using alumina (1.80 g) as a dispersing agent and 0.6 M hydrochloric acid (4 mL) as an extg. solvent. For a fixed hair sample mass of 0.050 g, the alumina mass to sample mass ratio obtained was 36. A previously conditioned Oasis HLB cartridge (2 mL methanol, plus 2 mL ultrapure water, plus 1 mL of 0.2 M/0.2 M sodium hydroxide/boric acid buffer soln. at pH 9.2) was attached to the end of the MSPD syringe for on column clean-up of the hydrochloric acid ext. and for transferring the target compds. to a suitable solvent for gas chromatog. (GC) anal. Therefore, the adsorbed analytes were directly eluted from the Oasis HLB cartridges with 2 mL of 2% acetic acid in methanol before concn. by N2 stream evapn. and dry ext. derivatization with N-methyl-tert-butylsilyltrifluoroacetamide (BSTFA) and chlorotrimethylsilane (TMCS). The optimization/evaluation of all the factors affecting the MSPD and on column clean-up procedures has led to a fast sample treatment, and analytes extn. and pre-concn. can be finished in approx. 30 min. The developed method has been applied to eight hair samples from poli-drug abusers and measured analyte concns. have been found to be statistically similar (95% confidence interval) to those obtained after a conventional enzymic hydrolysis method (Pronase E).(Hide)

The feasibility of pressurized conditions to assist enzymic hydrolysis of seafood tissues for arsenic speciation was novelty studied. A simultaneous in situ (in cell) clean-up procedure was also optimized, which speeds up the whole sample treatment. Arsenic species (As(III), MMA, DMA, As(V), AsB and AsC) were released from dried seafood tissues using pepsin as a protease, and the arsenic species were sepd./quantified by anion exchange high performance liq. chromatog. (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Variables inherent to the enzymic activity (pH, temp. and ionic strength), the amt. of enzyme (pepsin), and factors affecting pressurization (pressure, static time, no. of cycles and amt. of dispersing agent, C-18) were fully evaluated. Pressurized assisted enzymic hydrolysis (PAEH) with pepsin can be finished after few minutes (two cycles of 2 min each one plus 3 min to reach the hydrolysis temp. of 50 °C). A total sample solubilization is not achieved after the procedure, however it is efficient enough for breaking down certain bonds of bio-mols. and for releasing arsenic species. The developed method was found to be precise (RSDs lower than 6% for As(III), DMA and As(V); and 3% for AsB) and sensitive (LOQs of 18.1, 36.2, 35.7, 28.6, 20.6 and 22.5 ng/g for As(III), MMA, DMA, As(V), AsB and AsC, resp.). The optimized methodol. was successfully applied to different certified ref. materials (DORM-2 and BCR 627) which offer certified AsB and DMA contents, and also to different seafood products (mollusks, white fishes and cold water fishes). (Hide)

Test methods are needed to monitor Cu concentrations in reservoirs and water supplies. Dictyosphaerium chlorelloides (Chlorophyta) cells were immobilized in a silicate sol–gel and the toxic effects of Cu(II) were examined using different techniques: fluorescence measurements (using a spectrofluorometer with an optic fiber coupled to a flow cell or a 96-well-plate reader) or by Pulse Amplitude Modulation (PAM) parameters using a portable instrument and the pulse saturation method. Fm′ and qN were the most sensitive indicator parameters when performing Cu analysis in water. D. chlorelloides PAM biosensor presented a detection limit of 0.6 mg l−1 for Cu(II), within the limits to establish if Cu concentrations exceeded regulatory levels. Moreover, a 1.9 mg Cu l−1 (30 μM) resistant strain of the D. chlorelloides microalgae was produced in order to obtain more selectivity on the metal determination. (Hide)

We investigated the reaction of Pb2+, PbMe22+ and PbPh22+ with 3-(phenyl)-2-sulfanylpropenoic acid (H(2)pspa) to give the complexes [Pb(pspa)], [PbMe2(pspa)], [pbPh(2)(pspa)], [HQ](2)(Pb(pspa)(2)] and [HQ[(2)[PbPh2(pspa)(2)] (HQ = diisopropylammonium), which were characterized by IR and NMR (H-1, C-13 and Pb-207) spectroscopy and by fast atom bombardment (FAB) spectrometry. The structures of [PbMe2(pspa)], [PbPh2(pspa)], [PbPh2(pspa)(dmso)]center dot dmso and [HQ[(2)[(PbPh2(pspa)(2)] are interesting examples of unexplored Pb coordination kernels and supramolecular association. Pig renal proximal tubule LLC-PK1 culture cells were used to determine in vitro the effect of the pretreatment with H(2)pspa (alone or combined with vitamin B-6) and [HQ](2)(Zn(pspa)(2)] on the cytotoxicity of PbMe22+ and PbPh22+ by comparing the results with those of meso-2,3-dimercaptosuccinic acid (dmsa). The results show that the cell viability was scarcely affected by these agents. The ability of these reagents to decorporate lead was investigated in vivo by analysing the lead levels in the liver, kidney, brain and blood. In the case of the dimethyl derivative, and under certain protocols, undesirable effects such as an increase in brain and liver lead levels were detected. These increases were not detected when the diphenyl derivative was assayed but in this case a positive effect was not identified either. The blood lead levels also increased in the case of the dimethyl derivative and the activity of delta-ALAD was significantly recovered upon treatment with vitamin B-6 or H(2)pspa; neither the blood lead levels nor the delta-ALAD activity was modified in the case of the diphenyl derivative. (Hide)

Cu, Ni, Pb, Mn, Sn, Fe, Al and Zn in surface and deep seawater samples from Ría de Arousa estuary (Galicia, north-western Spain) collected before and after the Prestige spillage were determined. Data were then used to evaluate the impact of the Prestige accident in the Ría de Arousa by applying principal component analysis (PCA) and cluster analysis (CA). Surface water from Sar River and Ulla River was also analysed for the same elements. Determinations were performed by inductively coupled plasma–optical emission spectrometry (ICP–OES) after solid phase extraction (SPE) of element-8-hydroxyquinoline complexes onto commercial C18 cartridges. The highest concentrations were found in sampling stations along Ulla River, while Al, Fe and Sn offered the highest values in surface and deep seawater from the inner part of the estuary, area where the main villages and sport harbours are located. PCA and CA have shown an independent group formed by surface seawater from the East margin of the mouth of the estuary collected after the Prestige oil spill. However, independent groups were not observed when using deep seawater data, and the effect of the Prestige accident appears to be less evident.(Hide)

The BCR (the Community Bureau of Reference) of the European Union sequential extraction scheme for metal partitioning in estuarine sediments has been accelerated by using a matrix solid phase dispersion (MSPD) approach. The MSPD assisted BCR procedure consists of passing the extractants proposed by conventional BCR protocol (0.11 M acetic acid, 0.1 M hydroxylammonium chloride and 8.8 M hydrogen peroxide plus 1 M ammonium acetate) through the dispersed sample packaged inside a disposable syringe. Different silica-, magnesium- and aluminium-based materials were tested as dispersing agents and sea sand was found to offer the best performances. Variables for assisting the three stages of the BCR protocol were optimized, and accurate results were obtained when assisting the first and the third stages (exchangeable and oxidizable fractions, respectively). However, lack of accuracy was observed when assisting the second step (reducible fraction) and this result agrees with most of the assisted BCR procedures for which extracting the reducible fraction is the most troublesome stage. The organic matter oxidation (third stage) was successfully assisted by passing hydrogen peroxide at 50 °C through the dispersed sample inside de syringe just before passing ammonium acetate. Therefore, the time-consuming and unsafe conventional organic matter oxidation processes, commonly performed even for microwave/ultrasounds assisted BCR procedures, are totally avoided. Inductively coupled plasma-mass spectrometry (ICP-MS) was used as a selective detector. The target elements were Cd, Co, Cr, Mn, Ni, Sr and Zn (first stage), Cd, Co and Ni (second stage), and Co, Cr, Mn, Ni, Sr and Zn (third stage). Repeatability of the method (n = 7) was good, and RSDs values of 9, 10, 10, 8, 8, 3 and 8% was obtained for Cd, Co, Cr, Mn, Ni, Sr and Zn, respectively (first stage); 10, 9 and 9% for Cd, Co and Ni, respectively (second stage); and 6, 2, 3, 4, 7 and 9% Co, Cr, Mn, Ni, Sr and Zn, respectively (third stage). The procedure was also validated by analysing two certified reference materials (CRM 601 and CRM 701). Good accuracy was obtained for the target elements extracted at the first stage: Cd (4.0 ± 0.1 and 7.3 ± 0.09 μg g−1 in CRM 601 and CRM 701, respectively), Cr (0.36 ± 0.008 and 2.21 ± 0.08 μg g−1 in CRM 601 and CRM 701, respectively), Ni (8.0 ± 0.3 and 15.4 ± 0.3 μg g−1 in CRM 601 and CRM 701, respectively) and Zn (262 ± 3 and 203 ± 3 μg g−1 in CRM 601 and CRM 701, respectively). Also, good accuracy was observed for elements extracted at the third step: Cd (1.8 ± 0.09 and 0.29 ± 0.03 μg g−1 in CRM 601 and CRM 701, respectively), Cr (145 ± 4 μg g−1 in CRM 701), Ni (8.2 ± 0.7 and 15.1 ± 0.5 μg g−1 in CRM 601 and CRM 701, respectively) and Zn (45 ± 0.7 μg g−1 in CRM 701). (Hide)

This paper presents a temptative work dealing with the possibilities of using GFAAS on speciation analysis purposes of antimony species-namely, Sb(III) and Sb(V)-in presence of three different complexing reagents (DDC, APDC and TTA). When using TTA, both antimony species can be analyzed setting 800 and 1700 to 1800 degrees C as pyrolysis and atomization temperatures, respectively. However, the great differences detected between the values of the signals recorded for Sb(V) and for Sb(III) must be highlighted. Such differences suggest dissimilar sensitivities for both species, that are applied on speciation analysis purposes. (Hide)

A method for determining a group of phthalic esters (PAEs) in physiological saline solutions has been developed. The PAEs studied were dimethyl phthalate, diethyl phthalate, butyl benzyl phthalate and dibutyl phthalate. These groups of phthalates were determined by liquid chromatography-electrospray ionization-tandem mass spectrometry, working in positive ion mode. The compounds were separated by liquid chromatography working in gradient mode with acetonitrile-ultrapure water as a mobile phase. The separation was performed starting with 5% of acetonitrile and increasing to 75% in 5 min, followed by isocratic elution for 8 min. The method was precise (with relative standard deviation (RSD) from 1.0 to 6.8%) and sensitive, with LODs of 0.05, 0.38, 0.05 and 0.82 mu g L(-1) for DMP, DEP. BBP and DBP, respectively. The proposed analytical method has been applied to determine these compounds in different physiological saline solutions commercialized in plastic bottles. (Hide)

In-vivo and in-vitro gastrointestinal (GI) extractions, also known as oral bioaccessibility and bioavailability, are important approaches to assess chemical risk to humans. We give an overview of in-vivo and in-vitro bioaccessibility and bioavailability assays for testing arsenic, selenium and mercury (As, Se and Hg) species from food samples. We critically evaluate the parameters affecting in-vivo and in-vitro processes. In addition, we consider the effect of cooking food on bioaccessibility and bioavailability, and stability and transformation, of species during in-vivo or in-vitro processes. The bioaccessibility and bioavailability of As, Se and Hg species are affected by the sample matrix, cooking food and the experimental conditions applied (gastric and intestinal pH, incubation temperature and residence time). Regarding species degradation and transformation during in-vitro procedures, good stability has been observed for most As species, except for certain arsenosugars. Important transformations during in-vitro processes have been reported for Se species [e.g., conversion of gamma-glu-Se-MeSeCys to Se-MeSeCys, and organic Se species (MeSeCys, SeCys2 and Se Met) degradation to inorganic Se]. Finally, we summarize speciation and detection conditions for As, Se and Hg speciation, and quality control to assure reliable measurements. (Hide)

Different types of edible seaweeds (Kombu, Wakame, Non and Sea Lettuce) harvested in the Galician coast (Northwestern Spain) were analyzed for total arsenic quantification before and after being cooked following manufacturer's instructions. Furthermore, the total arsenic in the bioaccessible fraction obtained after simulating a human digestion by an in vitro process was determined in those raw and cooked seaweeds. The detection of the target element was performed by inductively coupled plasma-mass spectrometry (ICP-MS) which was equipped with a collision cell to avoid polyatomic interferences. Piperazine-NN-bis (2-ethane-sulfonic acid) disodium (PIPES) buffer solution at a pH of 7.0 and dialysis membranes of 10 kDa molecular weight cut-off (MWCO) were used for intestinal digestion. Accuracy of the method was assessed by analyzing a BCR-279 certified reference material. The accuracy of the in vitro procedures was established by a mass balance study for Nori and Sea Lettuce which led to good accuracy of the whole in vitro process, after statistical evaluation (95% confidence interval). Results showed that the effect of cooking seaweed causes the removal of the element into the cooking water. Dialyzability percentages found in raw seaweed samples were comparable to those found in cooked seaweed, except in the case of Sea Lettuce sample for which a lower dialyzability percentage was found when it was cooked. (Hide)

Introduction: Exposure to lead and cadmium is a public health problem due to the broad exposure to these toxic substances among the general population. The objective of this study is to determine blood lead and cadmium concentrations in a working population drawn from six university hospitals in Madrid, Getafe, Cartagena, Santiago de Compostela, Santander and Palma de Mallorca (Spain) and to identify associated factors. Materials and methods: 951 individuals participated in the study and were administered the standardized PESA (R) questionnaire regarding exposure to lead and cadmium. The blood lead and cadmium concentrations were measured by electrothermal atomization atomic absorption spectrometry with Zeeman background correction in Perkin-Elmer spectrometers, guaranteeing the transferability of the results. Results: The median overall blood lead concentration was: 1.6 mu g/dL (IQR: 0.9-2.7) and that of cadmium was: 0.21 mu g/L (IQR: 0.10-0.50). There were significant differences in lead levels between men (2 mu g/dL) and women (1.5 mu g/dL), postmenopausal (2.6 mu g/dL) and premenopausal women (1.1 mu g/dL), and between participants who cooked in earthenware (2.1 mu g/dL) and those who did not (1.5 mu g/dL). The median of cadmium in women (0.24 mu g/L) was higher than in men (0.11 mu g/L) and was also higher in subjects who smoked (0.70 mu g/L) than in non-smokers (0.13 mu g/L). Conclusions: A reduction in blood lead and cadmium levels was observed with respect to previous studies carried out in Spain. Nevertheless, the results suggest there are certain factors which increase risk such as age, gender, menopause, age of housing, cooking in lead-glazed earthenware and exposure to cigarette smoke. (Hide)

A method is proposed for the determination of antimony in mussels by slurry sampling-GFAAS, using 25.0 mu g mL(-1) each of palladium nitrate and magnesium nitrate as the chemical modifier. The best pyrolysis and atomization temperatures were found to be 1300 degrees C and 1700 degrees C, respectively. Due to the matrix effects observed, the standard additions method had to be applied.The sample LOD and LOQ obtained was 16 and 56 mu g kg(-1), respectively. The mean analytical recovery of the method was 96.2% and the method exhibits good precision. Real mussel samples collected in the estuary Ria de Arosa, in Galicia (Northwestern Spain) were analyzed. (Hide)

An on-line flow injection sorption preconcencentration in a knotted reactor coupled with electrothermal atomic absorption spectrometry (FI-KR-ETAAS) has been developed to determine chromium(VI) in seawater samples. The on-line complex formation between Cr(VI) and ammoniumpirrolidindithiocarbamate (APDC) was performed and the complex retained on the inner wall of the KR. Variables affecting the sorption preconcentration process, such as pH, APDC amount, load flow rate, preconcentration time, concentration and volume of washing solution, KR length, elution volume, and interferences, were studied.The complex was eluted with 40 mu L of ethanol and introduced directly into the graphite furnace. A preconcentration factor of 31 was obtained. The detection limit (3SD) was 7 ng L-1. The precision (RSD n = 11) was 4.4% at 0.2 µg L-1, and the recovery was 99.3 ± 1.70%. The method was applied to the Cr(VI) determination in seawater samples from the Ria de Arousa Estuarine in Galicia (Northwestern Spain), resulting in Cr(VI) concentrations ranging from 0.03 - 0.09 µg L-1.(Hide)

A fast and simple method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been applied to identify and quantify four phthalic acid esters (PAEs) in different contact lens cleaning solutions. A migration study of these compounds from contact lenses has also been performed. The PAEs studied were dimethyl phthalate, diethyl phthalate, butyl benzyl phthalate and dibutyl phthalate. The migration of PAEs from contact lenses was performed by suspending each contact lens in an artificial tear solution at 37 degrees C and shaking it at 130 rpm for 24 h. The purpose of this study was to determine a possible migration of these compounds to the eyes as a result of the use of contact lenses and their cleaning solutions. The method was precise (with relative standard deviation (RSD) from 2.2 to 11.9%). It was also sensitive, with LODs of 0.03, 0.19, 0.31 and 2.62 mu g L-1 for DMP, DEP, BBP and DBP respectively. The results obtained confirm the presence of these substances in some types of contact lens cleaning solutions. Furthermore. DBP and BBP were liberated from the contact lenses during the migration study. (Hide)

A mercury analyzer (Model SMS 100) was evaluated for the direct determination of mercury in whole human blood samples. The instrument is based on sample combustion in an oxygen-rich furnace, elimination of interferences in a catalytic furnace, mercury concentration by amalgamation with gold, and the release of mercury vapor and its transport in a stream of oxygen to the measurement cell. Mercury determination is performed by atomic absorption spectrometry at 253.7 nm. In order to obtain complete combustion of the blood sample without loss of mercury, all operating conditions were optimized. The temperatures and times of the combustion step were critical to avoid spluttering of the sample. It was found that the samples of whole human blood, the certified reference material of human blood, and the aqueous standards showed different behavior in this step. The optimized condition for the combustion step was 650 degrees C for 60 seconds. The temperatures and times for the other steps were also optimized. The calibration and the analytical performance of the method were also studied. The detection limit obtained for mercury was 0.02 ng, and the relative standard deviations were between 1.1 and 3.2%. The proposed method is an interesting approach to the determination of mercury in whole human blood samples, because sample dissolution with wet digestion methods is not necessary, resulting in the ability to analyze an important number (approximately 7) of samples per hour.(Hide)

A review of recent literature focused on iodine determination/speciation in environmental, biological and clinical materials is provided. The review covers the different sample pre-treatments to extract total iodine, as well as specific iodinated forms, and the most used analytical techniques for assessing total iodine (cathodic stripping voltammetry, differential pulse voltammetry, neutron activation analysis, catalytic spectrophotometry, and atomic spectrometric techniques, mainly inductively coupled plasma-mass spectrometry) and iodine speciation (nonchromatographic methods, and mainly high performance liquid chromatography, gas chromatography and capillary electrophoresis coupled to electrochemical, UV spectrophotometric and mass spectrometric detection).(Hide)

Enzymatic hydrolysis of seafood materials for isolating arsenic species (As(III), As(V), DMA and AsB) has been successfully performed by assisting the procedure with ultrasound energy (35 kHz) supplied by an ultrasound water-bath. The use of pepsin, as a proteolytic enzyme, under optimized operating conditions (pH 3.0, temperature 40 degrees C, enzyme to sample ratio of 0.3) led to an efficient assistance of the enzymatic process in a short period of time (from 4.0 to 30 mm). The enzymatic extract was then subjected to a clean-up procedure based on ENVI-Carb (TM) solid phase extraction (SPE). An optimized anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) permitted the fast separation (less than 15 min) of six different arsenic species (arsenite, As(III); arsenate, As(V); dimethylarsinic acid, DMA; and arsenobetaine. AsB; as well as monomethylarsonic acid, MMA; and arsenocholine. AsC) in a single run. Relative standard deviations (n = 11) of the over-all procedure were 7% for AsB and DMA, 11% for As(III) and 9% for MMA. HPLC-ICPMS determinations were performed using aqueous calibrations covering arsenic concentrations of 0, 5, 10, 25, 100 and 200 µg L-1 (expressed as arsenic) for As(III), As(V), MMA, DMA and AsC; and 0, 125, 250, 500, 750, 1000 and 2000 µg L-1 (expressed as arsenic) for AsB. Germanium (514) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 96 to 105% (enzymatic digests spiked with low target concentrations), from 97 to 104% (enzymatic digests spiked with intermediate target concentrations), and from 98 to 103% (enzymatic digests spiked with high target concentrations). The developed method was successfully applied to two certified reference materials (CRMs), DORM-2 and BCR 627, which offer certified AsB and DMA contents, and also to different seafood samples (mollusks, white fish and cold water fish). Good agreement between certified and found AsB concentrations was achieved when analyzing both CRMs; and also, between certified and found DMA concentrations in BCR 627. In addition, the sum of the different arsenic species concentrations found in most of the analyzed samples was statistically similar to the assessed total arsenic concentrations after a total sample matrix decomposition treatment. (Hide)

A fast and highly sensitive electrospray ionization tandem mass spectrometry (ESI-MS/MS) method has been developed for the simultaneous determination of morphine, 6-methylacetylmorphine (6-MAM), codeine, cocaine and benzoylecgonine (BZE) in hair from drug abusers. Pulverized hair samples were subjected to an optimized matrix solid phase dispersion (MSPD) procedure with alumina, followed by diluted hydrochloric acid elution on column solid-phase extraction (SPE) clean-up/pre-concentration. Alternatively, samples were also subjected to an optimized ultrasound assisted enzymatic hydrolysis (USEH) with Pronase E, followed by an off-line SPE clean up/pre-concentration procedure. Positive electrospray ionization and multiple reaction monitoring (MRM) with one precursor ion/product ion transition were used for the identification and quantification (deuterated analogues of each target as internal standards) of each analyte. The chromatographic pump and the autosampler were used for injecting the standards and the hair extracts (20 mu) as a flow injection analysis mode. The highest sensitivity was achieved when delivering the targets with an acetonitrile/water/formic acid (80/19.875/0.125) mixture. The limits of detection of the method were 39.2, 4.4, 6.8, 7.0 and 7.4 ng g(-1) for morphine, 6-MAM, codeine, cocaine and BZE, respectively. Relative standard deviations of intra- and inter-day precision were lower than 9 and 12%, respectively; whereas, analytical recoveries ranged from 96 ± 5 to 106 ± 4%. The developed method (MSPD-ESI-MS/MS) was applied to different hair samples from polydrug abusers, and results were statistically compared to those obtained after a conventional gas chromatography-mass spectrometry (GC-MS) analysis and also after USEH and ESI-MS/MS or GC-MS determinations. (Hide)

A selective and sensitive method was developed for the separation and preconcentration of V(TV) and V(V) from seawater samples using a Chelex (R)-100 column. The influence of different parameters in the separation procedure such as pH of the sample, volume and concentration of extracting agents [NH3for V(V) and HNO3 for V(IV)], sample load flow rate and the eluting flow rate were studied. The separated species were then determined by electrothermal atomic absorption spectrometry (ETAAS).The limits of detection (LODs) and limits of quantification (LOQs) obtained using 50 mL of a seawater sample were 0.15 and 0.50 mu gL-1, respectively, for V(IV) and 0.10 and 0.33 µg L-1, respectively, for V(V). The recovery percentages were 95.3 ± 3% and 92.3 ± 3% for V(IV) and V(V), respectively. The method was applied to the V(IV) and V(V) determination in seawater samples from the Galician coast. The only species detected in the three samples studied was V(V), which is the most toxic form and was found in concentration levels ranging from 0.1 to 0.25 µg L-1. The method is simple, quick, and low cost.(Hide)

Raw edible seaweed harvested in the Galician coast (Northwester Spain), including two red seaweed types (Dulse and Non), three brown seaweed (Kombu, Wakame and Sea Spaghetti), one green seaweed (Sea Lettuce) and one microalgae (Spirulina platensis) were analysed for total iodine and total bromine, as well as for iodine and bromine bioavailability by in-vitro methods (simulated gastric and intestinal digestion/dialysis). Similarly, a cooked seaweed sample (canned in brine) consisting of a mixture of two brown seaweed (Sea Spaghetti and Furbelows) and a derived product (agar-agar) from the red seaweed Gelidiumm sesquipedale, were also included in the study. All measurements were carried out by inductively coupled plasma-mass spectrometry using tellurium and yttrium as internal standards for iodine and bromine, respectively. An optimised microwave assisted alkaline (TMAH) digestion procedure was used as sample pre-treatment for total iodine and bromine determinations, as well as for the determination of both elements in the non-dialyzable fractions. PIPES buffer solution at a pH of 7.0 and dialysis membranes of 10 kDa molecular weight cut off (MWCO) were used for the intestinal digestion. Accuracy of the method (total bromine and iodine determinations) was assessed by analysing a NIES-09 certified reference material. The accuracy of the in-vitro procedure was established by a mass-balance study which led, after statistical evaluation (95% confidence interval), good accuracy of the whole in-vitro process. The highest dialyzability bromine percentages (36 +/- 0.7% and 47 +/- 3.0%) were obtained for red seaweed (Dulse and Non), while higher dialyzability iodine was assessed for the brown seaweed (Kombu), around 17% +/- 0.7%. (Hide)

A UV-Vis spectrophotometric method was developed as a preliminary approach to the determination of antimony in water samples from a river that flows very close to an abandoned mining site. The analyte is complexed with ammonium pyrrolidinedithiocarbamate and absorbance of the complex is measured at 291.06 nm. The standard additions method is mandatory in view of the matrix effect observed, and the response is linear at least up to 9.3 mu g/mL of antimony. The sensitivity of the method is 2.609.10(-2) mL/mu g, whereas the limits of detection and quantification are, respectively, 0.2 and 0.6 mu g/mL. The repeatability, expressed as mean relative standard deviation of the measurements within the calibration range, is 2.0%, whereas the repeatability of the entire procedure is 0.3%. The mean analytical recovery within the calibration range was 102.6%. The method was successfully applied to river water samples. (Hide)

Anion exchange high performance liquid chromatography hyphenated with inductively coupled plasma-mass spectrometry has been novelly applied to assess inorganic (iodide and iodate) and organic (3-iodotyrosine - MIT, and 3,5-diiodotyrosine - DIT) iodine species in a single chromatographic run. The optimized operating conditions (Dionex IonPac AS7, gradient elution with 175 mM ammonium nitrate plus 15% (v/v) methanol, pH 3.8, as a mobile phase and flow rates within the 0.5-1.5 mL min(-1) range) have also been used to perform inorganic bromine speciation analysis (bromide and bromate). The developed method has been applied for determining the bio-available contents of iodine and bromine species in dialyzates from edible seaweed. Reverse phase high performance liquid chromatography (Zorbax Eclipse XDB-C8, gradient elution with 0.2% (m/m) acetic acid, and 0.2% (m/m) acetic acid in methanol, as mobile phases, and a constant flow rate of 0.75 mL min(-1)) also hyphenated with inductively coupled plasma-mass spectrometry was used to confirm the presence of organic iodine species (MIT and DIT) in the dialyzates. The verification of the presence of iodinated amino acids (MIT and DIT) in the extracts was also performed by reverse phase high performance liquid chromatography-electrospray ionization-mass spectrometry (LTQ Orbitrap). The developed methods have provided good repeatability (RSD values lower than 10% for both anion exchange and reverse phase separations) and analytical recoveries within the 90-105% range for all cases. The in vitro bio-availability method consisted of a simulated gastric and an intestinal digestion/dialysis (10 kDa molecular weight cut-off - MWCO) two-stage procedure. Iodide and MIT were the main bio-available species quantified, whereas bromide was the major bromine species found in the extracts(Hide)

A simulated in vitro digestion method for the dialyzability assessment of trace metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, V and Zn) from different seafood and edible seaweed has been developed. Inductively coupled plasma-mass spectrometry was used for metal determination in the dialyzates and in the samples after a microwave assisted acid digestion pre-treatment. Trueness of the procedure for total metal determination has been assessed by analyzing different certified reference materials (DORM-2, BCR 279 and NIES-09); whereas, trueness for the in vitro bioavailability method has been established after performing a mass balance study. Low (2.6-10.8%) and moderate (21.5-41.3%) dialyzability percentages have been found in seafood samples. However, high dialyzability percentages (30.0-74.7%) have been found in edible seaweeds. Linear and quadratic models have shown that the bioavailability of some metals exhibited good positive correlation with the carbohydrate content and also with the dietary fibre level. Protein content showed good negative correlation with the bioavailability of certain metals, whereas, moderate negative correlation was found with fat content. (Hide)

Edible seaweed consumption is a route of exposure to arsenic. However, little attention has been paid to estimate the bioaccessibility and/or bioavailability of arsenosugars in edible seaweed and their possible degradation products during gastrointestinal digestion. This work presents first use of combined inductively coupled plasma mass spectroscopy (ICP-MS) with electrospray ionization tandem mass spectrometry (ESI-MS/MS) with two-dimensional HPLC (size exclusion followed by anion exchange) to compare the qualitative and quantitative arsenosugars speciation of different edible seaweed with that of their bioavailable fraction as obtained using an in vitro gastrointestinal digestion procedure. Optimal extraction conditions for As species from four seaweed namely kombu, wakame, nori and sea lettuce were selected as a compromise between As extraction efficiency and preservation of compound identity. For most investigated samples, the use of ammonium acetate buffer as extractant and 1 h sonication in a water bath followed by HPLC-ICP-MS resulted in 40-61% of the total As to be found in the buffered aqueous extract, of which 86-110% was present as arsenosugars (glycerol sugar, phosphate sugar and sulfonate sugar for wakame and kombu and glycerol sugar and phosphate sugar for nori). The exception was sea lettuce, for which the arsenosugar fraction (glycerol sugar, phosphate sugar) only comprised 44% of the total extracted As. Interestingly, the ratio of arsenobetaine and dimethylarsinic acid to arsenosugars in sea lettuce extracts seemed higher than that for the rest of investigated samples. After in vitro gastrointestinal digestion, approximately 11-16% of the total As in the solid sample was found in the dialyzates with arsenosugars comprising 93-120% and 41% of the dialyzable As fraction for kombu, wakame, nori and sea lettuce, respectively. Moreover, the relative As species distribution in seaweed-buffered extracts and dialyzates was found to be very similar. Collection of specific fractions from the size-exclusion column to be analysed using anion-exchange HPLC-ESI-MS/MS enabled improved chromatographic selectivity, particularly for the less retained arsenosugar (glycerol sugar), facilitating confirmation of the presence of arsenosugars in seaweed extracts and dialyzates. Using this approach, the presence of arsenobetaine in sea lettuce samples was also confirmed. (Hide)

The feasibility of multi-walled carbon nanotubes (MWCNTs) for extracting dissolved organic matter (DOM) from seawater has been investigated. Solid phase extraction (SUE) operating in column and batch modes was used as an extractive technique, and the latter mode offered better performance. DOM adsorption was achieved using 60 mg of MWCNTs per each 250 mL of seawater subsample, working at pH 1.0 and under an orbital-horizontal shaking at 180 rpm and 25 degrees C for 4 h. DOM desorption from the MWCNTs support implied an orbital-horizontal shaking (180 rpm and 25 ºC) for 2. It using 10 mL of a 0.1 M sodium hydroxide solution (DOM determination), or using 20 mL of alkaline methanol (pH 10.0) for DOM fractionation by size exclusion chromatography (SEC) with UV detection at 205 nm. A Total Organic Carbon (TOC) analyzer with wet DOM oxidation (30% (m/v) potassium peroxodisulphate in 6.0 M phosphoric acid) under super critical conditions and with Non-Dispersive Infra Red (NDIR) for CO2 detection was used for DOM measurements. Calibration covered TOC concentrations within the 0.13-1000 mg L-1 range. The percentage of DOM retained in the MWCNTs support was dependent on the seawater sample, and it varied from 34 to 81%. This means that only the DOM of certain molecular weights is capable to interact with the SUE support. Various SEC columns, ranging from 100 to 7000 and from 500 to 15,000 Da (optimum separation range for peptides), were therefore used for DOM fractionation. Results have shown that DOM of low molecular weight is retained in the MWCNTs (fractions within the ranges of 125-1102 Da and 6.88-125 Da). (Hide)

The objective of this study is to evaluate the performance of two lab-made systems based on the Multimode Introduction System (MSIS) and the modified MSIS, to generate and introduce vapors of Ag, Cu, Cd, Cu, Ni, Sn, Zn, and also Au in the ICP torch. An univariate procedure was used to select the optimized working conditions (Ar flow, sample, reductant and waste flows, and reagent concentrations). Optimum conditions for working with modified MSIS were: nitric acid concentration 0.35M, 8-hydroxyquinoline concentration: 40 mgL-1, sodium borohydride concentration: 1.75% (w/v)+0.4% (w/v) NaOH, argon purge flow to sweep the vapors to the torch: 1.2Lmin(-1), sample flow and sodium borohydride flows: 2.3 L min-1; waste flow: 7.7mL min-1. For the optimum working conditions for lab-made MSIS in dual mode the concentration of 8-hydroxyquinoline was 225mg L-1, the Ar purge flow was 0.75 L min-1, and the conventional nebulization flow was 2.3 L min-1. The sensitivity obtained was higher using the lab-made MSIS than using the lab-made modified MSIS or a forced outlet gas-liquid separator. The limits of detection were better for Au, Cd, Sn than those obtained using conventional nebulization; the measurements were precise (RSDs≤5% in dual mode) and a good accuracy was obtained in the determination of Cd, Cu, Ni and Zn in a wastewater reference material using aqueous calibration and the lab-made MSIS in dual mode. (Hide)

A bioavailability study based on an in vitro dialyzability approach has been applied to assess the bio-available fractions of iodine and bromine species from edible seaweed. Iodide, iodate, 3-iodo-tyrosine (MIT), 3,5-diiodo-tyrosine (DIT), bromide and bromate were separated by anion exchange chromatography under a gradient elution mode (175mM ammonium nitrate plus 15% (v/v) methanol, pH 3.8, as a mobile phase, and flow rates within the 0.5-1.5mLmin(-1) range). Inductively coupled plasma-mass spectrometry (ICP-MS) was used as a selective detector for iodine ((127)I) and bromine ((79)Br). Low dialyzability ratios (within the 2.0-18% range) were found for iodine species; whereas, moderate dialyzability percentages (from 9.0 to 40%) were obtained for bromine species. Iodide and bromide were the major species found in the dialyzates from seaweed, although MIT and bromate were also found in the dialyzates from most of the seaweed samples analysed. However, DIT was only found in dialyzates from Wakame, Kombu, and NIES 09 (Sargasso) certified reference material; whereas, iodate was not found in any dialyzate. Iodine dialyzability was found to be dependent on the protein content (negative correlation), and on the carbohydrate and dietary fibre levels (positive correlation). However, bromine dialyzability was only dependent on the protein amount in seaweed (negative correlation) (Hide)

Bioavailability of total arsenic, toxic (arsenite, As(III); and arsenate, As(V)), and non-toxic (monomethylarsonic acid, MA; dimethylarsonic acid, DMA; arsenobetaine, AB; and arsenocholine, AC) arsenic species has been assessed in different raw seafood samples (white fish, cold water fish and molluscs) by using an in vitro model that combines simulated gastric and intestinal digestion/dialysis methods. Correlations between arsenic species bioavailability and seafood nutrient contents (fat and protein) have also been established. Total arsenic content in seafood samples, and dialyzable and non-dialyzable fractions, were analyzed by inductively coupled plasma - mass spectrometry (ICP-MS) after a microwave-assisted acid digestion treatment. The determination of the different arsenic species concentrations in the samples (after an optimised matrix solid phase dispersion (MSPD) approach) and in the dialyzable fraction was done by high performance liquid chromatography (HPLC) coupled to ICP-MS as a selective detector. Accuracy of the procedure (total arsenic determination) was assessed by analyzing DORM-2 and BCR-627 certified reference materials. The accuracy of the in vitro procedure was established through a mass-balance study. After statistical evaluation (95% confidence interval), good accuracy of the whole in vitro process, for total arsenic and for arsenic speciation, was observed. High dialyzability percentages for total arsenic and for arsenic species were found (i.e. from 84.6 +/- 1.7% to 106 +/- 2.6%). Bioavailability of arsenic exhibits a negative correlation with the fat content of the seafood. However, no correlation was observed between the bioavailable fraction of total arsenic and arsenic species and the protein content of the seafood studied. (Hide)

This study evaluated the main parameters affecting Ag, Au, Cd, Cu, Ni, Sn and Zn vapor generation using a lab-made concomitant metal analyzer (CMA) as a reaction chamber and gas–liquid separator. The modifier used in the reaction media was 8-hydroxyquinoline, and Inductively-Coupled Plasma Optical Emission Spectrometry was used as detection technique. The performance of the lab-made concomitant analyzer was compared with the performance of a continuous flow gas–liquid separator and of a cyclonic spray chamber. Standards were prepared in acid media and included 1 mg L−1 of Co as a catalyzer. The optimum concentrations of the reagents in the standards were: 450 mg L−1 of 8-hydroxyquinoline and 0.4 M nitric acid. The optimum concentration of sodium borohydride to generate the vapors was 2.25% (w/v) (prepared in 0.4% (w/v) NaOH). The volatile species were swept from the CMA to the torch by an argon flow of 0.6 mL min−1. The use of the CMA led to an improvement of the detection limits for some elements compared to conventional nebulization: 1.1 μg L−1 for Ag, 7.0 μg L−1 for Au and 4.3 μg L−1 for Sn. The limit of detection for Cu was 1.4 μg L−1 and for Ni 22.5 μg L−1. The direct mixing of the reagents on the spray chamber was not effective for Cd and Zn; a deviation of the linearity was observed for these elements. (Hide)

This study examines the effects of cooking on the bioavailability of As, Co, Cr, Cu, Fe, Ni, Se and Zn from edible seaweed. Four edible Galician seaweed (Kombu, Wakame, Sea lettuce and Nori) were cooked following the manufacture's recommendations. Cr, Fe, Co, Ni, Cu, Zn, As and Se were analyzed in raw and cooked seaweed after subjecting them to an acid digestion. Metals were released into the cooking water during the heat treatment with the exception of Ni and Zn in Kombu, Cr, Fe and Co in Wakame, and Zn in Nori, for which almost 100% was retained in the seaweed. An in vitro digestion method was developed to assess the bioavailability percentages of those metals in the cooked seaweed. Results suggested that Fe, Zn and Cu are not bioavailable for body functions in the studied matrices. Low dialyzability percentages were found for Cr, Co, Ni, As and Se, ranging between 1.0-16.0%, 3.4-27%, 8.2-12.9%, 9.7-21.0% and 14.6-61.3%, respectively. Kombu seaweed was used as a model to perform a mass balance study for evaluating the accuracy of the bioavailability study of cooked seaweed. Standard deviations homogeneity was corroborated by means of the Cochran's and Bartlett's statistical tests (p-values > 0.05). An ANOVA test was used to compare the mean metal concentrations between and within groups. P-values higher than 0.05 showed that there were no statistical differences, then the mass balance was adequate. Finally, the influence of the main food constituents (fat, protein, dietary fibre and carbohydrate) on the metal bioavailability was evaluated. Correlation matrix and multivariate analysis based on multiple linear regression indicated positive and negative correlation between the type of seaweed and metal concentration. (Hide)

Seafood, including edible seaweed, contains high levels of arsenic. The intake of seaweed is a route to arsenic exposure. Due to the different toxic behaviors among arsenic species, speciation studies are a matter of vital importance to evaluate possible health risks for consumers. Most seaweeds are ingested after a heat treatment and these thermal procedures could lead to a change in arsenic speciation. In this work an arsenic speciation study of four edible seaweeds (Kombu, Wakame, Nori and Sea Lettuce) after cooking has been performed by anion-exchange HPLC connected to an ICP-MS for arsenical detection. Speciation studies were also carried out in the cooking waters of those samples. Powdered cooked seaweed was subjected to an in-vitro digestion procedure by using Piperazine-NN-bis (2-ethane-sulfonic acid) disodium (PIPES), as a buffer solution at a pH of 7.0 and dialysis membranes of 10 kDa molecular weight cut off (MWCO). Dialyzable fractions were analyzed to identify the arsenic species that become bioavailable for human body functions. Total arsenic concentrations were found between 5.3 and 79.1 μg g− 1, 3.6–36.7 μg g− 1 and 1.8–54.3 μg g− 1 for raw and cooked seaweed, and cooking water, respectively. Total arsenic bioavailability percentages were 20%, 29%, 18% and 11% for cooked Kombu, Nori, Wakame and Sea lettuce, respectively. Results suggest that the heat treatment and the acidic environment and enzymes used in the in-vitro gastrointestinal digestion are not sufficient to produce a change in the arsenic species of the four seaweeds studied. Arsenic species are comparable in each seaweed before and after being cooked, their cooking water and dialysate. Arsenosugars were the main arsenic species found. As(III) species and arsenobetaine (AB) were only found in the Sea Lettuce sample. Glycerol sugar and sulfonate sugar were the most bioavailable species for cooked Kombu and Wakame. Phosphate sugar showed to be in highest proportion in the dialyzable fraction of Nori. AB and glycerol sugar became more bioavailable in the Sea Lettuce sample. (Hide)

The feasibility of pressurized hot water extraction (PHWE) has been novelty investigated to speed up water soluble halide species (bromide, Br(-); bromate, BrO(3)(-); iodide, I(-) and iodate, IO(3)(-)) leaching from atmospheric particulate matter (PM(10) and PM(2.5)). Total bromine and iodine and total water soluble bromine and iodine have been assessed by inductively coupled plasma-mass spectrometry (ICP-MS). Water-soluble bromine and iodine species were also measured by ICP-MS after anion exchange high performance liquid chromatography (HPLC). Variables inherent to the pressurized hot water extraction process (temperature, modifier concentration, static time, pressure, number of cycles and dispersing agent mass) were fully studied. Results showed that the pressurized leaching procedure can be performed in 9 min (5 min for pre-heating, 2 min of static time, 1 min of purge time, and 1 min of end relief time). The use of diluted acetic acid as a modifier did not improve the target recoveries. Dispersing agent (diatomaceous earth) was not needed, which reduces the time for filling the cells. Water-soluble halides were reached under the following extraction conditions: extraction temperature of 100 °C, pressure of 1500 psi, static time of 2 min and 1 extraction cycle. Optimized HPLC conditions consisted of an isocratic elution with 175 mM ammonium nitrate plus 15% (v/v) methanol as mobile phase (optimum flow rate of at 1.5 mL min(-1)). Analytical performances, such as limits of detection and quantification, repeatability and analytical recoveries of the over-all procedure have been established. Results obtained show water soluble halides accounted for approximately 20.9±1.3 and 11.8±0.6% of the total bromine and total iodine, respectively. A 79 and 89% of bromine and iodine was non-water soluble, which may be organic non-water soluble species. Br(-) and IO(3)(-) were found to be the major species, and they accounted for 100% of the total water-soluble bromine and iodine. (Hide)

Phosphatidylethanol (PEth) is a phospholipid which requires for its metabolic formation the presence of relatively high ethanol levels. PEth is thus a promising marker to quentify ethanol abuse. Dispersive liquid-liquid microextraction has become a popular technique because it is fast, inexpensive, easy to operate and consumes low volume of organic solvent. In this method, the appropriate mixture of extraction solvent (230 µL dichloromethane) and disperser solvent (630 µL acetone) are injected into the sample by syringe, rapidly. The liquid chromatography method using a reversed phase-C8 column and a negative ion mode electrospray ionization tandem mass spectrometry detection instrument was developed for the determination of small amounts of PEth that might be present in blood samples, using phosphatidylbutanol (PBut) as an internal standard. The sensitivity of detection obtained with tandem MS was better than that of previous methods. Good linearity was obtained for a range of LOQ-10 µg/mL for PEth, whereas all of the deviations in precision and accuracy were less than 15% except for the LLOQ, where it should not exceed 20%. A set of 50 blood samples were analyzed by such method and whole blood concentrations of PEth 16:0/18:1 ranged from LLOQ to 1.71 µg/mL. (Hide)

In-vitro bioavailability of Se has been assessed in different raw seafood and edible seaweed samples by using a simulated gastric and intestinal digestion/dialysis method. Correlations between Se bioavailability and food nutrients content have also been established. Low dialyzability percentages of Se have been found for fish and mollusk samples (6.7 ± 3.4 and 5.5 ± 2.4%, respectively). However, high dialyzability percentages (within the 66.7 ± 31.1% range) have been found for seaweed. Se bioavailability exhibits a positive correlation with the carbohydrate content and with the dietary fiber. Negative correlation was obtained with the protein content. Finally, no correlation has been observed between the bio-available fraction of Se and the fat content of the studied samples. (Hide)

Size exclusion chromatography (SEC) followed by anion exchange chromatography (AEC) hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) was applied for fractionating metals bound to marine dissolved organic matter (DOM). Surface seawater samples (100. L) were subjected to tangential flow ultrafiltration (10,000. Da cut off) for isolating and pre-concentrating dissolved large molecules. The isolated fraction (retentate) consisted of 1. L, which was further freeze-dried and re-dissolved to 250. mL with ultrapure water. After HI Trap desalting of the re-dissolved retentate, SEC with UV detection showed marine DOM ranging from 6.5. kDa (lower than the permeable volume of the SEC column) to 16. kDa. A further characterization of this fraction by AEC with UV detection revealed the existence of four groups of macromolecules exhibiting retention times of 2.3, 2.8, 4.5 and 14.0. min. AEC hyphenated with ICP-MS showed the presence of strontium and zinc in the first AE fraction isolated from the SEC fraction; while manganese was found to be bound to the second AE fraction. Cobalt was found to be bound to molecules comprising the third AE fraction. (Hide)

A micro-analytical method based on spotting urine samples (20µL) onto blood/urine spot collection cards followed by air-drying and extraction (dried urine spot, DUS) was developed and validated for the screening/confirmation assay of morphine, 6-methylacetylmorphine (6-MAM), codeine, cocaine and benzoylecgonine (BZE). Acetonitrile (3mL) was found to be a useful solvent for target extraction from DUSs under an orbital-horizontal stirring at 180rpm for 10min. Determinations were performed by direct electrospray ionization tandem mass spectrometry (ESI-MS/MS) under positive electrospray ionization conditions, and by using multiple reaction monitoring (MRM) with one precursor ion/product ion transition for the identification and quantification (deuterated analogs of each target as internal standards) of each analyte. The limits of detection of the method were 0.26, 0.94, 1.5, 1.1, and 2.0ngmL-1, for cocaine, BZE, codeine, morphine and 6-MAM, respectively; whereas, relative standard deviations of intra- and inter-day precision were lower than 8 and 11%, respectively, and intra- and inter-day analytical recoveries ranged from 94±4 to 105±3%. The small volume of urine required (20µL), combined with the simplicity of the analytical technique makes it a useful procedure for screening/quantifying drugs of abuse. The method was successfully applied to the analysis of urine from polydrug abusers. (Hide)

This study examines the effects of cooking on the bioavailability of As, Co, Cr, Cu, Fe, Ni, Se and Zn from edible seaweed. Four edible Galician seaweeds (Kombu, Wakame, Sea Lettuce and Nori) were cooked following the manufacturer's recommendations. Cr, Fe, Co, Ni, Cu, Zn, As and Se were analyzed in raw and cooked seaweeds after subjecting them to an acid digestion. The metals were released into the cooking water during the heat treatment with the exception of Ni and Zn in Kombu, Cr, Fe and Co in Wakame, and Zn in Nori, for which almost 100% was retained in the seaweed. An in vitro digestion method was developed to assess the bioavailability percentages of those metals in the cooked seaweed. Results suggested that Fe, Zn and Cu are not bioavailable for body functions in the studied matrices. Low dialyzability percentages were found for Cr, Co, Ni, As and Se, ranging from 1.0-16.0%, 3.4-27%, 8.2-12.9%, 9.7-21.0%, and 14.6-61.3%, respectively.Kombu seaweed was used as a model to perform a mass balance study for evaluating the accuracy of the bioavailability study of cooked seaweed. Standard deviation homogeneity was corroborated by means of the Cochran's and Bartlett's statistical tests (p-values 0.05). An ANOVA test was used to compare the mean metal concentrations between and within groups. p-Values higher than 0.05 showed that there were no statistical differences, and the mass balance was adequate.Finally, the influence of the main food constituents (fat, protein, dietary fiber and carbohydrate) on the metal bioavailability was evaluated. Correlation matrix and multivariate analysis based on multiple linear regression indicated positive and negative correlations between the type of seaweed and metal concentration. (Hide)

In vitro bioavailability of total selenium and selenium species from different raw seafood has been assessed by using a simulated gastric and intestinal digestion/dialysis method. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to assess total selenium contents after a microwave assisted acid digestion, and also to quantify total selenium in the dialyzable and non-dialyzable fractions. Selenium speciation in the dialyzates was assessed by high performance liquid chromatography (HPLC) coupled with ICP-MS detection. Major Se species (selenium methionine and oxidized selenium methionine) from dialyzate were identified and characterized by HPLC coupled to mass spectrometry (HPLC-MS). Selenocystine was detected at low concentrations while Se-(Methyl)selenocysteine and inorganic selenium species (selenite and selenate) were not detected in the dialyzate. Low bioavailability percentages for total selenium (6.69 ± 3.39 and 5.45 ± 2.44% for fish and mollusk samples, respectively) were obtained. Similar bioavailability percentages was achieved for total selenium as a sum of selenium species (selenocystine plus oxidized selenium methionine and selenium methionine, mainly). HPLC-MS data confirmed SeMet oxidation during the in vitro procedure. (Hide)

The combination of reverse phase high performance liquid chromatography (RP-HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) was used for the determination of monoiodotyrosine (MIT) and diiodotyrosine (DIT) in edible seaweed. A sample pre-treatment based on ultrasound assisted enzymatic hydrolysis was optimized for the extraction of these iodinated amino acids. Pancreatin was selected as the most adequate type of enzyme, and parameters affecting the extraction efficiency (pH, temperature, mass of enzyme and extraction time) were evaluated by univariate approaches. In addition, extractable inorganic iodine (iodide) was also quantified by anion exchange high performance liquid chromatography (AE-HPLC) coupled with ICP-MS. The proposed procedure offered limits of detection of 1.1 and 4.3ngg-1 for MIT and DIT, respectively. Total iodine contents in seaweed, as well as total iodine in enzymatic digests were measured by ICP-MS after microwave assisted alkaline digestion with tetramethylamonium hydroxide (TMAH) for total iodine assessment, and also by treating the pancreatin extracts (extractable total iodine assessment). The optimized procedure was successfully applied to five different types of edible seaweed. The highest total iodine content, and also the highest iodide levels, was found in the brown seaweed Kombu (6646±45µgg-1). Regarding iodinated amino acids, Nori (a red seaweed) was by far the one with the highest amount of both species (42±3 and 0.41±0.024µgg-1 for MIT and DIT, respectively). In general, MIT concentrations were much higher than the amounts of DIT, which suggests that iodine from iodinated proteins in seaweed is most likely bound in the form of MIT residues. (Hide)

Dissolved proteins were assessed in surface and deep seawater by two-dimensional isoelectric focusing (IEF) OFFGEL-lab-on-chip (LOC) electrophoresis after tangential flow ultrafiltration followed by centrifugal ultrafiltration (preconcentration factor of 3000). Dissolved protein isolation was performed by treating the ultrafiltrated retentate with cold acetone and also with chloroform as precipitating reagents. The best electrophoretic behavior of the isolated proteins was obtained after protein precipitation with chloroform before different rinsing stages for removing methanol and water interferences. Metals bound to proteins in the different OFFGEL fractions were assessed by inductively coupled plasma-optical emission spectrometry and electrothermal atomic absorption spectrometry, under optimized operating conditions. Experiments regarding stability of the metal-binding proteins [superoxide dismutase (SOD) and alcohol dehydrogenase (ADH) as protein models] showed the integrity of the Zn-binding SOD/ADH under the OFFGEL electrophoretic conditions. However, stability of Cu bound to SOD is not guaranteed. The first electrophoretic dimension (IEF OFFGEL) showed that dissolved proteins in surface seawater exhibit alkaline isoelectric points (pIs of 8.10 and 8.37) and also acid Ips (4.82, 5.13, 5.43, and 5.73), while LOC showed that the isolated proteins exhibit a spread molecular weight range (within 15 - 63 kDa); although, high molecular weights were the most commonly found. Regarding deep seawater, isolated proteins were of acid Ips (from 3.30 to 4.22) and low molecular weight (within the 21-24 kDa range). Elements such as Cd, Cu, Mn, and Ni were mainly associated with dissolved proteins of alkaline pIs in surface seawater, while Zn was mainly associated to proteins of acid pIs. However, only Cu and Mn were found to be bound to dissolved proteins of higher Ips in deep seawater, and the amount of Mn (from 68 to 84 µg L-1) was higher than that found in dissolved proteins in surface seawater (22.4 µg L-1) (Hide)

Studies based on laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) have been performed to assess metal bound to dissolved proteins and proteins from marine plankton after two-dimensional polyacrylamide gel electrophoresis (2D PAGE). Dissolved proteins were pre-concentrated from surface seawater (60. L) by tangential ultrafiltration with 10. kDa molecular weight cut-off (MWCO) membranes and further centrifugal ultrafiltration (10. kDa) before proteins isolation by methanol/chloroform/water precipitation. Proteins isolation from plankton was assessed after different trichloroacetic acid (TCA)/acetone and methanol washing stages, and further proteins extraction with a phenol solution. LA-ICP-MS analysis of the electrophoretic profiles obtained for dissolved proteins shows the presence of Cd, Cr, Cu, and Zn in five spots analyzed. These proteins exhibit quite similar molecular weights (within the 10-14. kDa range) and pIs (from 5.8 to 7.3). Cd, Cr, Cu, and Zn have also been found to be associated to proteins isolated from plankton samples. In this case, Cd has been found to be bound to proteins of quite different molecular weight (9, 13 and 22. kDa) and pIs (4.5, 5.2, 5.5, and 10). However, trace elements such as Cr, Cu and Zn appear to be mainly bound to plankton proteins of low molecular weight and variable pI. (Hide)

Extraction procedures for protein analysis from plankton samples were studied. OFFGEL electrophoresis combined with Lab-on-a-chip technology has been applied for protein analysis in plankton samples. BCR-414 (plankton) certified reference material from the European Commission was used to evaluate the protein extraction procedures. Three protein extraction procedures were studied: (1) by using Tris-HCl buffer containing a protease inhibitor cocktail, (2) urea/triton X-100 buffer extraction, and (3) using the phenol/sodium dodecyl sulphate method after different washing steps with 10% trichloroacetic acid/acetone solution and methanol. The pellet of proteins obtained was dried and then dissolved in the OFFGEL buffer. Proteins were separated according to their isoelectric points by OFFGEL electrophoresis. This separation was performed using 24 cm, pH 3-10 IPG Dry Strips. The proteins present in each liquid fraction (24 fractions) were separated according to their molecular weight using a microfluidic Lab-on-a-chip electrophoresis with the Protein 80 LabChip kit. This kit allows for the separation of proteins with a molecular weight ranging from 5 to 80 kDa. Taking into account the intensity and the number of the protein bands obtained, the protein extraction procedure using the phenol/sodium dodecyl sulphate after different wash steps with 10% trichloroacetic acid/acetone solution was selected. The developed method was applied for protein determination in a fresh marine plankton sample. The proteins found in this sample have a molecular weight ranging from 6.4 to 57.3 kDa, and the proteins with highest molecular weight were in the OFFGEL fractions with an isoelectric point ranging from 4.40 to 8.60. The concentration of proteins were calculated using external calibration with Bovine Serum Albumin, and the protein concentrations varied from 50.0 to 925.9 ng µL-1. (Hide)

A sample pre-treatment method based on blood spot collection filter cards was optimized as a means of using small volume samples for the screening and confirmation of cocaine and opiates abuse. Dried blood spots (DBSs) were prepared by dispersing 20 µL of whole blood specimens previously mixed with the internal standards (deuterated analogs of each target), and subjecting the whole DBS to extraction with 5 mL of methanol under orbital-horizontal shaking (180 rpm) for 10 min. Determinations were based on direct electrospray ionization tandem mass spectrometry (ESI-MS/MS) by injecting the re-dissolved methanol extract with the delivery solution (acetonitrile-water-formic acid, 80:19.875:0.125) at a flow rate of 60 µL min-1, and using multiple reaction monitoring (MRM) mode with the m/z (precursor ion)?m/z (product ion) transitions for acquisition. Matrix effect has been found to be statistically significant (Multiple Range Test) when assessing cocaine, BZE, codeine and morphine, and the use of the standard addition method (dispersion of whole blood previously mixed with standards onto the filter papers) was needed for accurate determinations. The developed DBS-ESI-MS/MS procedure offered good intra-day and inter-day precisions (lower than 10% and 12%, respectively), as well as good intra-day and inter-day accuracies (inter-day absolute recoveries, expressed as the mean analytical recovery over three target concentration levels, of 103%, 100%, 101%, 98% and 100% for cocaine, BZE, codeine, morphine and 6-MAM, respectively). The high sensitivity inherent to MS/MS determinations combined with the minimal dilution of sample allowed low limits of quantification for all targets, and the developed method results therefore adequate for cocaine and opiates screening and confirmation purposes. The procedure was finally applied to DBSs prepared from whole blood from polydrug abusers, and results were compared with those obtained after a conventional sample pretreatment method based on solid phase extraction for plasma specimens and gas chromatography-mass spectrometry (Hide)

A procedure based on two-dimensional size exclusion chromatography (SEC) and anion exchange chromatography (AEC) with UV (205nm) and ICP-MS detection was used to assess dissolved organic matter (DOM) and trace metals associated to DOM in surface seawater. Marine DOM was isolated by tangential ultrafiltration (UF) using two different polyethersulfone membranes exhibiting different molecular weight cut-off (MWCO), 3 and 10kDa. The procedures require a volume of seawater sample of 100L, and marine DOM of molecular weight higher than 3 and 10kDa (UF membranes of 3 and 10kDa MWCO) was pre-concentrated in 0.5L (retentate), which implies a pre-concentration factor of 200. Retentate fractions obtained after the different UF procedures were further desalted by using HI Trap desalting mini-columns before two-dimensional SEC/AEC. Apparent molecular weights of isolated compounds after SEC with UV detection ranged from 1.5kDa (close to the permeable volume of the SEC column fixed by injecting vitamin B12) to 16 and 22kDa (UF membranes of 3 and 10kDa MWCO, respectively). Further AEC/UV characterization of SEC fractions showed a large group of macromolecules eluted at 4.5min, and small signals at shorter retention times (2.5 and 3.5min). In addition, AEC experiments of the isolated SEC fractions when using 10kDa MWCO UF membranes showed a group of substances eluted at high retention times (13min). SEC hyphenation with ICP-MS proved the existence of several trace elements (Ni, Co, Cu, Zn, Mn, Mo and Sr) bound to the isolated marine DOM. Mass balance studies after analyzing the retentate and permeate fractions for trace elements indicate good recoveries (close to 100%) for elements such as Mo, Sr, Ba and Zn when performing the UF with both 3 and 10kDa MWCO membranes. However, recoveries from 36 to 81% were obtained for the remaining studied elements after either UF procedure. SEC-ICP-MS experiments showed percentages of metals bound to the isolated marine DOM ranging from 0.055 and 0.077% (Zn) to 4.1 10-4 and 1.4 10-4% (Sr). (Hide)

The possibility of assisting enzymatic hydrolysis (EH) procedures by sample disruption mechanisms inherent to matrix solid phase dispersion (MSPD) has been explored in the current study. EH of hair specimens from poly-drug abusers was assisted by dispersing/blending the sample (0.05g) with alumina (2.25g) before loading the dissolved enzyme (6mL of 1mgmL-1 Pronase E in 1.4M/1.4M Tris/HCl, pH 7.3) through the hair-alumina solid phase packaged inside a disposable MSPD syringe. The MSPD-EH method was developed, and it proved to offer quantitative results when isolating cocaine, benzoylecgonine (BZE), codeine, morphine and 6-monoacethylmorphine (6-MAM) from human hair samples. The procedure allows an on column clean-up/pre-concentration procedure of the isolated targets by attaching a previously conditioned Oasis HLB cartridge to the end of the MSPD syringe. The EH procedure of human hair with Pronase E can therefore be shortened to approximately 30min. Within this time, sample blending/dispersion, MSPD syringe package, elution (EH when dissolved Pronase E is passing through the sample-dispersant bed), and extract clean-up and target pre-concentration stages are achieved. Gas chromatography-mass spectrometry (GC-MS) was used for determining each target after elution from the Oasis HLB cartridges with 2mL of 2% (v/v) acetic acid in methanol, concentration by N2 stream evaporation, and dried extract derivatization with N-methyl-tert-butylsilyltrifluoroacetamide (BSTFA) and chlorotrimethylsilane (TMCS). The method was validated according to the guidance for bioanalytical method validation of the US Department of Health and Human Services, Food and Drug Administration. The simplicity of the proposed approach makes it a useful procedure for screening/quantifying drugs of abuse in hair specimens from poly-drug abusers (Hide)

Analytical methods for the determination of total arsenic and arsenic species (mainly As(III) and As(V)) in human scalp hair have been developed. Inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) coupled to ICP-MS have been used for total arsenic and arsenic species determination, respectively. The proposed methods include a "green", fast, high efficient and automated species leaching procedure by pressurized hot water extraction (PHWE). The operating parameters for PHWE including modifier concentration, extraction temperature, static time, extraction steps, pressure, mean particle size, diatomaceous earth (DE) mass/sample mass ratio and flush volume were studied using design of experiments (Plackett-Burman design PBD). Optimum condition implies a modifier concentration (acetic acid) of 150 mM and powdered hair samples fully mixed with diatomaceous earth (DE) as a dispersing agent at a DE mass/sample mass ratio of 5. The extraction has been carried out at 100 °C and at an extraction pressure of 1500 psi for 5 min in four extraction step. Under optimised conditions, limits of quantification of 7.0, 6.3 and 50.3 ng g-1 for total As, As(III) and As(V), respectively were achieved. Repeatability of the overall procedure (4.4, 7.2 and 2.1% for total As, As(III) and As(V), respectively) was achieved. The analysis of GBW-07601 (human hair) certified reference material was used for validation. The optimised method has been finally applied to several human scalp hair samples. (Hide)

An analytical approach providing an insight into speciation of iodine in water insoluble fraction of edible seaweed (Nori) was developed. The seaweed, harvested in the Galician coast (Northwestern Spain), contained 67.7±1.3 µg g-1 iodine of which 25% was water soluble and could be identifies as iodide. Extraction conditions of water insoluble residue using urea, NaOH, SDS and Triton X-100 were investigated. The protein pellets obtained in optimized conditions (after precipitation of urea extracts with acetone), were digested with trypsin and protease XIV. Size exclusion chromatography-ICP- MS of both enzymatic digests demonstrated the occurrence of iodoaminoacids putatively present in proteins. Intact proteins could be separated by gel electrophoresis after an additional extraction of the protein extract with phenol. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) with laser ablation ICP-MS detection of 127I indicated the presence of iodine in protein bands corresponding to molecular masses of 110 kDa, 40 kDa, 27 kDa, 20 kDa and 10 kDa. 2D IEF-SDS PAGE with laser ablation ICP-MS 127I imaging allowed the detection of 5 iodine containing protein spots in the alkaline pI range. (Hide)

Mass spectrometry (MS) techniques are commonly used for protein identification and further analysis of selected protein spots after high resolution 2-D electrophoresis. Complementary gel-free approaches have been developed during the last few years and have shown to be useful tools in modern proteomics. The development and application of various gel-free electrophoresis devices for performing protein fractionation according to the pI differences is therefore a topic of interest. This review describes the current state of isoelectric focusing (IEF) gel-free electrophoresis based on the Agilent offgel 3100 fractionator. The review includes, therefore, (i) an overview on IEF as well as other previous IEF gel-free electrophoresis developments; (ii) offgel fundamentals and future trends; (iii) advantages and disadvantages of current offgel procedures; (iv) requirements of isolated protein pellets for further offgel fractionation; (v) offgel fraction requirements to perform the second dimensional analysis by advance electrophoresis and chromatographic techniques; and (vi) effect of the offgel operating conditions on the stability of metal-protein complexes. (Hide)

A fast high performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) method for assessing 9-tetrahydrocannabinol (9-THC), cannabidiol (CBD) and cannabinol (CBN) in hair has been developed and validated. Hair samples were oven digested with 2.0M sodium hydroxide (100°C, 10min), and targets were further extracted by liquid-liquid extraction with hexane/ethyl acetate (9:1). A chromatographic run based on a gradient elution (0.1% (v/v) formic acid in acetonitrile and in ultrapure water) was performed in 5min. The limits of detection were 0.25, 0.21, and 0.22ngg-1, for 9-THC, CBN and CBD, respectively. The relative standard deviation of intra- and inter-day precision was lower than 4 and 7%, respectively, and intra- and inter-day analytical recoveries ranged from 95 and 106%, and 93 and 105%, respectively. The method was applied to hair samples collected from proven cannabis abusers. (Hide)

The objective of this work was to optimize the conditions for the simultaneous determination of Au, Cd, Cu, Ni, Zn, and Sn by VG-ICP-OES (vapor generation-inductively coupled plasma optical emission spectrometry) using diethyldithiocarbamate (DDTC) or o-phenanthroline as reaction media modifier. A univariate procedure was used to select the working conditions (Ar flow, flow rates for sample, reductant and waste, and reagent concentrations). The optimum nitric acid concentration was 0.4M when using o-phenanthroline or 0.5M when using DDTC. The modifier concentration was 3.5 mg/L (o-phenanthroline) or 0.005% (w/v) DDTC. The optimum sodium borohydride concentration was 2.24% (w/v) + 0.4% (w/v) NaOH, argon purge flow to sweep the vapors to the torch 0.7 L/min, sample to reductant ratio 1:1, sample flow and sodium borohydride flow 2.0 mL/min for o-phenanthroline and 1.5 for DDTC mL/min, and the waste flow rate 7.7 mL/min. The limits of detection were lower than those obtained using conventional nebulization, except for Cu and Ni. With DDTC, the best limits of detection were for Au (3.6 µg/L) and Cd (0.53 µg/L); whereas for o-phenanthroline, the best limits of detection were obtained for Au (3 7 µg/L), Cu (2.5 µg/L), Ni (4.9 µg/L), Sn (1.1 µg/L), and Zn (0.98 µg/L). These LODs were better than those obtained with 8-hydroxyquinoline in the same vapor generation system, except for Ni. The measurements were precise (RSDs 10% for Au, Cd, Ni, Sn, and Zn; for Cd: 11.0-11.4%). (Hide)

Gold nanoparticles are attractive as sensing materials because of their size and shape are related with their optical properties. The color change produced by the aggregation of functionalized AuNPs allows the detection of arsenic at low levels. A simple, cheap and fast analytical procedure to perform arsenic determination using functionalized gold nanoparticles (AuNPs) and VIS spectrometry as a detection technique is studied. Three different synthesis procedures to obtain the AuNPs and two different functionalization modes were studied. AuNPs functionalized with GSH-DTT-CYs-PDCA were selected as the most adequate. The correlation between the decrease in the absorbance signal and the arsenic concentration was good in the 2-20 µg l-1interval. Repeatability, expressed as average of RSD (%), obtained for the different arsenic concentrations studied was 0.6%. The average value of the analytical recovery was 99.7%. The detection and quantifications limits were 2.5 and 8.4 µg l-1 respectively. These limits are sufficient to detect World Health Organization's guideline value of 10 µg l-1. (Hide)

The objective of this research work was to develop a simple, highly sensitive and precise method for spectrophotometric determination of osmium(IV). O-Methylphenyl thiourea (OMPT) coordinates with osmium(IV) as a 1:1 (osmium(IV)-OMPT) complex in hydrochloric acid media (0.8 mol l-1). The novelty of the investigated method is instant complex formation at room temperature with no need of heating or standing. The complex is stable for more than 8 days. The method is applicable over a wide linearity range (up to 110 µg ml-1). A low reagent concentration is required (2 ml, 0.009 mol l-1 in ethanol). The complex exhibits maximum absorption in the range of wavelength 510-522 nm and 514 nm was selected for further study. The molar absorptivity was 1.864 × 103 l mol-1 cm-1, Sandell's sensitivity was 0.102 µg of osmium(IV) cm-2. Proposed method was successfully applied for separation and determination of osmium(IV) from binary and ternary synthetic mixtures containing associated metal ions. A scheme for mutual separation of osmium(IV), rhodium(III) and platinum(IV) is developed. (Hide)

A method for trace Cd and Pb determination in fresh fish samples by Electrothermal Atomic Absorption Spectrometry (ETAAS) has been developed. A preconcentration step was necessary due to the low levels of these elements in fresh fish samples. Solid phase extraction (SPE) using ionic imprinted polymers (IIPs) as an adsorbent was selected as the preconcentration technique. The IIPs were prepared via precipitation polymerization using 2-(diethylamino) ethyl metacrilate (DEM) as a monomer and 8-hydroxyquinoline as a complexating agent. The 2,2'-azobisisobutyronitrile (AIBN) and acetonitrile/toluene (3:1) mixture were used as initiator and porogen, respectively. A microwave assisted acid digestion procedure using nitric acid and hydrogen peroxide was applied for sample preparation.The experimental parameters for SPE extraction in column mode, such as pH of the digested sample, sample volume, load rate, and elution rate, have been optimized. The optimum pH for quantitative Cd and Pb retention was 8.5, and the elution was completed with 2mL of 2.0M nitric acid. Cadmium and lead concentrations in the acid extracts were determined by ETAAS using palladium and magnesium nitrates as a chemical modifier. The limits of detection (LODs) and limits of quantification (LOQs) obtained were 0.15 and 0.52µgL-1 for Cd determination, and 0.50 and 1.68µgL-1 respectively for Pb determination. Taking into account the mass of sample used and the preconcentration factor (12.5), the LODs obtained were 0.21 and 0.67ngg-1 for Cd and Pb respectively. These limits are adequate to determine Cd and Pb at levels lower than the maximum levels allowed in fresh marine products, by the European Union legislation. The optimized method was applied for Cd and Pb determination in different seafood samples, such as squid, hake, sardine, horse mackerel, grouper and gilthead bream, and it was possible to detect both metals in all samples. (Hide)

Mercury is an environmental toxicant that causes numerous adverse effects on human health and natural ecosystems. The factors that determine the existance of adverse effects, as well as their severity are, among others: the chemical form of mercury (elemental, inorganic, organic), dosis, age, period of exposure, pathways of exposure and environmental, nutritional and genetic factors. In the aquatic cycle of mercury, once it has been deposited, it is transformed into methylmercury due to the action of certain sulphate-reducing bacteria, which bioaccumulates in the aquatic organisms and moves into the food chain. The methylmercury content of large, long-lived fish such as swordfish, shark, tuna or marlin, is higher. Methylmercury binds to protein in fish and is therefore not eliminated by cleaning or cooking the fish. Fetuses and small children are more vulnerable to the neurotoxic effects of methylmercury from the consumption of contaminated fish. Methylmercury is absorbed in the gastrointestinal tract and crosses the blood-brain barrier and the placenta. The intake of certain dietary components such as polyunsaturated fatty acids, selenium, fiber, thiol compounds, certain phytochemicals and other nutrients can modify methylmercury bioaccesibility and its toxicity. Apart from environmental factors, genetic factors can influence mercury toxicity and explain part of the individual vulnerability. (Hide)

Mercury is an environmental toxicant that causes numerous adverse effects on human health and natural ecosystems. The factors that determine the existance of adverse effects, as well as their severity are, among others: the chemical form of mercury (elemental, inorganic, organic), dosis, age, period of exposure, pathways of exposure and environmental, nutritional and genetic factors. In the aquatic cycle of mercury, once it has been deposited, it is transformed into methylmercury due to the action of certain sulphate-reducing bacteria, which bioaccumulates in the aquatic organisms and moves into the food chain. The methylmercury content of large, long-lived fish such as swordfish, shark, tuna or marlin, is higher. Methylmercury binds to protein in fish and is therefore not eliminated by cleaning or cooking the fish. Fetuses and small children are more vulnerable to the neurotoxic effects of methylmercury from the consumption of contaminated fish. Methylmercury is absorbed in the gastrointestinal tract and crosses the blood-brain barrier and the placenta. The intake of certain dietary components such as polyunsaturated fatty acids, selenium, fiber, thiol compounds, certain phytochemicals and other nutrients can modify methylmercury bioaccesibility and its toxicity. Apart from environmental factors, genetic factors can influence mercury toxicity and explain part of the individual vulnerability. (Hide)

Objetivo: Desarrollar un polímero de impronta molecular para la determinación de metilmercurio en muestras de alimentos de origen marino.

Material y métodos: Se sintetizó un polímero de impronta molecular (MIP) que emplea fenobarbital como ligando no vinilado para unirse al metilmercurio. Se utilizó la técnica de polimerización por precipitación. El MIP sintetizado fue empleado para funcionalizar nanopartículas magnéticas con el fin de mejorar el proceso de extracción del metilmercurio de las muestras.

Resultados: El MIP con fenobarbital fue aplicado para la determinación de la concentración de metilmercurio en dos materiales de referencia de concentración certificada para el análisis de muestras de alimentos marinos (BCR-463, tejido de atún, y TORT-2, hepatopáncreas de langosta). Los valores de concentración experimentales obtenidos fueron de 3,04±0,16 µg/g y 0,152±0,013 µg/g respectivamente, coincidiendo con los valores certificados de forma estadísticamente significativa (test t, 95% confianza).

Conclusión:Se ha sintetizado un MIP para la determinación de la concentración de metilmercurio a bajas concentraciones en muestras de alimentos de origen marino. (Hide)

The feasibility of pressurized hot water extraction (PHWE) has been novelty investigated to speed up water soluble halide species (bromide, Br(-); bromate, BrO(3)(-); iodide, I(-) and iodate, IO(3)(-)) leaching from atmospheric particulate matter (PM(10) and PM(2.5)). Total bromine and iodine and total water soluble bromine and iodine have been assessed by inductively coupled plasma-mass spectrometry (ICP-MS). Water-soluble bromine and iodine species were also measured by ICP-MS after anion exchange high performance liquid chromatography (HPLC). Variables inherent to the pressurized hot water extraction process (temperature, modifier concentration, static time, pressure, number of cycles and dispersing agent mass) were fully studied. Results showed that the pressurized leaching procedure can be performed in 9 min (5 min for pre-heating, 2 min of static time, 1 min of purge time, and 1 min of end relief time). The use of diluted acetic acid as a modifier did not improve the target recoveries. Dispersing agent (diatomaceous earth) was not needed, which reduces the time for filling the cells. Water-soluble halides were reached under the following extraction conditions: extraction temperature of 100 °C, pressure of 1500 psi, static time of 2 min and 1 extraction cycle. Optimized HPLC conditions consisted of an isocratic elution with 175 mM ammonium nitrate plus 15% (v/v) methanol as mobile phase (optimum flow rate of at 1.5 mL min(-1)). Analytical performances, such as limits of detection and quantification, repeatability and analytical recoveries of the over-all procedure have been established. Results obtained show water soluble halides accounted for approximately 20.9±1.3 and 11.8±0.6% of the total bromine and total iodine, respectively. A 79 and 89% of bromine and iodine was non-water soluble, which may be organic non-water soluble species. Br(-) and IO(3)(-) were found to be the major species, and they accounted for 100% of the total water-soluble bromine and iodine. (Hide)

Mercury is an environmental toxicant that causes numerous adverse effects on human health and natural ecosystems. The factors that determine the existance of adverse effects, as well as their severity are, among others: the chemical form of mercury (elemental, inorganic, organic), dosis, age, period of exposure, pathways of exposure and environmental, nutritional and genetic factors. In the aquatic cycle of mercury, once it has been deposited, it is transformed into methylmercury due to the action of certain sulphate-reducing bacteria, which bioaccumulates in the aquatic organisms and moves into the food chain. The methylmercury content of large, long-lived fish such as swordfish, shark, tuna or marlin, is higher. Methylmercury binds to protein in fish and is therefore not eliminated by cleaning or cooking the fish. Fetuses and small children are more vulnerable to the neurotoxic effects of methylmercury from the consumption of contaminated fish. Methylmercury is absorbed in the gastrointestinal tract and crosses the blood-brain barrier and the placenta. The intake of certain dietary components such as polyunsaturated fatty acids, selenium, fiber, thiol compounds, certain phytochemicals and other nutrients can modify methylmercury bioaccesibility and its toxicity. Apart from environmental factors, genetic factors can influence mercury toxicity and explain part of the individual vulnerability. (Hide)

The beneficial effects of fish consumption in both children and adults are well known. However, the intake of methylmercury, mainly from contaminated fish and shellfish, can have adverse health effects. the study group on the prevention of exposure to methylmercury (GEPREM-Hg), made up of representatives from different Spanish scientific societies, has prepared a consensus document in a question and ans wer format, containing the group's main conclusions, recommendations and proposals. the objective of the document is to provide broader knowledge of factors associated with methylmercury exposure, its possible effects on health among the Spanish population, methods of analysis, interpretation of the results and economic costs, and to then set recommendations for fish and shellfish consumption. the group sees the merit of all initiatives aimed at reducing or prohibiting the use of mercury as well as the need to be aware of the results of contaminant analyses performed on fish and shellfish marketed in Spain. In addition, the group believes that biomonitoring systems should be set up in order to follow the evolution of methylmercury exposure in children and adults and perform studies designed to learn more about the possible health effects of concentrations found in the Spanish population, taking into account the lifestyle, eating patterns and the Mediterranean diet. (Hide)

Trace levels of inorganic mercury, methyl-mercury and ethyl-mercury have been assessed in seawater by high performance liquid chromatography (HPLC) hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) after solid phase extraction (SPE) pre-concentration with a novel synthesized ionic imprinted polymer. The adsorbent material was prepared by trapping a non-vinylated chelating ligand (phenobarbital) via imprinting of a ternary mixed ligand complex of the non-vinylated chelating agent, the template (methyl-mercury), and the vinyl ligand (metacrylic acid, MAA). Ethylene dimetacrylate (EDMA) and 2,2'-azobisisobutyronitrile (AIBN) were used as cross-linker and initiator reagents, respectively; and the precipitation polymerization technique was used in a porogen of acetonitrile/water (4:1). The best retention properties for methyl-mercury, inorganic mercury and ethyl-mercury species from seawater were obtained when loading 200 mL of sample adjusted to pH 8.0 and at a flow rate of 2.0 mL min(-1) on a column-packed with 200mg of the material. Quantitative mercury species recoveries were obtained using 4 mL of an eluting solution consisting of 0.8% (v/v) 2-mercaptoethanol and 20% (v/v) methanol (pH adjusted to 4.5) pumped at a flow rate of 2.0 mL min(-1). Mercury species separation was achieved on a Kinetex C18 column working under isocratic conditions (0.4% (v/v) 2-mercaptoethanol, 10% (v/v) methanol, pH 2.5, flow rate 0.7 mL min(-1)). ICP-MS detection was performed by monitoring the mercury mass to charge ratio of 202. The limits of quantification of the method were 11, 6.7, and 12 ng L(-1), for inorganic mercury, methyl-mercury and ethyl-mercury, respectively (pre-concentration factor of 50); whereas, analytical recoveries ranged from 96 to 106%. The developed method was successfully applied to several seawater samples from unpolluted areas. (Hide)

Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D-SDS-PAGE) was applied to separate protein in dissolved organic matter (DOM) and in particulate organic matter (POM) from seawater. Dissolved proteins were concentrated and purified using tangential flow ultrafiltration (UF) and centrifugal ultrafiltration. Twelve proteins (Sypro Ruby stained 2D-gels) exhibited isoelectric points (pIs) ranging from 3.5 to 6.0, and molecular weights (MWs) within the 10-50. kDa range.Marine plankton were concentrated by centrifugation, and proteins were isolated by grounding the biomass under liquid nitrogen before several washing stages [10% trichloroacetic acid (TCA) in acetone followed by 0.1. M ammonium acetate in 80/20 methanol/water] and extraction with a phenol-SDS mixture. 2D-SDS-PAGE showed the presence of approximately 140 different protein spots (Sypro Ruby stained 2D-gels), and plankton proteins exhibited MWs ranging from 12 to 150. kDa with pIs between 3 and 10.Electrophoretically separated proteins were further enzymatically in-gel digested (trypsin) and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Dissolved proteins in eight of the twelve resolved spots were identified by mass mapping (eleven different proteins were assigned); whereas, seven of the twenty-four resolved plankton protein spots were identified, and four different proteins were successfully assigned. (Hide)

A molecularly imprinted polymer was synthesized using the precipitation method with methylmercury chloride as the template, phenobarbital as ligand, methacrylic acid (MMA) as monomer, and ethylene glycoldimethacrylate (EDMA) as cross-linking agent. The MIP was characterized using elemental analysis, infrared spectroscopy, energy dispersive X-ray fluorescence and scanning electron microscopy. The operating conditions for solid phase extraction (SPE) were optimized in column mode (pH, loading and elution flow rate using 1 M thiourea in 1 M HCl). The polymer was used for analyzing the toluene extracts of two reference materials (BCR-463 and TORT-2) with good accuracy. (Hide)

A new application of HR-CS FAAS (High Resolution-Continuum Source Flame Atomic Absorption Spectrometry) has been developed for the determination of several trace elements (Ca, Co, Cu, Fe, Mn, Ni, Na and Zn) in infusions made from tea, rooibos and tea with seaweed samples. The proposed methods are fast, inexpensive and show good performances: the mean analytical recovery was approximately 100%. The mean limit of detection was 29.4 µg/l, and the mean limit of quantification was 98.0 µg/l (both limits refer to the brewed samples). Due to the matrix effect observed, the standard addition method had to be applied. Preliminary classification (based on metal contents) using chemometric techniques such as PCA (Principal Component Analysis) and CA (Cluster Analysis), was successful for infusions made from rooibos and tea with seaweed, but inconclusive for black and green teas. (Hide)

Two-dimensional offgel and lab-on-a-chip (LOC) electrophoresis was performed for assessing proteins from marine plankton. Proteins were isolated from plankton samples by using a phenol/sodium dodecylsulfate (SDS) buffer (2:1) pH8.0 mixture as an extracting solution. The SDS buffer consisted of 30% (m/v) sucrose, 2% (m/v) SDS, 0.1M of Tris-HCl, pH8.0, 5% (v/v) ß-mercaptoethanol and protease inhibitor cocktail. Before protein extraction, the plankton were subjected to different washing steps involving 10% trichloroacetic acid (TCA)/acetone and methanol. Proteins exhibiting the highest molecular weights (MWs), within the 52.6-57.3kDa range, were found in offgel fractions of isoelectric points (pIs) ranging from 4.40 to 8.60; whereas, the highest protein concentrations were found in fraction 5 (100µgg-1 for a protein of pI of 4.5 and MW of 22.0kDa), fraction 16 (55µgg-1, protein of pI/MW of 7.4/19.1kDa), and fraction 8 (51µgg-1, pI/MW of 5.3/22.2kDa). Further studies were also developed for determining the amount of trace metals associated with the isolated proteins of similar pIs by electrothermal atomic absorption spectroscopy (ETAAS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Preliminary results indicate that Fe, Ni, Mn and Zn were found to be associated with proteins of variable MW (from 14 to 54kDa) and pIs (from 3.4 to 8.2). Otherwise, Cd was found to be associated with proteins of certain pIs (6.0-6.5) and with MWs ranging from 14.1 to 53.1kDa. (Hide)

A method has been developed for the determination of cyanide using gold nanoparticles stabilized with adenosine triphosphate (ATP), and in the presence of the Cu(DDTC)2 complex. Cyanide reacts with copper, and free diethyldithiocarbamate (DDTC) causes nanoparticle aggregation. The reaction was performed in a buffered medium (10 mM phosphate + 0.1 M NaCl) by mixing stabilized gold nanoparticles (1.27 × 10-9 M; 19.2 ± 4.0 nm), the Cu(DDTC)2 complex and cyanide solutions. The influences of the measurement time after the addition of cyanide, the pH of the reaction medium and the concentration of the complex were evaluated. The selected conditions were: time = 1 min, [Cu(DDTC)2] = 0.1 µM and pH = 10.4. The analytical performance of the assay was studied, with a LOD of 0.059 mg L-1 which is under the level proposed by the USEPA for drinking water (0.2 mg L-1). (Hide)

Novel ultrasonic slurry sampling methods combined with the ETAAS determination of As, Cd, Cr, Cu, Ni, and Pb in terrestrial moss samples were developed without using corrosive acids. A pulverized moss sample between 1 to 50 mg (depending on element concentration)was placed into a 2.5 mL autosampler cup with 2 mL of HN03 (0.2 M), containing 0.01% of Triton X-100 reagent. The sample was then sonicated directly into the autosampler cup, using an ultrasonic probe at 85% power setting of 7 W for 25 seconds before injection. Chemical modifiers were introduced directly into the graphite tube after sample introduction. An amount of 3 Mg of Mg(NO3)2 and 5 µg of Pd was used as the chemical modifier for the As and Cu determination. (Hide)

In this study, the main parameters affecting Ag, Au, Cd, Cu, Ni, Sn, and Zn vapor generation in a surfactant reaction media of cetyl trimethyl ammonium bromide (CTAB) were evaluated. Detection using inductively coupled plasma optical emission spectrometry has been optimized. Improvements in the analytical performance for Ag and Ni were also obtained when CTAB was combined with the ionic liquid l-butyl-3-methylimidazolium. Standards (1 mg L1) were prepared in acid media. The optimum concentrations of the reagents in the standards were: 2.5×10-5 M (CTAB) and 0.6 M (nitric acid), when only CTAB was used. When both modifiers were combined, the concentrations were: 2.5 ×10-3 M of 1-butyl-3-methylimidazolium bromide and 1.5 ×10-5 M CTAB. In this case, 0.3 M of nitric acid was added. The optimum concentration of sodium borohydride to generate the vapors was 2.2% (w/v) in 0.05% (w/v) NaOH. These vapors were swept from the forced outlet of a lab-made gas-liquid separator to the torch with an argon flow of O.7 mL min-1. The limits of detection ranged from 0.4 µg L-1 Cu to 6.9 µg L-1 Au. The detection limit for silver improved three-fold when CTAB was used together with l-butyl-3-methylimidazolium bromide (from 14.3 to 4.9 µg L-1). Relative standard deviations were below 5% (n=l 1) for all of the elements, except for Cd (11.3 µg L-1). Since best results were obtained for most elements using only CTAB, a study of interferences for this modifier was performed. It was observed that a surfactant agent, such as CTAB, was a better reagent to avoid interferences than a complexing agent, such as 8-hydroxyquinoline. Moreover, the method showed good accuracy when determining Cd, Cu, Ni, and Zn in a wastewater reference material. (Hide)

Trace levels of inorganic mercury, methyl-mercury and ethyl-mercury have been assessed in seawater by high performance liquid chromatography (HPLC) hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) after solid phase extraction (SPE) pre-concentration with a novel synthesized ionic imprinted polymer. The adsorbent material was prepared by trapping a non-vinylated chelating ligand (phenobarbital) via imprinting of a ternary mixed ligand complex of the non-vinylated chelating agent, the template (methyl-mercury), and the vinyl ligand (metacrylic acid, MAA). Ethylene dimetacrylate (EDMA) and 2,2'-azobisisobutyronitrile (AIBN) were used as cross-linker and initiator reagents, respectively; and the precipitation polymerization technique was used in a porogen of acetonitrile/water (4:1). The best retention properties for methyl-mercury, inorganic mercury and ethyl-mercury species from seawater were obtained when loading 200mL of sample adjusted to pH 8.0 and at a flow rate of 2.0mLmin-1 on a column-packed with 200mg of the material. Quantitative mercury species recoveries were obtained using 4mL of an eluting solution consisting of 0.8% (v/v) 2-mercaptoethanol and 20% (v/v) methanol (pH adjusted to 4.5) pumped at a flow rate of 2.0mLmin-1. Mercury species separation was achieved on a Kinetex C18 column working under isocratic conditions (0.4% (v/v) 2-mercaptoethanol, 10% (v/v) methanol, pH 2.5, flow rate 0.7mLmin-1). ICP-MS detection was performed by monitoring the mercury mass to charge ratio of 202. The limits of quantification of the method were 11, 6.7, and 12ngL-1, for inorganic mercury, methyl-mercury and ethyl-mercury, respectively (pre-concentration factor of 50); whereas, analytical recoveries ranged from 96 to 106%. The developed method was successfully applied to several seawater samples from unpolluted areas. (Hide)

Sorbent and solvent microextraction techniques, mainly solid-phase microextraction, stir-bar sorptive extraction, single-drop microextraction, dispersive liquid-liquid microextraction, and hollow-fiber liquid-phase microextraction, are well-established, environment-friendly procedures for treating a wide range of samples when isolating organic and inorganic targets. Recently, microextraction techniques combined with other sample pre-treatments were shown to be excellent approaches for improving target isolation, and, thus, for enhancing the quality of the whole analysis. This review therefore deals with recent advances when coupling several microextraction techniques as sample pre-treatment methods for liquid and solid environmental and biological materials. This review includes an updated overview on combined microextraction techniques (design and operational requirements), the advantages and the disadvantages of current developments, and future prospects. (Hide)

The objective of this work is to develop a method for the determination of metals in saline matrices using high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Module SFS 6 for sample injection was used in the manual mode, and flame operating conditions were selected. The main absorption lines were used for all the elements, and the number of selected analytical pixels were 5 (CP±2) for Cd, Cu, Fe, Ni, Pb and Zn, and 3 pixels for Mn (CP±1). Samples were acidified (0.5% (v/v) nitric acid), and the standard addition method was used for the sequential determination of the analytes in diluted samples (1:2). The method showed good precision (RSD(%) 4%, except for Pb (6.5%)) and good recoveries. Accuracy was checked after the analysis of an SPS-WW2 wastewater reference material diluted with synthetic seawater (dilution 1:2), showing a good agreement between certified and experimental results.(Hide)

The beneficial effects of fish consumption in both children and adults are well known. However, the intake of methylmercury, mainly from contaminated fish and shellfish, can have adverse health effects. The study group on the prevention of exposure to methylmercury (GEPREM-Hg), made up of representatives from different Spanish scientific societies, has prepared a consensus document in a question and answer format, containing the group’s main conclusions, recommendations and proposals. The objective of the document is to provide broader knowledge of factors associated with methylmercury exposure, its possible effects on health among the Spanish population, methods of analysis, interpretation of the results and economic costs, and to then set recommendations for fish and shellfish consumption. The group sees the merit of all initiatives aimed at reducing or prohibiting the use of mercury as well as the need to be aware of the results of contaminant analyses performed on fish and shellfish marketed in Spain. In addition, the group believes that biomonitoring systems should be set up in order to follow the evolution of methylmercury exposure in children and adults and perform studies designed to learn more about the possible health effects of concentrations found in the Spanish population, ta-combusking into account the lifestyle, eating patterns and the Mediterranean diet. (Hide)

The beneficial effects of fish consumption in both children and adults are well known. However, the intake of methylmercury, mainly from contaminated fish and shellfish, can have adverse health effects. the study group on the prevention of exposure to methylmercury (GEPREM-Hg), made up of representatives from different Spanish scientific societies, has prepared a consensus document in a question and ans wer format, containing the group's main conclusions, recommendations and proposals. the objective of the document is to provide broader knowledge of factors associated with methylmercury exposure, its possible effects on health among the Spanish population, methods of analysis, interpretation of the results and economic costs, and to then set recommendations for fish and shellfish consumption. the group sees the merit of all initiatives aimed at reducing or prohibiting the use of mercury as well as the need to be aware of the results of contaminant analyses performed on fish and shellfish marketed in Spain. In addition, the group believes that biomonitoring systems should be set up in order to follow the evolution of methylmercury exposure in children and adults and perform studies designed to learn more about the possible health effects of concentrations found in the Spanish population, taking into account the lifestyle, eating patterns and the Mediterranean diet. (Hide)

The beneficial effects of fish consumption are well-known. Nevertheless, there is worldwide concern regard methylmercury concentrations in fish, which is why many countries such as the United States, Australia, New Zealand, Canada and numerous European countries have made fish consumption recommendations for their populations, particularly vulnerable groups, in order to México methylmercury intake. Blood and hair are the best biological samples for measuring methylmercury. The most widely-used method to analyse methylmercury is cold vapor atomic absorption spectrometry, although there are also direct methods based on the thermal decomposition of the sample. In recent years, the number of laboratories that measure mercury by inductively coupled plasma mass spectrometry has increased. In addition, the different kinds of mercury can be distinguished by coupling chromatography methods of separation. Laboratories that analyse mercury in biological samples need to participate in external quality control programmes. Even if mercury emissions are reduced, mercury may remain in the environment for many years, so dietary recommendations are fundamental in order to reduce exposure. It is necessary to propose public health measures aimed at decreasing mercury exposure and to evaluate the benefits of such measures from the economic and social (Hide)

Porous membrane-protected micro-solid phase extraction (µ-SPE) using a molecularly imprinted polymer (MIP) as an adsorbent has been proposed as an integrated extraction-cleanup procedure for isolating cocaine (COC) and its metabolites [benzoylecgonine (BZE), ecgonine methyl ester (EME), and cocaethylene (CE)] from human urine. MIP beads have been synthesized using COC as a template molecule, ethylene dimethacrylate (EDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. High performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS) has been used for quantifying the analytes after MIP-µ-SPE. Variables such as urine pH, adsorption temperature and time, mechanical (orbital-horizontal) stirring; and composition of the eluting solution and eluting time, were evaluated. The proposed method was shown to be precise and accurate [relative standard deviations (RSDs) of intra- and inter-day tests ranging from 3 to 8% and from 2 to 10%, respectively]; and analytical recoveries in the range of 89-100%). In addition, excellent accuracy was also verified after analyzing a FDT +25% control material for BZE. The detection limits were in the range of 0.16-1.7 ng L-1, low enough for confirmative conclusions regarding cocaine abuse. The method was finally applied for screening/quantifying cocaine and metabolites in urine samples from poly-drug abusers. (Hide)

Arsenic (As) speciation in human urine was performed by anion exchange chromatography (AEC), followed by inductively coupled plasma mass spectrometry detection (ICP-MS). Separation of arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid [MMA(V)L dimethylarsinic acid [DMA(V], arsenobetaine (AsB), and arsenocholine (AsC) in urine samples was accomplished in 9 minutes, resulting in quantification limits within the 0.3-0.9 ug L-1 range. The gradient elution program comprises two different mobile phases consisting of ultrapure water (phase A) and aqueous 20 mM nitric acid (phase B), both modified with 2% (v/v) methanol. Sample pre-treatment is based on human urine centrifugation (5000 rpm, 10 min), followed by filtration (0.45 μm) and dilution (1:4) with ultrapure water. Relative standard deviations (N=l 1) of the overall procedure were 8% for AsB and DMA(V), 11% for As(III), and 9% for MMA(V), As(V), and AsC. Arsenics quantification was performed using the standard addition method covering arsenic concentration ranges of 0-100 μ L-1 (expressed as arsenic) for all species. Germanium (5 μg L-1) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 94 to 101% (urine sample spiked with low target concentrations), from 99-103% (urine sample spiked with intermediate target concentrations), and from 97-103% (urine sample spiked with high target concentrations). The developed procedure has been tested by analyzing the certified reference material NIST CRM 2669 Arsenic Species in Frozen Human Urine which offers certified contents for all arsenic species. After AEC and mass spectrometry detection, MMA(V), DMA(V), AsB, AsC, and also tetramethylarsonium ion (TETRA) were identified in several urine samples. The method has been applied to assess arsenic speciation in several human urine samples collected from volunteers not chronically exposed to arsenic via water and food. (Hide)

A magnetic molecularly imprinted polymer (MMIP) has been synthesized and applied for cocaine (COC) and metabolites (benzoylecgonine, BZE; cocaethylene, CE; and ecgonine methyl ester, EME) recognition/pre-concentration in urine samples. The MMIP has been prepared using COC as a template molecule, ethylene dimethacrylate (EDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, Fe3O4 magnetite as a magnetic component, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. The best results (MIP layer on the surface of the magnetic nanoparticles) and physical properties of the prepared MMIP were obtained when assisting the synthesis procedure with ultrasounds (325 W, 37 kHz, 30°C, 4 h). After solid phase extraction (SPE) with the prepared adsorbent material, analytes were determined by high performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS). Variables affecting the SPE process (batch mode) were fully evaluated. Optimum retention of analytes (1.8 mL of urine and 50 mg of MMIP) was achieved by fixing the urine pH at 5.5 (use of a KH2PO4/NaOH, pH 5.5 buffer solution), and magnetic stirring (25°C, 700 rpm) for 10 min. Elution was performed by using 2 mL of a dichloromethane/2-propanol/ammonium hydroxide (75:20:5) mixture under ultrasounds (325 W, 35 kHz, room temperature) for 5 min. The method was validated according to the guidance for bioanalytical method validation of the US Department of Health and Human Services, Food and Drug Administration. The detection limits were in the range of 0.39-1.4 ng L-1. The relative standard deviations of intra- and inter-day tests ranged from 5 to 11% and from 3 to 11%, respectively. Analytical recoveries were in the range of 79-106% when spiking drug-free urine samples at three concentration levels. Good results were also obtained after analyzing an FDT +25% control material. The applicability of the method was proved for screening/quantifying COC, BZE, CE and EME in several samples from poly-drug abusers. (Hide)

Mn-doped ZnS quantum dots (QDs) coated with a molecularly imprinted polymer (MIP) material selective toward cocaine and its metabolites have been prepared and applied to cocaine (COC) and metabolites assessment by spectrofluorimetry. Ultrasound irradiation (37. kHz) was novelty used for performing the Mn-doped ZnS QDs synthesis as well as for preparing the QD based MIP-coated composite by precipitation polymerization (imprinting process). This fact allowed the synthesis to be accomplished in four hours. In addition, the use of ultrasound irradiation during MIP-QDs synthesis increased the homogeneity of the QDs size, and reduced nanoparticles agglomeration. MIP was synthesized using COC as a template molecule, ethylene dimethacrylate (EDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. The fluorescence of MIP-coated QDs was quenched by the template (COC) and also by metabolites from COC such as benzoylecgonine (BZE), and ecgonine methyl ester (EME). Quenching was not observed when performing experiments with non-imprinted polymer (NIP)-coated QDs; and also, fluorescence quenching of MIP-coated QDs was not observed by other drugs of abuse and metabolites (heroin and cannabis abuse). This fact indicates that the prepared material recognize only COC (template) and metabolites. (Hide)

Dissolved proteins characterization in marine sediment pore water has been performed by offgel electrophoresis (OGE) and microfluidic lab-on-chip (LOC) electrophoresis, assessing for the first time dissolved protein characteristics such as isoelectric point (pIs), and molecular weight (MW). In addition, speciation studies of metal-protein complexes in sediment pore water have also been performed by direct analysis of offgel fractions by electrothermal atomic absorption spectrometry (ETAAS), and inductively coupled plasma optical emission spectrometry (ICP-OES). Samples were subjected to a tangential flow ultrafiltration (UF) followed by a centrifugal UF (10. kDa molecular weight cut-off, MWCO) procedure, which offered a pre-concentration factor of 450. Isolation of dissolved proteins from the extracts has been performed by treating the ultrafiltrated fractions with methanol-chloroform as a precipitating reagent. The protein pellets were dried, dissolved in the offgel buffer, and subjected to optimized OGE and LOC electrophoresis procedures. Results showed proteins of MWs ranging from 5.1 to 87.0. kDa, and proteins exhibiting the highest MW were found in offgel fractions comprising pIs within the 6.34-7.76 range. Regarding metal-protein complexes, cadmium (Cd), and lead (Pb) were not found in any of the analyzed offgel fractions, which implies low affinity of these elements to the isolated proteins. However, iron (Fe) was found to be associated to proteins with pIs between 3.0 and 10 (the highest Fe concentrations were found in proteins from offgel fractions with pIs 6.3 to 7.7). Finally, copper (Cu), manganese (Mn), and zinc (Zn) were found to be bound to proteins exhibiting low MWs. (Hide)

The quality of the quantitative information in single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) depends directly on the number concentration of the nanoparticles in the sample analyzed, which is proportional to the flux of nanoparticles through the plasma. Particle number concentrations must be selected in accordance with the data acquisition frequency, to control the precision from counting statistics and the bias, which is produced by the occurrence of multiple-particle events recorded as single-particle events. With quadrupole mass spectrometers, the frequency of data acquisition is directly controlled by the dwell time. The effect of dwell times from milli- to microseconds (10 ms, 5 ms, 100 μs, and 50 μs) on the quality of the quantitative data has been studied. Working with dwell times in the millisecond range, precision figures about 5 % were achieved, whereas using microsecond dwell times, the suitable fluxes of nanoparticles are higher and precision was reduced down to 1 %; this was independent of the dwell time selected. Moreover, due to the lower occurrence of multiple-nanoparticle events, linear ranges are wider when dwell times equal to or shorter than 100 μs are used. A calculation tool is provided to determine the optimal concentration for any instrument or experimental conditions selected. On the other hand, the use of dwell times in the microsecond range reduces significantly the contribution of the background and/or the presence of dissolved species, in comparison with the use of millisecond dwell times. Although the use of dwell times equal to or shorter than 100 μs offers improved performance working in single-particle mode, the use of conventional dwell times (3–10 ms) should not be discarded, once their limitations are known. (Hide)

Bioavailability of essential and toxic metals in edible nuts and seeds has been assessed by using an in vitro dialyzability approach. The samples studied included walnuts, Brazil nuts, Macadamia nuts, pecans, hazelnuts, chestnuts, cashews, peanuts, pistachios and seeds (almond, pine, pumpkin and sunflower). Metals were measured by inductively coupled plasma-mass spectrometry in dialyzates and also in samples after a microwave assisted acid digestion pre-treatment. Low dialyzability percentages were found for Al, Fe and Hg; moderate percentages were found for Ba, Ca, Cd, Co, Cu, K, Li, Mg, Mn, Mo, P, Pb, Se, Sr, Tl and Zn; and high dialyzability ratios were found for As, Cr and Ni. The highest dialyzability percentages were found in raw chestnuts and raw hazelnuts. Metal dialyzability was found to be negatively affected by fat content. Positive correlation was found between carbohydrate content and metal dialyzability ratios. Protein and dietary fibre content did not influence metal bioavailability. Predicted dialyzability for some metals based on fat and protein content could also be established. (Hide)

A simple sample pre-treatment method based on solid phase microextraction (SPME) and gas chromatography–mass spectrometry (GC-MS) has been optimized and validated for the assessment of 15 residual solvents (2-propanol, 2-methylpentane, 3-methylpentane, acetone, ethyl acetate, benzene, hexane, methylcyclohexane, methylcyclopentane, m-xylene, propyl acetate, toluene, 1,2,4-trimethylbenzene, dichloromethane, and ethylbenzene) in seized illicit cocaine and heroin. DMSO and DMF as sample diluents were found to offer the best residual solvent transference to the head space for further adsorption onto the SPME fiber, and the developed method therefore showed high sensitivity and analytical recovery. Variables affecting SPME were fully evaluated by applying an experimental design approach. Best conditions were found when using an equilibration time of 5 min at 70 °C and headspace sampling of residual solvents at the same temperature for 15 min. Method validation, performed within the requirements of international guidelines, showed excellent sensitivity, as well as intra- and inter-day precision and accuracy. The proposed methodology was applied to 96 cocaine samples and 14 heroin samples seized in Galicia (northwestern Spain) within 2013 and 2014. (Hide)

In this study, the content of sulfur in bovine serum albumin and L-cysteine was determined using high-resolution continuum source molecular absorption spectrometry of the CS molecule, generated in a reducing air-acetylene flame. Flame conditions (height above the burner, measurement time) were optimized using a 3.0% (v/v) sulfuric acid solution. A microwave lab station (Ethos Plus MW) was used for the digestion of both compounds. During the digestion step, sulfur was converted to sulfate previous to the determination. Good repeatability (4–10%) and analytical recovery (91–106%) was obtained. (Hide)

Metalloproteins and metal–protein complexes play key roles in all organisms. For example, certain metalloproteins are involved in metal homeostasis and detoxification, or oxidative stress protection; whereas, metals serve as essential cofactors in a large number of metal–protein complexes. Advances in analytical instrumentation as well as informatics have allowed a complete characterization/assessment of both metalloproteins and metal–protein complexes. In some cases, the identification of the protein is a key factor for understanding its physiological function, such as when assessing protein corona in nanoparticles–protein assemblies. On other occasions, the identification of the binding sites in the peptide chain and conformational changes as a consequence of the metal–protein interaction, as well as the lability of this interaction, can explain the role of these metal-based biomolecules in living organisms. This article attempts to critically review the current state-of-the-art of the available analytical techniques for characterizing metalloproteins and metal–protein complexes. Methods for assessing the structure, characterization of the metal-binding sites, as well as the class of proteins involved in some metal (metallic nanoparticle)-binding proteins are discussed. Recent developments when assessing metalloproteins and metal–protein complexes in the clinical, environmental, and food fields, and pioneering research regarding nanoparticle–protein characterization, are also reviewed. (Hide)

A novel adsorbent, magnetic molecularly imprinted polymer (MMIP) based on magnetite nanoparticles surface-covered with an MIP selective for cocaine (COC), was synthesised and used in batch micro-solid phase extraction (μ-SPE) for isolation of COC and metabolites (benzoylecgonine, BZE; cocaethylene, CE; and ecgonine methyl ester, EME) from plasma samples. High performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used for performing analysis. Parameters such as sample pH, magnetic stirring speed, extraction temperature and time (loading stage), composition and volume of the eluting solution, and desorption time, were optimised. Under the most favourable conditions, the highest extraction yields were obtained by using 0.1 to 1.0 mL of plasma (pH adjusted at 8.5) plus 50 mg of MMIP, and magnetic stirring (20 °C, 100 rpm) for 4 min. Elution was performed with 2 mL of a dichloromethane/2-propanol/ammonium hydroxide (75:20:5) mixture under ultrasound irradiation (325 W, 35 kHz) for 5 min. The limits of detection were between 0.013 and 0.36 ng L-1, and the limits of quantification were from 0.043 to 1.2 ng L-1. The relative standard deviations of intra- and inter-day tests (three concentration levels tested) ranged from 1 to 9% and from 2 to 10%, respectively. Analytical recoveries were in the range of 91-102% when spiking drug-free plasma samples at three concentration levels. Accurate results were also obtained after analysing a BTMF 1/11-B control material. (Hide)

A selective molecularly imprinted polymer synthesized for the selective retention of cocaine (COC) and its metabolites [benzoylecgonine (BZE), ecgonine methyl ester (EME), and cocaethylene (CE)] was used as a solid adsorbent for assessing cocaine abuse by plasma analysis. The MIP beads (50 mg) were loaded inside a cone shaped device made of a polypropylene (PP) membrane for micro-solid-phase extraction (μ-SPE). High performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used for quantifying the analytes after MIP-μ-SPE. The best retention capabilities were reached when loading plasma samples (within the 0.1-5.0 mL range), previously adjusted to pH 5.5 by orbital-horizontal shaking (150 rpm, 50 °C) for 10 min. Analyte elution was achieved by subjecting the MIP-μ-SPE device to ultrasound (37 kHz, 325 W) with 10 mL of dichloromethane/2-propanol/ammonium hydroxide (76:20:4) for 8 min. After eluate evaporation to dryness and re-dissolution in 100 μL of mobile phase, the MIP-μ-SPE method yielded a pre-concentration factor of 50. Precision was assessed by intra-day and inter-day assays, and accuracy (intraday and inter-day analytical recovery, as well as the analysis of a BTMF 1/11-B control serum sample) show that the developed method is highly precise and accurate. In addition, the limits of detection, ranging from 0.061 ng mL-1 for COC to 0.87 ng mL-1 for BZE, were low enough for confirmative conclusions regarding cocaine abuse. The method was used for screening/quantifying cocaine and metabolites in plasma samples from poly-drug abusers. (Hide)

A new molecularly imprinted polymer (MIP)-based fluorescent artificial receptor has been prepared by anchoring a selective MIP for cocaine (COC) on the surface of polyethylene glycol (PEG) modified Mn-doped ZnS quantum dots (QDs). The prepared material combines the high selectivity attributed to MIPs and the sensitive fluorescent property of the Mn-doped ZnS QDs. Simple and low cost methods have therefore been optimized for assessing cocaine abuse in urine by monitoring the fluorescence quenching when the template (COC) and also metabolites from COC [benzoylecgonine (BZE) and ecgonine methyl ester (EME)] are present. Fluorescence quenching was not observed when performing experiments with other drugs of abuse (and their metabolites) or when using nonimprinted polymer (NIP)-coated QDs. Under optimized operating conditions (1.5 mL of 200 mg L-1 MIP-coated QDs solution, pH 5.5, and 15 min before fluorescence scanning) two analytical methods were developed/validated. One of the procedures (direct method) consisted of urine sample 1:20 dilution before fluorescence measurements. The method has been found to be fast, precise, and accurate, but the standard addition technique for performing the analysis was required because of the existence of matrix effect. The second procedure performed a solid phase extraction (SPE) first, avoiding matrix effect and allowing external calibration. The limits of detection of the methods were 0.076 mg L-1 (direct method) and 0.0042 mg L-1 (SPE based method), which are lower than the cutoff values for confirmative conclusions regarding cocaine abuse. (Hide)

A method for total As and Cr determination in seawater samples has been developed. As and Cr were measured using the seaFAST2 automated sample introduction system coupled to an ICP-MS. The sampling system allows on-line sample dilution (10 times) before introduction into the ICP-MS. < /br> Calibration was performed using the standard addition method, working in the concentration range of 0 to 50 mu g L-1 for As and 0 to 25 mu g L-1 for Cr. The method shows good sensitivity resulting in LODs and LOQs of 0.3 and 0.9 mu g L-1, respectively, for As and of 0.03 and 0.09, respectively, for Cr determination. The method was precise (RSD <2%) and accurate. < /br> This method was applied to the determination of As and Cr in different seawater samples from the Galician coast of Spain. The concentrations found ranged from 0.3 to 3.1 mu g L-1 for As and from 0.03 to 0.1 mu g L-1 for Cr. (Hide)

Coordination of a triptycene-based ditopic Schiff base ligand (H2L) with Zn2+ leads to the formation of a novel trinuclear circular species. A combination of 1H NMR spectroscopy, infrared spectroscopy, mass spectrometry and elemental analysis allow the unambiguous characterization of H2L and Zn3L3·8H2O. DFT molecular modelling has been used to study the possible isomers of the cyclic trinuclear Zn(II) complex that results from the combination of conformational and optical isomers of the ligand. A NOESY experiment demonstrated that in the trinuclear circular zinc(II) helicate the three isomers of the ligand have an anti configuration of N,O-donor domains and an s-cis configuration of their imine bonds. Besides, a UV-VIS absorption and fluorescence emission study of H2L and Zn3L3·8H2O has been performed. (Hide)

A molecularly imprinted polymer (MIP) selective for cannabinoids [Δ(9)-tetrahydrocannabinol (Δ9-THC), 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol (Δ9-THC-COOH), and 11-hydroxy-Δ(9)-tetrahydrocannabinol (Δ9-THC-OH)] has been synthesized, fully characterized, and applied to the assessment of plasma and urine analysis of marijuana abuse by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Δ9-THC-COOH was used as a template molecule, whereas ethylene glycol dimethacrylate (EGDMA) was used as a functional monomer, divinylbenzene (DVB) as a cross-linker, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. The prepared MIP was found to be highly selective for cannabinoids typically found in blood and urine, and also for cannabinol (CBN) and cannabidiol (CBD). MIP beads (50 mg) were loaded inside a cone-shaped device made of a polypropylene (PP) membrane for microsolid-phase extraction (μ-SPE) in batch mode. Optimum retention of analytes (0.1 to 1.0 mL of plasma/urine) was achieved by fixing plasma/urine pH at 6.5 and assisting the procedure by mechanical shaking (150 rpm, 40 °C, 12 min). Optimum elution conditions implied 2 mL of a 90:10 methanol/acetic acid and ultrasound extraction (35 kHz, 325 W) for 6 min. Good precision was assessed by intra-day and inter-day assays. In addition, the method was found to be accurate after intra-day and inter-day analytical recovery assays and after analyzing control serum and urine control samples. The limits of quantification were in the range of 0.36-0.49 ng L(-1) (plasma analysis) and 0.47-0.57 ng L(-1) (urine analysis). These values are low enough for confirmative conclusions regarding marijuana abuse through blood and urine analysis. (Hide)

This chapter reviews the analytical methodology that used for arsenic speciation in marine food as well as bioavailability studies performed for arsenic species in this type of samples. During the first step of sample preparation, the byssus, shell, or both are removed from mollusk samples, while bone and entrails are removed from fish samples. The second step in sample pretreatment includes arsenic extraction procedures that can differ depending on the aim of the study: total arsenic determination, inorganic arsenic determination, or inorganic and organic arsenic species determination. Analytical techniques used for arsenic speciation in marine food samples include a separation step coupled with a specific detector. High-performance liquid chromatography (HPLC) coupled with different detectors such as inductively coupled plasma-mass spectrometry (ICP-MS), electrospray ionization-mass spectrometry (ESI-MS), hydride generation-atomic absorption spectroscopy (HG-AAS), and hydride generation-atomic fluorescence spectroscopy (HG-AFS) are the commonly used hyphenated techniques for arsenic speciation. (Hide)