Determination of inorganic oxyanions of As and Se by HPLC-ICPMS

A liquid chromatographic separation of inorganic oxyanions of As (As(V) and As(III)) and Se (Se(VI) and Se(IV)) using mixed ion-pairing reagents followed by ICPMS detection is described. The separation was accomplished in less than 4 min on Capcell C18 RP column using mixed ion-pairing modifier containing 5 mM of butane sulfonic acid (BSA), 2 mM malonic acid, 0.30 mM hexane sulfonic acid (HSA) and 0.5% methanol of pH 2.5. All four species were resolved with retention times of 2.4, 2.6, 3.0, and 3.1 min for Se(VI), As(V), As(III), and Se(IV), respectively. The detection limits were less than 0.08 and 0.77 μg l⁻¹ for arsenic and selenium species, respectively. The relative standard deviation of the proposed method for arsenic (at 2.5 μg l⁻¹) and selenium (at 10 μg l⁻¹) was less than 3.7 and 4.8%, respectively. The technique was used to determine inorganic oxyanions of As and Se in water samples (tap, well, and river) and extracts of coal fly ash and sediment. Low power microwave digestion was employed for extraction from fly ash and sediment samples.     

CZE for the speciation of arsenic in aqueous soil extracts

We developed two separation methods using CZE with UV detection for the determination of the most common inorganic and methylated arsenic species and some phenylarsenic compounds. Based on the separation method for anions using hydrodynamic sample injection the detection limits were 0.52, 0.25, 0.27, 0.12, 0.37, 0.6, 0.6, 1.2 and 1.0 mg As/L for phenylarsine oxide (PAO), p-aminophenylarsonic acid (p-APAA), o-aminophenylarsonic (o-APAA), phenylarsonic acid (PAA), 4-hydroxy-3-nitrobenzenearsonic acid (roxarsone), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenite or arsenious acid (As(III)) and arsenate (As(V)), respectively. These detection limits were improved by large-volume sample stacking with polarity switching to 32, 28, 14, 42, 22, 27, 26 and 27 microg As/L for p-APAA, o-APAA, PAA, roxarsone, MMA, DMA, As(III) and As(V), respectively. We have applied both methods to the analysis of the arsenic species distribution in aqueous soil extracts. The identification of the arsenic species was validated by means of both standard addition and comparison with standard UV spectra. The comparison of the arsenic species concentrations in the extracts determined by CZE with the total arsenic concentrations measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) indicated that CZE is suited for the speciation of arsenic in environmental samples with a high arsenic content. The extraction yield of phenylarsenic compounds from soil was derived from the arsenic concentrations of the aqueous soil extracts and the total arsenic content of the soil determined by ICP-AES after microwave digestion. We found that 6-32% of the total amount of arsenic in the soil was extractable by a one-step extraction with water in dependence on the type of arsenic species.     

微波辅助提取-液相色谱-氢化物发生-原子荧光光谱法分析沉积物中砷的形态

采用微波辅助提取-液相色谱-氢化物发生-原子荧光光谱法(LC-HG-AFS)联用技术分析了太湖沉积物中砷的形态[亚砷酸(As(III))、二甲基砷酸钠(DMA)、一甲基砷酸二钠(MMA)和砷酸As(V)]。测得沉积物中以无机砷为主,且以As(V)居多。选定以1mol/L的磷酸和0.1mol/L抗坏血酸为提取液,在微波辅助萃取(功率为60W,时间12min)下,萃取率达79.84%～91.57%,回收率在94.78%～107.6%之间。4种砷的形态在0～160μg/L之间时线性良好,检测限为0.6～2.3μg/L,相对标准偏差RSD为1.62%～2.20%。方法具有简便、快速、灵敏的特点。     

Arsenic speciation in freshwater organisms from the river Danube in Hungary

Total arsenic and arsenic species were determined in a range of freshwater samples (sediment, water, algae, plants, sponge, mussels, frog and fish species), collected in June 2004 from the river Danube in Hungary. Total arsenic concentrations were measured by ICPMS and arsenic species were measured in aqueous extracts of the samples by ion-exchange HPLC-ICPMS. In order to separately determine the efficiency of the extraction method and the column recovery, total arsenic concentrations in the extracts were obtained in three ways: (i) ICPMS determination after acid digestion; (ii) flow injection analysis performed directly on the extract; (iii) the sum of arsenic species eluting from the HPLC column. Extraction efficiencies were low (range 10-64%, mean 36%), but column recovery was acceptable (generally >80%) except for the fish samples, where substantial, currently unexplained, losses were observed. The dominating arsenic species in the extracts of freshwater algae were arsenosugars, whereas arsenate [As(V)] was present only as a minor constituent. On the other hand, plant extracts contained only inorganic arsenic, except for two samples which contained trace amounts of dimethylarsinate (DMA) and the tetramethylarsonium cation (TETRA). The oxo-arsenosugar-phosphate (ca. 35% of extractable arsenic) and the oxo-arsenosugar-glycerol (ca. 20%) as well as their thio-analogues (1-10%) were found in the mussel extracts, while arsenobetaine (AB) was present as a minor species only. In general, fish extracts contained only traces of arsenobetaine, and the oxo-arsenosugar-phosphate was the major arsenic compound. In addition, samples of white bream contained thio-arsenosugar-phosphate; this is the first report of a thio-arsenical in a fish sample. The frog presented an interesting arsenic speciation pattern because in addition to the major species, arsenite [As(III)] (30%) and the tetramethylarsonium cation (35%), all three intermediate methylation products, methylarsonate (MA), dimethylarsinate and trimethylarsine oxide (TMAO), and arsenate were also present. Collectively, the data indicate that arsenobetaine, the major arsenical in marine animals, is virtually absent in the freshwater animals investigated, and this represents the major difference in arsenic speciation between the two groups of organisms.     

Speciation of As(III), As(V), MMA and DMA in contaminated soil extracts by HPLC-ICP/MS

A method to separate and quantify two inorganic arsenic species As(III) and As(V) and two organic arsenic species, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), by HPLC-ICP/MS has been developed. The separation of arsenic species was achieved on the anionic exchange column IonPac AS11 (Dionex) with NaOH as mobile phase. The technique was successfully applied to analyze extracts of two contaminated soils, sampled at a former tannery site (soil 1) and a former paint production site (soil 2). The soils were extracted at pH values similar to the natural environment. Extractions were performed at different pH values with 0.3 M ammonium oxalate (pH = 3), milli-Q water (pH = 5.8), 0.3 M sodium carbonate (pH = 8) and 0.3 M sodium bicarbonate (pH = 11). No organically bound arsenic was found in the extracts. As(V) was the major component. Only up to 0.04% of the total arsenic contained in soil 1 were mobilized. The highest amount of extracted arsenic was found at the highest pH. In the milli-Q water extract of soil 1 As(III) and As(V) were found. High amounts of As(V) were found in the extracts of soil 2. Up to 20% of the total arsenic bound to soil 2 constituents were released. The results show that the mobilization of arsenic depended on the pH value of the extraction solution and the kind of extracted soil. Dramatic consequences have to be expected for pH changes in the environment especially in cases where soils contain high amounts of mobile arsenic.     

An evaluation of extraction techniques for arsenic species from freeze-dried apple samples

The extraction of arsenic from freeze-dried apples and subsequent determination of individual arsenic species by HPLC-ICP-MS is described. Solvent extraction with sonication using various aqueous and aqueous/solvent mixtures was initially evaluated by measuring total arsenic extracted by ICP-MS. A two step procedure using overnight treatment with alpha-amylase enzyme followed by sonication for 6 h with 40:60 acetonitrile-water was found to provide good extraction efficiency. The concentration of arsenic extracted was compared with the concentration of total arsenic in the samples determined using ICP-MS after microwave digestion in order to calculate extraction efficiency. Individual arsenic species in the extracts were measured using HPLC-ICP-MS. The three most abundant arsenic species found were arsenite, arsenate and dimethylarsinic acid. Total arsenic concentrations in the freeze-dried apple samples ranged from 8.2 to 80.9 micrograms kg-1 As, dry mass. By HPLC-ICP-MS, the relative amount of inorganic arsenic in the samples ranged from 73 to 90% of the sum of the arsenic species detected in each sample.     

Speciation and determination of bioavailable arsenic species in soil samples by one‐step solvent extraction and high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

A new analytical method was developed to determine the bioavailable arsenic species (arsenite, arsenate, monomethylarsonic acid, and dimethylarsonic acid) in soil samples using high‐performance liquid chromatography with inductively coupled plasma mass spectrometry. Bioavailable arsenic was extracted with ammonium phosphate buffer by a simplified one‐step solvent extraction procedure. To estimate the effect of variables on arsenic extraction, a two‐level Plackett–Burman factorial design was conducted to screen the significant factors that were further investigated by a separate univariate approach. The optimum conditions were confirmed by compromising the stability of arsenic species and the extraction efficiency. The concentration of arsenic species was determined in method blank and soil‐certified reference materials both spiked with standard solutions of arsenic species. All the target arsenic species were stable during the whole extraction procedure. Furthermore, the proposed method was applied to release bioavailable arsenic from contaminated soil samples, showing that the major arsenic species in soil samples were inorganic arsenic: arsenite and arsenate, of which the latter was dominant.     

Speciation of As(III), As(V), MMA and DMA in contaminated soil extracts by HPLC-ICP/MS

A method to separate and quantify two inorganic arsenic species As(III) and As(V) and two organic arsenic species, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), by HPLC-ICP/MS has been developed. The separation of arsenic species was achieved on the anionic exchange column IonPac^®AS11 (Dionex) with NaOH as mobile phase. The technique was successfully applied to analyze extracts of two contaminated soils, sampled at a former tannery site (soil 1) and a former paint production site (soil 2). The soils were extracted at pH values similar to the natural environment. Extractions were performed at different pH values with 0.3 M ammonium oxalate (pH = 3), milli-Q water (pH = 5.8), 0.3 M sodium carbonate (pH = 8) and 0.3 M sodium bicarbonate (pH = 11). No organically bound arsenic was found in the extracts. As(V) was the major component. Only up to 0.04% of the total arsenic contained in soil 1 were mobilized. The highest amount of extracted arsenic was found at the highest pH. In the milli-Q water extract of soil 1 As(III) and As(V) were found. High amounts of As(V) were found in the extracts of soil 2. Up to 20% of the total arsenic bound to soil 2 constituents were released. The results show that the mobilization of arsenic depended on the pH value of the extraction solution and the kind of extracted soil. Dramatic consequences have to be expected for pH changes in the environment especially in cases where soils contain high amounts of mobile arsenic.     

Optimization of microwave‐assisted extraction for six inorganic and organic arsenic species in chicken tissues using response surface methodology

Response surface methodology was applied to optimize the parameters for microwave‐assisted extraction of six major inorganic and organic arsenic species (As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p‐arsanilic acid, and roxarsone) from chicken tissues, followed by detection using a high‐performance liquid chromatography with inductively coupled mass spectrometry detection method, which allows the simultaneous analysis of both inorganic and organic arsenic species in the extract in a single run. Effects of extraction medium, solution pH, liquid‐to‐solid ratio, and the temperature and time of microwave‐assisted extraction on the extraction of the targeted arsenic species were studied. The optimum microwave‐assisted extraction conditions were: 100 mg of chicken tissue, extracted by 5 mL of 22% v/v methanol, 90 mmol/L (NH₄)₂HPO₄, and 0.07% v/v trifluoroacetic acid (with pH adjusted to 10.0 by ammonium hydroxide solution), ramping for 10 min to 71°C, and holding for 11 min. The method has good extraction performance for total arsenic in the spiked and nonspiked chicken tissues (104.0 ± 13.8% and 91.6 ± 7.8%, respectively), except for the ones with arsenic contents close to the quantitation limits. Limits of quantitation (S/N = 10) for As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p‐arsanilic acid, and roxarsone in chicken tissues using this method were 0.012, 0.058, 0.039, 0.061, 0.102, and 0.240 mg/kg (dry weight), respectively.     

Extraction and speciation of arsenic in plants grown on arsenic contaminated soils

A sequential arsenic extraction method was developed that yielded extraction efficiencies (EE) that were approximately double those using current methods for terrestrial plants. The method was applied to plants from two arsenic contaminated sites and showed potential for risk assessment studies. In the method, plants were extracted first by 1:1 water-methanol followed by 0.1 M hydrochloric (HCl) acid. Total arsenic in plant and soil samples collected from contaminated sites was mineralized by acid digestion and detected by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and hydride generation-atomic absorption spectrometry (HG-AAS). Arsenic speciation was done by high performance liquid chromatography coupled with HG-AAS (HPLC-HGAAS) and by HPLC coupled with ICP-mass spectrometry (HPLC-ICP-MS). Spike recovery experiments with arsenite (As(III)), arsenate (As(V)), methylarsonic acid (MA) and dimethylarsinic acid (DMA) showed stability of the species in the extraction processes. Speciation analysis by X-ray absorption near edge spectroscopy (XANES) demonstrated that no transformation of As(III) and As(V) occurred due to sample handling. Dilute HCl was efficient in extracting arsenic from plants; however, extraction and determination of organic species were difficult in this medium. Sequential extraction with 1:1 water-methanol followed by 0.1 M-HCl was most useful in extracting and speciating both organic and inorganic arsenic from plants. Trace amounts of MA and DMA in plants could be detected by HPLC-HGAAS aided by the process of separation and preconcentration of the sequential extraction method. Both organic and inorganic arsenic compounds could be detected simultaneously in synthetic gastric fluid extracts (GFE) but EEs by this method were lower than those of the sequential method. The developed sequential method was shown to be reliable and applicable to various terrestrial plants for arsenic extraction and speciation.     

Determination and pharmacokinetic properties of arsenic speciation in Xiao‐Er‐Zhi‐Bao‐Wan by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

A method of high performance liquid chromatography with a Hamilton PRP‐X100 ion‐exchange column (250 × 4.1 mm id, 10 μm) coupled to inductively coupled plasma mass spectrometry was employed to generate a full concentration–time profile of arsenic speciation after oral administration. The results exhibited good linearity and revealed that, in the pills, the average arsenic concentration was 10105.4 ± 380.7 mg/kg, and in the water extraction solution, the inorganic As(III) and As(V) concentrations were 220.1 ± 12.6 and 45.5 ± 2.3 mg/kg, respectively. No trace of monomethyl arsenic acid was detected in any of the plasma samples. We then successfully applied the established methodology to examine the pharmacokinetics of arsenic speciation. The resulting data revealed that, after oral administration in rats, the plasma concentration of each arsenic species reached C_max shortly after initial dosing, and that the distribution and elimination of As(V) was faster than that of As(III) and dimethyl arsenic acid. Additionally, the t_1/2 values of As(V), As(III), and dimethyl arsenic acid were 3.4 ± 1.6, 14.3 ± 4.0, and 19.9 ± 1.6 h, respectively. This study provides references for the determination of arsenic speciation in mineral‐containing medicines and could serve as a useful tool in measuring the true toxicity in traditional medicines that contain them.     

Arsenic Speciation in Sargassum fusiforme by Microwave-Assisted Extraction and LC-ICP-MS

Sargassum fusiforme, the common Chinese edible seaweeds, was investigated for total arsenic concentration by ICP-MS and for individual arsenic species by LC-ICP-MS. For this purpose, a microwave-assisted procedure was used for the extraction of arsenic species in freeze-dried seaweed and an analytical procedure for the sensitive and efficient speciation of the arsenic species As(III), dimethylarsinic acid, monomethyl arsonic acid, As(V), arsenobetaine and arsenocholine was optimized. Arsenic compounds were extracted from the seaweed with a methanol/water mixture; the extracts were evaporated to dryness, redissolved in water, and chromatographed on an anion exchange column. The arsenic species in Sargassum fusiforme are abundant. In some sample, the majority of arsenic compounds detected in the extracts were inorganic species, with a predominance of As (V). In addition, some significant amounts of unidentified arsenic compounds were also observed in the extracts.

     

Arsenic speciation in some environmental samples: a comparative study of HG–GC–QFAAS and HPLC–ICP–MS methods

Some water and soil extracts polluted with arsenic, and a sewage sludge certified for total arsenic have been analysed by high‐performance liquid chromatography–inductively coupled plasma–mass spectrometry (HPLC–ICP–MS) and hydride generation–gas chromatography– quartz furnace atomic absorption spectrometry (HG–GC–QFAAS techniques.) Detection limits in the range of 200–400 and 2–10 ng l⁻¹ respectively allowed the determination of inorganic [As(III), As(V)] and methylated (DMA, MMA, TMAO) arsenic species present in these samples. Results obtained by both methods are well correlated overall, whatever the arsenic chemical form and concentration range (8–10 000 μg l⁻¹). Comparison of these results enabled us to point out features and disadvantages of each analytical method and to reach a conclusion that they are suitable for arsenic speciation in these environmental matrices. Copyright © 2000 John Wiley & Sons, Ltd.     

Validated determination of total arsenic species of toxicological interest (arsenite, arsenate and their metabolites) by atomic absorption spectrometry after separation from dietary arsenic by liquid extraction: toxicological applications

A validated method for the selective extraction of total As species of toxicological interest (arsenite, arsenate and mono- and dimethylated arsenic species) from urine, followed by atomic absorption spectrometric determination, is described. The mechanisms involved in extraction were studied and the extraction method was optimized. The urine sample was acidified with concentrated HCl and KI and sodium hypophosphite were added. Under these conditions, As species were reduced to their corresponding iodide arsines, extracted with toluene and back-extracted with 1 mmol l-1 NaOH solution. Only inorganic arsenic and its metabolites in humans (monomethylarsonic and dimethylarsinic acid) were extracted. Arsenobetaine of dietary origin was not extracted. This method can detect if any As increase in urine originates from inorganic As intoxication or only from dietary non-toxic As species such as arsenobetaine.     

A method for rapid determination of arsenic species in vegetables using microwave‐assisted extraction followed by detection with HPLC hyphenated to inductively coupled plasma‐mass spectrometry

Driven by the significant need for characterization of the chemical speciation of arsenic in food, this work developed a method for rapid determination of four common arsenic species, namely, arsenite, arsenate, monomethyl arsenic acid, and dimethyl arsenic acid, in vegetables using microwave‐assisted extraction, followed by detection with high‐performance liquid chromatography hyphenated to inductively coupled plasma‐mass spectrometry. Initial screening results showed that microwave‐assisted extraction using 1% HNO₃ exhibited the highest overall efficiencies for all arsenic species without causing significant degradation of the organic ones. With the aid of response surface methodology, the optimum conditions established for extraction of arsenic species from vegetables were: 500 mg of freeze‐dried vegetable sample, extracted by closed vessel microwave‐assisted extraction using 10 mL of 2% v/v HNO₃ at 90°C for 17 min. Application of the method in the analysis of 24 market vegetable samples indicates that the extraction efficiencies for total arsenic species were in the range of 91.4–106%. Arsenite and arsenate were found to be the predominant arsenic species in the vegetables, which suggests that vegetable consumption could be an important route of inorganic arsenic exposure for the population with a heavy vegetable diet in arsenic polluted regions.     

Multi‐residue method for the analysis of pharmaceutical compounds in sewage sludge,compost and sediments by sonication‐assisted extraction and LC determination

A method for the simultaneous determination of 16 pharmaceutical compounds in three types of sewage sludge (primary, secondary and anaerobically digested dehydrated sludge), compost and sediment samples is described. Pharmaceutical compounds evaluated were nonsteroidal anti‐inflammatory drugs (acetaminophen, diclofenac, ibuprofen, ketoprofen, naproxen and salicylic acid), antibiotics (sulfamethoxazole and trimethoprim), an anti‐epileptic drug (carbamazepine), a β‐blocker (propranolol), a nervous stimulant (caffeine), estrogens (17α‐ethinylestradiol, 17β‐estradiol, estriol and estrone) and lipid regulators (clofibric acid, metabolite of clofibrate and gemfibrozil). The method is based on the ultrasonic‐assisted extraction, clean‐up by SPE and analytical determination by HPLC with diode array and fluorescence detectors. The best extraction recoveries were achieved in a three‐step extraction procedure with methanol and acetone as extraction solvents. Extraction recoveries of several pharmaceutical compounds as caffeine were highly dependent on the type of sample evaluated. The applicability of the method was tested by analyzing primary, secondary and anaerobically digested dehydrated sludge, compost and sediment samples from Seville (Southern Spain). Ten of the sixteen pharmaceutical compounds were detected in sludge samples and five in compost and sediment samples. The highest concentration levels were recorded for ibuprofen in sewage samples, whereas salicylic acid and 17α‐ethinylestradiol were detected in all of the samples analyzed.     

Quantitative Speciation of Arsenic in Water and Sediment Samples from the Mokolo River in Limpopo Province,South Africa

The Mokolo River is disposed to environmental contaminants such as arsenic (As) due to its proximity to several anthropogenic activities. Speciation of As in water and sediment samples from Mokolo River is crucial to evaluate the level and distribution of As in the river and underlying sediment since toxicity depends on its chemical forms. In this study, As species in water and sediment were determined by developing a new method for sediment extraction. Effective microwave-assisted extraction of As species in sediment samples was achieved using 0.3?M (NH₄)₂HPO₄ and 50?mM EDTA, which showed no species interconversion during extraction. The chromatographic separation and detection of As(III), dimethylarsinic acid (DMA), monomethylarsonic acid, and As(V) in water and sediment samples were achieved by coupling to high-performance liquid chromatography to inductively coupled plasma mass spectrometry. Baseline separation of four As species was achieved in 12?min using gradient elution with 10 and 60?mM NH₄NO₃ at pH 8.7 as the mobile phase. The analytical figures of merit and validation of analytical procedures were assessed and adequate performance and percentage recoveries ranging from 81.1 to 102% for water samples and 73.0–92.0% for sediments were achieved. The As species concentration in water and sediment samples was found to be in the range of 0.304–4.99?µg?L^?1 and 74.0–92.0?ng?g^?1, respectively. DMA was not detected in both water and sediment samples.     

Measurement of arsenic species in marine sediments by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

Extraction of sediments with phosphoric acid (0.5 M) and hydroxylamine hydrochloride (0.1 M) allowed the measurement of labile arsenic species while preserving the two redox states of arsenic. The forms and concentrations of arsenic species were measured using HPLC-ICP-MS. A Hamilton PRP X-100 strong anion exchange column using a 20 mM ammonium phosphate buffer (pH 6 and 9.2) was used to separate arsenic species. Recoveries of sediments spiked with As(V) were quantitative whereas for sediments spiked with As(III) recoveries of between 89 and 104% were obtained from four oxic certified reference sediments and an anoxic sediment. Application of the method to sediment samples from the marine Lake Macquarie, NSW, Australia, indicate that anoxic sediments can contain high concentrations of As(III), and two arsenosugars (sulfonate-ribose and sulfate-ribose). Extraction efficiencies for arsenic ranged between 6 and 82%. The arsenic species measured in sediments are strongly depended on the extraction procedure used. As(III) and arsenosugar concentrations in sediments that were freeze dried and oxidised were much less than in sediments that were not freeze dried and when exposure to air was keep to a minimum. Corresponding, As(V) concentrations tended to be higher in samples that were exposed to air.     

Identification of arsenic species in sheep‐wool extracts by different chromatographic methods

Sheep on the island of North Ronaldsay (Orkney, UK) feed mostly on seaweed, which contains high concentrations of dimethylated arsenoribosides. Wool of these sheep contains dimethylated, monomethylated and inorganic arsenic, in addition to unidentified arsenic species in unbound and complexed form. Chromatographic techniques using different separation mechanisms and detectors enabled us to identify five arsenic species in water extracts of wool. The wool contained 5.2 ± 2.3 µg arsenic per gram wool. About 80% of the arsenic in wool was extracted by boiling the wool with water. The main species is dimethylarsenic, which accounted for about 75 to 85%, monomethylated arsenic at about 5% and the rest is inorganic arsenic. Depending on the separation method and condition, the chromatographic recovery of arsenic species was between 45% for the anion exchange column, 68% for the size exclusion chromatography (SEC) and 82% for the cation exchange column. The SEC revealed the occurrence of two unknown arsenic compounds, of which one was probably a high molecular mass species. Since chromatographic recovery can be improved by either treating the extract with CuCl/HCl (CAT: 90%) or longer storage of the sample (CAT: 105%), in particular for methylated arsenic species, it can be assumed that labile arsenic–protein‐like coordination species occur in the extract, which cannot be speciated with conventional chromatographic methods. It is clear from our study of sheep wool that there can be different kinds of ‘hidden’ arsenic in biological matrices, depending on the extraction, separation and detection methods used. Hidden species can be defined as species that are not recordable by the detection system, not extractable or do not elute from chromatographic columns. Copyright © 2003 John Wiley & Sons, Ltd.     

Reactive supercritical fluid extraction and chromatography of arsenic species

Reactive supercritical fluid extraction has been used for the speciation of organic (DMA and MMA) and inorganic (As(III) and As(V)) arsenic compounds in solid samples. Derivatization with thioglycolic acid methylester (TGM) was performed in supercritical carbon dioxide. Different extraction conditions have been tested. The arsenic derivatives have been analyzed by GC. A capillary-SFC method was evaluated for the analysis of the TGM derivatives and compared with GC.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday