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High performance liquid chromatography coupled to ICP-AES detection provides a rapid, reliable and sensitive method for arsenic speciation. The separation of As(III), As(V), DMA and MMA was achieved with ion exchange chromatography coupled to an axially-viewed sequential ICP-AES. After optimization of the chromatographic parameters (pH and concentration of the mobile phase), a careful study of the interface was conducted. Five nebulizers associated to three spray chambers were tested. Response of the ICP to each arsenic species was strongly affected by the selection of the nebulizer and spray chamber, however similar responses were obtained for each arsenic species. Best signal-to-noise ratios were obtained by using a microconcentric nebulizer and a cyclone spray chamber and did not affect the chromatographic resolution. Detection limits better than 10 microg L(-1) were obtained for As(III), DMA, MMA and 20 microg L(-1) for As(V), which is a significant improvement over previously published results.
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PMID:Optimization of HPLC-ICP-AES for the determination of arsenic species. 1122 Mar 42

A speciation technique for arsenic has been developed using an anion-exchange high-performance liquid chromatography/inductively coupled argon plasma mass spectrometer (HPLC/ICP MS). Under optimized conditions, eight arsenic species [arsenocholine, arsenobetaine, dimethylarsinic acid (DMA(V)), dimethylarsinous acid (DMA(III)), monomethylarsonic acid (MMA(V)), monomethylarsonous acid (MMA(III)), arsenite (As(III)), and arsenate (As(V))] can be separated with isocratic elution within 10 min. The detection limit of arsenic compounds was 0.14-0.33 microg/L. To validate the method, Standard Reference Material in freeze-dried urine, SRM-2670, containing both normal and elevated levels of arsenic was analyzed. The method was applied to determine arsenic species in urine samples from three arsenic-affected districts of West Bengal, India. Both DMA(III) and MMA(III) were detected directly (i.e., without any prechemical treatment) for the first time in the urine of some humans exposed to inorganic arsenic through their drinking water. Of 428 subjects, MMA(III) was found in 48% and DMA(III) in 72%. Our results indicate the following. (1) Since MMA(III) and DMA(III) are more toxic than inorganic arsenic, it is essential to re-evaluate the hypothesis that methylation is the detoxification pathway for inorganic arsenic. (2) Since MMA(V) reductase with glutathione (GSH) is responsible for conversion of MMA(V) to MMA(III) in vivo, is DMA(V) reductase with GSH responsible for conversion of DMA(V) to DMA(III) in vivo? (3) Since DMA(III) forms iron-dependent reactive oxygen species (ROS) which causes DNA damage in vivo, DMA(III) may be responsible for arsenic carcinogenesis in human.
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PMID:Identification of dimethylarsinous and monomethylarsonous acids in human urine of the arsenic-affected areas in West Bengal, India. 1130 25

The metabolic pathways for arsenic were precisely studied by determining the metabolic balance and chemical species of arsenic to gain an insight into the mechanisms underlying the animal species difference in the metabolism and preferential accumulation of arsenic in red blood cells (RBCs) in rats. Male Wistar rats were injected intravenously with a single dose of arsenite (iAs(III)) at 2.0 mg of As/kg of body weight, and then the time-dependent changes in the concentrations of arsenic in organs and body fluids were determined. Furthermore, arsenic in the bile was analyzed on anion and cation exchange columns by high-performance liquid chromatography-inductively coupled argon plasma mass spectrometry (HPLC-ICP MS). The metabolic balance and speciation studies revealed that arsenic is potentially transferred to the hepato-enteric circulation through excretion from the liver in a form conjugated with glutathione (GSH). iAs(III) is methylated to mono (MMA)- and dimethylated (DMA) arsenics in the liver during circulation in the conjugated form [iAs(III)(GS)(3)], and a part of MMA is excreted into the bile in the forms of MMA(III) and MMA(V), the former being mostly in the conjugated form [CH(3)As(III)(GS)(2)], and the latter being in the nonconjugated free form. DMA(III) and DMA(V) were not detected in the bile. In the urine, arsenic was detected in the forms of iAs(III), arsenate, MMA(V), and DMA(V), iAs(III) being the major arsenic in the first 6-h-urine, and DMA(V) being increased in the second 6-h-urine. The present metabolic balance and speciation study suggests that iAs(III) is methylated in the liver during its hepato-enteric circulation through the formation of the GSH-cojugated form [iAs(III)(GS)(3)], and MMA(III) and MMA(V) are partly excreted into the bile, the former being in the conjugated form [CH(3)As(III)(GS)(2)]. DMA is not excreted into the bile but into the bloodstream, accumulating in RBCs, and then excreted into the urine mostly in the form of DMA(V) in rats.
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PMID:Glutathione-conjugated arsenics in the potential hepato-enteric circulation in rats. 1174 43

Urinary arsenic is generally considered as the most reliable indicator of recent exposure to inorganic arsenic and is used as the main bio-marker of exposure. However, due to the different toxicity of arsenic compounds, speciation of arsenic in urine is generally considered to be more convenient for health risk assessment than measuring total arsenic concentration. Additionally, it can give valuable information about the metabolism of arsenic species within the body. In our study, for exposed group--42 urine samples were collected from Datterhat (South) village of Madaripur district, Bangladesh and an average arsenic concentration in their drinking water was 376 microg/L (range 118 to 620 microg/L). For control group, 27 urine samples were collected from a non-affected district, Badhadamil village of Medinipur district, West Bengal, India, where arsenic concentration in their drinking water is below 3 microg/L. The arsenic species in the urine were separated and quantified by using HPLC-ICP-MS. The sum of inorganic arsenic and its metabolites was also determined by FI-HG-AAS. Results indicate that average total urinary arsenic metabolites in children's urine is higher than adults and total arsenic excretion per kg body weight is also higher for children than adults. For arsenic species between adults and children, it has been observed that inorganic arsenic (In-As) in average is 2.36% and MMA is 6.55% lower for children than adults while DMA is 8.91% (average) higher in children than adults. The efficiency of the methylation process is also assessed by the ratio between urinary concentration of putative product and putative substrate of the arsenic metabolic pathway. Higher values mean higher methylation capacity. Results show the values of the MMA/In-As ratio for adults and children are 0.93 and 0.74 respectively. These results indicate that first reaction of the metabolic pathway is more active in adults than children. But a significant increase in the values of the DMA/MMA ratio in children than adults of exposed group (8.15 vs. 4.11 respectively) indicates 2nd methylation step is more active in children than adults. It has also been shown that the distribution of the values of DMA/MMA ratio to exposed group decrease with increasing age (2nd methylation process). Thus from these results we may infer that children retain less arsenic in their body than adults. This may also explain why children do not show skin lesions compared to adults when both are drinking same contaminated water.
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PMID:Pattern of excretion of arsenic compounds [arsenite, arsenate, MMA(V), DMA(V)] in urine of children compared to adults from an arsenic exposed area in Bangladesh. 1263 21

Star polymers containing ruthenium complex in the core were prepared by ruthenium-catalyzed living radical polymerization, where the metal catalysts were directly encapsulated on linking reactions of living poly(MMA) in the presence of ethylene glycol dimethacrylate as a linker and diphenyl-4-styrylphosphine as a ligand incorporated in the core. The products were characterized by SEC/MALLS, UV-vis, NMR, AFM, TEM, and ICP-AES and were employed as polymer catalysts for the oxidation reaction of alcohol.
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PMID:Polymer catalysts from polymerization catalysts: direct encapsulation of metal catalyst into star polymer core during metal-catalyzed living radical polymerization. 1272 Apr 36

Although most edible vegetables do not accumulate As at a high rate, rice, carrots and certain others are exceptions. In addition to nutritional or toxicological considerations, the relatively high level and variety of As species present in rice make it a very suitable matrix for a candidate reference material representative of terrestrial biological samples.An analytical procedure was developed for As speciation in rice based on the use of a 1:1 methanol-water mixture for species extraction, an anion Hamilton PRPX-100 column (at pH 6, and phosphate mobile phase 10 mM), and a cation Hamilton PRP-X200 column (at pH 2.8 in pyridine formiate 4 mM) for species separation and final determination by HPLC-ICP-MS. The detection limits for dry flour rice expressed as As were 2 and 3 ng g(-1) for As(III) and AsB on the cation column and 3, 6 and 5 ng g(-1) for As(V), MMA and DMA, respectively, on the anion column. The methodology developed was applied to check the stability of As species in the water-methanol extract and also under different processing steps and storage time and temperature conditions. It was demonstrated that the As species in the water-methanol extracts stored at +4 degrees C remained stable for at least one month. Once the rice grains are ground, the MMA and As(V) species are not stable under any storage conditions probably due to microbiological activity. When ground rice is gamma-irradiated species remain stable although the AsB does not appear.
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PMID:Evaluation of stability of arsenic species in rice. 1273 24

Nail and hair are rich in fibrous proteins, i.e., alpha-keratins that contain abundant cysteine residues (up to 22% in nail and 10-14% in hair). Although they are metabolically dead materials in the epidermis, the roots are highly influenced by the health status of the living beings and their analyses are used as a tool to monitor occupational and environmental exposure to toxic elements. The aims of the present study are to speciate arsenicals in human nail and hair and also to judge whether they should be used as a biomarker to arsenic (As) exposure and/or toxicity. All human fingernail and hair samples (n = 47) were collected from the As-affected area of West Bengal, India. Speciation of arsenicals in water extracts of fingernails and hair at 90 degrees C was carried out by HPLC-inductively coupled argon plasma mass spectrometer (ICP MS). Fingernails contained iAs(III) (58.6%), iAs(V) (21.5), MMA(V) (7.7), DMA(III) (9.2), and DMA(V) (3.0), and hair contained iAs(III) (60.9%), iAs(V) (33.2), MMA(V) (2.2), and DMA(V) (3.6). Fingernails contained DMA(III), but hair did not. The higher percentage of iAs(III) both in fingernails and hair than that of iAs(V) suggests more affinity of iAs(III) to keratin. Although all arsenicals in fingernails and hair correlate to As exposure positively, As speciation in fingernails seems to be more correlated with arsenism than that in hair. Exogenous contamination is a confounding factor for hair to consider it as a biomarker, whereas this is mostly absent in fingernails, which recommends it to be a better biomarker to arsenic exposure. DMA(III) content in fingernails and DMA(V) contents in both fingernails and hair could be the biomarker to As exposure.
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PMID:Speciation of arsenic in human nail and hair from arsenic-affected area by HPLC-inductively coupled argon plasma mass spectrometry. 1278 25

This paper reports the assessment of total arsenic and six arsenic species (As(III), As(V), MMA, DMA, AsBet, AsCol) as contaminants of mussel samples collected around the island of Sardinia and in the Gulf of Venice. The samples were analysed using cation- and anion-exchange HPLC-HG-AFS for speciation and ICP-AES for the total As determination. To ensure the robustness of the routine analytical method, the technique was validated using a candidate reference material, BCR-710, and good agreement was obtained. It was recognised that higher total arsenic concentration in mussels does not necessarily result in higher toxicity of mussel samples.
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PMID:The potential of arsenic speciation in molluscs for environmental monitoring. 1282 32

Effects of cysteine on the cytotoxicity of arsenic compounds, such as arsenite, arsenate, methylarsonic acid (MMA), and dimethylarsinic acid (DMA), were investigated in cultured human HL-60 cells. Using adenosine triphosphate bioluminescence assay, the rank order of the mixtures of arsenicals with cysteine was: DMA > arsenite > arsenate > MMA. The IC50 of DMA with equimolar cysteine was approximately 7.7 microM, nearly two orders of magnitude lower than that of DMA alone. Apoptotic cells were examined by the TUNEL method, and cysteine was found to enhance the induction of apoptosis by arsenicals. Using LC-ICP-MS, trivalent arsenic was detected in the mixtures of arsenate, DMA, and MMA with cysteine. These results suggested that the trivalent arsenic in the mixtures of arsenicals with cysteine might account for the enhanced cytotoxicity as well as apoptosis, and that cysteine is involved in induction of the adverse effects of arsenicals in humans.
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PMID:Effects of cysteine on the cytotoxicity of arsenic compounds. 1467 84

Suitable techniques have been developed for the extraction of arsenic species in a variety of biological and environmental samples from the Pak Pa-Nang Estuary and catchment, located in Southern Thailand, and for their determination using HPLC directly coupled with ICP-MS. The estuary catchment comprises a tin mining area and inhabitants of the region can suffer from various stages of arsenic poisoning. The important arsenic species, AsB, DMA, MMA, and inorganic arsenic (As III and V) have been determined in fish and crustacean samples to provide toxicological information on those fauna which contribute to the local diet. A Hamilton PRP-X100 anion-exchange HPLC system employing a step elution has been used successfully to achieve separation of the arsenic species. A nitric acid microwave digestion procedure, followed by carrier gas nitrogen addition- (N2)-ICP-MS analysis was used to measure total arsenic in sample digests and extracts. The arsenic speciation of the biological samples was preserved using a Trypsin enzymatic extraction procedure. Extraction efficiencies were high, with values of 82-102%(As) for fish and crustacean samples. Validation for these procedures was carried out using certified reference materials. Fish and crustacean samples from the Pak Pa-Nang Estuary showed a range for total arsenic concentration, up to 17 microg g(-1) dry mass. The major species of arsenic in all fauna samples taken was AsB, together with smaller quantities of DMA and, more importantly, inorganic As. For sediment samples, arsenic species were determined following phosphoric acid (1 M H3PO4) extraction in an open focused microwave system. A phosphate-based eluant, pH 6-7.5, with anion exchange HPLC coupled with ICP-MS was used for separation and detection of AsIII, AsV, MMA and DMA. The optimum conditions, identified using an estuarine sediment reference material (LGC), were achieved using 45 W power and a 20 minute heating period for extraction of 0.5 g sediment. The stability and recovery of arsenic species under the extraction conditions were also determined by a spiking procedure which included the estuarine sediment reference material. The results show good stability for all species after extraction with a variability of less than 10%. Total concentrations of arsenic in the sediments from the Pak Pa-Nang river catchment and the estuary covered the ranges 7-269 microg g(-1)and 4-20 [micro sign]g g(-1)(dry weight), respectively. AsV was the major species found in all the sediment samples with smaller quantities of AsIII. The presence of the more toxic inorganic forms of arsenic in both sediments and biota samples has implications for human health, particularly as they are readily 'available'.
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PMID:Determination of arsenic species in fish, crustacean and sediment samples from Thailand using high performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). 1505 32


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