Arsenobetaine Research Articles

Sol-gel Synthesis of Alumina-titania Ceramic Membrane: Preparation and Characterization

Alumina-titania ceramic membrane with mesopore and narrow pore size distribution was prepared by the sol-gel process. Observations were based on membrane weight loss, morphology, pore size distribution and BET surface area. Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and N 2 adsorption-desorption analysis were employed for the membrane characterization. TGA curve shows that the suitable temperature for calcination of alumina-titania membrane is at 600°C. The SEM morphology displays a smooth and free-crack layer of alumina-titania membrane after calcination at temperature of 600°C. Furthermore, the membrane was also successfully coated with a good adhesion to complement with support. The thickness of the membrane layer was estimated at 4 μm. N 2 adsorption-desorption confirms the existence of a mesoporous structure for membrane as BET surface area and average pore size of the membrane layer were 292 m 2 g -1 and 1.8 nm respectively.

Measurement of arsenic compounds in littoral zone algae from the Western Mediterranean Sea. Occurrence of arsenobetaine

The determination of arsenic compounds in algae collected on the Catalan coast (Western Mediterranean) is reported. Ten algae species and the seagrass Posidonia oceanica were analyzed. Total arsenic in the samples was determined by microwave digestion and inductively coupled plasma mass spectrometry (ICPMS). Arsenic speciation in water extracts of samples was analyzed by liquid chromatography with both anionic and cationic exchange with ICPMS detection (LC–ICPMS). The total arsenic content of the algae samples ranged from 2.96 to 39.0 mg As kg −1. The following compounds were detected: arsenite (As(III)), arsenate (As(V)), methylarsonate (MA), dimethylarsinate (DMA), sulfonate sugar (SO 3-sug), sulfate sugar (SO 4-sug), phosphate sugar (PO 4-sug), arsenobetaine (AB), arsenocholine (AC), trimethylarsine oxide (TMAO) and glycerol sugar (Gly-sug). The main arsenic species found were arsenosugars. Significant percentages of arsenobetaine (0.54 mg As kg −1, 28% of the extractable arsenic and 0.39 mg As kg −1, 18% of the extractable arsenic) were found in Ulva rigida and Enteromorpha compressa. These results are discussed in relation to the presence of epiphytes.

Uptake and metabolism of arsenate, methylarsonate and arsenobetaine by axenic cultures of the phytoplankton Dunaliella tertiolecta

Abstract Axenic cultures of the phytoplankton Dunaliella tertiolecta were dosed with either arsenate [As(V)], methylarsonate (MA) or arsenobetaine (AB) at environmentally realistic concentrations (2 μg l-1) to investigate incorporation and transformation of arsenic species. Total arsenic concentrations in cultures dosed with As(V) were significantly higher than those dosed with MA and AB (6–10 μg g-1 compared to 1–3 μg g-1). Arsenic concentrations in As(V)-dosed cultures increased over time, whereas arsenic concentrations in MA- and AB-dosed cultures remained constant, indicating that As(V) is rapidly and continuously incorporated into the cell in comparison to MA and AB. Arsenic was found predominantly in the residue fractions (29–55%) of all cultures, irrespective of culture age. This was attributed to the ability of inorganic arsenic as arsenite [As(III)] to bind to proteins and/or phytochelatins. 2-Dimethylarsinoylethanol (DMAE) was the main arsenic species found in lipid cell fractions. Within the water-soluble and residue cell fractions, arsenic was isolated primarily as As(V), although it is likely the extraction procedure may have converted some As(III) to As(V). Small amounts of As(III), MA, dimethylarsinate (DMA) and arsenoribosides were also found in the lipid and water soluble As fractions. All cultures showed an increase in DMA and arsenoriboside species over time. The significance of these results is that while AB, the major arsenical in marine animals, is not produced or accumulated by this phytoplankton species, the possible precursors to AB formation are produced.

Complementary chromatography separation combined with hydride generation–inductively coupled plasma mass spectrometry for arsenic speciation in human urine

This study aimed to establish complementary high performance liquid chromatography (HPLC) methods including three modes of separation: ion pairing, cation exchange, and anion exchange chromatography, with detection by inductively coupled plasma mass spectrometry (ICPMS). The ion pairing mode enabled the separation of inorganic arsenate (As(V)), monomethylarsonic acid (MMA(V)), and dimethylarsinic acid (DMA(V)). However, the ion pair mode was unable to differentiate inorganic arsenite (As(III)) from arsenobetaine (AsB); instead, cation exchange chromatography was used to isolate and quantify AsB. Anion exchange chromatography was able to speciate all of the aforementioned arsenic species. Potential inaccurate quantification problem with urine sample containing elevated concentration of AsB, which eluted immediately after As(III) in anion exchange or ion pairing mode, was overcame by introducing a post-column hydride generation (HG) derivatization step. Incorporating HG between HPLC and ICPMS improved sensitivity and specificity by differentiating AsB from hydride-forming arsenic species. This paper emphasizes the usefulness of complementary chromatographic separations in combination with HG–ICPMS to quantitatively determine concentrations of As(III), DMA(V), MMA(V), As(V), and AsB in the sub-microgram per liter range in human urine.

Accurate determination of arsenic in arsenobetaine standard solutions of BCR-626 and NMIJ CRM 7901-a by neutron activation analysis coupled with internal standard method

Neutron activation analysis (NAA) coupled with an internal standard method was applied for the determination of As in the certified reference material (CRM) of arsenobetaine (AB) standard solutions to verify their certified values. Gold was used as an internal standard to compensate for the difference of the neutron exposure in an irradiation capsule and to improve the sample-to-sample repeatability. Application of the internal standard method significantly improved linearity of the calibration curve up to 1 μg of As, too. The analytical reliability of the proposed method was evaluated by k 0-standardization NAA. The analytical results of As in AB standard solutions of BCR-626 and NMIJ CRM 7901-a were (499 ± 55) mg kg −1 ( k = 2) and (10.16 ± 0.15) mg kg −1 ( k = 2), respectively. These values were found to be 15–20% higher than the certified values. The between-bottle variation of BCR-626 was much larger than the expanded uncertainty of the certified value, although that of NMIJ CRM 7901-a was almost negligible.

Reliability of spot urine samples in assessing arsenic exposure.

Urinary arsenic concentration is often used as a biomarker of arsenic exposure. First morning void (FMV) and spot urine samples from 131 participants in southeastern Michigan were analyzed using an HPLC-IC-PMS system for six different arsenic species: arsenobetaine (AsB), arsenite (As[III]), arsenate (As[V]), methylarsonous acid MMA[III], methylarsenic acid MMA[V], and dimethylarsenic DMA[V]. Bland-Altman plots, intraclass correlation coefficients (ICCs), and Pearson correlation procedures were used to evaluate the relationship between the arsenic species in FMV and spot urine collections after normalizing the samples by specific gravity. DMA[III] and MMA[III] were not detected in any of the samples. The sum of As[III], As[V], MMA[V], and DMA[V] was designated SumAs. The ICC between SumAs in FMV and SumAs in spot samples was 0.90. The ICC showed that 90% of variation comes from between individuals and not within individuals. A significant correlation (r=0.80 p<0.001) was observed between FMV and spot samples for SumAs. The spot sample were a good predictor of the MMA[V] (r=0.83 p<0.0001), and DMA[V] (r=0.77 p<0.0001) in the FMV sample. These associations suggest that either FMV or spot samples can be used as an adequate bioindicator of arsenic metabolites in human urine. The benefit of using spot urine samples, instead of 24-h or FMV urine samples, is the potential reduction in budgetary and logistic requirements in epidemiological studies.

High-Performance Liquid Chromatography−Inductively Coupled Plasma Mass Spectrometry Based Method for the Determination of Organic Arsenic Feed Additives and Speciation of Anionic Arsenics in Animal Feed

A novel method has been developed to detect two organic arsenic animal feed additives including roxarsone and p-arsanilic acid, as well as other arsenic species such as arsenite, dimethylarsinic acid, monomethylarsonic acid, arsenate, and 4-hydroxyphenylarsonic acid, by using high-performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC-ICP-MS). The influence of the type and concentrations of ion-pairing reagents on the separation efficiency of the different arsenic compounds was examined. The effects of the mobile phase pH on the retention of arsenic species on the chromatography column were studied. When a gradient elution procedure was used, the best separation of the seven arsenic species could be achieved in <20 min with a mobile phase consisting of 8% methanol and 92% aqueous tetrabutylammonium hydroxide (4 mM, pH 6.25) followed by 92% trifluoroacetic acid aqueous solution (0.1%, pH 2.0). Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used as an assistant tool to screen arsenobetain (AsB) in the feed samples by monitoring the reaction at m/z 179-->120. The extractions of arsenic compounds from formula feed samples were studied, and results showed that the extraction with methanol/water (1:1) mixture yielded the most efficient percent compound recovery and the fastest extraction time for all arsenic species. Under optimum conditions, the limits of detection were <1.7 microg of As kg(-1), and the recoveries of all seven arsenic species were >78.5% with the relative standard deviation of <10%. The ion-pair reversed phase HPLC-ICP-MS method was then successfully applied to the speciation of arsenic in feedstuff and formula feed samples.

Methods for the separation and quantification of arsenic species in SRM 2669: arsenic species in frozen human urine

Two independent liquid chromatography inductively coupled plasma-mass spectrometry (LC/ICP-MS) methods for the separation of arsenic species in urine have been developed with quantification by standard additions. Seven arsenic species have been quantified in a new NIST frozen human urine Standard Reference Material (SRM) 2669 Arsenic Species in Frozen Human Urine, Levels 1 and 2. The species measured were: arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), dimethylarsinate (DMA), arsenobetaine (AB), arsenocholine (AC), and trimethylarsine oxide (TMAO). The purity of each arsenic standard used for quantification was measured as well as the arsenic species impurities determined in each standard. Analytical method limits of detection (L(D)) for the various species in both methods ranged from 0.2 to 0.8 microg L(-1) as arsenic. The results demonstrate that LC/ICP-MS is a sensitive, reproducible, and accurate technique for the determination of low-level arsenic species in urine. Measurements of the arsenic species 3 years after initial production of the SRM demonstrate the stability of the arsenic species in the urine reference material.

In situ arsenic speciation on solid surfaces by desorption electrospray ionization tandem mass spectrometry

A simple and fast (<5 s) method for in situ arsenic speciation on solid surfaces has been developed based on desorption electrospray ionization-tandem mass spectrometry (DESI-MS). Arsenic-polluted environmental samples such as animal feed and plant tissues could be directly monitored by DESI-MS. Each arsenic species in this study, including monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), arsenocholine (AsC), 4-arsanilic acid (p-ASA), 4-hydroxyphenylarsonic acid (4-OH), Nitarsone, Roxarsone and two inorganic arsenic species, arsenate As(v) and arsenite As(iii), could be detected by their typical m/z and collision induced dissociation (CID) behavior respectively. By the characteristic information, mixtures of different arsenic species could be detected without any sample preparation and separation process. This method could give absolute detection limits of the arsenic species at ng/mm(2) to pg/mm(2) level with a best RSD of 5.3% (n = 5). The method could be potentially applied to in situ environmental monitoring of arsenic pollution, especially that caused by arsenic pesticides, animal feed additives, herbicides and wood treatment.

Determination of total arsenic in urine by hydride generation atomic fluorescence spectrometry: evaluation of three on-line oxidation methods

A method for the determination of total arsenic (As) in human urine by hydride generation atomic fluorescence spectrometry (HG-AFS) is described. Total As includes the four toxic species; arsenous acid, i.e., As(III), arsenic acid, i.e., As(V), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) and the three major dietary species trimethylarsine oxide (TMAO), arsenobetaine (AsB), and arsenocholine (AsC). It is necessary to normalize signals from all As compounds present beforehand because the HG reaction is dependent on the species. We evaluated three on-line oxidation systems designed to convert As into As(V): (1) microwave-assisted heating (MW); (2) UV-photooxidation (UV-1); and (3) UV-photooxidation with post-reaction heating (UV-2). Each system was used with K2S2O8/NaOH as the oxidant, and was coupled to a commercial HG-AFS instrument for As detection. The efficiencies of the three on-line oxidation systems were compared. Under optimal conditions, all three achieved a signal (normalized to As(V)) within a range of 90–110% at a given concentration, for each of the six As species studied. Calibration using aqueous As(V) standards was achieved for the two UV systems while matrix-matched calibration, i.e., base urine spiked with As(V), was mandatory for the MW system. The requirement for matrix matching with the MW is a key difference compared to the UV systems making the former less suitable for routine analyses. Method detection limits (3 SD) for MW, UV-1, and UV-2 were 9.4, 6.0, and 2.7 μg L−1 respectively, detected as As(V). The performance of each system was evaluated by analysis of certified reference materials and archived urine proficiency testing (PT) materials from three different External Quality Assessment (EQA) schemes. Values obtained for archived PT materials with all three methods were within the acceptable ranges established by each EQA scheme. However, the UV-2 arrangement had some advantages with respect to a lower detection limit and shorter analysis times compared to the other systems.

Determination of five arsenic species in whole blood by liquid chromatography coupled with inductively coupled plasma mass spectrometry

A method was developed to quantify five arsenic species (As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and arsenobetaine (AsB)) in whole blood, using liquid chromatography (LC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). The method can be used for routine monitoring of arsenic species in whole blood as well as in urine, but with different sample preparation. Whole blood was diluted 1 + 4 with reagents containing 3 mM HgCl2, which prevents As(III) from binding to the LC column. The diluted blood was subjected to ultrafiltration so as to remove molecules larger than 3,000 Daltons. Analysis was completed within 12 min, for the determination of arsenic species in whole blood, and within 11 min in urine; the method detection limit is < 0.3 μg L−1 for each arsenic species. The sum of arsenic species measured by the proposed method agreed well with assigned values for total arsenic in whole blood and urine reference materials, and in archived proficiency testing materials. Some urine reference materials provided additional information on the arsenic species present, and our testing results agreed well with the documented values.

Arsenic speciation in freshwater fish: Focus on extraction and mass balance

Arsenic (As) speciation in muscle tissues of freshwater fish was investigated with special emphasis on extraction yields and mass balances. For the quantification of water-soluble As compounds, samples were extracted using a 1:1 (v/v) methanol/water mixture. Various extraction parameters, such as extraction volume, number of additional extractions, intermediate and final volume in sample preconcentration were optimized so as to improve the extraction efficiency. Arsenic compounds were determined by HPLC with online ICP-MS, using both cation and anion exchange separation. The species studied were eel (Anguilla anguilla L.), flathead grey mullet (Mugil cephalus L.), chub (Leuciscus cephalus L.), and carp (Cyprinus carpio L.). Mean total As concentrations ranged from 354 microg kg(-1) dry weight (carp) to 1804 microg kg(-1) dry weight (mullet). Under optimized conditions, the percentage of total As extracted ranged from 64% for carp, to 82%, 84%, and 89% for grey mullet, eel and chub, respectively. Extraction of lipid-rich eel with n-hexane recovered some additional 3% of total As. The sizeable effect of sample matrix on HPLC retention time of some organoarsenicals in gradient elution cation exchange chromatography was exploited to achieve separation of coeluting compounds by analysing the same sample at different dilutions. The recovery of As from chromatographic columns was 101%, 102%, 103% and 104% for carp, chub, mullet and eel, respectively, indicating that no As was retained during chromatography. Arsenobetaine (AB) was the dominating As compound, but several other arsenicals, including arsenous acid (Asiii), arsenic acid (Asv), methylarsonic acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), arsenocholine ion (AC), tetramethylarsonium ion (TETRA), oxo-arsenosugar-glycerol (AS1), oxo-arsenosugar-phosphate (AS2), oxo-arsenosugar-sulfate (AS4), thio-arsenosugar-phosphate (ThioAS2), and three unknown As compounds, were found. Arsenic speciation in carp was different compared to the other fish species, and a lower proportion of AB along with a high contribution of AS2 and ThioAS2 was found. DMA and TMAO were noteworthy minor compounds in eel and carp, respectively. Arsenic speciation and the chemical composition of fish muscle both appeared to affect the extraction yield.

An Automated Hydride Generation Interface to ICPMS for Measuring Total Arsenic in Environmental Samples

An automated hydride generation (AHG) interface to inductive coupled plasma mass spectroscopy (ICPMS) was developed for measuring arsenic in environmental samples. This technique provides statistically indistinguishable response slopes (within about 3%) for hydride generation-ICPMS (HG-ICPMS) analysis of all major As species, inorganic As(III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and inorganic As(V); this has not previously been achieved. Previously, sample pretreatment to convert all forms of As into As(V) has been a prerequisite for measuring total arsenic in complex matrices. Under our operating conditions, arsenobetaine (AsB), until now regarded to be inert, also generates a hydride (albeit the response is only approximately 7% of others). The limit of detection (LOD) based on three times the standard deviation of the blank with this technique for AsB, DMA, As(III), MMA, and As(V) is 90, 66, 63, 63, and 63 pg As, respectively. This AHG-ICPMS technique was compared with a flow injection-UV photolysis-HG-ICPMS (FI-UV-ICPMS) and liquid chromatography-UV-HG-ICPMS analysis of arsenic content in National Institute of Standards & Technology (NIST) standard rice flour (standard reference material: SRM 1568a) and rice samples collected from West Bengal, India. Both oxidative acid digestion and methanol:water (1:1) extraction were used. The analytical results for total As in the SRM 1568a digest were 99.2 +/- 0.6 and 100.2 +/- 0.8% of the certified value (290 +/- 3 microg As/kg) by the AHG-ICPMS and the FI-UV-HG-ICPMS techniques, respectively. For rice extracts and the digests, the two techniques provided results that were correlated with linear r2 values of 0.9988 and 0.9987 with intercepts statistically indistinguishable from zero. Chromatographic analysis indicated that As in these rice samples were 75-90% inorganic.

Rejoinder: Arsenic Exposure and Prevalence of Type 2 Diabetes

Rejoinder: Arsenic Exposure and Prevalence of Type 2 Diabetes

Capabilities of mixed-mode liquid chromatography coupled to inductively coupled plasma mass spectrometry for the simultaneous speciation analysis of inorganic and organically-bound selenium

This work investigates for the first time the potential of mixed-mode (anion-exchange with reversed-phase) high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS) for the simultaneous retention and selective separation of a range of inorganic and organically-bound selenium (Se) species. Baseline separation and detection of selenocystine (SeCys 2), Se-methyl-selenocysteine (SeMC), selenomethionine (SeMet), methylseleninic acid (MSA), selenite, γ-glutamyl-methyl-selenocysteine (γ-glutamyl-SeMC), and selenate in a Se standard mixture by mixed-mode HPLC-ICP-MS was achieved by switching between two citrate mobile phases of different pH and ionic strength within a single chromatographic run of 20 min. Limits of detection obtained for these Se species ranged from 80 ng kg −1 (for SeMC) to 123 ng kg −1 (for selenate). Using this approach as developed for selenium speciation, an adequate separation of inorganic and organic As compounds was also achieved. These include arsenite, arsenate, arsenobetaine (AsB) and dimethylarsenic acid (DMA), which may coexist with Se species in biological samples. Application of the newly proposed methodology to the investigation of the elemental species distribution in watercress (used as the model sample) after enzymatic hydrolysis or leaching in water by accelerated solvent extraction (ASE) was addressed. Only SeMet, SeMC and selenate could be tentatively identified in watercress extracts by mixed-mode HPLC-ICP-MS and retention time matching with standards. Recoveries ( n = 3) of these Se species from samples spiked with standards averaged 102% (for SeMC), 94.9% (for SeMet) and 98.3% (for selenate). Verification of the presence of SeMet and SeMC in an enzymatic watercress extract was achieved by on-line HPLC-ESI MS/MS in selected reaction monitoring (SRM) mode.

Arsenic speciation in marine product samples: Comparison of extraction–HPLC method and digestion–cryogenic trap method

For the arsenic speciation in marine product samples, two types of pretreatment-analysis combination were compared. One is the combination of solvent extraction and high performance liquid chromatography (HPLC) followed by a highly sensitive arsenic detection, while the other is the combination of alkaline digestion and cryogenic trap (CT) method followed by a highly sensitive arsenic detection. For six certified reference materials (CRMs) of marine animal samples, the concentrations of arsenobetaine (AsB) obtained from the extraction–HPLC method were very consistent with those of trimethylated arsenic species measured by the digestion–CT method. For four seaweed samples, the determination of three arsenosugars (Sugar-1, Sugar-2, and Sugar-3) was favorably carried out by the extraction–HPLC method. Those seaweed samples were also subjected to the digestion–CT method, and the amounts of dimethylated arsenic species measured by the method were approximately equal to the sum of the amounts of dimethylarsinic acid (DMAA) and three arsenosugars (Sugar-1 + Sugar-2 + Sugar-3) obtained from the extraction–HPLC method.

Simultaneous determination of arsenic and selenium species in fish tissues using microwave-assisted enzymatic extraction and ion chromatography–inductively coupled plasma mass spectrometry

A microwave-assisted enzymatic extraction (MAEE) method was developed for the simultaneous extraction of arsenic (As) and selenium (Se) species in fish tissues. The extraction efficiency of total As and Se and the stability of As and Se species were evaluated by analyzing DOLT-3 (dogfish liver). Enzymatic extraction using pronase E/lipase mixture assisted by microwave energy was found to give satisfactory extraction recoveries for As and Se without promoting interspecies conversion. The optimum extraction conditions were found to be 0.2 g of sample, 20 mg pronase E and 5 mg lipase in 10 mL of 50 mM phosphate buffer, pH 7.25 at 37 °C. The total extraction time was 30 min. The speciation analysis was performed by ion chromatography–inductively coupled plasma mass spectrometry (IC–ICP–MS). The accuracy of the developed extraction procedure was verified by analyzing two reference materials, DOLT-3 and BCR-627. The extraction recoveries in those reference materials ranged between 82 and 94% for As and 57 and 97% for Se. The accuracy of arsenic species measurement was tested by the analysis of BCR 627. The proposed method was applied to determine As and Se species in fish tissues purchased from a local fish market. Arsenobetaine (AsB) and selenomethionine (SeMet) were the major species detected in fish tissues. In the analyzed fish extracts, the sum of As species detected was in good agreement with the total As extracted. However, for Se, the sum of its species was lower than the total Se extracted, revealing the presence of Se-containing peptides or proteins.

On-line separation and identification of inorganic and organic arsenic species in ethanolic kelp and bladderwrack extracts through liquid chromatography/particle beam-electron ionization mass spectrometry (LC/PB-EIMS)

Ion-pair, reversed-phase high-performance liquid chromatography (IP-RP-HPLC) and ion exchange chromatography (IEC), coupled to particle beam-electron ionization mass spectrometry (PB-EIMS), are employed for the separation and identification of inorganic and organic arsenic compounds (As (III) chloride, arsenobetaine (AB), dimethylarsinic acid (DMA) and an arsenosugar (oxo-arsenosugar-glycerol, As 328) in commercial ethanolic kelp and bladderwrack extracts. The reversed-phase separation was performed on a C18 column using an isocratic mobile phase composition of water:methanol (96:4) containing 0.1% of trifluoroacetic acid (TFA) as an ion-pairing agent. The flow rate was optimized at 0.7 mL min−1 and the separation accomplished in less than 8 minutes. Baseline resolution was achieved in an elution window of about 4 minutes. The ion-exchange separation was performed on an anion-exchange column using a gradient mobile phase composition of 0.5 mM nitric acid containing 2% methanol and 50 mM nitric acid. The separation was accomplished in less than 8 minutes at a flow rate of 0.9 mL min−1. The eluted species were detected and identified using a PB-EIMS system providing species-specific information. The influence of various instrument parameters was evaluated to achieve optimal mass spectrometric response for the test compounds. The absolute detection limits of arsenic species with HPLC/PB-EIMS were 0.03, 0.05, 0.008 ng and 0.005 (5 µL injection) in the SIM mode and 0.1, 0.14, 0.04 and 0.01 ng in the TIC mode for As (III), DMA, AB and As 328 respectively. These investigations revealed that the majority (90–95%) of the arsenic present in the ethanolic extract samples is in the form of inorganic arsenic, with minor amounts of As (5–10% of the total As) present in the form of DMA. There were no detectable levels of AB and arsenosugars. The total arsenic content in the ethanolic extracts was verified by ICP-OES and validated by analyzing NIST SRM 3241 Ephedra sinica Stapf Native Extract and SRM 3243 Ephedra-Containing Solid Oral Dosage Form. These investigations indicate that PB-EIMS is a viable approach for comprehensive speciation of various botanical extracts.

Arsenic biotransformation in earthworms from contaminated soils

Two species of arsenic (As) resistant earthworm, Lumbricus rubellus and Dendrodrillus rubidus, their host soils and soil excretions (casts) were collected from 23 locations at a former As mine in Devon, UK. Total As concentrations, measured by ICP-MS, ranged from 255 to 13,080 mg kg(-1) in soils, 11 to 877 mg kg(-1) in earthworms and 284 to 4221 mg kg(-1) in earthworm casts from a sub-sample of 10 of the 23 investigated sites. The samples were also measured for As speciation using HPLC-ICP-MS to investigate potential As biotransformation pathways. Inorganic arsenate (As(V)) and arsenite (As(III)) were the only species detected in the soil. As(V) and As(III) were also the dominant species found in the earthworms and cast material together with lower proportions of the organic species methylarsonate (MA(V)), dimethylarsinate (DMA(V)), arsenobetaine (AB) and three arsenosugars. Whilst the inorganic As content of the earthworms increased with increasing As body burden, the concentration of organic species remained relatively constant. These results suggest that the biotransformation of inorganic arsenic to organic species does not contribute to As resistance in the sampled earthworm populations. Quantification of As speciation in the soil, earthworms and cast material allows a more comprehensive pathway for the formation of AB in earthworms to be elucidated.

Determination of seven arsenic compounds in urine by HPLC-ICP-DRC-MS: a CDC population biomonitoring method

A robust analytical method has been developed and validated by use of high-performance liquid chromatography inductively coupled plasma mass spectrometry with Dynamic Reaction Cell (DRC) technology that separates seven arsenic (As) species in human urine: arsenobetaine (AB), arsenocholine, trimethylarsine oxide (TMAO), arsenate (As(V)), arsenite (As(III)), monomethylarsonate, and dimethylarsinate. A polymeric anion-exchange (Hamilton PRP X-100) column was used for separation of the species that were detected at m/z 75 by ICP-DRC-MS (PerkinElmer SCIEX ELAN DRCII) using 10% hydrogen-90% argon as the DRC gas. The internal standard (As) is added postcolumn via an external injector with a sample loop. All analyte peaks were baseline-separated except AB and TMAO. Analytical method limits of detection for the various species ranged from 0.4 to 1.7 microg L(-1) as elemental As. As(III) conversion to As(V) was avoided by adjusting the urine sample to <pH 6. Analyses of the National Institute of Standards and Technology standard reference material (SRM) 2670 and 2670a elevated and National Institute for Environmental Studies certified reference material (CRM) no. 18 for arsenic species yielded results within the certified SRM-CRM limits for As species; likewise, the sum of all species compared favorably to SRM 2670 and 2670a target values for total As. This As speciation method is now being used in a production mode for the analysis of a US population survey, the National Health and Nutrition Examination Survey, as well as for other biomonitoring studies of As exposure. This method meets our requirement for sample throughput of 2,000-3,000 sample analyses per year.