Flow-injection hydride generation atomic absorption spectrometric study of the automated on-line pre-reduction of arsenate, methylarsonate and dimethylarsinate and high-performance liquid chromatographic separation of their -cysteine complexes

An automated on-line pre-reduction of arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) using flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) is feasible. The kinetics of pre-reduction and complexation depend strongly on the concentration of -cysteine and on the temperature in the following increasing order: inorganic As(V)<DMA<MMA. Arsenate is pre-reduced/complexed within less than 50 s at 70–100°C compared to 1 h at room temperature, while MMA and DMA require 1.5–2 min at 70–100°C and up to 1–2 h at room temperature. The characteristic masses and concentrations for 100 μl injections are 0.01 ng and 0.1 μg l⁻¹ in integrated absorbance and 0.2 ng and 2 μg l⁻¹ in peak height measurements, and the limits of detection are ca. 0.5 ng and 5 μg l⁻¹, respectively. In a high-performance liquid chromatography (HPLC)–HGAAS system, the -cysteine complexes of inorganic As(III), MMA and DMA are best separated within 7 min by HPLC on a strongly acidic cation exchange column such as Spherisorb S SCX 120×4 mm (5 μm) with a mobile phase containing 12 mmol l⁻¹ phosphate buffer (KH₂PO₄/H₃PO₄)–2.5 mmol l⁻¹ -cysteine, pH 3.3–3.5. Upon dilution to -cysteine levels below 10 mmol l⁻¹, which are compatible with HPLC separations, the DMA–cysteine complex is unstable on storage. No baseline separations are possible with anion exchange and reverse phase C₁₈ HPLC columns. The limits of detection with 50 μl injections in peak area mode are ca. 0.5 ng and 10 μg l⁻¹, respectively.     

A new hydride generation system applied in determination of arsenic species with ion chromatography-hydride generation-atomic fluorescence spectrometry (IC-HG-AFS)

A novel procedure was developed for the determination of arsenite (As(III)), arsenate (As(V)), monomethylarsonic (MMA) and dimethylarsinic acid (DMA) with ion chromatography-hydride generation-atomic fluorescence spectrometry (IC-HG-AFS) by employing a new gas-liquid separator (GLS). The effective separation of the four arsenic species was achieved in about 12 min. With a sample loading volume of 20 μl, the measurable minimum for As(III), DMA, MMA and As(V) were 0.02, 0.045, 0.043 and 0.166 ng, respectively, along with relative standard deviations of 1.1, 1.1, 1.7 and 2.2% at the 100 μg l⁻¹ level (n = 6) for As(III), DMA, MMA and As(V), respectively. The present procedure was applied for the speciation of arsenic in underground water and in urine samples, and the sum of the four arsenic species by IC-HG-AFS was in good agreement with the total value by HG-AFS.     

Arsenic speciation in water samples containing high levels of copper: removal of copper interference affecting arsine generation by continuous flow solid phase chelation

A simple continuous flow method is proposed to eliminate copper interference in arsenic speciation by hydride generation, based on the selective retention of this interfering ion in an iminodiacetate chelating resin previous to the hydride generation process. The arsines generated were cold trapped and measured by ICP/OES. The proposed method allows about 98% of the copper present in the samples to be removed. Minor co-retention of As(V) was observed as a result of electrostatic interaction between the arsenate anion and the nitrogen of the iminodiacetate group of the chelating resin Muromac A-1, the charge distribution of which is modified when copper is chelated. The species As(III), MMA and DMA were not retained in the microcolumn, probably because these species are mainly in the molecular form at the working pH value (4.5). In synthetic samples containing 50 g l^–1 of each arsenic species together with 100 mg l^–1 copper, the recoveries obtained were: As(V) 97.6%, As(III) 100%, MMA 99.8%, and DMA 99.9%. The method was applied to arsenic speciation in river water samples containing high levels of copper.     

Arsenic speciation in Chinese brake fern by ion-pair high-performance liquid chromatography-inductively coupled plasma mass spectroscopy

Ion-pair reverse-phase HPLC-inductively coupled plasma (ICP) MS was employed to determine arsenite [As(III)], dimethyl arsenic acid (DMA), monomethyl arsenic (MMA) and arsenate [As(V)] in Chinese brake fern (Pteris vittata L.). The separation was performed on a reverse-phase C18 column (Haisil 100) by using a mobile phase containing 10 mM hexadecyltrimethyl ammonium bromide (CTAB) as ion-pairing reagent, 20 mM ammonium phosphate buffer and 2% methanol at pH 6.0. The detection limits of arsenic species with HPLC-ICP-MS were 0.5, 0.4, 0.3 and 1.8 ppb of arsenic for As(III), DMA, MMA, and As(V), respectively. MMA has been shown for the first time to experimentally convert to DMA in the Chinese brake fern, indicating that Chinese brake fern can convert MMA to DMA by methylation.     

Determination of arsenic compounds in beverages by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

Arsenic compounds including arsenous acid (As(III)), arsenic acid (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were separated by high-performance liquid chromatography (HPLC) and detected by inductively coupled plasma mass spectrometry (ICP-MS). A Hamilton PRX-100 anionic-exchange column and a pH 8.5 K₂HPO₄/KH₂PO₄ 5.0 × 10⁻³ mol L⁻¹ mobile phase were used to achieve arsenic speciation. The separation of arsenic species provided peaks of As(III) at 2.75 min, DMA at 3.33 min, MMA at 5.17 min and As(V) at 12.5 min. The detection limits, defined as three times the standard deviation of the lowest standard measurements, were found to be 0.2, 0.2, 0.3 and 0.5 ng mL⁻¹ for As(III), DMA, MMA and As(V), respectively. The relative standard deviation values for a solution containing 5.0 μg L⁻¹ of As(III), DMA, MMA and As(V) were 1.2, 2.1, 2.5 and 3.0%, respectively. This analytical procedure was applied to the speciation of arsenic compounds in drinking (soft drink, beer, juice) samples. The validation of the procedure was achieved through the analysis of arsenic compounds in water and sediment certified reference materials.     

On-line separation and preconcentration of inorganic arsenic and selenium species in natural water samples with CTAB-modified alkyl silica microcolumn and determination by inductively coupled plasma-optical emission spectrometry

A new, simple, and selective method has been presented for the separation and preconcentration of inorganic arsenic (As(III)/As(V)) and selenium (Se(IV)/Se(VI)) species by a microcolumn on-line coupled with inductively coupled plasma-optical emission spectrometry (ICP-OES). Trace amounts of As(V) and Se(VI) species were separated and preconcentrated from total As and Se at desired pH values by a conical microcolumn packed with cetyltrimethylammonium bromide (CTAB)-modified alkyl silica sorbent in the absence of chelating reagent. The species adsorbed by CTAB-modified alkyl silica sorbent were quantitatively desorbed with 0.10 ml of 1.0 mol l⁻¹ HNO₃. Total inorganic arsenic and selenium were similarly extracted after oxidation of As(III) and Se(IV) to As(V) and Se(VI) with KMnO₄ (50.0 μmol l⁻¹). The assay of As(III) and Se(IV) were based on subtracting As(V) and Se(VI) from total As and total Se, respectively. All parameters affecting the separation/preconcentration of As(V) and Se(VI) including pH, sample flow rate and volume, eluent solution and volume have been studied. With a sample volume of 3.0 ml, the sample throughput was 24 h⁻¹ and the enrichment factors for As(V) and Se(VI) were 26.7 and 27.6, respectively. The limits of detection (LODs) were 0.15 μg l⁻¹ for As(V) and 0.10 μg l⁻¹ for Se(VI). The relative standard deviations (RSDs) for nine replicate determinations at 5.0 μg l⁻¹ level of As(V) and Se(VI) were 4.0% and 3.6%, respectively. The calibration graphs of the method for As(V) and Se(VI) were linear in the range of 0.5–1000.0 μg l⁻¹ with a correlation coefficient of 0.9936 and 0.9992, respectively. The developed method was successfully applied to the speciation analysis of inorganic arsenic and selenium in natural water samples with satisfactory results.     

Voltammetric determination of arsenic in high iron and manganese groundwaters

Determination of the speciation of arsenic in groundwaters, using cathodic stripping voltammetry (CSV), is severely hampered by high levels of iron and manganese. Experiments showed that the interference is eliminated by addition of EDTA, making it possible to determine the arsenic speciation on-site by CSV. This work presents the CSV method to determine As(III) in high-iron or -manganese groundwaters in the field with only minor sample treatment. The method was field-tested in West-Bengal (India) on a series of groundwater samples. Total arsenic was subsequently determined after acidification to pH 1 by anodic stripping voltammetry (ASV). Comparative measurements by ICP-MS as reference method for total As, and by HPLC for its speciation, were used to corroborate the field data in stored samples. Most of the arsenic (78 ± 0.02%) was found to occur as inorganic As(III) in the freshly collected waters, in accordance with previous studies. The data shows that the modified on-site CSV method for As(III) is a good measure of water contamination with As. The EDTA was also found to be effective in stabilising the arsenic speciation for longterm sample storage at room temperature. Without sample preservation, in water exposed to air and sunlight, the As(III) was found to become oxidised to As(V), and Fe(II) oxidised to Fe(III), removing the As(V) by adsorption on precipitating Fe(III)-hydroxides within a few hours.     

Evaluation of liquid chromatography inductively coupled plasma mass spectrometry for arsenic speciation in water from industrial treatment of shale

This work describes an arsenic speciation analysis in aqueous effluent from a shale industrial plant using liquid chromatography coupled to inductively coupled plasma mass spectrometry (LC–ICP–MS). Arsenic species have been separated through an anion-exchange column and several parameters investigated, such as retention time, pH, flow rate and concentration of the mobile phase (ammonium carbonate), chloride interference and column conditioning time. The best conditions have been found by fixing the pH of the mobile phase at 8.7. Keeping the mobile phase flow rate at 1.5 ml min^− 1, arsenic species were separated by varying the concentration of the mobile phase and the time of elution, as follow: 1.5 mmol l^− 1 for 10 min, 12 mmol l^− 1 for 10 min and 20 mmol l^− 1 for 10 min, respectively. Up to 13 As species present in the samples were separated under these conditions and the following species could be identified and quantified: arsenite [As(III)], dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate [As(V)]. The limits of detection of the LC–ICP–MS method were 0.02, 0.06, 0.04 and 0.10 μg l^− 1 of As(III), DMA, MMA, and As(V), respectively. The concentration of these species in the samples were from 3.7 to 6.4 μg l^− 1, 6.9 to 13.2 μg l^− 1, 100 to 142 μg l^− 1 and 808 to 1363 μg l^− 1 for As(III), DMA, MMA and As(V), respectively. The accuracy, evaluated by recovery tests, varied from 94 to 105% and the precision, evaluated by the relative standard deviation was typically lower than 10%.     

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.     

Non-chromatographic speciation of toxic arsenic in fish

A rapid, sensitive and economic method has been developed for the direct determination of toxic species of arsenic present in fish and mussel samples. As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) were determined by hydride generation-atomic fluorescence spectrometry using a series of proportional equations without the need of a chromatographic previous separation. The method is based on the extraction of arsenic species from fish through sonication with HNO₃ 3 mol l⁻¹ and 0.1% (m/v) Triton and washing of the solid phase with 0.1% (m/v) EDTA, followed by direct measurement of the corresponding hydrides in four different experimental conditions. The limit of detection of the method was 0.62 ng g⁻¹ for As(III), 2.1 ng g⁻¹ for As(V), 1.8 ng g⁻¹ for MMA and 5.4 ng g⁻¹ for DMA, in all cases expressed in terms of sample dry weight. The mean relative standard deviation values (R.S.D.) in actual sample analysis were: 6.8% for As(III), 10.3% for As(V), 8.5% for MMA and 7.4% for DMA at concentration levels from 0.08 mg kg⁻¹ As(III) to 1.3 mg kg⁻¹ DMA. Recovery studies provided percentages greater than 93% for all species in spiked samples. The analysis of SRM DORM-2 and CRM 627 certified materials evidenced that the method is suitable for the accurate determination of arsenic species in fish.     

Arsenic speciation in natural waters by cathodic stripping voltammetry

Contamination of groundwater with arsenic (As) is a major health risk through contamination of drinking and irrigation water supplies. In geochemically reducing conditions As is mostly present as As(III), its most toxic species. Various methods exist to determine As in water but these are not suitable for monitoring arsenic speciation at its original pH and without preparation. We present a method that uses cathodic stripping voltammetry (CSV) to determine reactive As(III) at a vibrating, gold, microwire electrode. The As(III) is detected after adsorptive deposition of As(OH)₃⁰, followed by a potential scan to measure the reduction current from As(III) to As(0). The method is suitable for waters of pH 7-12, has an analytical range of 1 nM to 100 μM As (0.07-7500 ppb) and a limit of detection of 0.5 nM with a 60 s deposition time. The As speciation protocol involves measuring reactive As(III) by CSV at the original pH and acidification to pH 1 to determine inorganic As(III) + As(V) by anodic stripping voltammetry (ASV) using the same electrode. Total dissolved As is determined by ASV after UV-digestion at pH 1. The method was successfully tested on various raw groundwater samples from boreholes in the UK and West Bengal.     

Speciation of arsenic in natural waters by HPLC-NAA

Neutron activation analysis (NAA) in combination with mainly high-performance liquid chromatography (HPLC) has been developed for the determination of low levels of five arsenic species, namely As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and arsenobetaine (AsB) in water samples. Organically bound arsenic (OBAs) and total arsenic have also been determined. In addition to anion-exchange HPLC, solid phase extraction and open-column cation-exchange chromatographic methods have also been used. The detection limits of the method have been found to be 0.005 ng·cm⁻³ for OBAs, 0.02 ng·cm⁻³ for AsB, DMA, MMA, As(III), and As(V) and 0.12 ng·cm⁻³ for total arsenic. This revised version was published online in July 2006 with corrections to the Cover Date.     

Urinary arsenic speciation by high-performance liquid chromatography/atomic absorption spectrometry for monitoring occupational exposure to inorganic arsenic

Total urinary arsenic determinations are often used to assess occupational exposure to inorganic arsenic. Ingestion of sea food can increase the normal background levels of total arsenic in urine by up to an order of magnitude, but this arsenic has relatively little toxicity; it is tightly bound as arsenobetaine. The excretion of inorganic arsenic and its metabolites dimethylarsenic acid (DMA) and monomethylarsonic acid (MMA) is not influenced by the consumption of arsenic from sea food. Specific measurements of DMA, MMA and inorganic arsenic provide a more reliable indicator or exposure than total urinary arsenic levels. An automated atomic absorption method involving high-performance liquid chromatographic separation of the arsenic species and continuous hydride generation is described for the determination of arsenite, arsenate, DMA and MMA at μg As l^?1 levels. The method is used to study normal urinary arsenic levels in laboratory staff and arsenic excretion by exposed workers.     

Continuous flow hydride generation-atomic fluorescence spectrometric determination and speciation of arsenic in wine

Methods for the atomic fluorescence spectrometric (AFS) determination of total arsenic and arsenic species in wines based on continuous flow hydride generation (HG) with atomization in miniature diffusion flame (MDF) are described. For hydride-forming arsenic, l-cysteine is used as reagent for pre-reduction and complexation of arsenite, arsenate, monomethylarsonate and dimethylarsinate. Concentrations of hydrochloric acid and tetrahydroborate are optimized in order to minimize interference by ethanol. Procedure permits determination of the sum of these four species in 5–10-fold diluted samples with limit of detection (LOD) 0.3 and 0.6 μg l^− 1 As in white and red wines, respectively, with precision between 2% and 8% RSD at As levels within 0.5–10 μg l^− 1.Selective arsine generation from different reaction media is used for non-chromatographic determination of arsenic species in wines: citrate buffer at pH 5.1 for As(III); 0.2 mol l^− 1 acetic acid for arsenite + dimethylarsinate (DMA); 8 mol l^− 1 HCl for total inorganic arsenic [As(III) + As(V)]; and monomethylarsonate (MMA) calculated by difference. Calibration with aqueous and ethanol-matched standard solutions of As(III) is used for 10- and 5-fold diluted samples, respectively. The LODs are 0.4 μg l^− 1 for As(III) and 0.3 μg l^− 1 for the other three As species and precision is within 4–8% RSDs.Arsenic species in wine were also determined by coupling of ion chromatographic separation on an anion exchange column and HG-flame AFS detection. Methods were validated by means of recovery studies and comparative analyses by HG-AFS and electrothermal atomic absorption spectrometry after microwave digestion. The LODs were 0.12, 0.27, 0.15 and 0.13 μg l^− 1 (as As) and RSDs were 2–6%, 5–9%, 3–7% and 2–5% for As(III), As(V), MMA and DMA arsenic species, respectively. Bottled red and white wines from Bulgaria, Republic of Macedonia and Italy were analyzed by non-chromatographic and chromatographic procedures and the As(III), arsenite, has been confirmed as major arsenic species.     

Use of perchloric acid as a reaction medium for speciation of arsenic by hydride generation-atomic absorption spectrometry

Simple and inexpensive methods for the speciation of arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in environmental water samples were developed. In these methods a hydride generation-atomic absorption spectrometry (HG-AAS) technique was employed and perchloric acid (as a reaction medium), L-cysteine (as a pre-reducing agent for a certain contact time between its addition and analysis) and sodium tetrahydroborate(III) (NaBH4, as a reducing agent) were used. The use of L-cysteine greatly enhances the absorption signals of all four arsenic species at low acid concentration (0.001-0.04 M). The methods developed for the determination of total arsenic and total inorganic arsenic and speciation of the four arsenic species in environmental water samples are as follows. (i) DMA: 0.005 M acid and 0.04% NaBH4 in the absence of L-cysteine. DMA can also be speciated in the presence of L-cysteine as follows: 2 M acid, 2.5% L-cysteine after a contact time of approximately 5 min and 0.6% NaBH4. (ii) As(III): 5 M acid and 0.08% NaBH4 in the absence of L-cysteine. (iii) Total inorganic arsenic (As(III) + As(V)]: 8 M acid and 0.6% NaBH4 in the absence of L-cysteine. (iv) Total arsenic: 0.01 M acid, 5% L-cysteine after a contact time of 5 min and 2% NaBH4. (v) MMA: 8 M acid, 3% L-cysteine after a contact time of 50 min and 0.6% NaBH4. (vi) As(V): by difference. Detection limits and recoveries of added spikes for all analyses were found to be 0.5-1.7 ppb and 90-112% respectively.     

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.     

Evaluation of atomic fluorescence spectrometry as a sensitive detection technique for arsenic speciation

The potential of coupling anion-exchange high-performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC–HG–AFS) for arsenic speciation is considered. The effects of hydrochloric acid and sodium tetrahydroborate concentrations on signal-to-background ratio, as well as argon and hydrogen flow rates, were investigated. Detection limits for arsenite, dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate were 0.17, 0.45, 0.30 and 0.38 μg l⁻¹, respectively, using a 20-μl loop. Linearity ranges were 0.1–500 ng for As(III) and MMA (as arsenic), and 0.1–800 ng for DMA and As(V) (as arsenic). Arsenobetaine (AsB) was also determined by introducing an on-line photo-oxidation step after the chromatographic separation. In this case the limits of detection and linear ranges for the different species studied were similar to the values obtained previously for As(V). The technique was tested with a human urine reference material and a volunteer's sample. © 1998 John Wiley & Sons, Ltd.     

Extraction of arsenic species from airborne particulate filters—Application to an industrial area of Greece

In the present study, the extraction of the arsenic species arsenite (As(III)), arsenate (As(V)), monomethyarsonic (MMA) and dimethylarsinic acid (DMA) from airborne particulate filters was investigated and optimized. For this purpose, total suspended particulate matter as well as size fractionated aerosol samples were collected from the industrial area of Aspropyrgos, Greece, in glass fibre and polycarbonated filters, respectively. Among H₃PO₄ and HCl, tested in various concentrations, concentrated HCl was found to be the most effective extractant for arsenic from both polycarbonated and glass fibre filters, without provoking any arsenic species transformation. However, the quantitative extraction of arsenic species from glass fibre filters required the subsequent washing of the filters with ultrapure water after their leaching with concentrated HCl. The developed procedure was applied to airborne particulate filters for arsenic speciation in Aspropyrgos' atmosphere. The results showed an enrichment of As in the fine (PM_2.5) compared with the coarse (PM_10–2.5) fraction of airborne particulates, while As(V) was found to be the predominant arsenic species in all samples. Finally, As concentration in the PM₁₀ fraction, for the investigated area and time period from December 2004 to June 2006, was below the target value of 6 ng As m^− 3, referred in the Directive 2004/107 of European Union.     

Speciation of major arsenic species in seawater by flow injection hydride generation atomic absorption spectrometry

Arsenic present at 1 μg L^–1 concentrations in seawater can exist as the following species: As(III), As(V), monomethylarsenic, dimethylarsenic and unknown organic compounds. The potential of the continuous flow injection hydride generation technique coupled to atomic absorption spectrometry (AAS) was investigated for the speciation of these major arsenic species in seawater. Two different techniques were used. After hydride generation and collection in a graphite tube coated with iridium, arsenic was determined by AAS. By selecting different experimental hydride generation conditions, it was possible to determine As(III), total arsenic, hydride reactive arsenic and by difference non-hydride reactive arsenic. On the other hand, by cryogenically trapping hydride reactive species on a chromatographic phase, followed by their sequential release and AAS in a heated quartz cell, inorganic As, MMA and DMA could be determined. By combining these two techniques, an experimental protocol for the speciation of As(III), As(V), MMA, DMA and non-hydride reactive arsenic species in seawater was proposed. The method was applied to seawater sampled at a Mediterranean site and at an Atlantic coastal site. Evidence for the biotransformation of arsenic in seawater was clearly shown.     

Determination of As(III), As(V), MMA and DMA in drinking water by solid phase extraction and neutron activation

A combination of solid phase extraction, coprecipitation, and neutron activation techniques has been used to develop a speciation analysis method based on green chemistry for the major arsenic species in drinking water. Arsenate as As(V), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) are separated and preconcentrated by strongly anion and cation exchange columns in tandem while As(III) remains in the effluent. These species are then selectively eluted and As(III) coprecipitated with bismuth sulphide. This simple method has been applied to the analysis of water reference materials with good results. The detection limits are 0.9, 1.7, 1.6, 3.8 and 16 ng mL⁻¹ for As(III), As(V), MMA, DMA and total arsenic, respectively, using a neutron flux of 2.5 × 10¹¹ cm⁻² s⁻¹ at the Dalhousie University SLOWPOKE-2 reactor (DUSR) facility and anti-coincidence gamma-ray spectrometry.