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.     

Speciation of organic and inorganic arsenic by HPLC-HG-ICP

This paper deals with the application of high performance liquid chromatography (HPLC), hydride generation (HG) and inductively coupled plasma atomic emission spectrometry (ICP) to determine four species of arsenic: As(III), As(V), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). The coupling conditions of HPLC-HG-ICP are given. Two anionic exchange columns (Nucleosil-5SB and Hamilton PRP X-100) are tested and the separation conditions optimized. Two acids (H₂SO₄ and HCl at different concentrations) are tested to obtain the hydrides. The proposed method is applied to determine four arsenic species in a synthetic matrix simulating a fish extract.     

Speciation of arsenic in a contaminated soil by solvent extraction

Soil collected from a disused cattle dip in northern New South Wales was studied with the aim of developing an inexpensive, yet effective method for quantitative determination of arsenic(III), arsenic(V) and total organic arsenic in a contaminated soil. Hydrochloric acid extractions were used as a method for removal of the arsenic from the soil in a form suitable for speciation. It was found that the extraction efficiency varied with the ratio of soil to acid, and the concentration of the acid. Arsenic(III), as arsenic trichloride, was selectively extracted into chloroform from a solution highly concentrated in hydrochloric acid. This was followed by back-extraction of the arsenic into water. Total inorganic arsenic was determined in a similar manner after the reduction of arsenic(V) to the trivalent state with potassium iodide. Arsenic(V) was determined by the difference between the results for arsenic(III) and total inorganic arsenic. All analyses for the various arsenic species were performed by hydride generation-atomic absorption spectroscopy; concentrations of total arsenic in the soil were confirmed using X-ray fluorescence spectrometry. It was found that all the arsenic in the soil was present as inorganic arsenic in the pentavalent state. This reflects the ability of arsenic to interchange between species, since the original species in cattle dipping solution is arsenic(III).     

Speciation studies for arsenic and mercury-applications and prospects

Methods are described for the speciation of arsenic and mercury in biological and environmental materials. For arsenic various methods were developed to distinguish between more or less toxic arsenic compounds and non-toxic compounds. For the determination of methylmercury a modification of the Westöö procedure was applied for higher contents as well as anion exchange down to levels below 0.1 g/kg in solids and below 0.1 ng/1 in liquids.     

Speciation analysis of arsenic in groundwater from Inner Mongolia with an emphasis on acid-leachable particulate arsenic

Arsenic in drinking water affects millions of people around the world. While soluble arsenic is commonly measured, the amount of particulate arsenic in drinking water has often been overlooked. We report here determination of the acid-leachable particulate arsenic and soluble arsenicals in well water from an arsenic-poisoning endemic area in Inner Mongolia, China. Water samples (583) were collected from 120 wells in Ba Men, Inner Mongolia, where well water was the primary drinking water source. Two methods were demonstrated for the determination of soluble arsenic species (primarily inorganic arsenate and arsenite) and total particulate arsenic. The first method used solid phase extraction cartridges and membrane filters to separate arsenic species on-site, followed by analysis of the individual arsenic species eluted from the cartridges and filters. The other method uses liquid chromatography separation with hydride generation atomic fluorescence detection to determine soluble arsenic species. Analysis of acidified water samples using inductively coupled plasma mass spectrometry provided the total arsenic concentration. Arsenic concentrations in water samples from the 120 wells ranged from <1 to ∼1000 μg L⁻¹. On average, particulate arsenic accounted for 39 ± 38% (median 36%) of the total arsenic. In some wells, particulate arsenic was six times higher than the soluble arsenic concentration. Particulate arsenic can be effectively removed using membrane filtration. The information on particulate and soluble arsenic in water is useful for optimizing treatment options and for understanding the geochemical behavior of arsenic in groundwater.     

Speciation analysis of arsenic and selenium compounds by capillary electrophoresis

High-performance capillary electrophoresis is applied to the separation of different inorganic and organic arsenic and selenium compounds. In comparison with UV-detection, an approach with conductivity detection is described expecting higher sensitivity and universality. In this case the capillary was statically modified with CTAB before the electromigration procedure. The separation was performed with an electrolyte system consisting of CHES and Triton X-100. Detection limits of 0.06 mg/L or lower were obtained for As(V) and Se(VI). Water samples of an arsenic-polluted tailing of tin mining processes were analysed for anions as well as arsenic and selenium species.     

Speciation and instrumental neutron activation analysis for arsenic in water samples

Ground water samples obtained from West Bengal, India were analyzed for total arsenic and its inorganic species contents by instrumental neutron activation analysis (INAA). Two anion exchange separation methods using Dowex 1X8 in chloride and acetate forms were standardized for the speciation of As(III) and As(V) using radiotracers. The method by Dowex 1X8 in the acetate form was validated using synthetic mixtures of As(III) and As(V), and applied to water samples; the species concentrations were determined by INAA. The accuracy of the INAA method was evaluated by analyzing the NRCC CRM DORM-2 for total arsenic.     

Speciation analysis of arsenic and selenium compounds by capillary electrophoresis

High-performance capillary electrophoresis is applied to the separation of different inorganic and organic arsenic and selenium compounds. In comparison with UV-detection, an approach with conductivity detection is described expecting higher sensitivity and universality. In this case the capillary was statically modified with CTAB before the electromigration procedure. The separation was performed with an electrolyte system consisting of CHES and Triton X-100. Detection limits of 0.06 mg/L or lower were obtained for As(V) and Se(VI). Water samples of an arsenic-polluted tailing of tin mining processes were analysed for anions as well as arsenic and selenium species.     

Speciation analysis of arsenic in samples containing high concentrations of chloride by LC-HG-AFS

Analytical and Bioanalytical Chemistry - Chloride widely exists in the environment and will cause serious interference for arsenic speciation analysis. The determination of four arsenic species...     

毛细管电泳-电感耦合等离子体质谱法测定藻类中6种不同形态的砷化合物

建立了一种利用毛细管电泳与电感耦合等离子体质谱联用技术(CE-ICP-MS)分析检测6种不同形态砷化合物的方法。详细研究了缓冲溶液的种类、pH值和浓度,分离电压以及进样时间等因素对6种砷化合物的分离度、灵敏度和重现性等的影响。结果表明,在最佳条件下,三价砷(As3+)、一甲基砷(MMA)、二甲基砷(DMA)、五价砷(As5+)、砷胆碱(AsC)和砷甜菜碱(AsB)6种化合物在25 min内得到完全分离。6次平行测定中,6种砷化合物峰面积的相对标准偏差(RSD)为3%～5%,检出限(以As计)(3倍信噪比)为0.08～0.12 μg/L。应用该方法成功地对海带中6种砷化合物进行了分析,回收率为90%～103%。该方法具有耗时短、灵敏度高、样品消耗量少、稳定性好等优点,可用于藻类样品中不同形态砷化合物的分析。     

Speciation of arsenic using capillary gas chromatography with atomic emission detection

A gas chromatography method with atomic emission detection (GC-AED) for the determination of dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and inorganic arsenic was optimized. The analytes were derivatized in the sample solutions with methyl thioglycolate (TGM) and the products were extracted into cyclohexane before an aliquot of this organic phase was directly injected into the chromatograph. The procedure was applied to the analysis of seawaters, wines, beers and infant foods, the last requiring an additional enzymatic reaction prior to analyte derivatization. Detection limits in seawaters and beverages were 0.05, 0.15 and 0.8 ng mL⁻¹ for DMA, MMA and inorganic arsenic, respectively. In infant foods the detection limits were 1, 10 and 25 ng g⁻¹ for DMA, MMA and inorganic arsenic, respectively. Inorganic arsenic was detected in some of the seawater samples and three of the wines analyzed at concentration levels in the range 1-40 ng mL⁻¹, and DMA in several of the infant foods in the range 20-80 ng g⁻¹. The method was validated by analyzing a certified reference material and by recovery studies. All the samples were also analyzed by hydride generation and atomic fluorescence spectrometry (HG-AFS), which provided data for the total arsenic content.     

Speciation of inorganic arsenic by electrochemical hydride generation atomic absorption spectrometry

A simple procedure was developed for the speciation of inorganic arsenic by electrochemical hydride generation atomic absorption spectrometry (EcHG–AAS), without pre-reduction of As(V). Glassy carbon was selected as cathode material in the flow cell. An optimum catholyte concentration for simultaneous generation of arsine from As(III) and As(V) was 0.06 mol l⁻¹ H₂SO₄. Under the optimized conditions, adequate sensitivity and difference in ratio of slopes of the calibration curves for As(III) and As(V) can be achieved at the electrolytic currents of 0.6 and 1 A. The speciation of inorganic arsenic can be performed by controlling the electrolytic currents, and the concentration of As(III) and As(V) in the sample can be calculated according to the equations of absorbance additivity obtained at two selected electrolytic currents. The calibration curves were linear up to 50 ng ml⁻¹ for both As(III) and As(V) at 0.6 and 1 A. The detection limits of the method were 0.2 and 0.5 ng ml⁻¹ for As(III) and As(V) at 0.6 A, respectively. The relative standard deviations were of 2.1% for 20 ng ml⁻¹ As(III) and 2.5% for 20 ng ml⁻¹ As(V). The method was validated by the analysis of human hair certified reference material and successfully applied to speciation of soluble inorganic arsenic in Chinese medicine.     

Speciation of arsenic(V) and arsenic(III) by cathodic stripping voltammetry in fresh water samples

A voltammetric stripping procedure is described for the determination of arsenic(V) in a mannitol-sulphuric acid medium. The arsenic is coprecipitated with copper and selenium and reduced to arsine at the hanging mercury drop electrode. Using an accumulation time of 240 s, the detection limit is 0.52 μg L^–1, the determination limit is 0.9 μg L^–1. The method has been applied to the determination of arsenic in water samples. By varying the composition of the supporting electrolyte it is possible to differentiate between arsenic(III) and arsenic(V). As both oxidation states have different toxicological characteristics, the ability to discriminate between both is an distinct advantage of the proposed method. Received: 25 October 1996 / Revised: 7 February 1997 / Accepted: 12 February 1997     

Determination of arsenic in biological fluids by electrothermal atomic absorption spectrometry

A procedure for the determination of the total content of arsenic in urine, serum and blood by electrothermal atomic absorption spectrometry (ETAAS) is described. Zeeman correction is used to compensate the high background signals. The samples are diluted (1 + 1 for urine and 1 + 3 for both serum and blood samples) in a medium containing 0.1% w/v Triton X-100 before being introduced directly into the furnace. A solution containing 15% w/v hydrogen peroxide, 0.65% w/v nitric acid and 0.5% w/v nickel is also introduced into the atomizer by means of a separate injection. Calibration is carried out against aqueous standards for blood and serum samples and using the standard additions method for urine samples. The detection limit is 20 pg (2 ng ml-1). The reliability of the procedure is checked by analyzing three certified reference materials and by recovery studies.     

燃煤电厂煤及其燃烧副产物中砷形态分析

燃煤电厂煤中砷（As）的形态在燃烧过程中不可避免地会发生转化。煤及其副产物中砷的形态与人体健康和环境安全密切相关，亟待鉴别。然而目前针对煤燃烧相关产物中砷形态的前处理手段和分析方法尚缺乏。本研究采用高效液相色谱-氢化物发生-原子荧光光谱法（HPLC-HG-AFS）成功测定了电厂煤、粉煤灰和石膏中砷的形态，优化了仪器参数、提取试剂和前处理方法（超声和微波辅助）。优化后，无机砷的分离时间缩短至7 min，As（Ⅲ）和As（V）的检出限分别为1.8 ng/g和4.6 ng/g。砷形态的高效提取剂为1.0 mol/L 磷酸和0.1 mol/L 抗坏血酸的混合溶液。微波辅助（2000 W、80 ℃、40 min）和超声辅助（40 kHz、20 ℃、40 min）分别是煤/粉煤灰和石膏样品中砷形态的最佳提取方法。在微波和超声波辅助提取条件下，As（Ⅲ）/As（V）的回收率分别为95.8%/104.5%和90.6%/89.7%。样品分析结果表明，煤中砷主要以As（V）形式存在，As（Ⅲ）所占比例很小，而在粉煤灰和石膏中只观察到As（V）。该研究揭示了As（Ⅲ）向As（V）的转化是气态砷捕获的关键，可以为控制电厂砷排放提供科学依据。