Speciation of arsenic by ion chromatography inductively coupled plasma mass spectrometry using ammonium eluents

Ammonium acetate as a novel buffer for highly selective robust urinary HPLC-ICP-MS arsenic speciation methodology

Ammonium acetate is employed in order to develop a novel HPLC-ICP-MS arsenic speciation methodology applicable to six arsenic species, i.e, AC, AB, As^III, As^V, DMA and MMA. The most predominant species in the toxicological field are covered in a 30-min chromatogram with reproducible and repeatability peak area ratio. Moreover, typical problems from traditional methods are sorted out by using a robust, high-selective and ⁷⁵ArCl⁺ interference-free methodology. Chromatographic and detector optimization ensures low LOQs for each species with acceptable precision and accuracy values obtained using four urinary arsenic speciation PTS enabling to be useful for sub ng mL^-1 arsenic exposure assessments.

Speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry

In this work, a methodology for chemical speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry is proposed. Doehlert design and desirability function were used to find the optimum conditions for hydride generation (1.0 mol L^-1 HCl and 0.9% m v^-1 NaBH₄). The accuracy of the analytical method was evaluated by analysis of reference material fly ash (BCR 176R), addition and recovery tests for inorganic As species, and comparison of independent methods for Sb determination in urban dust samples. The determination of the total concentrations of As and Sb and their inorganic species presented good accuracy, between 80 ± 1 and 101 ± 6%. Precision was expressed as the relative standard deviation and was better than 4.7% (n = 3). The limit-of-quantification values were 0.23 and 1.03 mg kg^-1 for As and Sb, respectively. The methodology was applied to eight samples of dust collected in an urban area of Salvador and Jaguaquara cities, Bahia, Northeast, Brazil, with an aerodynamic size lower than 38 μm. Concentrations of pentavalent inorganic species (iAs⁵⁺ and iSb⁵⁺) in relation to trivalent species (iAs³⁺ and iSb³⁺) were found in urban dust collected in the city of Salvador, which are regarded as more toxic for both elements. The enrichment factor and geoaccumulation index (I_geo) values showed that for some samples, the concentrations of iAs and iSb presented strong enrichment and, and regarding environment, strong to moderately polluted by iAs and iSb, with an indication of anthropogenic contributions. The occurrence of these inorganic constituents in the urban area of Salvador can be related with intense industrial activities and vehicular traffic.

Analytical Methodologies for the Determination of Organoarsenicals in Edible Marine Species: A Review

Setting regulatory limits for arsenic in food is complicated, owing to the enormous diversity of arsenic metabolism in humans, lack of knowledge about the toxicity of these chemicals, and lack of accurate arsenic speciation data on foodstuffs. Identification and quantification of the toxic arsenic compounds are imperative to understanding the risk associated with exposure to arsenic from dietary intake, which, in turn, underscores the need for speciation analysis of the food. Arsenic speciation in seafood is challenging, owing to its existence in myriads of chemical forms and oxidation states. Interconversions occurring between chemical forms, matrix complexity, lack of standards and certified reference materials, and lack of widely accepted measurement protocols present additional challenges. This review covers the current analytical techniques for diverse arsenic species. The requirement for high-quality arsenic speciation data that is essential for establishing legislation and setting regulatory limits for arsenic in food is explored.

Sequential determination and chemical speciation analysis of inorganic As and Sb in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by HG AAS

In this work, fast sequential determination and chemical speciation analysis of inorganic arsenic and antimony in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by hydride generation atomic absorption spectrometry (HG-AAS) is proposed. A Doehlert design was applied to optimise the hydride generation conditions of As and Sb for fast sequential determination in the same aliquot of particulate matter samples after preparation of the slurry. The limits of quantification (LoQ) obtained for As and Sb were 0.3 and 0.9 ng m^-3, respectively. The accuracy of the analytical method was confirmed by analysis of the certified reference material of urban particulate matter (SRM NIST 1648a), presenting concordance with certified values of 92.7±7.7% for As and 91.2±9.5% for Sb. Precision was expressed as relative standard deviation (% RSD, n=3), with our results presenting values better than 3.4% and 4.2% for total inorganic As and Sb, respectively. For all analysed samples, total As concentrations and its inorganic species were below the LoQ of the analytical method (<0.3 ng m^-3). However, the averages of total inorganic Sb concentrations in airborne particulate matter, collected as total suspended outdoor particles (TSP_outdoor), inhalable particulate matter (PM₁₀), and total suspended indoor particles (TSP_indoor), were 3.1±0.5, 2.4±0.6, and 2.6±0.4 ng m^-3, respectively. Trivalent Sb (Sb³⁺) was the predominant inorganic species in all samples investigated, with mean percentages of 76%, 72%, and 73% in TSP_outdoor, PM₁₀, and TSP_indoor, respectively. The presence of Sb and its predominant inorganic form (Sb³⁺) can be attributed to vehicular traffic close to the sampled urban areas. Therefore, fast sequential determination of As and Sb and their inorganic species in particulate matter samples prepared as slurry by FS-HG-AAS is an efficient, accurate, and precise method and can be successfully applied to routine analysis.

Arsenic Species Analysis at Trace Level by High Performance Liquid Chromatography with Inductively Coupled Plasma Mass Spectrometry

A sensitive and accurate simultaneous continuous analysis for six arsenic species including arsenobetaine (AsB), arsenocholine (AsC), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenite (As^III), and arsenate (As^V) has been developed by high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). An anion-exchange column of Hamilton PRP-X100 (Switzerland) was applied for separation of the six arsenic species with gradient elution of 1.25 mmol/L Na₂HPO₄ and 11.0 mmol/L KH₂PO₄ as the mobile phase A and 2.5 mmol/L Na₂HPO₄ and 22.0 mmol/L KH₂PO₄ as the mobile phase B. The linearity ranges for AsB, AsC, MMA, DMA, As^III, and As^V were between 0.5 and 50.0 μg/L, and the detection limits of the six arsenic species were all within 0.01–0.35 ng/L. The relative standard deviations (RSDs) were within 2.26–3.68% and the recovery rates of samples ranged from 95 to 103%. The proposed method was applied for the arsenic speciation analysis of sediment pore-water samples, which were taken from the supernatant after centrifugation and filtration.

Concentrations of inorganic arsenic in groundwater, agricultural soils and subsurface sediments from the middle Gangetic plain of Bihar, India

Concentrations of inorganic forms [arsenite, As(III) and arsenate, As(V) of arsenic (As) present in groundwater, agricultural soils and subsurface sediments located in the middle Gangetic plain of Bihar, India were determined. Approximately 73% of the groundwater samples (n=19) show As(III) as the dominant species while 27% reveals As(V) was the dominant species. The concentration of As(III) in agricultural soil samples varies from not detectable to 40μg/kg and As(V) was observed as the major species (ranging from 1050 to 6835μg/kg) while the total As concentration varied from 3528 to 14,690μg/kg. Total extracted concentration of As was higher in the subsurface sediments (range 9119-20,056μg/kg in Methrapur and 4788-19,681μg/kg in Harail Chapar) than the agricultural soil, indicating the subsurface sediment as a source of As. Results of X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) revealed the presence of hematite and goethite throughout the vertical section below while magnetite was observed only in the upper oxidized layer at Methrapur and Harail Chapar. Alteration of Fe-oxides and presence of fibrous goethite indicating presence of diagenetic sediment. Siderite plays a crucial role as sinks to the As in subsurface sediments. The study also concluded that decomposition of organic matter present in dark and grey sections promote the redox conditions and trigger mobilization of As into groundwater.

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.

Application of hyphenated techniques in speciation analysis of arsenic, antimony, and thallium

Due to the fact that metals and metalloids have a strong impact on the environment, the methods of their determination and speciation have received special attention in recent years. Arsenic, antimony, and thallium are important examples of such toxic elements. Their speciation is especially important in the environmental and biomedical fields because of their toxicity, bioavailability, and reactivity. Recently, speciation analytics has been playing a unique role in the studies of biogeochemical cycles of chemical compounds, determination of toxicity and ecotoxicity of selected elements, quality control of food products, control of medicines and pharmaceutical products, technological process control, research on the impact of technological installation on the environment, examination of occupational exposure, and clinical analysis. Conventional methods are usually labor intensive, time consuming, and susceptible to interferences. The hyphenated techniques, in which separation method is coupled with multidimensional detectors, have become useful alternatives. The main advantages of those techniques consist in extremely low detection and quantification limits, insignificant interference, influence as well as high precision and repeatability of the determinations. In view of their importance, the present work overviews and discusses different hyphenated techniques used for arsenic, antimony, and thallium species analysis, in different clinical, environmental and food matrices.

Simultaneous characterization of selenium and arsenic analytes via ion-pairing reversed phase chromatography with inductively coupled plasma and electrospray ionization ion trap mass spectrometry for detection applications to river water, plant extract and urine matrices

With an increased awareness and concern for varying toxicities of the different chemical forms of environmental contaminants such as selenium and arsenic, effective methodologies for speciation are paramount. In general, chromatographic methodologies have been developed using a particular detection system and a unique matrix for single element speciation. In this study, a routine method to speciate selenium and arsenic in a variety of "real world" matrices with elemental and molecular mass spectrometric detection has been successfully accomplished. Specifically, four selenium species, selenite, selenate, selenomethionine and selenocystine, and four arsenic species, arsenite, arsenate, monomethlyarsonate and dimethylarsinate, were simultaneously separated using ion-pairing reversed phase chromatography coupled with inductively coupled plasma and electrospray ionization ion trap mass spectrometry. Using tetrabutylammonium hydroxide as the ion-pairing reagent on a C(18) column, the separation and re-equilibration time was attained within 18min. To illustrate the wide range of possible applications, the method was then successfully applied for the detection of selenium and arsenic species found naturally and spiked in river water, plant extract and urine matrices.