Inorganic Arsenic Species Research Articles

Portable and rapid arsenic speciation in synthetic and natural waters by an As(V)-selective chemisorbent, validated against anodic stripping voltammetry

Inorganic arsenic speciation, i.e. the differentiation between arsenite and arsenate, is an important step for any program aiming to address the global issue of arsenic contaminated groundwater, whether for monitoring purposes or the development of new water treatment regimes. Reliable speciation by easy-to-use, portable and cost-effective analytical techniques is still challenging for both synthetic and natural waters. Here we demonstrate the first application of an As(V)-selective chemisorbent material for simple and portable speciation of arsenic using handheld syringes, enabling high sample throughput with minimal set-up costs. We first show that ImpAs efficiently removes As(V) from a variety of synthetic groundwaters with a single treatment, whilst As(III) is not retained. We then exemplify the potential of ImpAs for simple and fast speciation by determining rate constants for the photooxidation of As(III) in the presence of a TiO2 photocatalyst. Finally, we successfully speciate natural waters spiked with a mix of As(III) and As(V) in both Indian and UK groundwaters with less than 5 mg L−1 dissolved iron. Experimental results using ImpAs agreed with anodic stripping voltammetry (ASV), a benchmark portable technique, with analysis conditions optimised here for the groundwaters of South Asia. This new analytical tool is simple, portable and fast, and should find applications within the overall multi-disciplinary remediation effort that is taking place to tackle this worldwide arsenic problem.

Simultaneous preconcentration and determination of trace quantities of inorganic arsenic species in water using Ni0.5Zn0.5Fe2O4 magnetic nanoparticles

Nickel–zinc ferrite (Ni0.5Zn0.5Fe2O4) nanosorbent was prepared and used for the efficient simultaneous preconcentration of arsenite and arsenate ions from aqueous solutions. The prepared nanoparticles were characterized by XRD measurements which indicated that the Ni0.5Zn0.5Fe2O4 nanoparticles were synthesized well. The SEM results showed an average diameter of 27 nm for the nanoparticles. The adsorption capacity was found to be 35.8 and 62.5 mg g−1 for As(III) and As(V), respectively. The adsorbed ions were then quantitatively eluted using 2 mL of 2 M NaOH solution as an elution solvent and determined spectrophotometrically. The maximum preconcentration factor for both the investigated ions was found to be 100. As(III) and As(V) species were determined in the mixture based on the difference in their adsorption behavior at different pHs. For an initial sample volume of 200.0 mL, the calibration graph was linear in the range 0.3–50.0 ng mL−1 of As(III) and 0.2–75.0 ng mL−1 of As(V) concentration. The method resulted in a successful determination of As(III) and As(V) in water samples.

Ionic imprinted polymer solid-phase extraction for inorganic arsenic selective pre-concentration in fishery products before high-performance liquid chromatography – inductively coupled plasma-mass spectrometry speciation

Low levels of inorganic arsenic [As(III) and As(V)] in fishery products have been selectively isolated from fish extracts (1.0 g of wet fish samples pre-treated with 10 mL of 1:1 methanol/water under sonication at 25 °C for 30 min) by ionic imprinted polymer (IIPs) based solid phase extraction procedure (on-column mode). The selective adsorbent was synthesized using sodium (meta) arsenite as a template, 1-vinyl imidazole as a functional monomer, divinylbenzene as a cross-linker, and 2,2′-azobisisobutyronitrile as an initiator. Optimized pre-concentration conditions imply fish extract (10 mL) pH adjustment at 8.5 before loading (flow rate of 0.25 mL min−1), and elution with ultrapure water (2 mL) at 0.50 mL min−1. A pre-concentration factor of 50 was finally obtained after evaporation to dryness (N2 stream) and re-dissolution in 0.2 mL of ultrapure water before HPLC-ICP-MS. Synthesized material was found to pre-concentrate inorganic arsenic species; whereas organic arsenic compounds, mainly arsenobetaine (the major organoarsenic compound in fish/seafood products), were not found to interact with the adsorbent. The developed selective method gave limits of quantification of 1.05 and 1.31 µg kg−1 for As (III) and As (V), respectively, and good precision [relative standard deviations lower than 12% in fish extracts spiked at several As (III) and As (V) levels]. The proposed method was finally applied to the selective determination of As (III) and As (V) species in several fishery products.

Arsenic species in electronic cigarettes: Determination and potential health risk

Human exposure to contaminants from electronic cigarettes (e-cigarettes) and the associated health effects are poorly understood. There has been no report on the speciation of arsenic in e-liquid (solution used for e-cigarettes) and aerosols. We report here determination of arsenic species in e-liquids and aerosols generated from vaping the e-liquid. Seventeen e-liquid samples of major brands, purchased from local and online stores in Canada and China, were analyzed for arsenic species using high-performance liquid chromatography and inductively coupled plasma mass spectrometry. Aerosols condensed from vaping the e-liquids were also analyzed and compared for arsenic species. Six arsenic species were detected, including inorganic arsenate (iAsV), arsenite (iAsIII), monomethylarsonic acid (MMA), and three new arsenic species not reported previously. In e-liquids, iAsIII was detected in 59%, iAsV in 94%, and MMA in 47% of the samples. In the condensate of aerosols from vaping the e-liquids, iAsIII was detected in 100%, iAsV in 88%, and MMA in 13% of the samples. Inorganic arsenic species were predominant in e-liquids and aerosols of e-cigarettes. The concentration of iAsIII in the condensate of aerosols (median 3.27 μg/kg) was significantly higher than that in the e-liquid (median 1.08 μg/kg) samples. The concentration of inorganic arsenic in the vaping air was approximately 3.4 μg/m3, which approaches to the permissible exposure limit (10 μg/m3) set by the United States Occupational Safety and Health Administration (OSHA). According to the Environmental Protection Agency's unit risk factor (4.3 × 10−3 per μg/m3) for inhalation exposure to inorganic arsenic in the air, the estimated excess lung cancer risk from lifetime exposure to inorganic arsenic in the e-cigarette vaping air (3.4 μg/m3), assuming e-cigarette vaping at 1% of the time, is as high as 1.5 × 10−4. These results raise health concerns over the exposure to arsenic from electronic cigarettes.

Capillary electrophoresis coupled to electrospray mass spectrometry for the determination of organic and inorganic arsenic compounds in water samples

Some compounds of arsenic are extremely toxic to the human body even at low levels. Long-term exposure from drinking contaminated water causes adverse health effects. This has led the European Union and other global organizations to reduce the maximum residue limit for the total arsenic up to 10 μg L−1 in water for human consumption. The toxicity of arsenic depends on the oxidation state, chemical structure and solubility in the biological environment. Main analytical procedures report on the determination of arsenic species in water samples which have been developed based on atomic spectroscopy –speciation performed in the sample treatment step– and inductively coupled plasma-mass spectrometry (ICP-MS). In such cases, speciation is performed by coupling to high-performance liquid chromatography (HPLC). As far as we know, the determination of arsenic species in water samples at low concentration levels by capillary electrophoresis (CE) coupled to electrospray mass spectrometry (ESI-MS) has not been described up to now. In this research CE-ESI(−)-MS is proposed for the identification and simultaneous quantification of organic and inorganic arsenic species in water samples for human consumption. The target compounds were dimethylarsinate (DMA), mono-methylarsonate (MMA), arsenite (i-As(III)) and arsenate (i-As(V)). Optimization of the composition and nature of both the electrophoretic separation medium –using hexafluoro-2-propanol (HFIP) as an additive– and the sheath liquid was performed and aimed at achieving the best sensitivity and separation efficiency for the CE-ESI(−)-MS coupling. Two simple sample treatments were proposed: one based on dispersive liquid-liquid micro-extraction (DLLME) intended for a rapid determination of the total content of inorganic arsenic in the water sample; and the second based on partial evaporation of the water sample to detect each of the four main arsenic species. For the second, limits of detection between 0.02 and 0.04 μg L-1 were found, which are similar results as the ones achieved with methods based on HPLC-ICP-MS.The DLLME + CE-ESI(−)-MS method was applied to the determination of total inorganic arsenic in eleven water samples in the province of Salamanca (Spain). Five of the analyzed samples had values close to, or superior to the maximum residue limit for the total of arsenic in water intended for human consumption (10 μg L-1). The validated method CE-ESI(−)-MS for arsenic speciation was applied with success to the analysis of the weakly mineralized water sample (dry residue < 50 mg L-1) of both groundwater and bottled water.

Synthesis and application of a surface ionic imprinting polymer on silica-coated Mn-doped ZnS quantum dots as a chemosensor for the selective quantification of inorganic arsenic in fish.

A novel room temperature phosphorescence chemosensor probe has been successfully developed and applied to the selective detection and quantification of inorganic arsenic (As(III) plus As(V)) in fish samples. The prepared material (IIP@ZnS:Mn QDs) was based on Mn-doped ZnS quantum dots coated with (3-aminopropyl) triethoxysilane and an As(III) ionic imprinted polymer. The novel use of vinyl imidazole as a complexing reagent when synthesizing the ionic imprinted polymer guarantees that both inorganic arsenic species (As(III) and As(V)) can interact with the recognition cavities in the ionic imprinted polymer. After characterization, several studies were performed to enhance the interaction between the targets (As(III) and As(V) ions) and the IIP@ZnS:Mn QDs nanoparticles. The optimization and validation process showed that the composite material offers high selectivity (high imprinting factor) for inorganic arsenic species. The limit of quantification for total inorganic As was 29.6μgkg-1, value lower than the EU/EC regulation limits proposed for other foodstuffs than fish, such as rice. The proposed method is therefore simple, requires short analysis times and offers good sensitivity, precision (inter-day relative standard deviations lower than 10%), and quantitative analytical recoveries. The method has been successfully applied to assess total inorganic arsenic in several fishery products, showing good agreement with the total inorganic arsenic concentration (As(III) plus As(V)) found after applying other advanced and expensive methods such those based on high-performance liquid chromatography hyphenated to inductively coupled plasma-mass spectrometry. Graphical abstract.

Comparative Cytotoxicity of Inorganic Arsenite and Methylarsenite in Human Brain Cells

The overall goal of this study is to elucidate the potential effect(s) of arsenic on a variety of human brain cells. Arsenic is the most pervasive Group A human environmental carcinogen. Long-term exposure to arsenic is associated with human diseases including cancer, cardiovascular disease, and diabetes. More immediate are the health effects on neurological development and associated disorders in infants and children exposed to arsenic in utero. Arsenic is metabolized in various organs and tissues into more toxic methylated species, including methylarsenite (MAs(III)), so the question arises whether the methylate species are responsible for the neurological effects of arsenic. Arsenic enters the brain through the blood-brain barrier and produces toxicity in the brain microvascular endothelial cells, glia (astrocytes and microglia), and neurons. In this study, we first assessed the toxicity in different types of brain cells exposed to either inorganic trivalent As(III) or MAs(III) using both morphological and cytotoxicity cell-based analysis. Second, we determined the methylation of arsenicals and the expression levels of the methylation enzyme, As(III) S-adenosylmethionine (SAM) methyltransferase (AS3MT), in several types of brain cells. We showed that the toxicity to neurons of MAs(III) was significantly higher than that of As(III). Interestingly, the differences in cytotoxicity between cell types was not due to expression of AS3MT, as this was expressed in neurons and glia but not in endothelial cells. These results support our hypothesis that MAs(III) is the likely physiological neurotoxin rather than inorganic arsenic species.

Soluble Inorganic Arsenic Species in Atmospheric Submicron Particles in Two Polish Urban Background Sites

This paper presents results of the research on soluble inorganic As(III) and As(V) bound to submicron atmospheric particles (PM1) in two Polish urban background sites (Zabrze and Warsaw). The purpose of the research was to give some insight on the susceptibility to leaching of PM1-bound arsenic species from easily water-soluble compounds, i.e., considered potentially bioavailable based on its daily and seasonal changes. Quantitative analysis for 120 PM1 samples (collected from 24 June 2014 to 8 March 2015) was performed by using a high-performance liquid chromatography in combination with inductively coupled plasma mass spectrometry. The mean seasonal concentrations of dominant soluble As specie—As(V)—ranged from 0.27 ng/m3 in the summer season in Warsaw to 2.41 ng/m3 in the winter season in Zabrze. Its mean mass shares in total As were 44% in Warsaw and 75% in Zabrze in the winter and 18% and 48%, respectively, in the summer. Obtained results indicated fossil fuel combustion as the main source of PM1-bound As(V) and road traffic emission as its minor sources. In opposite to As(V), soluble As(III) was not clearly seasonally variable. In both seasons, its mean concentrations were higher in Zabrze than in Warsaw. As(III) concentrations were not preferentially shaped by an exact emission from road traffic in both cities.

Inter‐and intra-stock bioaccumulation of anionic arsenic species in an endangered catfish from South American estuaries: Risk assessment through consumption

Monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), inorganic arsenic (iAs), and non-toxic species (i.e. arsenobetaine) were determined by HPLC-ICP-MS as mg kg−1 wet weight in muscle, liver and gill of catfish (Genidens barbus) from Argentina (N = 12) and from Brazil (N = 11). Concentrations (mean ± standard deviation) of non-toxic arsenic species were 10.4 ± 2.89 and 14.9 ± 5.94 for muscle, 1.48 ± 0.58 and 2.21 ± 1.24 for liver, and 0.66 ± 0.39 and 2.44 ± 1.93 for gill, respectively, for Argentina and Brazil, and represented 95.5%–99.5% of the total arsenic for each tissue. Toxic arsenic (iAs) levels were 0.048 and 0.013 for muscle, 0.24 and 0.011 for liver, and 0.037 and 0.012 for gill and represented 0.45–4.93 % of the total arsenic for Argentina and 0.24-0.60 % for Brazil. The iAs concentrations for all tissues were below the recommended international and local legislations of 0.1-1.0. Based on iAs in muscle, target hazard quotients were 0.032 and 0.018, respectively, for Argentina and Brazil. Risks external (skin) cancer and internal (bladder/lung) cancer were 1.4 × 10-5 and 1.9 × 10-4 for Argentina and 7.3 × 10-6 and 9.9 × 10-5 for Brazil, suggesting that populations may be exposed to an internal cancer risk through chronic consumption. Risk assessments need to be based on specific fish and their iAs concentrations in muscle.

The speciation of inorganic arsenic in soil and vegetables irrigated with treated municipal wastewater.

In this research, an environmental friendly, green and efficient sample preparation method using vortex-assisted microextraction based on a deep eutectic solvent (VAME-DES) followed by graphite furnace atomic absorption spectrometry (GFAAS) was developed for the preconcentration and determination of As(iii)/As(v) and total inorganic arsenic in soil and vegetables irrigated with treated municipal wastewater from Tehran and Kermanshah, Iran. In the proposed method, a novel DES, characterized by its low density, was prepared by mixing choline chloride and citric acid monohydrate at a molar ratio of 1 : 1. Under optimal conditions, the proposed method enabled the achievement of a good enrichment factor of 175. The calibration graph was linear in the range of 0.3–100 μg kg−1 and the limit of detection (LOD) was 0.10 μg kg−1. The repeatability and reproducibility of the method based on seven replicate measurements of 50 μg kg−1 As(iii) in analysed samples were 4.2% and 6.5, respectively. The relative recoveries from soil and vegetables that were spiked with different levels of As(iii) and As(v) were 94.2–104.3 and 91.0–107.0%, respectively. The main advantage of the proposed method is the use of a non-toxic and non-volatile DES instead of volatile organic solvents. The accuracy of the proposed procedure was also assessed by the speciation of arsenic in two standard reference materials (GBW10014 cabbage and GBW10015 spinach). The extraction methodology is simple, rapid, cheap and green, since only small amounts of non-toxic solvents are necessary.

Development of modified kaolins for the removal of As (III) in waters

Some inorganic species of arsenic (As) present in drinking waters are highly dangerous for human health. Adsorption technique is considered a promising technology for the selective removal of As from aqueous systems. Iron (Fe), and iron-containing clays are adsorbents commonly used for arsenic elimination from water due to the strong affinity between Fe and inorganic species of As. Natural and acid-treated kaolinites, impregnated with iron oxides (30 % and 20 % of the Fe (III)) were developed in the present work. The selected clays were physico-chemically characterised, and the As adsorption capability was tested in batch experiments at pH = 7. Arsenic removal studies showed 97% effectiveness for the 30% iron sedimented kaolinite at 1 h of treatment, being the most effective developed material. These preliminary results showed that the Fe (III) impregnated kaolinites could be considered as promising adsorbent materials for As removal from aqueous systems.

Sensitivity enhancement of inorganic arsenic analysis byin situmicroplasma preconcentration coupled with liquid chromatography atomic fluorescence spectrometry

A novel liquid chromatography hydride generation-in situdielectric barrier discharge trap-atomic fluorescence spectrometry instrument was fabricated. It was used to preconcentrate inorganic arsenic species from food samples.

In silico analysis of functional linkage among arsenic induced MATE genes in rice

MATE genes play an important role in cellular detoxification processes. Nine MATE genes were identified by a transcriptomics study previously. Candidate gene prioritization was done where 29 new genes were found to interact with 09 guide genes. Therefore, a total of 38 genes were analyzed here to predict a concise model by gene prioritization study. Those genes were analyzed further in Rice Interactions Viewer programme, and based on high ICV, 10 new genes were found to interact among themselves at protein level. Surprisingly, only 05 genes were found to play a key role at protein level. These 15 genes were analyzed for their interaction with soil available inorganic arsenic species. Maximum expression levels were found mostly at young inflorescence and seed development stage for those genes. So, these genes may have a direct role in arsenic sequestration from cells and thereby providing safety to the developing embryo within the seed.

Simulated solar light driven roxarsone degradation and arsenic immobilization with hematite and oxalate

Solar light driven organoarsenicals degradation and simultaneous inorganic arsenic immobilization with naturally abundant hematite is very promising for organoarsenicals remediation, but suffers from the fast electron-hole charge recombination of hematite. Herein, we report that oxalate, widely existed in soil and water environments, can greatly enhance the photocatalytic molecular oxygen activation of hematite to degrade a typical organoarsenical roxarsone and immobilize the resulted inorganic arsenic. It was found that oxalate could chelate with surface Fe(III) of hematite to generate plenty of •OH via a surface Fe(III)/Fe(II) cycle mediated oxygen molecular activation process under a simulated solar light, and thus induced 85.1% of roxarsone transformation into inorganic arsenic species, mainly As(V), within 6 h. The generated As(V) could be further adsorbed on hematite surface with prolonging the reaction time to 24 h in dark, avoiding secondary pollution. More importantly, hematite was reusable for the simulated solar light driven roxarsone degradation and As(V) immobilization in the presence of oxalate. This study offers a green and effective strategy for organoarsenicals remediation, and also sheds light on the environmental effects of iron oxides and oxalate.

In–spray chamber hydride generation by multi–mode sample introduction system (MSIS) as an interface in the hyphenated system of high performance liquid chromatography and inductivity coupled plasma optical emission spectrometry (HPLC/HG–ICP–OES) in arsenic species determination

The paper presents a new usage of a commercial in–spray chamber hydride generator, Multi–mode Sample Introduction System (MSIS) as a connector of high pressure liquid chromatography and inductivity coupled plasma optical emission spectrometry (HPLC/HG–ICP–OES). This hyphenated technique was applied in a determination of inorganic and organic arsenic species. The optimization of a hydride generation process in MSIS and a chromatographic separation (using anion–exchange HPLC column with phosphate buffer as a mobile phase) were carried out compositely. The method allowed to determine three arsenic forms, As(III), As(V) and dimethylarsinate (DMA) within 400s of a single analysis. The obtained limits of detection (LODs) were 2.08 μg L−1 for As(III); 6.97 μg L−1 for As(V); 6.15 μg L−1 for DMA and precision 2.7%, 4.8%, and 5.7%, respectively, for 100 μg L−1. The described method was used for environmental and food samples analyses.

Introducing Frontal Chromatography-Inductively Coupled Plasma-Mass Spectrometry as a Fast Method for Speciation Analysis: The Case of Inorganic Arsenic.

A frontal chromatography-ICP-MS method (FC-ICP-MS) is proposed as an innovative approach for fast elemental speciation analysis: inorganic arsenic speciation was selected as the first case study to prove the feasibility of the technique and to explore its potentialities and limits. The principal benefits of the FC-ICP-MS approach are the short analysis time and the very simple instrumental setup. As(III) and As(V) front separation is performed over a strong anion exchanger at pH 7.5. After the optimization of the instrumental setup and the frontal chromatographic parameters, As(III) and As(V) concentrations up to 240 μg/kg can be determined within 120-140 s using different univariate and multivariate calibration approaches. Best results in terms of accuracy in prediction were obtained using the partial least squares (PLS) calibration achieving limits of detection of 0.18 and 0.21 μg/kg for As(III) and As(V), respectively. This approach was also used to establish the figures of merit of the method. The proved feasibility and good performances (in terms of analysis time and accuracy) of this technique lay the groundwork for future applications of FC-ICP-MS for the speciation of other elements.

Differently shaped nanocrystalline (Fe, Y)3O4 and its adsorption efficiency toward inorganic arsenic species

Herein we report effects of partial substitution of Fe3+ by Y3+ in magnetite (Fe3O4) on morphology and inorganic arsenic species adsorption efficiency of the Fe3−xYxO4 nanoparticles formed. The series of Fe3−xYxO4 (x = 0.00, 0.042 and 0.084, labeled as Y00, Y05 and Y10, respectively) was synthesized using co-precipitation followed by microwave-hydrothermal treatment (MW) at 200 °C. With increase of yttrium content (x value), both the morphological inhomogeneity of the samples and the fraction of spinel nanorods as compared to spinel pseudospherical particles increased. By both transmission electron microscopy and x-ray powder diffraction analyses, it was determined that the direction of growth of the spinel nanorods is along the [110] crystallographic direction. The Fe3−xYxO4 affinities of adsorption toward the inorganic arsenic species, As(III) (arsenite, AsO33−) and As(V) (arsenate, AsO43−), were investigated. Increased Y3+ content related to changes in sample morphology was followed by a decrease of As(III) removal efficiency and vice versa for As(V). The increase in Y3+ content, in addition to increasing the adsorption capacity for As(V), significantly expanded the optimum pH range for the maximum removal and decreased the contact time for necessary 50% removal (t1/2) of As(V) (Y00: pH 2–3, t1/2 = 3.12 min; Y05: pH 2–6, t1/2 = 2.12 min and Y10: pH 2–10, t1/2 = 1.12 min). The results point to incorporation of Y3+ in the crystal lattice of magnetite, inducing nanorod spinel structure formation with significant changes in sorption properties important for the removal of inorganic arsenic from waters.

Optimized extraction of inorganic arsenic species from a foliose lichen biomonitor.

To assess the two most toxicologically relevant species of As, namely arsenite (As(III)) and arsenate (As(V)), chromatographic separations often require two separate chromatographic columns to address the co-elution of arsenobetaine (AsB) with As(III). This issue is typically observed using conventional isocratic methods on anion exchange columns, increasing cost and analysis time. Here, we optimize the extraction of inorganic As from a lichen air biomonitor and develop an isocratic method for the chromatographic separation of five common As species on a PRP X-100 anion exchange column, resulting in the complete baseline separation of all species under study. This method was then applied to lichen biomonitors from an urban and rural site to demonstrate its use. In order of abundance, the various arsenic species in lichens from the urban site in South Africa were As(V) > As(III) > AsB > dimethylarsinic acid (DMA) > monomethylarsonic acid (MMA), and As(V) > AsB > As(III) > DMA > MMA for the rural site, where MMA was present in extremely low, non-quantifiable concentrations in lichens from both sites. Total concentrations of As were higher in samples from the urban site (6.43 ± 0.25 μg/g) than in those from the rural site (1.87 ± 0.05 μg/g), with an overall extraction efficiency of 19% and 40%, respectively. The optimized method utilized relatively inexpensive solvents and is therefore low-cost and eco-friendly in comparison with conventional chromatographic techniques. This is the first study which addresses the optimized extraction and characterization of As species in a South African lichen biomonitor of air pollution. Graphical abstract .

Vortex-assisted supramolecular solvent microextraction based on solidification of floating drop for preconcentration and speciation of inorganic arsenic species in water samples by molybdenum blue method

A new vortex-assisted supramolecular solvent microextraction based on solidification of floating drop (VA-SSM-SFD) has been developed for preconsentration and spectrophotometric determination of inorganic arsenic (iAs) species in various water samples. The method is based on the formation of arsenomolybdenium blue complex followed by VA-SSM-SFD procedure and subsequent spectrophotometric determination in a microcell. The supramolecular solvents consisted of reverse micelles of 1-dodecanol in tetrahydrofuran (THF) which were formed by in-situ coacervation of 1-dodecanol micelles in aqueous samples. Under optimized conditions, iAs (V) formed hetroploy blue complex and was directly determined. The concentration of iAs (III) was determined by subtracting iAs (III) from the total iAs following the oxidation of iAs (III) to iAs (V) by permanganate in acidic medium. Under optimal conditions, the calibration curve for iAs determination showed good linearity in the range of 5.0–140.0 μg L−1(R2 = 0.9988) and detection limit was found to be 0.4 μg L−1, which is much lower than WHO guideline of 10 μg L−1 for iAs in drinking water. The repeatability and reproducibility for 20 μg L−1 were found to be 2.47 and 3.9%, respectively. The proposed method was successfully applied to speciation of iAs species in real water samples.

The use of zirconium stationary phase to determine the four major arsenoriboses concentrations in marine organisms by high-performance liquid chromatography coupled to inductively coupled plasma–mass spectrometry

HPLC-ICP-MS utilising a ZirChrom®-SAX column with an aqueous 10 mM ammonium dihydrogen phosphate mobile phase at pH 7.5 (adjusted with aqueous ammonia) was evaluated for measuring glycerol arsenoriboside (OH-ribose), phosphate arsenoriboside (PO4-ribose), sulfonate arsenoriboside (SO3-ribose) and sulfate arsenoriboside (OSO3-ribose) in marine macroalgae and animals by analysis of seven reference materials. The results obtained were compared to those obtained using PRP-X100 anion-exchange chromatography. Inorganic arsenic species were not eluted from the zirconium column due to the strong interaction with the zirconia stationary phase. Measurements of SO3-ribose and OSO3-ribose concentrations were in close agreement with those obtained using the PRP-X100 column with a 0.005 mg As kg−1 detection limit. Peak shapes of these arsenoriboses were improved allowing lower amounts to be quantified. The quantification of OH-ribose and PO4-ribose, however, was sample dependent and not possible if arsenobetaine (AB) and (DMA) were present at large concentrations in samples because of coelution of these species with OH-ribose and PO4-ribose, respectively. In the absence of OH-ribose, AB can be determined using the zirconium column while AB on the PRP-X100 column coelutes with arsenic cations.