Determination Of Total Arsenic Research Articles

Cadmium-Assisted Photochemical Vapor Generation of Arsenic from Low Concentration of Formic Acid Media.

A highly sensitive method for the determination of total arsenic (As) has been developed using photochemical vapor generation (PVG) coupled with inductively coupled plasma mass spectrometry (ICP MS). The efficient PVG of As is reported for the first time in the presence of Cd(II) in diluted formic acid (FA) medium. The PVG efficiency of 93 ± 1% can be achieved in the system with 0.15% (v/v) FA and 40.0 mg L-1 Cd(II) under 100 s UV irradiation. The limit of detection (LOD, 3σ) for As was determined to be 0.2 ng L-1, which was enhanced about 43-fold over the traditional solution nebulization method. The anti-interference capability against sample matrices was enhanced compared to previous PVG systems that used diluted formic acid alone or a combination of sodium formate and sodium sulfite as the medium. The established method was applied for the analysis of natural waters and certified reference materials (CRMs) of rice with satisfactory results. The mechanism of the PVG system was investigated, and the generation of volatile As species as AsH3 was found in all investigated systems, including monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), As (III), and As(V). Additionally, volatile cadmium species were also generated simultaneously. The efficient reduction of As in diluted FA observed in this study is beneficial to understanding the interaction between As and Cd in the photochemical process.

A novel block copolymer containing gadolinium oxide nanoparticles in ultrasound assisted-dispersive solid phase microextraction of total arsenic in human foodstuffs: A multivariate optimization methodology

A new poly(3-hydroxy butyrate)-b-poly(dimethyl amino ethyl methacrylate) amphiphilic block copolymer containing gadolinium oxide nanoparticles (PHB-PDMAEMA-Gd2O3-NPs) were synthesized and used as composite adsorbent for extraction of total arsenic. Characterization of the composite adsorbent material PHB-PDMAEMA-Gd2O3-NP was studied using spectroscopic techniques. Plackett-Burman design and central composite design were employed to screening and optimization of the experimental parameters. This composite adsorbent was utilized in ultrasound assisted-dispersive solid phase microextraction (UA-dSPµE) for the determination of total inorganic arsenic in foodstuffs through hydride generation atomic absorption spectrometry (HG-AAS). It demonstrates a linear relationship across arsenic concentration range of 0.07–1.12 µg/L with a correlation coefficient (0.996). It’s showed an enrichment factor of 128 and a limit of detection 0.02 µg/L for total inorganic arsenic determination. Accuracy of the developed method was confirmed through the analysis of certified reference materials with 96.0–98.5% recovery. It proved to be significantly useful UA-dSPµE method for determining total inorganic arsenic in different foodstuffs.

Voltammetric determination of inorganic arsenic in mildly acidified (pH 4.7) groundwaters from Mexico and India

Routine monitoring of inorganic arsenic in groundwater using sensitive, reliable, easy-to-use and affordable analytical methods is integral to identifying sources, and delivering appropriate remediation solutions, to the widespread global issue of arsenic pollution. Voltammetry has many advantages over other analytical techniques, but the low electroactivity of arsenic(V) requires the use of either reducing agents or relatively strong acidic conditions, which both complicate the analytical procedures, and require more complex material handling by skilled operators. Here, we present the voltammetric determination of total inorganic arsenic in conditions of near-neutral pH using a new commercially available 25 μm diameter gold microwire (called the Gold Wirebond), which is described here for the first time. The method is based on the addition of low concentrations of permanganate (10 μM MnO4−) which fulfils two roles: (1) to ensure that all inorganic arsenic is present as arsenate by chemically oxidising arsenite to arsenate and, (2) to provide a source of manganese allowing the sensitive detection of arsenate by anodic stripping voltammetry at a gold electrode. Tests were carried out in synthetic solutions of various pH (ranging from 4.7 to 9) in presence/absence of chloride. The best response was obtained in 0.25 M chloride-containing acetate buffer resulting in analytical parameters (limit of detection of 0.28 μg L−1 for 10 s deposition time, linear range up to 20 μg L−1 and a sensitivity of 63.5 nA ppb−1. s−1) better than those obtained in acidic conditions. We used this new method to measure arsenic concentrations in contrasting groundwaters: the reducing, arsenite-rich groundwaters of India (West Bengal and Bihar regions) and the oxidising, arsenate-rich groundwaters of Mexico (Guanajuato region). Very good agreement was obtained in all groundwaters with arsenic concentrations measured by inductively coupled plasma-mass spectrometry (slope = +1.029, R2 = 0.99). The voltammetric method is sensitive, faster than other voltammetric techniques for detection of arsenic (typically 10 min per sample including triplicate measurements and 2 standard additions), easier to implement than previous methods (no acidic conditions, no chemical reduction required, reproducible sensor, can be used by non-voltammetric experts) and could enable cheaper groundwater surveying campaigns with in-the-field analysis for quick data reporting, even in remote communities.

An electrochemical sensor for the detection of arsenic using nanocomposite-modified electrode

The aim of this research is to develop an electrochemical sensor based on a conducting polymer, polyaniline, and a cationic polymer, poly(diallyldimethylammonium chloride), reinforced with graphene oxide nanosheets functionalized with acrylic acid. The two-dimensional nature of acrylic acid functionalized graphene oxide nanosheets and clusters made of conductive polymers and acrylic acid functionalized graphene oxide nanosheets were confirmed by microscopic tests. The prepared nanocomposite was deposited on the glassy carbon electrode in order to prepare an electrochemical sensor for the detection of arsenic by cyclic voltammetry and differential pulse voltammetry methods. It should be mentioned that the presence of acrylic acid functionalized graphene oxide nanosheets increases the surface area due to the nano size effect and better dispersion of this nanomaterial, poly(diallyldimethylammonium chloride), increases the adsorption capacity of the analyte due to electrostatic interaction between the negatively charged analyte and positively charged surface, and polyanilin increases the charge transfer rate due to the good conductivity. The results show that the prepared electrode has a sensitivity equal to 1.79 A/M with 0.12 μM as the detection limit. The proposed sensor could be used for the determination of total inorganic arsenic by first oxidative pretreatment for conversion of As(III) to As(V).

Optimization of sample preparation conditions in the determination of total arsenic in fish and seafoods by atomic absorption spectrometry with electrothermal atomization

The conditions for sample preparation and determination of total arsenic in fish and seafoods by atomic absorption spectroscopy with electrothermal atomization have been optimized. When using a standard sample preparation procedure (GOST R 53100), a complete decomposition of the organic arsenic compound, arsenobetaine, appeared impossible which leads to underestimated results. A novel sample preparation procedure for the determination of total arsenic, including the addition of concentrated sulfuric acid for complete decomposition of the organic forms of arsenic to inorganic ones is proposed. During the atomization of the sample, an additional stage of drying was introduced with smooth heating from 200 to 250°C, which contributed to a complete removal of sulfuric acid residues from the injected sample volume. The correctness of the proposed methodology was verified using the ICP-MS method and in the analysis of reference samples of fish and seafoods.

Получение биологически полноценной продукции птицеводства при применении комплексного витаминизированного препарата

The article presents the results of studies of the effect of the complex fortified preparation of domestic production «Nitamin» on broiler chickens and the biological usefulness of the resulting meat. The experimental part of the work was carried out in the vivarium of the Department of Parasitology and Veterinary and Sanitary Expertise of the Federal State Budgetary Educational Institution of Higher Education of the MGAVMiB-MVA named after K. I. Skryabin. The drug «Nitamin » was given to broiler chickens with drinking water at a dose of 1 ml per 1 liter of drinking water, according to the scheme from 2 days to 5 days and from 15 days to 18 days, the birds were slaughtered on the 42nd day of keeping. The material for the research was the muscle tissue of broiler chickens of the experimental and control groups, the determination of the content of the amino acid composition, as well as trace elements of selenium and iron, was carried out in accordance with GOST R 55569–2013 Feed, compound feed, compound feed raw materials. Determination of proteinogenic amino acids by capillary electrophoresis, GOST 31707–2012 (EN 14627:2005) Food products of trace elements. Determination of total arsenic and selenium by atomic absorption spectrometry with generation of hydrides with preliminary mineralization of the sample under pressure and GOST 30178–96 Raw materials and food products. Atomic absorption method for the determination of toxic elements. The studied meat samples of broiler chickens, which were fed with the drug «Nitamin», have an increased biological value, the amount of essential amino acids increased by 14,38 % compared to the control. When studying the content of trace elements in the muscle tissue of experimental broiler chickens, an increase in the iron content by 81,8 % was noted in relation to the control group.

Unified analysis method for total and inorganic As determination in foodstuffs by hydride generation high-resolution continuum source quartz tube atomic absorption spectrometry.

A unified analytical method applicable to common foodstuff matrices was developed and characterized for total and inorganic arsenic determination by hydride generation high-resolution continuum source quartz tube atomic absorption spectrometry, which was established based on different sample preparation procedures. This new method was found to be interference-free and cost-effective in terms of reagents consumption for sample preparation and derivatization to arsine for the inorganic arsenic fraction. Microwave-assisted digestion in HNO3-H2O2 for total arsenic and extraction in 0.28 mol L-1 HNO3 by mechanical stirring in a water bath or ultrasound-assisted extraction in 0.01 mol L-1 HCl without separation of inorganic As, all coupled with arsine generation in 0.01 mol L-1 HCl medium with 0.6% NaBH4 in 0.01% NaOH in the presence of 0.2% L-cysteine was found to be suitable for all matrices. The results were statistically compared by applying Tukey's and Dunnett's multiple comparison methods (p > 0.05). The use of external calibration with As(III) standards and standard addition method for quantification showed the lack of non-spectral interferences from the multimineral matrices, resulting in a reliable method for total/inorganic As determination in various foodstuffs. The limits of detection for total/inorganic As using peak height measurement were 0.0044 ± 0.0005/0.0022 ± 0.0003 mg kg-1 (n = 25 days). The overall recovery for total/inorganic As in the certified reference materials was in the range of 98% ± 22%, and 99% ± 24% (k = 2). The extraction of inorganic As in 0.01 mol L-1 HCl and 0.28 mol L-1 HNO3 provided the recovery of 106% ± 25% and 100% ± 25% (k = 2), which was better than in 10 mol L-1 HCl. The precision of measurements in real samples of fish muscle, meat and organs, rice and rice-based baby foods with contents of 0.052-5.29 mg kg-1 total As and 0.005-0.063 mg kg-1 inorganic As was 9.8-18.8% and 8.7-32.0%, respectively, which was calculated based on the combined uncertainty.

Solid phase extraction of arsenic on modified MWCNT/Fe3O4 magnetic hybrid nanoparticles from copper ores samples with ETAAS determination

A simple procedure for the synthesis of magnetic hybrid nanoparticles (MHNP) was developed by combining multi-walled carbon nanotubes modified by microwave energy and magnetic iron oxide nanoparticles. MHNP were introduced as sorbents in a magnetic solid phase extraction methodology for the total Arsenic determination in copper ore samples. Arsenic is penalized contaminant element in copper ores. Arsenic was determined by electrothermal atomic absorption spectrometry with a reduced temperature program. Arsenic adsorption corresponded to 96 - 104%, at ug g−1 levels. After a variable screening stage using a Placket-Burman (PBD) experimental design, the developed methodology was optimized using a Box-Behnken experimental design. Based on the optimal working parameters, a detection limit of 30 ng L−1 was reached, with a relative standard deviation of 7.1% and a preconcentration factor (PF) of 50. The Certified Geochem Base Metal Reference Material Product Code GBM900-10 was analyzed for the validation stage.

Simple and reliable determination of total arsenic and its species in seafood by ICP-MS and HPLC-ICP-MS

Quantitative, rapid, selective and sensitive methods for the determination of total arsenic (tAs) and six arsenic compounds (arsenite (As(III)), arsenate (As(V)), arsenobetaine (AsB), arsenocholine (AsC), monomethylarsonic acid (MMA), dimethylarsonic acid (DMA)) in seafood were developed. The measurement of the tAs concentration was performed using quadrupole inductively-coupled plasma mass spectrometry (ICP-MS). Microwave-assisted extraction was used for the isolation of arsenic species. The separation and quantification of analysed compounds were performed by ion-exchange chromatography coupled with ICP-MS in one chromatographic run using ammonium carbonate-based buffers, which has little effect on ICP-MS sensitivity compared to commonly used phosphate buffers. The results of validation and proficiency tests confirmed the reliability, robustness, and applicability of the developed procedures to various types of matrices. The proposed methods are relatively simple, time- and cost-efficient, therefore could be used to routinely analyse tAs content and arsenic species in different types of seafood at trace and ultra-trace levels.

The effect of a complex fortified preparation on the quality indicators of broiler chicken meat

The article presents the results of the conducted studies on the effect of the complex fortified preparation "Nitamin" on the quality indicators of meat of broiler chickens of the Cobb-500 cross. The preparation was administered with drinking water at a dose of 1 ml per 1 liter of drinking water, according to the scheme from 2 day to 5 day of keeping and from 15 to 18 day, poultry slaughter was carried out on 42 day of keeping. The composition of the preparation includes vitamins A; D3; E; trace elements organic iodine and selenium. The research material was the muscle tissue of broiler chickens of the studied groups, according to generally accepted methods, the content of amino acid composition and trace elements of selenium and iron was determined according to GOST R 55569-2013 Feed, compound feed, compound feed raw materials. Determination of proteinogenic amino acids by capillary electrophoresis, GOST 31707-2012 (EN 14627:2005) Trace element food products. Determination of total arsenic and selenium by atomic absorption spectrometry with generation of hydrides with preliminary mineralization of the sample under pressure and GOST 30178-96 Raw materials and food products. Atomic absorption method for the determination of toxic elements. According to the results obtained, the meat of broiler chickens treated with Nitamin was superior in amino acid composition to the meat of broiler chickens of the control group (essential amino acids by 14.38%, nonessential amino acids by 10.9%). When studying the content of trace elements in the muscle tissue of broiler chickens treated with Nitamin, an increase in the iron content of 10 mg/kg was noted, no iron was found in the muscle tissue of broiler chickens of the control group.

Validation of an analytical method for the determination of inorganic, organic, and total arsenic in fish sauce based on hydride generation atomic absorption spectrometry

An atomic absorption spectrometric (AAS) method was performed to determine the total, inorganic, and organic arsenic in fish sauce. The total organic arsenic was calculated from the total and inorganic arsenic values quantified using the hydride generation AAS (HG-AAS). Under optimal experimental conditions at the absorbance wavelength of 193.7 nm, the concentration of inorganic arsenic in fish sauce ranged from 0.05 to 1.2 mg/L, with a limit of detection (LOD) of 0.015 mg/L. The detectable total arsenic concentrations varied widely, ranging from 0.03 to 2.5 mg/L with the LOD of as low as 0.01 mg/L. The practical applicability of the method was demonstrated with the recovery in the range from 97 to 102% for inorganic arsenic, and 97 to 101% for organic arsenic. The method was applied to the analysis of commercial products from Nha Trang, Phan Thiet, and Phu Quoc City, Vietnam. The total organic arsenic in fish sauce samples determined by HG-AAS was compared with the results of liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP/MS). The f-test and t-test showed null hypothesis for acceptable variance and mean at a confidence level of 95%. The results showed that the HG-AAS method had high efficiency, accuracy, and sensitivity in quantifying inorganic and total organic arsenic in fish sauce using simple instrumentation.

Determination of Arsenic(III) and Total Arsenic at Trace Levels in Baby Food Samples via a New Functionalized Magnetic Graphane Oxide Nanocomposite.

Baby food safety is an essential issue in health policy. For this reason, a simple, cheap, and fast analytical procedure to developed arsenic(III) and total arsenic determination in baby food samples using functionalized magnetic graphane oxide nanocomposite. A new nanocomposite anchored of tiopronin (TSH) magnetic graphane oxide (GO-PG4@Fe3O4-TSH) was first synthesized/characterized and used as an adsorbent to determine arsenic(III) and total arsenic for baby food samples. Arsenic(III) was directly determined on GO-PG4@Fe3O4-TSH nanocomposite at pH 4.5. The determination of total arsenic used KI and L( +) ascorbic acid solution as reducing reagents. The parameters influential on arsenic(III) determination in the baby food samples including the sample's pH, adsorption time, amount of GO-PG4@Fe3O4-TSH, eluent type, sample volume, reducing reagent type and amount, and also foreign ion effect were investigated. The GO-PG4@Fe3O4-TSH carrying As(III) could easily be separated from baby food samples via applying an external magnetic field. The detection limit for arsenic(III) was found as 0.11μg L-1, while the limit of quantification values was computed as 0.37μg L-1. The precision of results, expressed as relative standard deviation, was always lower than 1.6% at 1mg L-1 As(III) levels. The accuracy of this method was confirmed by analysis of certified reference material. The method was successively applied to determine arsenic(III) and total arsenic in baby food samples.

Evaluation of Arsenic Concentration in Poultry and Calf Meat Samples by Hydride Generation Atomic Fluorescence Spectrometry

A simple, cost effective hydride generation atomic florescence spectrometry (HG-AFS) method was used for determination of total arsenic (As) in poultry and calf meat samples. The samples were digested in long necked glass digestion tubes using concentrated HNO3, HClO4 and H2SO4 as a mixture. The volume of acids (HNO3, HClO4) and the amount of sample to be used for digestion were optimized to achieve appropriate digestion. The accuracy of the proposed HG-AFS method was tested with certified reference material (DOLT 3 Dogfish Liver, NRC, Canada) and obtained results were in good agreement with certified value. The method limit of detection (LOD) value was calculated as 0.3 ng/g and dynamic range was 25 – 5000 pg/ml. Arsenic concentrations of poultry and calf meat samples were determined accurately by using aqueous calibration standards. Totally 31 samples (calf, chicken and turkey) obtained from local markets were analyzed. It was found that the average As concentration in calf meat (12.1 ± 3.9 ng/g) was significantly higher than the poultry samples whereas the arsenic concentrations were similar in turkey (3.1 ± 1.2 ng/g) and chicken (2.8 ± 1.1 ng/g) samples. In addition, dietary intake estimation of arsenic through consumption of calf and poultry meat was calculated and according to the gathered results daily intake of arsenic via calf meat was almost two times higher than poultry meat.

An Investigation of Toxic Metal Levels (Pb, Cd, Cr, As, Hg) in Dried Porphyra and Laminaria Collected from Coastal Cities, China.

This investigation was aimed at determining the concentration levels of five toxic heavy metals (lead, cadmium, chromium, arsenic, and mercury) in dried Porphyra and Laminaria samples from coastal city of China. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for determination of lead, cadmium and total arsenic. Atomic fluorescence spectrometry was used for mercury, and liquid chromatography coupled with ICP-MS was used for arsenic speciation. The mean concentrations of lead, cadmium, chromium, total arsenic, and mercury were 0.96 ± 0.03mg/kg, 2.62 ± 0.07mg/kg, 1.64 ± 0.08mg/kg, 36.67 ± 0.53mg/kg, and 7.56 ± 0.42μg/kg for Porphyra samples and 0.61 ± 0.03mg/kg, 0.48 ± 0.02mg/kg, 3.78 ± 0.56mg/kg, 43.85 ± 1.42mg/kg, and 46.61 ± 2.02μg/kg for Laminaria samples. The results were comparable with previous similar research. The potential health risk assessment was conducted by comparing the calculated weekly intakes of toxic metals from Porphyra and Laminaria with provisional tolerable weekly intake. Consumption of these seaweeds does not seem to pose a risk for the consumers' health regarding their content of heavy metals. However, the potential health risk of cadmium should not be overlooked for consumers with high intake of Porphyra.

Aptamer-functionalized screen-printed electrode coupled with graphene oxide and methylene blue nanocomposite as enhanced signal label for total arsenic determination in shellfish

Abstract This work introduces an aptamer-functionalized screen-printed electrode (SPE) coupled with enhanced signal label for total arsenic (As) detection in shellfish, where total As is extracted with dry-ashing method and reduced to detectable As(III). Working electrode array is fabricated on a homemade SPE, proven to be superior to single electrode with equivalent modifications. Au nanoparticles (AuNPs) are electrodeposited onto the SPE to self-assemble As(III)-sensitive aptamer (Ars-3). As(III) response is successfully amplified with an enhanced signal label from the Ars-3/AuNPs/SPE, as provided by the synergistic effect between methylene blue (MB) and graphene oxide (GO). The modifications of AuNPs and Ars-3, as well as the incubation process of GO-MB nanocomposite, are examined by morphological and electrochemical methods. With optimizations of electrochemical setups and sample pretreatments, this method is adopted in a series of analyses with laboratorial and real samples. The limit of detection is 2 × 10−4 mg L-1, and the wide dynamic range up to 10 mg L-1 is well found. The Ars-3/AuNPs/SPE with the GO-MB signal label shows good reproducibility and long-term stability, and presents a high tolerance to possible interference ions. The applicability for real shellfish detection is confidently validated by different means as standard reference material, recovery test and certified ICP-MS.

Determination of total arsenic and hydrophilic arsenic species in seafood

Marine organisms are vital sources of staple and functional food but are also the major dietary route of human exposure to total arsenic. We surveyed the total arsenic content and the mass fractions of hydrophilic arsenic species from five different marine food types cutting across the food chain from microalgae, macroalgae, bivalve clam, crustaceans and finfish. Total arsenic was determined using inductively coupled plasma-mass spectrometry (ICP-MS) while arsenic speciation analysis was performed using high-performance liquid chromatography (HPLC) coupled to ICP-MS as the detector. The total arsenic contents ranged from 133 ± 11 ng/g to 26,630 ± 520 ng/g. The mass fractions of inorganic arsenic (iAs), arsenobetaine (AsB), dimethylarsinic acid (DMA), and the four commonly occurring arsenosugars (AsSugars) are reported. Extractable hydrophilic arsenic species accounted for 10 % (aquacultured shrimp) to 95 % (kelp) of the total arsenic. DMA was established to be a byproduct of the decomposition of AsSugars in acid extracts of samples known to contain these species.

A electrochemical biosensor for As(III) detection based on the catalytic activity of Alcaligenes faecalis immobilized on a gold nanoparticle–modified screen–printed carbon electrode

A electrochemical biosensor for As(III) determination has been developed by immobilization of the Alcaligenis faecalis bacteria on gold nanoparticle–modified screen–printed carbon electrode (AuNPs–SPCE). The detection of As(III) is due to the catalytic activity of arsenite oxidase enzyme which oxidizes As(III) to As(V) producing an analytical signal. To enhance the performance of the biosensor, was optimized the amount of bacteria, amount of glutaraldehyde and incubation time applied in the preparation of the electrode, in addition to the effect of pH and applied potential. The analytical application was carried out applying 300 mV (pH = 7) obtaining a LOD of 6.61 μmol L−1 (R = 0.9975) and 700 mV (pH = 12) obtaining a LOD of 1.84 μmol L−1 (R = 0.9983). AF/AuNPs–SPCE was applied to the determination of total arsenic in Loa river water samples after reduction, with satisfactory results.

Arsenic species and their transformation pathways in marine plants. Usefulness of advanced hyphenated techniques HPLC/ICP-MS and UPLC/ESI-MS/MS in arsenic species analysis

The growing popularity of algae as a foodstuff around the world raises concern for the safety of this food type with respect to arsenic content in algae. The need for determination of total arsenic content and arsenic speciation in algae food has become an important issue. In this paper we have developed a complete analytical procedure for arsenic determination in algae products comprised of 1) total arsenic (tAs) determination in native algae samples after digestion, 2) extraction of As species with the use of two extraction methods with three extracting agents, 3) extracted total arsenic (extracted tAs) determination in algae extracts, 4) bespoke As speciation, 4) mass balance estimation based on extracted tAs and bespoke As speciation results, 5) unknown arsenic (uAs) species identification. Two advanced hyphenated techniques, HPLC/ICP-MS and UPLC/ESI-MS/MS, were employed along with the HPLC/ICP-MS method validation. Total As content in edible algae samples was found to range from (19.28 ± 0.45) mg kg−1 up to (72.6 ± 2.7) mg kg−1. Bespoke arsenic speciation of edible algae samples has revealed the presence of some known inorganic and simple organic As compounds such as As(III) from <LOD to (8.97 ± 0.59) mg kg−1, As(V) from <LOD to (5.95 ± 0.29) mg kg−1 and DMA from <LOD to (0.766 ± 0.040) mg kg−1. Mass balance calculation carried out on the basis of tAs and bespoke As speciation results has shown that the amount of unknown As species in edible algae samples varied from 28% to 100% of extracted tAs. Identification of uAs species in edible algae samples has shown the presence of a high variety of As-sugars (12 compounds) and confirmed the presence of simple inorganic and organic As species such as As(V) and DMA along with 8 more simple organic As compounds. The results obtained in this study have confirmed that the high amounts of tAs do not correspond to the toxicity of algae based food due to the lack of the inorganic As in the tested samples.

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.

DETERMINACIÓN ESPECTROFOTOMÉTRICA DE ESPECIES INORGÁNICAS ARSENICALES (III) Y (V) EN AGUA USANDO EL MÉTODO DEL AZUL DE MOLIBDENO.

Arsenic surface water and groundwater pollution is a reported issue in many developing countries, thus it is of great concern to quantify this species by using economic techniques easy to handle. In this work, a spectrophotometric method for the quantification and speciation of arsenic in the presence of phosphorous in water was developed. It is based on the generation of a colored complex (heteropolyacid) in acid media, by arsenate reaction with molybdate. For total arsenic determination, potassium iodate was used for the quantitative oxidation of trivalent arsenic. Trivalent arsenic was determined from the difference between the total arsenic quantified and the arsenate. Phosphorous (V) was quantified by using L-cysteine, by the selective reduction of pentavalent arsenic. The developed method allowed to quantify arsenic at ultra-trace levels (µg/L), presenting the following figures of merit of the analysis: Detection limit 6 μg/ L, quantification limit 18 μg/L, linearity from 18 to 1600 μg/L; 96.9 % of recovery and 1.24 % of precision. The results were comparable to those obtained by atomic absorption spectrometry with graphite furnace.