Determination of arsenic species: A critical review of methods and applications, 2000–2003

Potentially toxic trace elements in the muscle of coastal South American fish: Implications for human consumption and health risk assessment

Micropogonias furnieri and Urophycis brasiliensis are two coastal demersal fish species distributed in the southwestern Atlantic Ocean. Considering that many coastal areas in the southwestern Atlantic Ocean suffer from anthropogenic pressure, the aim of this study was to assess the level of potentially toxic trace elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sr, V and Zn) in the muscle of coastal species, and evaluated the human health risk related to the consumption of muscle. Mercury, inorganic As (Asi), V, and Se showed a higher contribution to the total THQ. Considering two possible scenarios, Asi represents 1 % or 5 % of the total As, the total THQ was <1 for general population and of some health concerns for fishermen population (Total THQ > 1; 5 % Asi). Consequently these results show the importance of quantifying As species in muscle to generate more reliable risk estimates for human health.

Methylation of arsenic in rice: Mechanisms, factors, and mitigation strategies

Arsenic contamination in rice poses a significant health risk to rice consumers across the globe. This review examines the impact of water source and type on the speciation and methylation of arsenic in rice. The review highlights that groundwater used for irrigation in arsenic-affected regions can lead to higher total arsenic content in rice grains and lower proportions of methylated arsenic species. The methylation of As in rice is influenced by microbial activity in groundwater, which can methylate arsenic that is taken up by rice plants. Reclaimed water irrigation can also increase the risk of arsenic accumulation in rice crops, although the use of organic amendments and proper water management practices can reduce arsenic accumulation. Different water management regimes, such as continuous flooding irrigation, alternate wetting and drying, aerobic rice cultivation, and subsurface drip irrigation, can affect the speciation and methylation of As in rice. Continuous flooding irrigation reduces methylation of As due to anaerobic conditions, while alternate wetting and drying and aerobic rice cultivation promote methylation by creating aerobic conditions that stimulate the activity of arsenic-methylating microorganisms. Subsurface drip irrigation reduces total arsenic content in rice grains and increases the proportion of less toxic methylated arsenic species. The review also discusses the complex mechanisms of As-methylation and transport in rice, emphasizing the importance of understanding these mechanisms to develop strategies for reducing arsenic uptake in rice plants and mitigating health risks. The review addresses the impact of water source and type on arsenic speciation and methylation in rice and highlights the need for proper water management and treatment measures to ensure the safety of the food supply as well as aiding future research and policies to reduce health risks from rice consumption. The critical information gaps that this review addresses include the specific effects of different water management regimes on As-methylation, the role of microbial communities in groundwater in As-methylation, and the potential risks associated with the use of reclaimed water for irrigation.

Strategies for the analysis of arsenolipids in marine foods: A review

Arsenic-containing lipids, also named arsenolipids (AsLs), are a group of organic compounds usually found in a variety of marine organisms such as fish, algae, shellfish, marine oils, and microorganisms. Numerous AsLs have been recognised so far, from simple compounds such as arsenic fatty acids (AsFAs), arsenic hydrocarbons (AsHCs), and trimethylarsenio fatty alcohols (TMAsFOHs) to more complex arsenic-containing species, of which arsenophospholipids (AsPLs) are a case in point. Mass spectrometry, both as inductively coupled plasma (ICP-MS) and liquid chromatography coupled by an electrospray source (LC-ESI-MS), was applied to organic arsenicals playing a key role in extending and refining the characterisation of arsenic-containing lipids in marine organisms. Herein, upon the introduction of a systematic notation for AsLs and a brief examination of their toxicity and biological role, the most relevant literature concerning the characterisation of AsLs in marine organisms, including edible ones, is reviewed. The use of both ICP-MS and ESI-MS coupled with reversed-phase liquid chromatography (RPLC) has brought significant advancements in the field. In the case of ESI-MS, the employment of negative polarity and tandem MS analyses has further enhanced these advancements. One notable development is the identification of the m/z 389.0 ion ([AsC10H19O9P]-) as a diagnostic product ion of AsPLs, which is obtained from the fragmentation of the deprotonated forms of AsPLs ([M - H]-). The pinpointing product ions offer the possibility of determining the identity and regiochemistry of AsPL side chains. Advanced MS-based analytical methods may contribute remarkably to the understanding of the chemical diversity characterising the metalloid As in natural organic compounds of marine organisms.

Negative Impacts of Arsenic on Plants and Mitigation Strategies

Arsenic (As) is a metalloid prevalent mainly in soil and water. The presence of As above permissible levels becomes toxic and detrimental to living organisms, therefore, making it a significant global concern. Humans can absorb As through drinking polluted water and consuming As-contaminated food material grown in soil having As problems. Since human beings are mobile organisms, they can use clean uncontaminated water and food found through various channels or switch from an As-contaminated area to a clean area; but plants are sessile and obtain As along with essential minerals and water through roots that make them more susceptible to arsenic poisoning and consequent stress. Arsenic and phosphorus have many similarities in terms of their physical and chemical characteristics, and they commonly compete to cause physiological anomalies in biological systems that contribute to further stress. Initial indicators of arsenic's propensity to induce toxicity in plants are a decrease in yield and a loss in plant biomass. This is accompanied by considerable physiological alterations; including instant oxidative surge; followed by essential biomolecule oxidation. These variables ultimately result in cell permeability and an electrolyte imbalance. In addition, arsenic disturbs the nucleic acids, the transcription process, and the essential enzymes engaged with the plant system's primary metabolic pathways. To lessen As absorption by plants, a variety of mitigation strategies have been proposed which include agronomic practices, plant breeding, genetic manipulation, computer-aided modeling, biochemical techniques, and the altering of human approaches regarding consumption and pollution, and in these ways, increased awareness may be generated. These mitigation strategies will further help in ensuring good health, food security, and environmental sustainability. This article summarises the nature of the impact of arsenic on plants, the physio-biochemical mechanisms evolved to cope with As stress, and the mitigation measures that can be employed to eliminate the negative effects of As.

Arsenic in Lake Geneva (Switzerland, France): long term monitoring, and redox and methylation speciation in an As unpolluted, oligo-mesotrophic lake

Arsenic speciation was followed monthly along the spring productivity period (January-June 2021) in the Petit Lac (76 m deep) and in April and June 2021 in the Grand Lac (309.7 m deep) of Lake Geneva (Switzerland/France). Lake Geneva is presently an oligo-mesotrophic lake, and As-unpolluted. The water column never becomes anoxic but the oxygen saturation at the bottom of the Grand Lac is now below 30% owing to lack of water column mixing since 2012. Thus, this lake offers excellent conditions to study As behaviour in an unpolluted, oxic freshwater body. The following 'dissolved' As species: iAs(III), iAs(III + V), MA(III), MA(III + V), DMA(III + V), and TMAO were analysed by HG-CT-ICP-MS/MS. Water column measurements were complemented with occasional sampling in the main rivers feeding the lake and in the interstitial waters of a sediment core. The presence of MA(III) and TMAO and the predominance of iAs(V) in lake and river samples has been confirmed as well as the key role of algae in the formation of organic species. While the total 'dissolved' As concentrations showed nearly vertical profiles in the Petit Lac, As concentrations steadily increase at deeper depths in the Grand Lac due to the lack of mixing and build up in bottom waters. The evaluation of 25 years of monthly data of 'dissolved' As concentrations showed no significant temporal trends between 1997 and 2021. The observed seasonal character of the 'dissolved' As along this period coincides with a lack of seasonality in As mass inventories, pointing to a seasonal internal cycling of As species in the water column with exchanges between the 'dissolved' and 'particulate' (i.e., algae) fractions.

A review on arsenic in the environment: contamination, mobility, sources, and exposure

Arsenic is one of the regulated hazard materials in the environment and a persistent pollutant creating environmental, agricultural and health issues and posing a serious risk to humans. In the present review, sources and mobility of As in various compartments of the environment (air, water, soil and sediment) around the World are comprehensively investigated, along with measures of health hazards. Multiple atomic spectrometric approaches have been applied for total and speciation analysis of As chemical species. The LoD values are basically under 1 μg L-1, which is sufficient for the analysis of As or its chemical species in environmental samples. Both natural and anthropogenic sources contributed to As in air, while fine particulate matter tends to have higher concentrations of arsenic and results in high concentrations of As up to a maximum of 1660 ng m-3 in urban areas. Sources for As in natural waters (as dissolved or in particulate form) can be attributed to natural deposits, agricultural and industrial effluents, for which the maximum concentration of 2000 μg L-1 was found in groundwater. Sources for As in soil can be the initial contents, fossil fuel burning products, industrial effluents, pesticides, and so on, with a maximum reported concentration up to 4600 mg kg-1. Sources for As in sediments can be attributed to their reservoirs, with a maximum reported concentration up to 2500 mg kg-1. It is notable that some reported concentrations of As in the environment are several times higher than permissible limits. However, many aspects of arsenic environmental chemistry including contamination of the environment, quantification, mobility, removal and health hazards are still unclear.

Speciation of inorganic arsenic with mixed mode HPLC-ESI-MS and Arsenite Oxidation

It has been challenging to analyze inorganic arsenic (iAs) with anion exchange HPLC-Electrospray Ionization-Mass spectrometry (HPLC-ESI-MS), because arsenite (As(III)) is difficult to retain on column and the salts in mobile phase causes ionization suppression of iAs. To address these issues, a method has been developed involving the determination of arsenate (As(V)) with mixed mode HPLC-ESI-MS and the conversion of As(III) to As(V) for total iAs. As(V) was separated from other chemicals on Newcrom B, a bi-modal HPLC column involving anion exchange and reverse phase interaction. The elution employed a two-dimensional gradient, including a formic acid gradient to elute As(V) and a concurrent alcohol gradient to elute organic anions used in sample preparations. As(V) was detected by Selected Ion Recording (SIR) in negative mode at m/z = 141 with a QDa (single quad) detector. As(III) was quantitatively converted to As(V) by mCPBA oxidation and measured for total iAs. By replacing salt with formic acid in elution, the ionization efficiency for As(V) was greatly enhanced in ESI interface. The limit of detection (LOD) for As(V) and As(III) were 0.0263 μM (1.97 ppb) and 0.0398 μM (2.99 ppb), respectively. The linear range was 0.05-1 μM. The method has been used to characterize iAs speciation change in the solution and precipitation in a simulated iron-rich groundwater caused by air exposure.

Robust, reliable and quantitative sensing of aqueous arsenic species by Surface-enhanced Raman Spectroscopy: The crucial role of surface silver ions for good analytical practice

Arsenic speciation analysis is important for pollution and health risk assessment. Surface-enhanced Raman Spectroscopy (SERS) is supposed to be a promising detection technology for arsenic species owing to the unique fingerprints. However, further application of SERS is hampered by its poor repeatability. Herein, the role of surface silver ions on colloidal Ag was revealed in SERS analysis of arsenic species. Arsenic species were adsorbed on Ag nanoparticles (Ag NPs) driven by surface silver ions and were simultaneously sensed by the SERS "hot spots" generated from the aggregation of Ag NPs. So, the inconsistent SERS activities of Ag NPs synthesized from different batches can be significantly improved by modifying external silver ions onto Ag NPs (AgNPs@Ag⁺), Specific binding affinity of surface silver ions to arsenic species generated higher sensitivity (detection limit, 4.0 × 10^-11 mol L^-1 for arsenite, 8.0 × 10^-11 mol L^-1 for arsenate), wider linear range, faster response, cleaner spectra background and better reproducibility. Batch-to-batch reproducibility was significantly improved with a variation below 3.1%. The method was also demonstrated with drinking and environmental water with adequate recovery and high interference resistance. Our findings displayed good analytical practice of the surface silver ions derived SERS method and its great potential in the rapid detection of hazardous materials.

The effects of acidification on arsenic concentration and speciation in offshore shallow water system

The effects of acidification on speciation and transportation of arsenic in shallow seawater system were investigated based on data from acidification simulation experiments in lab scale tanks, in which enhanced levels of pCO₂ corresponding to pH_T were processed. The results showed that: (1) the concentration of DIAs (Dissolved inorganic arsenic), As⁵⁺ and As³⁺ in the overlying water increased with experimental CO₂ enrichment; (2) while the ratio of As⁵⁺/As³⁺ decreased; (3) acidification could cause more DIAs transport into the overlying water from sediments or suspended particulate matters, and would be favorable to the existence of As³⁺. Thus, DIAs is available to microorganisms and can be taken in effectively by microorganisms in the shallow water system, resulting in toxic effects of As on microorganisms and thus the inhibition of the growth of microorganisms.

New Method for Simultaneous Arsenic and Selenium Speciation Analysis in Seafood and Onion Samples

This paper presents a new method for the simultaneous speciation analysis of arsenic (As(III)-arsenite, As(V)-arsenate, DMA-dimethylarsinic acid, MMA-methylarsonic acid, and AsB-arsenobetaine) and selenium (Se(IV)-selenite, Se(VI)-selenate, Se-Methionine, and Se-Cystine), which was applied to a variety of seafood and onion samples. The determination of the forms of arsenic and selenium was undertaken using the High-Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC-ICP-MS) analytical technique. The separation of both organic and inorganic forms of arsenic and selenium was performed using two analytical columns: an anion exchange column, Dionex IonPac AS22, containing an alkanol quaternary ammonium ion, and a double bed cation-anion exchange guard column, Dionex Ion Pac CG5A, containing, as a first layer, fully sulfonated latex for cation exchange and a fully aminated layer for anion exchange as the second layer. The ammonium nitrate, at pH = 9.0, was used as a mobile phase. The method presented here allowed us to separate the As and Se species within 10 min with a suitable resolution. The applicability was presented with different sample matrix types: seafood and onion.

Usage of Si, P, Se, and Ca Decrease Arsenic Concentration/Toxicity in Rice, a Review

Rice is one of the most important routes for arsenic to enter the human food chain and threatens more than half of the world’s population. In addition, arsenic-contaminated soils and waters increase the concentration of this element in various tissues of rice plants. Thus, direct or indirect—infecting livestock and poultry—increase diseases such as respiratory diseases, gastrointestinal tract, liver, and cardiovascular diseases, cancer, and ultimately death in the long term. Therefore, finding different ways to reduce the uptake and transfer of arsenic by rice would reduce the contamination of rice plants with this dangerous element and improve animal and human nutrition and ultimately disease and mortality. In this article, we aim to take a small step in improving sustainable life on earth by referring to the various methods that researchers have taken to reduce rice contamination by arsenic in recent years. Adding micronutrients and macronutrients as fertilizer for rice is one way to improve this plant’s growth and health. In this study, by examining two types of macronutrients and two types of micronutrients, their role in reducing arsenic toxicity and absorption was investigated. Therefore, both calcium and phosphorus were selected from the macronutrients, and selenium and silicon were selected from the micronutrients, whose roles in previous studies had been investigated.

Urinary Concentrations of Metals and Metalloids in Malaysian Adults

Exposure to environmental pollutants in humans can be conducted through direct measurement of biological media such as blood, urine or hair. Assessment studies of metals and metalloids in Malaysia is very scarce although cross-sectional nationwide human biomonitoring surveys have been established by the USA, Canada, Germany, Spain, France, and Korea. This study aims to assess urinary metal levels namely cadmium (Cd), nickel (Ni), lead (Pb) and arsenic (As) among Malaysian adults. This was a cross-sectional study involving 1440 adults between the age of 18 and 88 years old. After excluding those with 24 h urine samples of less than 500 ml, urine creatinine levels < 0.3 or > 3.0 g/L and those who refuse to participate in the study, a total of 817 respondents were included for analysis. A questionnaire with socio-demographic information such as age, gender, occupation, ethnic, academic qualification and medical history was administered to the respondents. Twenty-four-hour urine samples were collected in a container before being transported at 4 °C to the laboratory. Samples were then aliquoted into 15 ml tubes and kept at - 80 °C until further analysis. Urine was diluted ten-fold with ultrapure water, filtered and analysed for metals and metalloids using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The geometric mean of urinary As, Ni, Cd and Pb concentrations among adults in Malaysia was 48.21, 4.37, 0.32, and 0.80 µg/L, respectively. Males showed significantly higher urinary metal concentrations compared to females for As, Cd and Pb except for Ni. Those who resided in rural areas exhibited significantly higher As, Cd and Pb urinary concentrations than those who resided in urban areas. As there are no nationwide data on urinary metals, findings from this study could be used to identify high exposure groups, thus enabling policy makers to improve public health strategically.

Arsenic methylation - Lessons from three decades of research

Between 1990 and 2020, our understanding of the significance of arsenic biomethylation changed in remarkable ways. At the beginning of this period, the conversion of inorganic arsenic into mono- and di-methylated metabolites was viewed primarily as a process that altered the kinetic behavior of arsenic. By increasing the rate of clearance of arsenic, the formation of methylated metabolites reduced exposure to this toxin; that is, methylation was detoxification. By 2020, it was clear that at least some of the toxic effects associated with As exposure depended on formation of methylated metabolites containing trivalent arsenic. Because the trivalent oxidation state of arsenic is associated with increased potency as a cytotoxin and clastogen, these findings were consistent with methylation-related changes in the dynamic behavior of arsenic. That is, methylation was activation. Our current understanding of the role of methylation as a modifier of kinetic and dynamic behaviors of arsenic is the product of research at molecular, cellular, organismic, and population levels. This information provides a basis for refining our estimates of risk associated with long term exposure to inorganic arsenic in environmental media, food, and water. This report summarizes the growth of our knowledge of enzymatically catalyzed methylation of arsenic over this period and considers the prospects for new discoveries.

Source contribution and origin of PM10 and arsenic in a complex industrial region (Huelva, SW Spain)

Air pollution coming from industrial activities is a matter of interest since their emissions can seriously affect to the human health of nearby populations. A more detailed study about industrial emissions is required in order to discriminate different activities contributing to pollutant sources. In this sense, gaseous pollutants (NO₂, SO₂ and O₃) and PM10 levels has been studied in a complex industrial area in the southwest of Spain (La Rabida and the nearby city of Huelva) during the period 1996-2017. Hourly, daily, monthly and annual variations of PM10 and gaseous pollutants concentrations point to the industrial activity as the main SO₂ source. Furthermore, traffic and resuspension emissions contribute to the NO₂ and PM10 levels, respectively. Results from chemical composition of PM10 at both sites during the period 2015-2017 are characterized by high concentrations of the crustal components derived from natural and local resuspension. Arsenic is found to be the main geochemical anomaly at La Rabida (annual mean of 7 ng m^-3), exceeding the European annual target of 6 ng m^-3, which supposes a risk for the nearby population. An emission source from Cu-smelter has been identified in La Rabida and Huelva. A second source corresponding to emissions from polymetallic sulfides handling in a port area has been described for the first time in La Rabida. In addition, arsenic speciation results have identified three different As impacts scenarios as a function of the dominant wind direction, the SO₂ episodes and the As extraction efficiency: impact of the Cu-smelter, impact of the bulk polymetallic sulfides and a mixed impact of both sources.

Origins, fate, and actions of methylated trivalent metabolites of inorganic arsenic: progress and prospects

The toxic metalloid inorganic arsenic (iAs) is widely distributed in the environment. Chronic exposure to iAs from environmental sources has been linked to a variety of human diseases. Methylation of iAs is the primary pathway for metabolism of iAs. In humans, methylation of iAs is catalyzed by arsenic (+ 3 oxidation state) methyltransferase (AS3MT). Conversion of iAs to mono- and di-methylated species (MAs and DMAs) detoxifies iAs by increasing the rate of whole body clearance of arsenic. Interindividual differences in iAs metabolism play key roles in pathogenesis of and susceptibility to a range of disease outcomes associated with iAs exposure. These adverse health effects are in part associated with the production of methylated trivalent arsenic species, methylarsonous acid (MAs^III) and dimethylarsinous acid (DMAs^III), during AS3MT-catalyzed methylation of iAs. The formation of these metabolites activates iAs to unique forms that cause disease initiation and progression. Taken together, the current evidence suggests that methylation of iAs is a pathway for detoxification and for activation of the metalloid. Beyond this general understanding of the consequences of iAs methylation, many questions remain unanswered. Our knowledge of metabolic targets for MAs^III and DMAs^III in human cells and mechanisms for interactions between these arsenicals and targets is incomplete. Development of novel analytical methods for quantitation of MAs^III and DMAs^III in biological samples promises to address some of these gaps. Here, we summarize current knowledge of the enzymatic basis of MAs^III and DMAs^III formation, the toxic actions of these metabolites, and methods available for their detection and quantification in biomatrices. Major knowledge gaps and future research directions are also discussed.

Cacodylate Sensors and their Application in the Determination of Amino Acid Levels in Biological Samples

BACKGROUND

The importance of recognizing and quantifying chemical anions/cations found in various types of samples, including environmental and biological samples, has been extensively studied. Recent findings suggest the possibility of health risks caused by organic compound dimethylarsinic acid (DMAs) rather than its inorganic arsenic metabolite.

OBJECTIVE

This article aims to fabricate polymeric-membrane electrochemical sensors with high sensitivity and selectivity for the cacodylic acid sodium salt dimethylarsinate (DMAs) based on silver diethyldithiocarbamate (AgDDTC) and CuIIphthalocyanine (CuPC) as novel neutral carriers and their applications.

METHOD

DMAs calibration relations and titrations were carried out using a potentiometric workstation equipped with a double-junction reference electrode, in conjunction with the fabricated working electrodes.

RESULTS

Sensors revealed fast and stable anionic response with near-Nernstian slopes (-38.6 ± 0.9 and -31.5 ± 0.6 mV/decade), within concentration ranges (1.7 × 10-5 -1.0 × 10-2 and 3.0 × 10-5 -1.0 × 10-2 M) and detection limits (1.0 × 10-5 and 1.6 × 10-5 M) for AgDDTC- and CuPC-based sensors, respectively. Sensors are characterized by extended life-time, signal stability, high precision and short response times. Selectivity for the cacodylate anion over most common anions was tested for the proposed electrodes. Sensors were satisfactorily applied for DMAs quantification in biological matrices with recoveries ranging between 96.2 and 99.0%. Membrane sensors were interfaced with a flow-through system for continuous monitoring of DMAs. The sensors were tested for the assay of different amino acids based on their reaction with cacodylate, where reaction end points were monitored with the proposed electrodes using direct potentiometric determination and flow injection analysis (FIA).

CONCLUSIONS

Potentiometric ion-selective PVC-membrane electrodes based on silver diethyldithiocarbamate (AgDDTC) and CuIIphthalothyanine (CuPC) provide adequate and reliable means for the determination of dimethylarsenate anion (cacodylate anion, DMAs). These membrane electrodes are easy to manufacture, they have the advantages of high selectivity and sensitivity, broad dynamic ranges, low detection limits, quick response times and cost effectiveness. Such properties make these sensors suitable for the assay of DMAs levels in aqueous solutions by direct potentiometry, flow injection and potentiometric titration, as well as in monitoring of the titration end points of the reactions between various amino acids and DMAs anion in aqueous solutions.

HIGHLIGHTS

Simple electrochemical membranes for dimethylarsinate (DMAs) were prepared, based on diethyldithiocarbamate (AgDDTC) and CuIIphthalocyanine (CuPC). - DMAs sensors were fabricated in two different modules: batch (for static) and flow-through (for hydrodynamic) approaches. - Levels of DMAs were determined in spiked biological samples. - AgDDTC-based sensors were successfully applied in the determination of several amino acids via potentiometric titration with DMAs.

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.

Reduction by, ligand exchange among, and covalent binding to glutathione and cellular thiols link metabolism and disposition of dietary arsenic species with toxicity

Arsenic (As) is a common contaminant in the earth's crust and widely distributed in food and drinking water. As exposures have been associated with human disease, including cancer, diabetes, lung and cardiovascular disorders, and there is accumulating evidence that early life exposures are important in the etiology. Mode-of-action analysis includes a critical role for metabolic activation of As species to reactive trivalent intermediates that disrupt cellular regulatory systems by covalent binding to thiol groups. The central role of glutathione (GSH) in the chemical reactions of metabolism and disposition of arsenic species was investigated here. The chemical kinetics were measured for reactions in which GSH is a ligand for trivalent As complex formation, a reductant for pentavalent As species, and a participant in ligand exchange reactions with other biological As-thiol complexes. The diverse reactions of GSH with As species demonstrate prominent roles in: (1) metabolic activation via reduction; (2) transport from tissues that are the primary sources of reactive trivalent As intermediates following ingestion (intestine and liver) to downstream target organs (e.g., lung, kidney, and bladder); and (3) oxidation to the terminal metabolite, dimethylarsinic acid (DMA^V), which is excreted. Studies of As metabolism and disposition emphasize the link between metabolic activation vs. excretion of As (i.e., internal dosimetry of reactive species) and the disruption of critical cellular thiol-based regulatory processes that define the dose-response characteristics of disease in human epidemiological studies and animal models and underpin risk assessment.

Arsenic speciation in the bracket fungus Fomitopsis betulina from contaminated and pristine sites

Uptake, distribution and speciation of arsenic (As) were determined in the bracket fungus Fomitopsis betulina (previously Piptoporus betulinus), commonly known as the birch polypore, collected from a woodland adjacent to a highly contaminated former mine in the Southwest UK and at an uncontaminated site in Quebec, Canada, with no past or present mining activity. The fruiting body was divided into cap, centre and pores representing the top, middle and underside to identify trends in the distribution and transformation of As. Total As, determined by inductively coupled plasma-mass spectrometry (ICP-MS), was approximately tenfold higher in the mushroom from the contaminated compared to the uncontaminated site. Overall, accumulation of As was low relative to values reported for some soil-dwelling species, with maximum levels of 1.6 mg/kg at the contaminated site. Arsenic speciation was performed on aqueous extracts via both anion and cation high-performance liquid chromatography-ICP-MS (HPLC-ICP-MS) and on whole dried samples using X-ray absorption near edge structure (XANES) analysis. Seven As species were detected in F. betulina from the contaminated site by HPLC-ICP-MS: arsenite (As^III), arsenate (As^V), dimethylarsinate (DMA^V), methylarsonate (MA^V), trimethylarsine oxide (TMAO), tetramethylarsonium ion (Tetra) and trace levels of arsenobetaine (AB). The same As species were observed at the uncontaminated site with the exception of TMAO and Tetra. Arsenic species were localized throughout the fruiting body at the contaminated site, with the cap and pores containing a majority of As^V, only the cap containing TMAO, and the pores containing higher concentrations of DMA^V and MA^V as well as tetra and a trace of AB. XANES analysis demonstrated that the predominant form of As at the contaminated site was inorganic As^III coordinated with sulphur or oxygen and As^V coordinated with oxygen. This is the first account of arsenic speciation in F. betulina or any fungi of the family Fomitopsidaceae.

CRM rapid response approach for the certification of arsenic species and toxic trace elements in baby cereal coarse rice flour certified reference material BARI-1

With recently legislated maximum levels of inorganic arsenic (iAs) in white and brown rice in Canada, the regulatory bodies are evaluating the need for regulation of As levels in infant food products. Rice is a major part of infants' diet, and therefore, the presence of As in this staple food causes concerns. So far, the scientific community was lacking suitable certified reference material (CRM) which could be used to assess the accuracy of developed analytical methods for As speciation in infants' food products. As a result, we have developed BARI-1, a baby cereal coarse rice flour reference material which was certified for total arsenic (0.248 ± 0.018 mg kg^-1), cadmium (0.0134 ± 0.0014 mg kg^-1), mercury (0.0026 ± 0.0003 mg kg^-1), lead (0.0064 ± 0.0016 mg kg^-1), inorganic As (0.113 ± 0.016 mg kg^-1) and dimethylarsinic acid (DMA) (0.115 ± 0.010 mg kg^-1), and reference value for monomethylarsonic acid (MMA) (0.0045 ± 0.0008 mg kg^-1) was reported. We also observed trace amounts of an unknown As compound, with chromatographic retention time close to DMA. Participating laboratories were allowed to use their in-house-validated extraction and/or digestion methods, and the detection of total metals was done by ICP-MS whereas HPLC-ICP-MS was used for As speciation. Despite the diversity in sample preparation and quantitation methods, reported values were in good agreement. For iAs measurement, the comparison between hydride generation ICP-MS and HPLC-ICP-MS found iAs overestimation with the former method, possibly due to interference from DMA. The certification was accomplished with a CRM rapid response approach in collaborative, focused effort completing the CRM development in few months instead of the typical multiyear project. This approach allowed to respond to measurement needs in a timely fashion. Graphical abstract.

Occurrence, Seasonal Variation, and Size Resolved Distribution of Arsenic Species in Atmospheric Particulate Matter in an Urban Area in Southeastern Austria

Extensive information is available on total arsenic in particulate matter (PM), but little is known about the relative contribution of each individual species. Recent studies often focus on inorganic arsenic as arsenite and arsenate, neglecting the organoarsenicals, i.e., methylarsine, dimethylarsine, and trimethylarsine or the corresponding oxidized forms methylarsonate, dimethylarsinate, and trimethylarsine oxide, although they were already first detected in PM in the mid-1970s. This work presents results from more than 300 daily PM₁₀ and further size-resolved atmospheric PM samples in the size range from 15 nm to 10 μm collected in an urban environment in Austria during the course of a year. An ion-exchange-HPLC (with anion and cation exchange columns) and an ICPMS/MS system were used to study the seasonal variations of total arsenic and all species known to exist in PM. Inorganic arsenic was present in significant amounts in all samples with highest concentrations during winter, but also all organoarsenicals were detected throughout the year. We show that their contribution cannot be ignored, as particles smaller than <1 μm can contain up to 35% of the water+H₂O₂ extractable arsenic as methylated species, but only dimethylarsinate showed a clear seasonal trend throughout the year.

A Scientometric Analysis of Recent Literature on Arsenic Bioaccumulation and Biotransformation in Marine Ecosystems

Arsenic (As) bioaccumulation and biotransformation in marine ecosystems involve a number of fields and disciplines such as Environmental Sciences & Ecology, Marine & Freshwater Biology, and Toxicology. Arsenic research in these areas has been developing rapidly in recent years. It is crucial to keep up with the emerging trends and critical development of the collective knowledge. Therefore, a progressively synthesized network was achieved from 6396 original publications that cited 500 articles obtained from an initial topic search between 2010 and 2019. CiteSpace was used to analyze the progress and emerging trends. Results showed that these publications were divided into 13 different but closely related clusters. A major ongoing trend was identified in Cluster #3 and #5, concerning As and other heavy metals as heterogeneous complexants and assessing their overall impacts on human health. Other new emerging trends include evaluating the As profile in estuarial ecosystems and assessing its bioaccumulation and biotransformation along the food chain. Overall, the scientometric analytics of targeting literature performed in this review has offered a valuable and timely approach to evaluate the new emerging trends, providing researchers with up-to-date and critical information in research areas relevant to the searching topic.

Possible food safety hazards of ready-to-eat raw fish containing product (sushi, sashimi)

It is undeniable that with the popularity of sushi and sashimi over the last decade the consumption of raw fish has extremely increased. Raw fish is very appreciated worldwide and has become a major component of human diet because of its fine taste and nutritional properties. Possible hazards concerning fish safety and quality are classified as biological and chemical hazards. They are contaminants that often accumulate in edible tissue of fish and transmit to humans via the food chain affecting the consumer's health. Although their concentration in fish and fishery products are found at non-alarming level of a daily basis period, they induce hazardous outcome on human health due to long and continuous consumption of raw fish. Regular sushi and sashimi eaters have to be aware of the contaminants found in the other components of their dish that often add up to acceptable residue limits found in fish. Hence, there is the urge for effective analytical methods to be developed as well as stricter regulations to be put in force between countries to monitor the safety and quality of fish for the interest of public health.

Environmental geochemistry and cancer: a pertinent global health problem requiring interdisciplinary collaboration

Primary prevention is a key strategy to reducing the global burden of cancer, a disease responsible for ~ 9.6 million deaths per year and predicted to top 13 million by 2030. The role of environmental geochemistry in the aetiology of many cancers-as well as other non-communicable diseases-should not be understated, particularly in low- and middle-income countries where 70% of global cancer deaths occur and reliance on local geochemistry for drinking water and subsistence crops is still widespread. This article is an expansion of a series of presentations and discussions held at the 34th International Conference of the Society for Environmental Geochemistry and Health in Livingstone, Zambia, on the value of effective collaborations between environmental geochemists and cancer epidemiologists. Key technical aspects of each field are presented, in addition to a case study of the extraordinarily high incidence rates of oesophageal cancer in the East African Rift Valley, which may have a geochemical contribution. The potential merit of veterinary studies for investigating common geochemical risk factors between human and animal disease is also highlighted.

Biotic and Abiotic Factors Influencing Arsenic Biogeochemistry and Toxicity in Fluvial Ecosystems: A Review

This review is focused on the biogeochemistry of arsenic in freshwaters and, especially, on the key role that benthic microalgae and prokaryotic communities from biofilms play together in through speciation, distribution, and cycling. These microorganisms incorporate the dominant iAs (inorganic arsenic) form and may transform it to other arsenic forms through metabolic or detoxifying processes. These transformations have a big impact on the environmental behavior of arsenic because different chemical forms exhibit differences in mobility and toxicity. Moreover, exposure to toxicants may alter the physiology and structure of biofilms, leading to changes in ecosystem function and trophic relations. In this review we also explain how microorganisms (i.e., biofilms) can influence the effects of arsenic exposure on other key constituents of aquatic ecosystems such as fish. At the end, we present two real cases of fluvial systems with different origins of arsenic exposure (natural vs. anthropogenic) that have improved our comprehension of arsenic biogeochemistry and toxicity in freshwaters, the Pampean streams (Argentina) and the Anllóns River (Galicia, Spain). We finish with a briefly discussion of what we consider as future research needs on this topic. This work especially contributes to the general understanding of biofilms influencing arsenic biogeochemistry and highlights the strong impact of nutrient availability on arsenic toxicity for freshwater (micro) organisms.

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.

Arsenosugar standards extracted from algae: Isolation, characterization and use for identification and quantification purposes

Sulfate (SO4-sug) and sulfonate (SO3-sug) arsenosugar standard solutions were obtained using preparative liquid chromatography. Several commercial algae samples were characterized (total contents and speciation) to select the most appropriate in relation to their arsenosugar contents. Water extracts from the selected sample (Fucus vesiculosus) were fractionated using a Hamilton PRP-X100 preparative column, and the presence of arsenic species in the isolated fractions was ascertained by IC-ICP-MS. Two of the fractions successfully presented only one arsenic species corresponding to sulfate and sulfonate arsenosugars at suitable concentrations. To unequivocally confirm the presence of both compounds, high-resolution mass spectrometry (ESI-TOF/MS) was used and the exact mass determined with errors lower than 0.5 ppm. The standard solutions obtained were successfully used to identify and quantify SO4-sug and SO3-sug in several edible algae samples purchased in local market. Total arsenic content for analyzed samples ranged from 34 to 57 mg kg-1, concentration values found for SO3-sug ranged from 5 to 36 mg As kg-1 and SO4-sug was only found in fucus with a concentration of 9.3 mg As kg-1.

A Comprehensive Review of Microfluidic Water Quality Monitoring Sensors

Water crisis is a global issue due to water contamination and extremely restricted sources of fresh water. Water contamination induces severe diseases which put human lives at risk. Hence, water quality monitoring has become a prime activity worldwide. The available monitoring procedures are inadequate as most of them require expensive instrumentation, longer processing time, tedious processes, and skilled lab technicians. Therefore, a portable, sensitive, and selective sensor with in situ and continuous water quality monitoring is the current necessity. In this context, microfluidics is the promising technology to fulfill this need due to its advantages such as faster reaction times, better process control, reduced waste generation, system compactness and parallelization, reduced cost, and disposability. This paper presents a review on the latest enhancements of microfluidic-based electrochemical and optical sensors for water quality monitoring and discusses the relative merits and shortcomings of the methods.

Nutrient distribution and structure affect the behavior and speciation of arsenic in coastal waters: A case study in southwestern coast of the Laizhou Bay, China

The effects of nutrient distribution and structure on the behavior and speciation of dissolved inorganic arsenic (DIAs) in coastal waters were analyzed based on the data of 48 surface water samples collected in the southwestern coast of Laizhou Bay and its adjacent rivers (SWLZB). The concentration of DIAs in the SWLZB ranged from 0.016 to 0.099 μmol l^-1 and generally decreased from west to south. The inshore waters exhibited higher DIAs level than the open ocean. The As⁵⁺/As³⁺ ratio was significantly positively correlated with the concentration of TDN, NO₃-N, PO₄-P, DSi, Chl-a and DO. The concentration of DIAs was strongly correlated with the concentration of PO₄-P and DSi, suggesting that adsorption/desorption was an important process for regulating the total DIAs concentration. The results indicated that the distribution of nutrients might well be an important environmental factor affecting the speciation and behavior of DIAs in surface water of the SWLZB.

An improved rapid analytical method for the arsenic speciation analysis of marine environmental samples using high-performance liquid chromatography/inductively coupled plasma mass spectrometry

Arsenic contamination in marine environments is a serious issue because some arsenicals are very toxic, increasing the health risks associated with the consumption of marine products. This study describes the development of an improved rapid method for the quantification of arsenic species, including arsenite (As^III), arsenate (As^V), arsenocholine (AsC), arsenobetaine (AsB), dimethylarsinic acid (DMA), and monomethyl arsonic acid (MMA), in seaweed, sediment, and seawater samples using high-performance liquid chromatography/inductively coupled plasma-mass spectrometry (HPLC/ICP-MS). ICP-MS based on dynamic reaction cells was used to eliminate spectral interference. Ammonium nitrate- and phosphate-based eluents were used as the mobile phases for HPLC analysis, leading to shorter overall retention time (6 min) and improved peak separation. Arsenicals were extracted with a 1% HNO₃ solution that required no clean-up process and exhibited reasonable sensitivity and peak resolution. The optimized method was verified by applying it to hijiki seaweed certified reference material (CRM, NMIJ 7405-a) and to spiked blank samples of sediment and seawater. The proposed method measured the concentration of As^V in the CRM as 9.6 ± 0.6 μg/kg dry weight (dw), which is close to the certified concentration (10.1 ± 0.5 μg/kg dw). The recovery of the six arsenicals was 87-113% for the sediment and 99-101% for the seawater. In the analysis of real samples, As^V was the most abundant arsenical in hijiki and gulfweed, whereas AsB was dominant in other seaweed species. The two inorganic arsenicals (As^III and As^V) and As^V were the most dominant in the sediment and seawater samples, respectively.

Replacing fish meal with insect meal in the diet of Atlantic salmon (Salmo salar) does not impact the amount of contaminants in the feed and it lowers accumulation of arsenic in the fillet

Insects are promising sources of protein and lipid in feeds for farmed animals. In the European Union, the use of insect meal (IM) and insect oil is permitted in fish feed. However, the European Food Safety Authority has highlighted the lack of data regarding the chemical safety of insects and products thereof. In this study, Atlantic salmon (Salmo salar) were fed diets in which fish meal (FM) was partially or fully substituted with IM, resulting in four diets with an FM replacement of 0%, 33%, 66% and 100% by IM. The IM was produced from Black soldier fly (Hermetia illucens) larvae fed media containing 60% seaweed (Ascophyllum nodosum). After 16 weeks of feeding, fish fillet samples were collected. The concentrations of undesirable substances, e.g., heavy metals, arsenic, dioxins, mycotoxins, pesticides, in the IM, the diets and fillets were determined. The concentrations of the analysed compounds in the IM were all below EU maximum levels for feed ingredients, except for arsenic. However, for complete feeds the concentrations of these compounds in the feeds, including arsenic, were all below EU MLs. Arsenic was transferred from seaweed to IM, resulting in arsenic levels in IM similar to what has been documented for FM. Transfer of arsenic from feed to fillet was observed; however, total arsenic concentrations in the fillet significantly decreased when fish were fed diets with more IM and less FM. Arsenic speciation analysis of the diets showed that although total arsenic levels were similar, the arsenic species were different. Arsenobetaine was the major organoarsenic species in the diets containing FM, while in diets containing IM several unidentified arsenic species were detected. The results suggest that the lower feed-to-fillet transfer of arsenic when FM is replaced by IM may be due to the presence of arsenic species with low bioavailability in the IM.

The Rate of Oxidation of Dimethylarsinous Acid to Dimethylarsinic Acid is Ph Dependent: Implications for the Analysis and Toxicology of Arsenic Metabolites in Urine

A 1H NMR spectroscopic study has shown the rate oxidation of dimethylarsinous acid to dimethylarsinic acid in buffered aqueous solutions to depend upon pH. Dimethylarsinous acid has been reported to be a highly toxic arsenical metabolite and component of the urine of persons exposed to inorganic arsenic, particularly through drinking water. As the pH of human urine can range from 4.5 to 8, the pH dependence of the oxidation rate of dimethylarsinous acid to dimethylarsinic acid has profound implications for the detection and analysis of these compounds in urine samples, and for the relevance of the experimental toxicology of dimethylarsinous acid.

Total Arsenic and Arsenic Species Determination in Freshwater Fish by ICP-DRC-MS and HPLC/ICP-DRC-MS Techniques

Analytical methods for the determination of total arsenic (TAs) and arsenic species (arsenite-As(III), arsenate-As(V), monomethylarsenic acid-MMA, dimethylarsenic acid-DMA and arsenobetaine-AsB) in freshwater fish samples were developed. Inductively coupled plasma mass spectrometry with dynamic reaction cell (ICP-DRC-MS) and high-performance liquid chromatography hyphenated to ICP-DRC-MS were used for TAs and arsenic species determination, respectively. The DRC with oxygen as a reaction gas was used. Sample preparation, digestion, and extraction were optimized. Microwave assisted digestion and extraction provided good recovery and extraction efficiency. Arsenic species were fully separated in 8 min using 10 mmol L-1 of ammonium dihydrogen phosphate and 10 mmol L-1 of ammonium nitrate. Overlapping of AsB and As(III) of arsenic species in the presence of a high concentration of AsB and trace amounts of As(III) were studied. Detailed validation of analytical procedures proved the reliability of analytical measurements. Both procedures were characterized by short-term and long-term precision: 2.2% (TAs) up to 4.2% (AsB), and 3.6% (TAs) up to 7.2% (DMA), respectively. Limits of detection (LD) were in the range from 0.056 µg L-1 for TAs to 0.15 µg L-1 for As(V). Obtained recoveries were in the range of 85%⁻116%. Developed methods were applied to freshwater fish samples analysis.

Occurrence, toxicity, and speciation analysis of arsenic in edible mushrooms

Owing to the strong concentration and biotransformation of arsenic, the influence of some edible mushrooms on human health has attracted widespread attention. The toxicity of arsenic greatly depends on its species, so the speciation analysis of arsenic is of critical importance. The aim of the present review is to highlight recent advances in arsenic speciation analysis in edible mushrooms. We summarized the contents and distribution of arsenic species in some edible mushrooms, the methods of sample preparation, and the techniques for their identification and quantification. Stability of the arsenic species during sample pretreatment and storage is also briefly discussed.

Inhibition of arsenite methylation induces synergistic genotoxicity of arsenite and benzo(a)pyrene diol epoxide in SCC-7 cells

A comprehensive analytical method was developed to investigate the synergistic genotoxicity of BPDE and As(iii) in SCC-7 cells.

On-line detection of radioactive and non-radioactive heavy metals in tobacco smoke using portable laser-induced breakdown spectroscopy

A portable laser-induced breakdown spectroscopy (PLIBS) device is proposed for on-line detection of radioactive and non-radioactive heavy metals in tobacco smoke with ultra-high sensitivity.

Methylated arsenic species throughout a 4-m deep core from a free-floating peat island

Arsenic (As) occurs in soils mostly in inorganic forms, whereas the organic forms usually occur only in trace amounts. Peatlands are waterlogged, generally anoxic, organic soils representing the first step in coal formation; the contribution of organic vs. inorganic As species in this environment has received little research attention. Here, 57 peat samples collected throughout a 4-m deep, free-floating mire were analysed for total As and for its organic species, including dimethylarsinic acid (DMA), methylarsonic acid (MA), trimethylarsine oxide (TMAO) and arsenobetaine (AB), by HPLC-ICPMS. Aqueous trifluoroacetic acid was used as extractant, resulting in an average extraction efficiency of almost 80%. Total As concentration throughout the profile ranged between 0.2 and 9.8mg/kg_peat (mean: 1.4±1.2mg/kg_peat). Organic As species (DMA+MA+TMAO+AB) accounted, on average, for 28±10% of total As (range: 6-51%), and for 37±13% of the extracted As (range: 7-64%). The relative abundance of organoarsenicals generally followed the order DMA>TMAO~MA≫AB. A positive correlation (p<0.001) was found among all organic As compounds, whereas their concentrations were negatively correlated with total sulfur content. The submerged zone (bottom 300cm) showed average and maximum concentrations of organoarsenic compounds that were almost twice those found in the top 100cm. This study shows that significant proportions of methylated As species occur even in peat samples characterized by low total As concentration (mostly <2mg/kg). Finally, this work provides the first evidence of organoarsenic species in free-floating mires, i.e., a globally distributed but scarcely investigated ecosystem.

A unique arsenic speciation profile in Elaphomyces spp. ("deer truffles")-trimethylarsine oxide and methylarsonous acid as significant arsenic compounds

Arsenic and its species were investigated for the first time in nine collections of Elaphomyces spp. ("deer truffles") from the Czech Republic with inductively coupled plasma mass spectrometry (ICPMS) and high-performance liquid chromatography coupled to ICPMS. The total arsenic concentrations ranged from 12 to 42 mg kg-1 dry mass in samples of E. asperulus and from 120 to 660 mg kg-1 dry mass in E. granulatus and E. muricatus. These concentrations are remarkably high for terrestrial organisms and demonstrate the arsenic-accumulating ability of these fungi. The dominating arsenic species in all samples was methylarsonic acid which accounted for more than 30% of the extractable arsenic. Arsenobetaine, dimethylarsinic acid, and inorganic arsenic were present as well, but only at trace concentrations. Surprisingly, we found high amounts of trimethylarsine oxide in all samples (0.32-28% of the extractable arsenic). Even more remarkable was that all but two samples contained significant amounts of the highly toxic trivalent arsenic compound methylarsonous acid (0.08-0.73% of the extractable arsenic). This is the first report of the occurrence of trimethylarsine oxide and methylarsonous acid at significant concentrations in a terrestrial organism. Our findings point out that there is still a lot to be understood about the biotransformation pathways of arsenic in the terrestrial environment. Graphical abstract Trimethylarsine oxide and methylarsonous acid in "deer truffles".

Speciation analysis of arsenic in seafood and seaweed: Part II-single laboratory validation of method

Single laboratory validation of a method for arsenic speciation analysis in seafood and seaweed is presented. The method is based on stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively. While the water-soluble arsenicals were speciated by anion and cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), the non-polar arsenicals were collectively determined by ICP-MS after digestion in acid. The performance characteristics and broad application of the method were evaluated by analyzing eight commercial samples (cod, haddock, mackerel, crab, shrimp, geoduck clam, oyster, and kombu) and four reference materials (fish protein (DORM-4), lobster hepatopancreas (TORT-3), mussel tissue (SRM 2976), and hijiki seaweed (CRM 7405-a)) representing finfish, crustaceans, molluscs, and seaweed. Matrices spiked at three levels in duplicates were also analyzed. The stepwise extraction provided 76-106% extraction of the total arsenic from the test materials. The method demonstrated satisfactory repeatability for analysis of replicate extracts prepared over several days. The accuracy of the method was evaluated by analyzing reference materials certified for both total arsenic and a few arsenicals; the experimental results were 90-105% of the certified values. Comparison between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species gave 80-92% mass balance. While spike recoveries of most arsenicals were in the acceptance range set by CODEX, a few species spiked into cod, haddock, and shrimp were poorly recovered due to transformation to other forms. After thorough investigations, strategies were devised to improve the recoveries of these species by averting their transformations. Limits of quantification (LOQ) for the extraction and quantification of 16 arsenicals using the current method were in the range 6-16 ng g^-1 arsenic.