Arsenic speciation analysis: A review with an emphasis on chromatographic separations

High through-put groundwater arsenic speciation analysis using an automated flow analyzer

The occurrence of geogenic arsenic (As) in groundwater is a global public health concern. However, there remain large gaps in groundwater As data, making it difficult to identify non-compliant domestic wells, partly due to lack of low-cost methods capable of rapid As analysis. Therefore, the development of high through-put and reliable on-site determination methods for inorganic As is essential. Herein, a portable automated analyzer was developed for the determination of arsenite (As(III)), arsenate (As(V)) and phosphate in As contaminated groundwater based on a previously adapted method for molybdenum blue spectrophotometry. After the optimization of the chemical reactions and flow manifold, the system demonstrated a high sample through-put (4.8/h for As(III), As(V) and phosphate analysis), allowing this system to screen 125 samples in 24 h. Other advantages include low operational costs (0.3 CNY per sample), appropriate sensitivity for contaminated groundwater (detection limits of 4.7 µg/L, 8.3 µg/L and 5.4 µg/L for As(III), As(V) and phosphate, respectively), good linearity (R2 > 0.9996 at As concentrations up to 1600 µg/L) and high precision (relative standard deviations of 3.5% and 2.8% for As(III) and As(V), respectively). The portable system was successfully used for As speciation analysis in 5 groundwater samples collected from multi-level wells at Yinchuan Plain, northwestern China, with total As concentrations ranging from 75.7 to 295.0 µg/L, independently assessing As speciation, providing a promising novel method for the rapid on-site screening of As in tens of millions of domestic wells worldwide.

Arsenic speciation in more than 1600 freshwater fish samples from fifty-three waterbodies in Alberta, Canada

We report here arsenic speciation in 1643 freshwater fish samples, representing 14 common fish species from 53 waterbodies in Alberta, Canada. Arsenic species were extracted from fish muscle tissue. Arsenic species in the extracts were separated using anion-exchange high-performance liquid chromatography (HPLC) and quantified using inductively coupled plasma mass spectrometry (ICPMS). The total arsenic concentrations in fish ranged from 2.8 to 1200 µg/kg (in wet weight of sample) (mean 71 ± 101 µg/kg), which are all below the 2000 µg/kg (wet weight) maximum allowable total arsenic in fish, recommended by the Ontario Ministry of the Environment. In 99.7%, or 1638 of all 1643 freshwater fish samples analyzed, arsenobetaine (AsB) was detectable, with concentrations higher than the method detection limit of 0.25 µg/kg (wet weight). Dimethylarsinic acid (DMA) was detectable (concentration >0.25 µg/kg) in 92.1%, or 1514 of the 1643 freshwater fish samples. Inorganic arsenate (iAsV) was detectable (>0.25 µg/kg) in 1119 fish (i.e., 68.1% of 1643 samples). Monomethylarsonic acid (MMA) was detectable (>0.25 µg/kg) in 418 fish (25.4% of 1643 samples). The concentrations of arsenic species in the 1643 fish samples varied by as much as three orders of magnitude, ranging from below the method detection limit of 0.25 µg/kg to the maximum concentrations of 380 µg/kg for AsB, 150 µg/kg for DMA, 70 µg/kg for iAsV, and 51 µg/kg for MMA. AsB made up 46.1% ± 26.2% of total arsenic species. Arsenic speciation patterns varied between lake whitefish, northern pike, and walleye, the three most common types of fish analyzed. The relative proportion of DMA in northern pike was larger than in lake whitefish and walleye, and conversely, the relative proportion of iAsV was lower in northern pike. Seven unknown arsenic species were detected, and their chromatographic retention time did not match with those of available arsenic standards. At least one unknown arsenic species was detected in 33.4%, or 549 of 1643 freshwater fish samples. The concentrations of unknown arsenic species were as high as 61 µg/kg. Future research is necessary to identify unknown arsenic species and to determine contributing factors to the observed arsenic species patterns and concentrations.

Arsenic speciation in freshwater fish using high performance liquid chromatography and inductively coupled plasma mass spectrometry

Arsenic speciation in freshwater fish is crucial for providing meaningful consumption guidelines that allow the public to make informed decisions regarding its consumption. While marine fish have attracted much research interest due to their higher arsenic content, research on freshwater fish is limited due to the challenges in quantifying and identifying arsenic species present at trace levels. We describe here a sensitive method and its application to the quantification of arsenic species in freshwater fish. Arsenic species from fish tissues were extracted using a methanol/water mixture (1:1 vol. ratio) and ultrasound sonication. Anion-exchange high-performance liquid chromatography (HPLC) enabled separation of arsenobetaine (AsB), inorganic arsenite (iAsIII), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), inorganic arsenate (iAsV), and three new arsenic species. Inductively coupled plasma mass spectrometry (ICPMS) provided highly sensitive and specific detection of arsenic. A limit of detection of 0.25 µg/kg (wet weight fish tissue) was achieved for the five target arsenic species: AsB, iAsIII, DMA, MMA, and iAsV. A series of experiments were conducted to ensure the accuracy and validity of the analytical method. The method was successfully applied to the determination of arsenic species in lake whitefish, northern pike, and walleye, with AsB, DMA, and iAsV being frequently detected. Three new arsenic species were detected, but their chromatographic retention times did not match with those of any available arsenic standards. Future research is necessary to elucidate the identity of these new arsenic species detected in freshwater fish.

New insights into efficient iron sulfide oxidation for arsenic immobilization by microaerophilic and acidophilic Fe(II)-oxidizing bacteria under micro-oxygen and acidic conditions

Microbial-mediated FeS oxidation to Fe(Ⅲ) minerals via chemolithoautotrophic Fe(Ⅱ) oxidizers under pH/O₂ limitations engages As immobilization. However, this process is constrained under the dual stress of micro-oxygen and acidic conditions due to the critically diminished Fe(Ⅱ) oxidation capacity. Therefore, the interplay between Fe(Ⅱ) oxidation, carbon metabolism, and As immobilization in Fe(Ⅱ)-oxidizing bacteria under micro-oxygen and acidic conditions remains unclear. This study presents the first successful enrichment of microaerophilic and acidophilic Fe(II)-oxidizing bacteria (MAFeOB). These bacteria are capable of oxidizing FeS to Fe(III) minerals and immobilizing up to 27,835 mg/kg of As(Ⅴ) under micro-oxygen content (below 3.2 mg/L) and acidic pH (4.5-6.2). Through comprehensive metagenomic analysis, it was speculated that MAFeOB harbor a suite of genes potentially participating in critical processes, including carbon fixation, Fe(II) oxidation, and arsenic detoxification. Notably, a potential electron transfer pathway from Cyc2_repCluster2 to Cytochrome cbb3-type oxidases facilitates Fe(II) oxidation. Furthermore, As(Ⅲ) efflux pump (arsA, arsB, acr3) and As(Ⅲ) oxidase (aioA) genes indicate MAFeOB's potential for As immobilization. Our findings underscore the pivotal role of MAFeOB in overcoming limitations associated with Fe(III) mineral formation, thereby enhancing arsenic immobilization under micro-oxygen and acidic water.

Bright yellow fluorescent N-doped Ti3C2 MXene quantum dots as an "on/off/on" nanoprobe for selective As3+ ion detection

Ti3C2 MXene quantum dots (MQDs) are considered to be an emerging nanomaterial in recent times, but the majority of MQDs exhibit limited emission properties in the blue-light region. Longer-wavelength emissive quantum dots are highly desirable in terms of various biological aspects including deep tissue penetration, superior signal-to-noise ratio, reduced radiation damage, etc. In this study, bright yellow fluorescent nitrogen-doped MQDs (N-MQDs) were successfully prepared using a one-pot hydrothermal method. The synthesized N-MQDs showed maximum emission at 570 nm upon excitation at a wavelength of 420 nm, with an optimum fluorescence quantum yield of 13.8%. Interestingly, the emission of the N-MQDs was significantly quenched upon the addition of As3+ ions. A mechanistic investigation revealed that static quenching was involved in the decrease in the fluorescence via the formation of a non-fluorescent complex due to the interaction of the functional groups of the N-MQDs and As3+. The quenched fluorescence was surprisingly recovered upon treatment of the complex with 2-amino-6-methoxybenzothiazole (MBTZ). The strong interaction of MBTZ with As3+ led to the detachment of the quencher from the N-MQDs, resulting in fluorescence recovery. The re-appearance of the functional groups of the N-MQDs after the addition of MBTZ was confirmed via spectroscopic study. Thus, the fluorescence "on/off/on" phenomenon of the N-MQDs nanoprobe was utilised for the instantaneous detection of As3+ and MBTZ. The limit of detection values were calculated to be 30 nM and 0.44 μM with a good linearity for As3+ and MBTZ, respectively. In addition, a solid sensor has been fabricated to recognize As3+ in wastewater, revealing its potential for on-site application in the near future.

Feasible approaches for arsenic speciation analysis in foods for dietary exposure assessment: a review

Arsenic (As) occurs naturally in different forms and oxidation states. Amongst them, inorganic arsenic (iAs) is classified as both genotoxic and carcinogenic whilst other organic arsenic species are considered less toxic. As in rice is mainly present in the form of iAs which therefore poses a health risk to populations that consume rice as a staple food. In 2011, the Joint Food and Agriculture Organisation/World Health Organisation Expert Committee on Food Additives determined the iAs benchmark dose lower confidence limit for a 0.5% increased incidence of lung cancer in humans (BMDL0.5) which computed to be 3.0 μg/kg body weight (bw)/day. However, the European Food Safety Authority (EFSA) has recently lowered the BMDL0.5 of iAs to 0.06 μg iAs/kg bw per day based on a low risk of bias case-control/cohort study on skin cancer as a Reference Point (RP). Subsequently, EFSA established a BMDL10 of 18.2 mg monomethylarsenic (V) (MMA(V))/kg bw/day and 1.1 mg dimethylarsenic (V) (DMA(V))/kg bw/day as RPs with reference to studies on skin cancer and urinary bladder tumours in rats respectively. Therefore, As speciation is essential when conducting dietary exposure assessment. Recent studies showed thiolated counterparts of MMA and DMA were found in certain foodstuffs, especially grain. However, these thiolated As species were not recognised in acidic, basic or peroxide systems as they transformed to MMA and DMA in these extractants. Therefore, one of the objectives of this review was to assess whether published analytical methods are fit for As speciation analysis, especially for iAs, MMA and DMA, in foodstuffs. Besides, discussion was conducted on whether limits of detection are sufficiently low for dietary exposure assessment with respect to recently established RPs of iAs, MMA and DMA when an upper bound approach is applied. Moreover, possible future research gaps are identified based on current knowledge and existing literature.

A novel method for multi-matrix arsenic speciation analysis by anion-exchange HPLC-ICP-MS in the framework of the third (French) total diet study

This study presents the development and validation of a precise analytical method for the speciation analysis of arsenic (As) compounds, including inorganic species [As(III) and As(V)] and organic species such as monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). The method employs anion-exchange high-performance liquid chromatography (AE HPLC) coupled with inductively coupled plasma-mass spectrometry (ICP-MS). To optimize the sample preparation process, microwave-assisted extraction (MAE) and heat-assisted extraction (HAE) techniques were evaluated and compared. Separation of all four arsenic species was achieved with baseline resolution within 10 min, utilizing an anion-exchange column and a mobile phase gradient of 0.5 and 5 mM ammonium carbonate with 3% (v/v) methanol at a pH of 9.3. The method validation followed the accuracy profile approach, employing six different food matrices analyzed in duplicate over six separate days within a 6-week period. The method demonstrated good intermediate reproducibility, with coefficients of variation (CVR) ranging from 4.7% to 5.5%, while the bias was < 3%. The limit of quantification (LOQ) for the four species was 6.25 μg/kg (dry weight, dw), and the limit of detection (LOD) was 1.88 µg/kg (dw). These results confirm the robustness, accuracy, and suitability of the method for routine As speciation analysis across a variety of food matrices. The method is specifically intended to be applied to the analysis of a panel of food samples as part of the ongoing (French) third total diet study.

Variable power functional dilution adjustment of spot urine

Spot-urinary biomarkers are crucial in medical, epidemiological, and environmental studies, but their variability due to hydration levels requires precise dilution adjustments. Traditional methods, like conventional creatinine correction (CCRC), are limited in compensating for variations in urine concentration, causing substantial inconsistencies, particularly at the extremes of the diuresis spectrum. While restricting the creatinine (CRN) range to 0.3-3 g/L is recommended to ensure result stability, this approach excludes a substantial proportion of samples and permits notable fluctuations within the accepted range. This study introduces a novel variable power functional creatinine correction method (V-PFCRC) to normalize analytes to 1 g/L CRN by utilizing uncorrected analyte levels and two analyte-specific coefficients, c and d. Based on extensive urinary total weight arsenic data (n = 5,553), the mathematical derivation of these coefficients is detailed in this paper and forms the foundation of the corrective V-PFCRC formulas. The generalizability of V-PFCRC was evaluated using large spot-urinary datasets for four additional metals and an extensive dataset of urinary iodine levels (n > 58,000) and blood iodine. Validation against conventional methods-assessing vital statistical data, residual CRN bias, and correlations with concurrently detected blood levels of total arsenic and iodine- demonstrated the superior performance of V-PFCRC in reducing residual CRN bias and enhancing blood-urine correlations. The V-PFCRC method effectively addresses nonlinear hydration bias and the exposure-dependent variability of this bias, providing a more accurate representation of exposure and supply levels. The adaptability and efficiency of V-PFCRC suggest its broad applicability across various scientific disciplines, potentially transforming the precision and reliability of urinary biomarkers.

Comparative Analysis of pK a Predictions for Arsonic Acids Using Density Functional Theory-Based and Machine Learning Approaches

Arsonic acids (RAsO(OH)2), prevalent in contaminated food, water, air, and soil, pose significant environmental and health risks due to their variable ionization states, which influence key properties such as lipophilicity, solubility, and membrane permeability. Accurate pK a prediction for these compounds is critical yet challenging, as existing models often exhibit limitations across diverse chemical spaces. This study presents a comparative analysis of pK a predictions for arsonic acids using a support vector machine-based machine learning (ML) approach and three density functional theory (DFT)-based models. The DFT models evaluated include correlations to the maximum surface electrostatic potential (V S,max), atomic charges derived from a solvation model (solvation model based on density), and a scaled solvent-accessible surface method. Results indicate that the scaled solvent-accessible surface approach yielded high mean unsigned errors, rendering it less effective. In contrast, the atomic charge-based method on the conjugated arsonate base provided the most accurate predictions. The ML-based approach demonstrated strong predictive performance, suggesting its potential utility in broader chemical spaces. The obtained values for pK a from V S,max show a weak prediction level, because the way of predicting pK a is related only to the electrostatic character of the molecule. However, pK a is influenced by many factors, including the molecular structure, solvation, resonance, inductive effects, and local atomic environments. V S,max cannot fully capture these different interactions, as it gives a simplistic view of the overall molecular potential field.

Preliminary analysis of the presence of metals and metalloids in cigarette butts and fibers discarded on a tourist beach in Cartagena, Colombia

Cigarette butts are classified as plastic waste due to their composition of cellulose acetate fibers and are commonly found in beach sand. Their persistence in the environment, low biodegradability, and potential to interact with metals and metalloids during the aging process make them a significant subject of interest for research on coastal marine ecosystems. The aim of this study is to investigate the presence of metals such as hexavalent chromium Cr (VI), cadmium (Cd), and the metalloid arsenic (As) in cigarette butts (CBs), cigarette butt fibers (CBFs), and sand on a tourist beach in Cartagena, Colombia. The goal is to establish a baseline for potential contamination on the beach due to these elements. The methodology includes collecting samples of CBs, CBFs, and sand from different beach usage zones (active, rest, and service) and conducting standardized laboratory tests using atomic absorption spectroscopy for As and Cd and the standard colorimetric method for Cr (VI). The main findings indicate that arsenic levels reached 7.69, 5.75, and 3.47 mg As/kg in the sand, CBs, and CBFs, respectively. Cadmium and hexavalent chromium were found to be below the detection limit for the applied methodology. Additionally, mercury was detected at a concentration of 0.37 mg Hg/L in CBFs in the active zone in October.

Determination of toxicological relevant arsenic species in urine by hydride generation microwave-induced plasma optical emission spectrometry

An analytical method for the determination of toxicological relevant species of arsenic in urine was developed and validated using hydride generation microwave-induced emission spectrometry (HG-MP-AES). This strategy can be used as an alternative to HG-HPLC-ICP-MS considered as a reference technique for arsenic speciation. This procedure is notably less expensive than other techniques and sample preparation and requires only a few steps.•Hydride generation with MP-AES detection has proven to be an effective technique for measuring arsenic metabolites in urine, which is relevant for occupational monitoring and health risk assessment purposes.•This method offers simplicity and cost-effectiveness, serving as an alternative to classical analytical procedures typically used for arsenic analysis in urine.•The methodology has been successfully applied for the purpose of workers' health surveillance.

Direct ion chromatographic method for speciation micro analysis of arsenic forms in industrial samples with "rich" matrix composition

The speciation analysis of arsenic has consistently been a subject of great interest. However, it remains challenging to analyze complex matrix samples that contain both arsenic and interfering components. In this case, it can be hard to choose the right combinations of different instrumental methods, or a separation method followed by detection, which is usually done using a spectral approach (hybrid methods). In the production control of copper electrorefining, the determination of the concentration of As (III) and As (V) helps to improve the quality of the cathode copper produced. This work investigated the possibility of directly determining both arsenic forms and total As in an electrolyte bath using ion chromatography (IC) with conductometric detection. The use of the ion chromatographic approach for the determination of As(V) in complex matrix samples such as copper electrolyte must take into account the presence of potential interferences from anions such as sulphates, sulfites, selenites, selenates, etc. The results revealed that the method is accurate and precise, with As(V) quantification limits of 15 µg.L-1 and detection limits of 5 µg.L-1. This method is suitable for assessing various types of arsenic in the production of electrolytic copper, with the aim of replacing the current technique that requires liquid-liquid extraction and ICP-OES detection. This led to the following improvements: Enhanced efficiency: The method eliminates the need for extensive and time-consuming sample preparation for the initial separation of arsenic forms. At the same time, the method's characteristics are comparable to those of ICP-OES with liquid-liquid extraction, which is often used in the speciation analysis of arsenic. The method is environmentally friendly as it avoids the use of organic and poisonous extractants. The method can simultaneously analyze other anions (PO43-, SO42-, F-, Cl-, etc.) with arsenates with appropriate calibration.

Fast On-Site Speciation and High Spatial Resolution Imaging of Labile Arsenic in Freshwater and Sediment Using the DGT-SERS Sensor

Diffusive gradients in thin films (DGT) technique is renowned for in situ passive sampling but not for rapid on-site analysis, whereas surface-enhanced Raman spectroscopy (SERS) excels in ultrasensitive on-site detection but is limited by substrate contamination from complex matrices. Here, a hierarchical nanostructure of silver (Ag) mirror-supported large Ag nanoparticles (∼120 nm) was grown in situ in polyacrylamide hydrogel with a restricted pore size (PAM/Ag mirror/AgNPs) to serve as both the DGT binding phase and the SERS substrate. The substrate exhibited a maximum electric field enhancement factor of 9.9 × 108 and a signal relative standard error of 4.8%. Using the DGT-SERS sensor, As(III) and As(V) in freshwater were simultaneously detected at limits of 0.9 and 0.8 μg L-1, respectively, applicable across a wide range of environmental conditions. The DGT-SERS effectively mitigated the interfacial reduction of As(V) caused by humic acid by excluding it from plasmonic hotspots through size exclusion of the diffusive layer. The Raman analysis of a DGT sample in the field requires only 2 s using a portable spectrometer without DGT device disassembly. More importantly, the DGT-SERS captured the first two-dimensional image of As(III) and As(V) in one DGT at the micron scale resolution, revealing their spatially supplementary distribution patterns at the sediment-water interface. This study paves the way for next-generation speciation imaging DGT and the application of SERS in complex environments.

Environmental fate of monosodium methanearsonate (MSMA)-Part 1: Conceptual model

Monosodium methanearsonate (MSMA), the sodium salt of monomethylarsonic acid (MMA), is used as a selective, broad-spectrum contact herbicide to control weeds in cotton and a variety of turf. In water, MSMA dissociates into ions of sodium (Na+) and of MMA-, which is the herbicide's active component. Certain soil microorganisms can methylate MMA to dimethylarsinic acid (DMA) other microorganisms can demethylate MMA to inorganic arsenic (iAs). To predict the groundwater concentration of iAs that may result from MSMA application, the processes affecting the environmental behavior of MSMA must be quantified and modeled. There is an extensive body of literature regarding the environmental behavior of MSMA. There is a consensus among scientists that the fate of MMA in soil is controlled by microbial activity and sorption to solid surfaces and that iAs sorption is even more extensive than that of MMA. The sorption and transformation of MMA and its metabolites are affected by several factors including aeration condition, temperature, pH, and the availability of nutrients. The precise nature and extent of each of these processes vary depending on site-specific conditions; however, such variability is constrained in typical MSMA use areas that are highly managed. Monomethylarsonic acid is strongly sorbed on mineral surfaces and becomes sequestered into the soil matrix. Over time, a greater portion of MMA and iAs becomes immobile and unavailable to soil microorganisms and to leaching. This review synthesizes the results of studies that are relevant for the behavior of MSMA used as a herbicide to reliably predict the fate of MSMA in its use conditions. Integr Environ Assess Manag 2024;20:1859-1875. © 2024 The Author(s). Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Sensitive and isotopic interference-free analysis of Sb using hydride generation-microwave plasma torch-mass spectrometry under ambient condition

A sensitive and isotopic interference-free analysis method for Sb was developed based on hydride generation-microwave plasma torch-mass spectrometry (HG-MPT-MS). Compared to the conventional ICP-MS, MPT coupled to an ion trap mass spectrometer enabled much "softer" ionization of Sb under ambient condition, which provided multi-detection modes and various ion forms, such as Sb+, SbO+, SbO2-, SbO++H2O and so on. These ion formations can be easily regulated by tuning capillary voltage and tube lens voltage, which facilitated elimination of isotopic interference during analysis, for instance the interference of 123Te on 123Sb could be effectively excluded by optimizing parameters of capillary voltage and tube lens voltage. The potential application of HG-MPT-MS for Sb isotope ratio analysis was also demonstrated, which could be determined in different forms, e.g., 123Sb/121Sb or 123Sb16O/121Sb16O. The value of 123Sb/121Sb was determined to be 0.75110 ± 0.00038 (2σ, n > 50). In addition, the detection limit, linearity and spike recovery were also studied. Overall, HG-MPT-MS performed equally well on detection limit (0.05 μg/L) with ICP-MS or HG-AFS. The linearity (R2 = 0.998) was checked in the concentration range of 10-500 μg/L. Spike recovery were evaluated with two soil samples, and the obtained spike recovery ranged 90-100 %. In general, HG-MPT-MS was expected to be a versatile tool for study the biochemical or geochemical behaviors of Sb and other hydride forming elements under ambient condition in a much simpler and more efficient way.

Seasonal and spatial variations of arsenic and its species in particulate matter in an urban environment of Brno, Czech Republic

The present paper deals with an analysis of total arsenic concentration using ICP-MS/MS and an analysis of concentration of several arsenic species, arsenite (AsIII), arsenate (AsV), monomethylarsonate (MMA), dimethylarsenite (DMA), and trimethylarsine oxide (TMAO), using HPLC-ICP-MS/MS in the PM10 fraction of airborne urban aerosol. The samples were collected during two campaigns, in the autumn of 2022 and in the winter of 2023, at three locations within the central European city of Brno, with the aim to evaluate the seasonal and spatial variations in the PM10 composition. The results confirmed only the seasonal variability in the content of the methylated arsenic species in PM10 influenced by biomethylation processes. To gain better understanding of the possible arsenic origin, a supplementary analysis of the total arsenic concentrations was performed in samples of different size fractions of particulate matter collected using ELPI + . Local emissions, including industrial activities and heating during the winter season, were suggested as the most likely predominant source contributing to the total As content in PM10.

Recent developments in speciation and determination of arsenic in marine organisms using different analytical techniques. A review

Marine organisms play a vital role as the main providers of essential and functional food. Yet they also constitute the primary pathway through which humans are exposed to total arsenic (As) in their diets. Since it is well known that the toxicity of this metalloid ultimately depends on its chemical forms, speciation in As is an important issue. Most relevant articles about arsenic speciation have been investigated. This extended not only from general knowledge about As but also the toxicity and health related issues resulting from exposure to these As species from the food ecosystem. There can be enormous side effects originating from exposure to As species that must be measured quantitatively. Therefore, various convenient approaches have been developed to identify different species of As in marine samples. Different extraction strategies have been utilized based on the As species of interest including water, methanol and mixtures of both, and many other extraction agents have been explained in this article. Furthermore, details of hyphenated techniques which are available for detecting these As species have been documented, especially the most versatile and applied technique including inductively coupled plasma mass spectrometry.

Thiol-Functionalized Adsorbents through Atomic Layer Deposition and Vapor-Phase Silanization for Heavy Metal Ion Removal

The removal of toxic heavy metal ions from water resources is crucial for environmental protection and public health. In this study, we address this challenge by developing a surface functionalization technique for the selective adsorption of these contaminants. Our approach involves atomic layer deposition (ALD) followed by vapor-phase silanization of porous substrates. We utilized porous silica gel powder (∼100 μm particles, 89 m2/g surface area, ∼30 nm pores) as an initial substrate. This powder was first coated with ∼0.5 nm ALD Al2O3, followed by vapor-phase grafting of a thiol-functional silane. The modified powder, particularly in acidic conditions (pH = 4), showed high selectivity in adsorbing Cd(II), As(V), Pb(II), Hg(II), and Cu(II) heavy metal ions in mixed ion solutions over common benign ions (e.g., Na, K, Ca, and Mg). Langmuir adsorption isotherms and breakthrough adsorption studies were conducted to assess heavy metal binding affinity and revealed the order of Cd(II) < Pb(II) < Cu(II) < As(V) < Hg(II), with a significantly higher affinity for As(V) and Hg(II) ions. Time-dependent uptake studies demonstrated rapid removal of heavy metal ions from aqueous environments, with Hg(II) exhibiting the fastest adsorption kinetics on thiol-modified surfaces. These findings highlight the potential of ALD and vapor-phase silanization to create effective adsorbents for the targeted removal of hazardous contaminants from water.

Risk assessment of small organoarsenic species in food

The European Commission asked EFSA for a risk assessment on small organoarsenic species in food. For monomethylarsonic acid MMA(V), decreased body weight resulting from diarrhoea in rats was identified as the critical endpoint and a BMDL10 of 18.2 mg MMA(V)/kg body weight (bw) per day (equivalent to 9.7 mg As/kg bw per day) was calculated as a reference point (RP). For dimethylarsinic acid DMA(V), increased incidence in urinary bladder tumours in rats was identified as the critical endpoint. A BMDL10 of 1.1 mg DMA(V)/kg bw per day (equivalent to 0.6 mg As/kg bw per day) was calculated as an RP. For other small organoarsenic species, the toxicological data are insufficient to identify critical effects and RPs, and they could not be included in the risk assessment. For both MMA(V) and DMA(V), the toxicological database is incomplete and a margin of exposure (MOE) approach was applied for risk characterisation. The highest chronic dietary exposure to DMA(V) was estimated in 'Toddlers', with rice and fish meat as the main contributors across population groups. For MMA(V), the highest chronic dietary exposures were estimated for high consumers of fish meat and processed/preserved fish in 'Infants' and 'Elderly' age class, respectively. For MMA(V), an MOE of ≥ 500 was identified not to raise a health concern. For MMA(V), all MOEs were well above 500 for average and high consumers and thus do not raise a health concern. For DMA(V), an MOE of 10,000 was identified as of low health concern as it is genotoxic and carcinogenic, although the mechanisms of genotoxicity and its role in carcinogenicity of DMA(V) are not fully elucidated. For DMA(V), MOEs were below 10,000 in many cases across dietary surveys and age groups, in particular for some 95th percentile exposures. The Panel considers that this would raise a health concern.

Unveiling New Arsenic Compounds in Plants via Tailored 2D-RP-HPLC Separation with ICP and ESI MS Detection

Arsenic (As) speciation analysis is scientifically relevant due to the pivotal role the As chemical form plays in toxicity, which, in turn, directly influences the effect it has on the environment. The objective of this study was to develop and optimize a method tailored for studying As compounds in plant samples. Different extraction procedures and HPLC methods were explored to assess their efficiency, determine mass balance, and improve the resolution of compounds in the chromatograms. Conventionally applied anion-exchange chromatography facilitated the separation of well-documented As compounds in the extracts corresponding to 19 to 82% of As present in extracts. To gain insight into compounds which remain undetectable by anion chromatography (18 to 81% of As in the extracts), but still possibly metabolically relevant, we explored an alternative chromatographic approach. The procedure of sample purification and preconcentration through solid-phase extraction, facilitating the detection of those minor As compounds, was developed. The system was further refined to achieve an online 2D-RP-HPLC system, which was employed to analyze the extracts more comprehensively with ICP and ESI MS. Using this newly developed method, As(III)-phytochelatins, along with other arseno-thio-compounds, were detected and identified in extracts derived from the tree roots of seedlings grown in the presence of As(III) and As(V), and a group of arseno lipids was detected in the roots of plants exposed to As(V).

Assessing the Impact of PM2.5-Bound Arsenic on Cardiovascular Risk among Workers in a Non-ferrous Metal Smelting Area: Insights from Chemical Speciation and Bioavailability

Inhalation of fine particulate matter PM2.5-bound arsenic (PM2.5-As) may cause significant cardiovascular damage, due to its high concentration, long transmission range, and good absorption efficiency in organisms. However, both the contribution and the effect of the arsenic exposure pathway, with PM2.5 as the medium, on cardiovascular system damage in nonferrous smelting sites remain to be studied. In this work, a one-year site sample collection and analysis work showed that the annual concentration of PM2.5-As reached 0.74 μg/m3, which was 120 times the national standard. The predominant species in the PM2.5 samples were As (V) and As (III). A panel study among workers revealed that PM2.5-As exposure dominantly contributed to human absorption of As. After exposure of mice to PM2.5-As for 8 weeks, the accumulation of As in the high exposure group reached equilibrium, and its bioavailability was 24.5%. A series of animal experiments revealed that PM2.5-As exposure induced cardiac injury and dysfunction at the environmental relevant concentration and speciation. By integrating environmental and animal exposure assessments, more accurate health risk assessment models exposed to PM2.5-As were established for metal smelting areas. Therefore, our research provides an important scientific basis for relevant departments to formulate industry supervision, prevention and control policies.

Amphibian tolerance to arsenic: microbiome-mediated insights

Amphibians are often recognized as bioindicators of healthy ecosystems. The persistence of amphibian populations in heavily contaminated environments provides an excellent opportunity to investigate rapid vertebrate adaptations to harmful contaminants. Using a combination of culture-based challenge assays and a skin permeability assay, we tested whether the skin-associated microbiota may confer adaptive tolerance to tropical amphibians in regions heavily contaminated with arsenic, thus supporting the adaptive microbiome principle and immune interactions of the amphibian mucus. At lower arsenic concentrations (1 and 5 mM As3+), we found a significantly higher number of bacterial isolates tolerant to arsenic from amphibians sampled at an arsenic contaminated region (TES) than from amphibians sampled at an arsenic free region (JN). Strikingly, none of the bacterial isolates from our arsenic free region tolerated high concentrations of arsenic. In our skin permeability experiment, where we tested whether a subset of arsenic-tolerant bacterial isolates could reduce skin permeability to arsenic, we found that isolates known to tolerate high concentrations of arsenic significantly reduced amphibian skin permeability to this metalloid. This pattern did not hold true for bacterial isolates with low arsenic tolerance. Our results describe a pattern of environmental selection of arsenic-tolerant skin bacteria capable of protecting amphibians from intoxication, which helps explain the persistence of amphibian populations in water bodies heavily contaminated with arsenic.

Inorganic arsenic in seaweed: a fast HPLC-ICP-MS method without coelution of arsenosugars

Seaweed is becoming increasingly popular in the Western diet as consumers opt for more sustainable food sources. However, seaweed is known to accumulate high levels of arsenic-which may be in the form of carcinogenic inorganic arsenic (iAs). Here we propose a fast method for the routine measurement of iAs in seaweed using HPLC-ICP-MS without coelution of arsenosugars that may complicate quantification. The developed method was optimised using design of experiments (DOE) and tested on a range of reference materials including TORT-3 (0.36 ± 0.03 mg kg-1), DORM-5 (0.02 ± 0.003 mg kg-1), and DOLT-5 (0.07 ± 0.007 mg kg-1). The use of nitric acid in the extraction solution allowed for the successful removal of interferences from arsenosugars by causing degradation to an unretained arsenosugar species, and a recovery of 99 ± 9% was obtained for iAs in Hijiki 7405-b when compared with the certified value. The method was found to be suitable for high-throughput analysis of iAs in a range of food and feed matrices including Asparagopsis taxiformis seaweed, grass silage, and insect proteins, and offers a cost-effective, fast, and robust option for routine analysis that requires minimal sample preparation. The method may be limited with regards to the quantification of dimethylarsenate (DMA) in seaweed, as the acidic extraction may lead to overestimation of this analyte by causing degradation of lipid species that are typically more abundant in seaweed than other marine matrices (i.e. arsenophospholipids). However, the concentrations of DMA quantified using this method may provide a better estimation with regard to exposure after ingestion and subsequent digestion of seaweed.

Microalgae for freshwater arsenic bioremediation: examining cellular toxicity, bioconcentration factor and eluding an alternative arsenic detoxification pathway

Microalgae are photoautotrophic organisms in freshwater systems known to uptake and bioremediate arsenic, a heavy metal. In this study, we compared the growth and arsenic uptake of two microalgae strains, Nostoc and Chlorella, to determine their suitability for arsenic bioremediation. As compared to the control, our results showed that treatment with As (III) enhanced the Nostoc growth by approximately 15% when grown in the absence of phosphate. The highest bioconcentration factor of Nostoc at this treatment was 1463.6, whereas 0.10 mg L-1 As (V) treatment improved the Chlorella growth by 25%, in the presence of phosphate. However, arsenic uptake reduced from 175.7 to 32.3 throughout the cultivation period for Chlorella. This suggests that Nostoc has an upper advantage in the bioremediation of arsenic as compared to the Chlorella strain. To gain insights into the potential of Nostoc in arsenic bioremediation, we further conducted SEM analysis on the vegetative cell surface. The SEM results showed that As (III) disrupted the Nostoc vegetative cell surface and structure. Further to this, pathway analysis and polymerase chain reaction (PCR) were conducted to identify the potential arsenic pathway regulated by Nostoc. The primary As (III)-related pathways elucidated include the arsA transporter and arsD complex that require ATP and As (III) methylation to S-adenosylmethionine. The phosphate deficiency condition resulting in the inability to generate ATP caused As (III) could not be excreted from the Nostoc cells, potentially contributing to the high arsenic concentration accumulated under phosphate-depleted conditions. These insights contribute to understanding the efficacy of microalgae strains in freshwater arsenic bioremediation.

Pro-vegetarian dietary patterns and essential and heavy metal exposure in children of 4-5-years from the INfancia y medio Ambiente cohort (INMA)

Dietary patterns provide a comprehensive assessment of food consumption, including essential nutrients and potential exposure to environmental contaminants. While pro-vegetarian (PVG) dietary patterns have shown health benefits in adults, their effects on children are less well studied. This study aims to explore the association between children's adherence to the most common PVG dietary patterns and their exposure to metals, assessed through urine concentration. In our study, we included a population of 723 children aged 4-5-years from the INfancia y Medio Ambiente (INMA) cohort in Spain. We calculated three predefined PVG dietary patterns, namely general (gPVG), healthful (hPVG), and unhealthful (uPVG), using dietary information collected through a validated Food Frequency Questionnaire. Urinary concentrations of various essential and heavy metals (Co, Cu, Zn, Se, Mo, Pb, and Cd) were measured using mass spectrometry. Additionally, urinary arsenic speciation, including arsenobetaine (AsB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and inorganic arsenic (iAs), was measured. The sum of urinary MMA and iAs was used to assess iAs exposure. We estimated primary (PMI) and secondary iAs methylation (SMI) indices. To explore the association between PVG dietary patterns in quintiles and metal exposure, we utilized multiple-adjusted linear regression models and the quantile g-computation approach. Compared with the lowest quintile, participants in the highest quintile of gPVG showed a 22.7% lower urinary Co (95% confidence interval (CI): -38.7; -1.98) and a 12.6% lower Se (95%CI: -22.9; -1.00) concentrations. Second quintile of adherence to hPVG was associated with a 51.7% lower urinary iAs + MMA concentrations (95%CI: -74.3; -8.61). Second quintile of adherence to an uPVG was associated with a 13.6% lower Se levels (95%CI: -22.9; -2.95) while the third quintile to this pattern was associated with 17.5% lower Mo concentrations (95%CI: -29.5; -2.95). The fourth quintile of adherence to gPVG was associated with a 68.5% higher PMI and a 53.7% lower SMI. Our study showed that adherence to a gPVG dietary pattern in childhood may modestly reduce the intakes of some essential metals such as Co and Se. Further investigations are warranted to explore any potential health implications.

Determination and speciation of arsenic in drinking water samples by X-ray spectrometry technique

Arsenic is ranked as the first compound in the Substance Priority List 2023 by the Agency for Toxic Substances and Disease Registry (ATSDR). The most prominent entrance to the human body is through drinking water wherein the predominant species are arsenite and arsenate. The more toxic As(III) has rigorously threatened human health worldwide; hence, speciation and separation are the need of the hour. In this article, we have reported a simple method of arsenic speciation by wavelength dispersive X-ray fluorescence (WD-XRF) spectrometer. Valence to core (VtC) electronic transitions, i.e., AsKβ2,5 fluorescence lines were used for arsenic speciation. This speciation study by WD-XRF entails direct measurement of activated alumina pellets containing arsenate and arsenite species adsorbed from water sample without separation of the trivalent and pentavalent species. This is the first report wherein the X-ray technique has been explored for speciation analysis of arsenic and the biggest advantage of the method lies in its applicability to direct analysis of synthesized nanotubes or other solid-phase extraction sorbents entrapping both the arsenic species. For determination of total arsenic using activated alumina as adsorbent, the most intense AsKα1,2 analytical lines were used and the instrumental limit of detection and the lower limit of quantification were 0.23 μg/L and 0.89 μg/L, respectively. For speciation, these limits were calculated to be 50 μg/L and 200 μg/L, respectively.

Isolation and characterisation of Fe(II)-oxidising bacteria and their application in the removal of arsenic in an aqueous solution

Arsenic (As) is a toxic metalloid disseminated in water, soil, and air. Arsenic contamination is currently a major public health concern. This study investigated arsenic removal by Fe(II)-oxidising bacteria in an aqueous solution. A bacterial strain, Z1, isolated from concentrated sludge, was identified as Sphaerotilus natans based on microscopic morphology, culture characteristics, and 16s rRNA gene sequences. After arsenic-resistant acclimation, Sphaerotilus natans Z1 successfully survived and propagated in high arsenic conditions (100 mg·L-1 As(V) or As(III)). To a certain extent, the isolated strain could decrease the concentration of As(III)/As(V) by biosorption under organic substance supply. Partial As(V) could be reduced to As(III) due to cytoplasmic arsenic reduction of bacteria. In addition, ferrihydrite, one of the iron oxides, was formed by the mediation of Sphaerotilus natans in the Winogradsky medium. Most of As(III)/As(V) could be effectively removed by sorbing onto the resultant ferrihydrite mineral. Thus, iron oxide minerals facilitated by Sphaerotilus natans may be an alternative remediation strategy for scavenging arsenic in the water environment.

Effects of Dietary Intake of Arsenosugars and Other Organic Arsenic Species on Studies of Arsenic Methylation Efficiency in Humans

Extensive research has used dimethylarsinic acid (DMA) in urine as a marker of arsenic methylation. The premise is that humans methylate inorganic arsenicals to monomethylarsonic acid (MMA) and DMA and excrete these arsenic species into the urine. However, DMA in urine not only comes from the methylation of inorganic arsenic but also could be a result of metabolism of other arsenic species, such as arsenosugars and arsenolipids. Most environmental health and epidemiological studies of arsenic methylation might have overlooked confounding factors that contribute to DMA in urine. Here we critically evaluate reported studies that used methylation indexes, concentration ratios of methylated arsenicals, or the percentage of DMA in urine as markers of arsenic methylation efficiency. Dietary intake of arsenosugars potentially confounds the calculation and interpretation of the arsenic methylation efficiencies. Many studies have not considered incidental dietary intake of arsenosugars, arsenolipids, and other organic arsenic species. Future studies should consider the dietary intake of diverse arsenic species and their potential effect on the urinary concentrations of DMA.

Toxicity, arsenic speciation and characteristics of hyphenated techniques used for arsenic determination in vegetables. A review

Arsenic (As) speciation is an interesting topic because it is well recognized that the toxicity of this metalloid ultimately depends on its chemical form. More than 300 arsenicals exist naturally. However, As can be present in four oxidation states: As-III, As0, AsIII and AsV. Long-term exposure to As from different sources, such as anthropogenic processes, or water, fauna and flora contaminated with As, has put human health at risk for decades. There are many side-effects correlated with exposure to InAs species, such as skin problems, respiratory diseases, kidney problems, cardiovascular diseases and even cancer. There are different levels and types of As in foods, particularly in vegetables. Furthermore, different chemical methods and techniques have been developed. Therefore, this review focuses on the general properties of various approaches used to identify As species in vegetation samples published worldwide. This includes various approaches (different solvents and techniques) used to extract As species from the matrix. Then, versatile chromatographic and non-chromatographic systems to separate different forms of As are reviewed. Finally, the general properties of the most common instruments used to detect As species from samples of interest are listed.

Arsenic fractionation and speciation in different textured soils supplied with farmyard manure and accumulation by sunflower under alkaline calcareous conditions

Arsenic (As) is a naturally occurring element that is found in soil, water, and rocks. However, it can also be released into the environment through human activities. Arsenic is considered an environmental hazard because it is toxic to humans and animals and can cause serious health problems. Additionally, As-contaminated soil can limit plant growth and reduce crop yields, leading to economic losses for farmers. So, decreasing metal/metalloid solubility in soil by synthetic and organic amendments leads to better crop productivity on contaminated soils. The current study aimed to evaluate farmyard manure (FYM)-mediated changes in soil arsenic (As) behavior, and subsequent effects on achene yield of sunflower. Treatment plan comprised of two As levels, i.e., As-60 (60 mg kg-1) and As-120 (120 mg kg-1), four FYM levels (0, 20, 35, and 50 g kg-1), three textural types (sandy, loamy and clayey), and replicated thrice. Seven As fractions including water soluble-As (WS-As), labile-As (L-As), calcium-bound As (Ca-As), aluminum-bound As (Al-As), iron-bound As (Fe-As), organic-matter-bound As (OM-As), and residual-As (R-As) were determined which differed significantly (P ≤ 0.05) with FYM and soil texture. FYM supplementation decreased WS-As, L-As, Ca-As, and Al-As while increased Fe-As, OM-As, and R-As. The immobilizing effect of FYM increased with increasing its rate of application, and maximum effect was found in clayey soil. As speciation in soil also significantly (P ≤ 0.05) affected by FYM and soil texture, with a reduction in arsenate while increase in arsenite, mono-methyl arsenate, and di-methyl arsenate with increasing the rate of FYM supplementation. Bioaccumulation factor reduced with FYM addition, and highest reduction of 38.65 and 42.13% in sandy, 34.24 and 36.26% in loamy while 29.16 and 35.10% in clayey soils at As-60 and As-120, respectively, by 50 g kg-1 FYM compared with respective As treatments without FYM. As accumulation in plant parts was significantly (P ≤ 0.05) reduced by FYM with the subsequent improvement in achene yield.

TiO2 nanoparticle-Coated 3D-Printed porous monoliths enabling highly sensitive speciation of inorganic Cr, As, and Se

Post-printing functionalization can enhance the functionality and applicability of analytical devices manufactured using three-dimensional printing (3DP) technologies. In this study we developed a post-printing foaming-assisted coating scheme-through respective treatments with a formic acid (30%, v/v) solution and a sodium bicarbonate (0.5%, w/v) solution incorporating titanium dioxide nanoparticles (TiO2 NPs; 1.0%, w/v)-for in situ fabrication of TiO2 NP-coated porous polyamide monoliths in 3D-printed solid phase extraction columns, thereby enhancing the extraction efficiencies of Cr(III), Cr(VI), As(III), As(V), Se(IV), and Se(VI) for speciation of inorganic Cr, As, and Se species in high-salt-content samples when using inductively coupled plasma mass spectrometry. After optimizing the experimental conditions, the 3D-printed solid phase extraction columns with the TiO2 NP-coated porous monoliths extracted these species with 5.0- to 21.9-fold enhancements, relative to those obtained with the uncoated monolith, with absolute extraction efficiencies ranging from 84.5 to 98.3% and method detection limits ranging from 0.7 to 32.3 ng L-1. We validated the reliability of this multi-elemental speciation method through determination of these species in four reference materials [CASS-4 (nearshore seawater), SLRS-5 (river water), 1643f (fresh water), and Seronorm Trace Elements Urine L-2 (human urine); relative errors between certified and measured concentrations: 5.6 to +4.0%] and spike analyses of seawater, river water, agriculture waste, and human urine samples (spike recoveries: 96-104%; relative standard deviations of these measured concentrations all below 4.3%). Our results demonstrate that post-printing functionalization has great potential for future applicability in 3DP-enabling analytical methods.

Arsenic speciation in freshwater fish: challenges and research needs

Food and water are the main sources of human exposure to arsenic. It is important to determine arsenic species in food because the toxicities of arsenic vary greatly with its chemical speciation. Extensive research has focused on high concentrations of arsenic species in marine organisms. The concentrations of arsenic species in freshwater fish are much lower, and their determination presents analytical challenges. In this review, we summarize the current state of knowledge on arsenic speciation in freshwater fish and discuss challenges and research needs. Fish samples are typically homogenized, and arsenic species are extracted using water/methanol with the assistance of sonication and enzyme treatment. Arsenic species in the extracts are commonly separated using high-performance liquid chromatography (HPLC) and detected using inductively coupled plasma mass spectrometry (ICPMS). Electrospray ionization tandem mass spectrometry, used in combination with HPLC and ICPMS, provides complementary information for the identification and characterization of arsenic species. The methods and perspectives discussed in this review, covering sample preparation, chromatography separation, and mass spectrometry detection, are directed to arsenic speciation in freshwater fish and applicable to studies of other food items. Despite progress made in arsenic speciation analysis, a large fraction of the total arsenic in freshwater fish remains unidentified. It is challenging to identify and quantify arsenic species present in complex sample matrices at very low concentrations. Further research is needed to improve the extraction efficiency, chromatographic resolution, detection sensitivity, and characterization capability.

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.

Biomarkers of seafood intake during pregnancy - Pollutants versus fatty acids and micronutrients

Intake of fish and seafood during pregnancy may have certain beneficial effects on fetal development, but measurement of intake using questionnaires is unreliable. Here, we assessed several candidate biomarkers of seafood intake, including long-chain omega 3 fatty acids (n-3 LCPUFA), selenium, iodine, methylmercury, and different arsenic compounds, in 549 pregnant women (gestational week 29) in the prospective birth cohort NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment). Proportions of the fatty acids eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) in erythrocytes were measured using gas chromatography with flame ionization detector. Selenium was measured in blood plasma and erythrocytes, mercury and arsenic in erythrocytes, and iodine and several arsenic compounds in urine, using inductively coupled plasma mass spectrometry, arsenic compounds after first being separated by ion exchange high-performance liquid chromatography (HPLC). Each biomarker was related to intake of total seafood and to intake of fatty and lean fish, and shellfish in third trimester, estimated from a semi-quantitative food frequency questionnaire filled out in gestational week 34. The pregnant women reported a median total seafood intake of 184 g/week (5th-95th percentiles: 34-465 g/week). This intake correlated most strongly with erythrocyte mercury concentrations (rho = 0.49, p < 0.001), consisting essentially of methylmercury, followed by total arsenic in erythrocytes (rho = 0.34, p < 0.001), and arsenobetaine in urine (rho = 0.33, p < 0.001), the main form of urinary arsenic. These biomarkers correlated well with intake of both fatty fish, lean fish, and shellfish. Erythrocyte DHA and plasma selenium correlated, although weakly, mainly with fatty fish (rho = 0.25 and 0.22, respectively, both p < 0.001). In conclusion, elevated concentrations of erythrocyte mercury and urinary arsenobetaine can be useful indicators of seafood intake, more so than the n-3 LCPUFAs. However, the relative importance of the biomarkers may differ depending on the type and amount of seafood consumed.

Gold Nanoparticles as Exquisite Colorimetric Transducers for Water Pollutant Detection

Gold nanoparticles (AuNPs) are useful nanomaterials as transducers for colorimetric sensors because of their high extinction coefficient and ability to change color depending on aggregation status. Therefore, over the past few decades, AuNP-based colorimetric sensors have been widely applied in several environmental and biological applications, including the detection of water pollutants. According to various studies, water pollutants are classified into heavy metals or cationic metal ions, toxins, and pesticides. Notably, many researchers have been interested in AuNP that detect water pollutants with high sensitivity and selectivity, while offering no adverse environmental issues in terms of AuNP use. This review provides a representative overview of AuNP-based colorimetric sensors for detecting several water pollutants. In particular, we emphasize the advantages of AuNP as colorimetric transducers for water pollutant detection in terms of their low toxicity, high stability, facile processability, and unique optical properties. Next, we discuss the status quo and future prospects of AuNP-based colorimetric sensors for the detection of water pollutants. We believe that this review will promote research and development of AuNP as next-generation colorimetric transducers for water pollutant detection.

Simultaneous measurement of labile As (III) and As (V) in soils combining DGT and HPLC-ICP-MS

The speciation of arsenic (As) determines its biogeochemistry and ecotoxicity in soils. However, the approach to in situ monitor labile As (III) and As (V) in soils still requires more exploration. In this study, we developed a method for simultaneously obtaining in-situ data on labile As (III) and As (V) in soils using diffusive gradients in thin films (DGT) and high performance liquid chromatography-inductively coupled plasma mass spectrometry. The Fe₂O₃∙xH₂O DGT sampler exhibited rapid and simultaneous accumulation of As (III) and As (V) in solutions within 90 min. The high efficiency of simultaneous elution of As (III) (~84 %) and As (V) (~97 %) was achieved using 0.8 % H₃PO₄ as eluent at 90 °C for 80 min. The method detection limits for As (III) and As (V) were 0.01 and 0.005 μg/L, respectively. This method was applied to reveal the labile As (III) and As (V) in soils in the water level fluctuation zones of the Three Gorges Reservoir, which is the largest reservoir in China. The concentrations of As (III) and As (V) measured by DGT varied with different sampling sites, ranging from 0.01 μg/L to 1.20 μg/L and from 0.01 μg/L to 0.26 μg/L, respectively. The labile As (III) exhibited the higher resupply rate from soil solid phase to soil solution than labile As (V). This study helps to achieve simultaneous in-situ quantification of labile As (III) and As (V) in soils, and will improve the understanding of As mobilization and ecotoxicity in soils.

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.

Characterization and Quantification of Arsenic Species in Foodstuffs of Plant Origin by HPLC/ICP-MS

Arsenic is a well-known carcinogenic, mutagenic and toxic element and occurs in the environment both as inorganic arsenic (iAs) and organoarsenical compounds (oAsCs). Since the toxicity of arsenic compounds depends on their chemical form, the identification and determination of arsenic species are essential. Recently, the European Food Safety Authority, following the European Commission request, published a report on chronic dietary exposure to iAs and recommended the development and validation of analytical methods with adequate sensitivity and refined extraction procedures for this determination. Moreover, the authority called upon new arsenic speciation data for complex food matrices such as seaweeds, grains and grain-based products. Looking at this context, an optimized, sensitive and fast analytical method using high performance liquid chromatography followed by inductively coupled plasma-mass spectrometry (HPLC/ICP-MS) was developed for the determination of iAs (sum of arsenite-As^III and arsenate-As^V) and the most relevant oAsCs, arsenobetaine, dimethylarsinic acid and monomethylarsonic acid. The method was validated with satisfactory results in terms of linearity, sensitivity, selectivity, precision, recovery, uncertainty, ruggedness and matrix effect, and then successfully applied for the analysis of several matrices, i.e., processed and unprocessed cereal and cereal products, fruits, vegetables, legumes, seaweeds, nuts and seeds. The results obtained indicate that not only seaweed and rice matrices but also many cereals, legumes and plant-based foods for infants and young children contain significant concentrations of iAs and oAsCs. These findings contribute to the data collection necessary to assess the role of these matrices in the total arsenic exposure and if specific maximum limits have to be established.

Selenium-enriched plant foods: Selenium accumulation, speciation, and health functionality

Selenium (Se) is an essential element for maintaining human health. The biological effects and toxicity of Se compounds in humans are related to their chemical forms and consumption doses. In general, organic Se species, including selenoamino acids such as selenomethionine (SeMet), selenocystine (SeCys₂), and Se-methylselenocysteine (MSC), could provide greater bioactivities with less toxicity compared to those inorganics including selenite (Se IV) and selenate (Se VI). Plants are vital sources of organic Se because they can accumulate inorganic Se or metabolites and store them as organic Se forms. Therefore, Se-enriched plants could be applied as human food to reduce deficiency problems and deliver health benefits. This review describes the recent studies on the enrichment of Se-containing plants in particular Se accumulation and speciation, their functional properties related to human health, and future perspectives for developing Se-enriched foods. Generally, Se's concentration and chemical forms in plants are determined by the accumulation ability of plant species. Brassica family and cereal grains have excessive accumulation capacity and store major organic Se compounds in their cells compared to other plants. The biological properties of Se-enriched plants, including antioxidant, anti-diabetes, and anticancer activities, have significantly presented in both in vitro cell culture models and in vivo animal assays. Comparatively, fewer human clinical trials are available. Scientific investigations on the functional health properties of Se-enriched edible plants in humans are essential to achieve in-depth information supporting the value of Se-enriched food to humans.

Facile Lego-Spinner Pretreatment Device for Analysis of Arsenic Species in Dried Blood Spots by Ion Chromatography-Inductively Coupled Plasma-Mass Spectrometry

Dried blood spot (DBS) detection has the advantages of small blood collection, convenience, and reliability, which provides a possibility for large-scale evaluation of arsenic exposure in human population. Herein, a facile Lego-spinner pretreatment device is rationally designed for speciation analysis of arsenic in DBSs by ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS). In the mixing mode of the Lego-spinner, the magnetic stir bar in the centrifuge tube rotates under a magnetic field to assist the dispersive extraction of arsenic species in the DBS with reagents. In the centrifugation mode of the Lego-spinner, the arsenic extract is separated from the blood matrix for the subsequent IC-ICP-MS analysis. For the DBS prepared from 80 μL of whole blood, the whole pretreatment operation can be completed within 25 min. The detection limits of arsenobetaine, arsenite, dimethylarsenate, monomethylarsonate, and arsenate in the DBS are 0.09-0.15 μg L^-1, and precisions are <11%. The concentrations of these five arsenic species are highly correlated between whole blood and the DBS (r² > 0.97), and Bland-Altman analysis indicates that the concentration difference of arsenic species between whole blood and the DBS is within ±20%. The DBS sampling approach can effectively preserve arsenic species for at least 30 days at 4 °C, and the contents of arsenic species in the DBS prepared from capillary blood are in a reasonable agreement with those of venous whole blood (gold standard). This Lego-spinner provides a handy and efficient tool for fast extraction of arsenic species in DBSs, facilitating the in-depth study of arsenic migration and transformation in the human body.

Quantitation and speciation of inorganic arsenic in a biological sample by capillary ion chromatography combined with inductively coupled plasma mass spectrometry

The toxicity and biological activity of arsenic depend on its chemical form. In particular, inorganic arsenics are more toxic than organic ones. Apart from the determination of total arsenics, their accurate speciation is important for toxicity assessment. To separate arsenic species using a cation or an anion separation column, at least 0.5–1.0 mL of sample is required because conventional ion chromatography columns use a sample loop of 100–200 μL. It is thus difficult to analyze samples with small volumes, such as clinical and biological samples. In this study, a method for separating arsenic species using a 5-μL sample loop combined with a capillary ion exchange column has been developed for analyzing small volume of samples. The separated arsenics were determined by inductively coupled plasma mass spectrometry. By oxidizing As(III) to As(V) prior to analysis, the total inorganic arsenics, As(III) and As(V), could be well separated from the organic ones. Linear calibration curves (0.5–50 μg/kg) were obtained for total inorganic arsenics dissolved in water. Sub-picogram-level detection limit was obtained. The analytical capability of this method was successfully validated for certified reference materials, namely water and human urine, with total inorganic arsenic recovery efficiencies of 100% and 121%, respectively. Our method requires less than ~ 10 μL of sample and will be very useful to analyze valuable samples available in limited amounts.

[Magnetic ion imprinting techniques for the separation and analysis of elemental speciation]

Metal and metalloid elements have various possible isotopic compositions and oxidation states and often form coordination or covalent compounds with inorganic and organic small molecules or biological macromolecules, resulting in complex elemental speciation. Different species of the same element often have different properties, which dictate their behavior. Thus, elemental speciation analysis is vital for comprehensively and accurately assessing an element's environmental and biological effects and the corresponding risks. Because elemental speciation determines the behavior of an element in different environmental and biological processes, the analysis of elemental species has, in recent years, been important in various subjects, including analytical chemistry, environmental chemistry, geochemistry, ecology, agronomy, and biomedicine. The complexity of environmental and biological sample matrices, as well as the multiformity, low levels, and lability of chemical forms pose severe challenges in elemental speciation analysis. Therefore, the highly selective identification and efficient separation of native species is necessary for conducting the identification, quantification, ecotoxicity evaluation, and physiological function study of elemental speciation. Sample pretreatment by solid-phase extraction is an effective solution to the aforementioned problems, but the existing methods do not meet the requirements of current research. The transition of the target species from pre-processing to the detection device includes both on- and off-line arrangements. Compared with the on-line approach, the off-line approach requires more manual participation, increasing the analysis workload. However, the off-line approach can improve the analysis efficiency through high-throughput pretreatment when large batches of samples are encountered, meaning the off-line approach is still an effective model. Ion imprinting technology has been developed based on existing molecular imprinting technology, with four main steps present in the synthesis of ion imprinted polymers. First, ion imprinting technology uses metal ions as templates. Then, these templates are combined with the functional monomers through coordination, electrostatic or hydrogen bonding. The functional monomers simultaneously surround and fix the templates, after which the cross-linkers and functional monomers polymerize to prepare ion-imprinted polymers with a specific structure and composition. Finally, the imprinted holes are created in the polymers by eluting the template ions. Therefore, the template molecules, functional monomers, and cross-linkers are three precursors necessary for synthesizing ion-imprinted polymers. These polymers can specifically bind to the imprinted metal ions with accuracy, sensitivity, and reliability. In recent years, they have been widely used in separating, enriching, analyzing, and detecting elemental species. During solid-phase extraction, the non-magnetic adsorbent materials dispersed in the sample solution need to be separated by centrifugation or filtration, which is time-consuming and laborious. Because an external magnetic field can be used for rapid magnetic solid-phase extraction, it has become a potential method for separating and enriching elemental species. This review systematically summarizes the latest progress in ion-imprinting technology, including its principle and the preparation methods of ion-imprinted polymers. The challenges faced by ion imprinting technology are analyzed in the context of the development of ion-imprinting magnetic solid-phase extraction in elemental speciation analysis. Finally, the direction of future development and the strategies of ion imprinting technology in elemental speciation analysis are proposed. It is important to exploit novel organic-inorganic hybrid polymerization-based multifunctional ion-imprinted magnetic nanocomposites for the magnetic solid-phase extraction and separation of elemental species. By establishing the pretreatment protocols with high recognition selectivity, strong separation ability, large adsorption capacity, and good speciation stability, we expect to achieve the research objectives of simultaneously separating and enriching the multiple-species of typical metal/metalloid elements in environmental and biological samples.

Collaborative Construction of a Silver Nanocluster Fluorescent Probe Using the Pyridinium-Based Ionic Liquid [C4py][DCA]

A silver nanocluster fluorescent probe was synthesized by using the pyridinium-based ionic liquid [C₄py][DCA] as the protective agent, AgNO₃ as the precursor, and NaBH₄ as the reducing agent. The presence of pyridine group enhanced the fluorescence intensity of Ag nanoclusters and facilitated the coordination interaction between Ag nanoclusters and AsO₃ ^3-. Therefore, the collaborative construction of a silver nanocluster probe using the pyridinium-based ionic liquid [C₄py][DCA] offered outstanding selectivity and sensitivity to detect AsO₃ ^3- in water. More interestingly, the fluorescent probe quenched by AsO₃ ^3- could be recovered with the addition of H₂O₂. This fluorescent probe provided a rapid and superior method for the detection of As(III) in the linear concentration range of 0-60 ppb with the lowest detection limit of 0.60 ppb. The mechanism of fluorescence quenching was a static quenching, considered to be due to electron migration between functional groups on the surface of Ag nanoclusters constructed with [C₄py][DCA] and AsO₃ ^3-.