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Speciation analysis of arsenic in samples containing high concentrations of chloride by LC-HG-AFS
Abstract
Chloride widely exists in the environment and will cause serious interference for arsenic speciation analysis. The determination of four arsenic species including arsenite (As(III)), arsenate (As(V)), monomethylarsenate (MMA), and dimethylarsonate (DMA) in samples containing high concentrations of Cl− was carried out in this work by coupling of liquid chromatography (LC) with hydride generation atomic fluorescence spectrometry (HG-AFS). The interference of Cl− was successfully eliminated by coupling two anion-exchange chromatographic columns in series and eluting with 35.0 mmol L−1 (NH4)2HPO4 (pH = 6.00). A novel pre-treatment system was subsequently developed to realize on-line column switch and pre-reduction of As(V). The analysis time was shortened by an isocratic elution but programmed flow rate method, and the sensitivity of As(V) was also enhanced by the introduction of pre-reduction using the developed system. The proposed method can resist at least 10 g L−1 Cl− without any pre-treatment operations. Since LC-HG-AFS is low-cost and can be afforded or self-assembled by most labs, the developed method can be adopted as a routine analysis method for arsenic species in chloride-bearing samples, such as urine and seawater.
Graphical abstract
... Arsenic participates in complex biological and chemical processes, and naturally occurs in the environment (soil, air, water, etc.) in different oxidation states and species that have different chemical behaviours and toxicities [1,2]. Inorganic species are more toxic than organic arsenic compounds like monomethyl-and dimethyl arsenic, which are predominant in living organisms [3]. The reduced inorganic species, trivalent arsenic As(III), is approximately 60 times more toxic than oxidized, pentavalent arsenic As(V) [4,5]. ...
... The stability of As(III) in groundwater was reported to be 2 days [8], 3 weeks [9], and even 3 months [10]. The addition of ascorbic acid, HCl, HNO 3 and H 2 SO 4 as preservative agents has been described previously in the literature. It has been published that ascorbic acid oxidizes As(III) in natural water samples as well as HNO 3 [8]. ...
... The addition of ascorbic acid, HCl, HNO 3 and H 2 SO 4 as preservative agents has been described previously in the literature. It has been published that ascorbic acid oxidizes As(III) in natural water samples as well as HNO 3 [8]. HCl is not suitable when inductively coupled plasma mass spectrometry (ICP-MS) is used for detection, due to the 40 Ar 35 Cl + molecular interference on monoisotopic 75 As + [11,12]. ...
In this study, the preservation of As(III) in model solutions and natural groundwater samples from four locations in Croatia was conducted. Model laboratory samples were spiked with As(III) and As(V), and different complexing agents. Solutions were analysed in intervals of 24, 48 h and during ten days after preparation. Model samples containing citric acid, sodium citrate, sodium oxalate and potassium sodium tartrate in combination with acetic acid, spiked with As(III)and As(V), showed good species preservation. As(III), in model samples, was preserved for 7 days with citric acid, and citric acid in combination with acetic acid, as well as with tartrate. As(III), in natural samples, was preserved for 6 to 12 days with potassium sodium tartrate, citric acid, and citric acid in combination with acetic acid and showed improvement, compared with unpreserved samples (oxidation in 3 days). The results showed that acetic acid alone was not successful in preserving As speciation. Good resolution of inorganic arsenic species was achieved using differential pulse anodic stripping voltammetry technique (DPASV). Since this technique is comparatively cheaper and more convenient to use than other available techniques it could become a method of choice for arsenic speciation in water.
In this work, a new dendrimer modified magnetic graphene oxide (GO) was used as a substrate for electrodeposition of Au nanoparticles. The modified magnetic electrode was employed for sensitive measuring of As(III) ion as a well-established human carcinogen. The prepared electrochemical device exhibits excellent activity towards As(III) detection using the square wave anodic stripping voltammetry (SWASV) protocol. At optimum conditions (deposition potential at -0.5 V for 100 s in 0.1 M acetate buffer with pH 5.0), a linear range from 1.0 to 125.0 μgL-1 with a low detection limit (calculated by S/N = 3) of 0.47 μg L-1 was obtained. In addition to the simplicity and sensitivity of the proposed sensor, its high selectivity against some major interfering agents, such as Cu(II) and Hg(II) makes it an appreciable sensing tool for the screening of As(III). In addition, the sensor revealed satisfactory results for detection of As(III) in different water samples, and the accuracy of obtained data were confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) setup. Accounting for the high sensitivity, remarkable selectivity and good reproducibility, the established electrochemical strategy has great potential for analysis of As(III) in environmental matrices.
This update covers publications from the second half of 2019 to the middle of 2020. Techniques and applications relevant to clinical and biological materials, foods and beverages are discussed in the text, presenting key aspects of the work referenced, while the tables provide a summary of the publications considered. A new table has been introduced to include the large number of sample preparation papers that were seen. Reference intervals for quite specific groups and environmental settings were reported, reflecting focussed concerns rather than large general populations. Technical developments include applications of spICP-MS and ICP-QQQMS, particularly to NPs and elemental speciation. Measuring elements as tags for indirect clinical determinations is featured in this ASU as the number of such papers is gradually increasing. As in previous reviews, work featuring cancer and Alzheimer’s disease continues, but obesity, Cu metabolism and absorption of metals through skin are of current interest among the clinical applications of atomic spectroscopy. As meat-avoidance increases in many populations the elemental composition of vegetarian and vegan foods is attracting more attention. A study of As in rice-based infant formulas and foods reported levels above the EU limit in all samples, with much of it as iAs. On a similar theme, concentrations of elements in milk from yak and camel were measured alongside the less exotic species, cow, goat and buffalo. Elemental analysis of wines to discriminate authenticity is regularly included in these updates but this approach is now applied to saffron and coconut sugar, as foods which attract commercial interest.
In this work, an in situ dielectric barrier discharge trap (DBDT) was first utilized to preconcentrate inorganic arsenic (iAs) species coupled with liquid chromatography hydride generation atomic fluorescence spectrometry (LC-HG-AFS), and a novel LC-HG-in situ DBDT-AFS instrument was thereby fabricated. Considering the relatively deficient sensitivity of LC-HG-AFS and retention of As(V) in strong anion exchange column, As(V) was chosen as a model species for iAs preconcentration. During the extraction of arsenic speciation in rice sample using 1% (v:v) HNO3 and 1% (v:v) H2O2, As(III) was oxidized to As(V) being regarded as iAs. After LC separation, according to the retention time, only As(V) was trapped by 11 kV discharging under 110 mL min-1 air mixed with Ar; following sweeping by Ar gas with 190 s, iAs was released with 13 kV at 180 mL min-1 H2 mixed with Ar to the AFS for measurement. Via preconcentration, the limit of detection (LOD) of iAs reached 0.05 μg/L with ~10 times enhancement of analytical sensitivity; the linearity (r) was > 0.997 ranging from 0.5 μg L-1 to 50 μg L-1 with 1.9% RSD (5 μg L-1, n = 6). The measured iAs in certified reference materials (CRMs) were all within their certified values, and the spiking recoveries were in the range of 93-102%. With sensitivity, robustness, low power, small size and easy operation, the combination of LC and DBDT fulfilled the analysis of ultratrace iAs in rice sample. In fact, other arsenic species can be also preconcentrated and detected to enhance the sensitivity by this proposed LC-HG-in situ DBDT technique via precisely controlling the chromatographic separation time matched with DBD trap and release. To focus on the food safety, iAs was chosen as a model arsenic speciation to verify the availability of in situ DBDT. Considering the versatility of DBD, in situ DBDT demonstrates a promising application for elemental speciation analysis and LC atomic spectrometric instrumentation.
A high-performance liquid chromatography (HPLC) in combination with inductively coupled plasma mass spectrometry (ICP-MS) as an elemental specific detector was used for the speciation analysis of arsenic compounds in urine and serum samples from Vietnam. Five arsenic species including arsenite (As III ), arsenate (As V ), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and arsenobetaine (AsB) were studied. A gradient elution of ammonium carbonate ((NH 4 ) 2 CO 3 ), ethylenediaminetetraacetic acid disodium salt (Na 2 EDTA), and methanol at pH 9.0 utilizing Hamilton PRP-X100 strong anion-exchange column allowed the chromatographic separation of five arsenic species. In this study, urine and serum samples were prepared by dilution in solvent and protein precipitation by trichloroacetic acid, respectively. The extraction efficiency was greater than 91% for urine matrix, and recoveries from spiked samples were in the range of 94–139% for the arsenic species in human serum. The method limit of detection (MDL) and limit of quantification (MQL), which were calculated by signal to noise ratio, were found to be 0.3–1.5 and 1.0–5.0 ng·mL ⁻¹ , respectively. The concentration of arsenic species in 17 pairs of urine and serum samples from Vietnam was also quantified and evaluated. The major species of arsenic in the urine and serum samples were AsB and DMA.
Measuring arsenic in urine provides important information for clinical and epidemiological studies. While many researchers have studied ways to improve sample storage and understand why arsenic species undergo species interconversion, none have investigated inline dilution as a solution for arsenic speciation sample stability. A fast inline dilution method for AsB, DMA, MMA, As III, and As V was demonstrated in this work. Inline dilution calibrations from a single stock standard were shown to have good linearity and resulted in LODs in the single digit ppt range. Inline dilutions of 30X, 50X, and 100X resulted in 0.1 s to 1.1 s variation in retention time. Manual sample preparation resulted in poor recovery (61%) for As III over a 24 h time period, which was a direct result of As III converting to As V. Inline dilution of urine spiked with As III resulted in good recovery (101%) and reduced the species interconversion of As III to As V to ∼1%. Accuracy to NIST SRM 2669 (arsenic in frozen urine) was found to be within reported values for the five arsenic species tested for in this method.
Arsenic (As) contamination of freshwater is largely due to geogenic processes, but As is also released into the environment because of improper anthropic activities. The European regulatory limits in drinking water are of 10 μg L⁻¹ As. However, knowledge of the genotoxic effects induced by low doses of As in freshwater environments is still scanty. This study was designed to investigate arsenate (As(V)) and arsenite (As(III)) toxicity and low-dose genotoxicity in Gammarus elvirae, which has proved to be a useful organism for genotoxicity assays in freshwater. As(V) and As(III) toxicity was assessed on the basis of the median lethal concentration, LC(50), while estimates of DNA damage were based on the Comet assay. The G. elvirae LC (50–240 h) value we calculated was 1.55 mg L⁻¹ for As(V) and 1.72 mg L⁻¹ for As(III). Arsenic exposure (240 h) at 5, 10, and 50 µg L⁻¹ of As in assays with either arsenate or arsenite-induced DNA damage in hemocytes of G. elvirae in a concentration-dependent manner. Our study provides a basis for future genotoxic research on exposure to freshwater that contains low levels of arsenic.
Reports from the US media have raised the attention towards a possible contamination of apple juices by As. The study here described presents the development of an analytical procedure using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) for determination of As in apple and orange juices commercialized in the Tetra Pack® package. The microwave-assisted acid digestion of juice was carried out using closed vessels and 2 mol/L HNO3 plus H2O2. These conditions are favorable for a better analytical blank control. Suitable recoveries were reached when promoting reaction with O2 inside the octopole reaction system (ORS³), and the monitoring of ⁷⁵As¹⁶O⁺ significantly improved the accuracy of the analysis reaching a limit of detection of 0.013 μg/L. Recoveries varied from 88 to 109 % in the MS/MS mass-shift mode. The As concentrations determined in fruit juices ranged from 0.126 to 1.45 μg/L, and they were significantly lower than the maximum tolerable limits imposed by the US and Brazilian legislations. Thus, ICP-MS/MS operated in the reaction mode was an effective instrumental strategy for overcoming spectral interferences, such as ⁴⁰Ar³⁵Cl⁺, in As determination as ⁷⁵As¹⁶O⁺ and allowed the accurate determination of As at trace levels.
X-ray absorption near-edge spectroscopy (XANES) was used for arsenic speciation in mine processing and waste samples from two mines in northern Australia. XANES fitting of model compound spectra to samples was used, in combination with in vitro bioaccessibility data for the pure compounds, to predict bioaccessibility of each mine waste sample (Pearson's correlation R-2 = 0.756, n = 51). The XANES fitting data for a smaller set of the samples (n = 12) were compared with in vivo bioavailability and in vitro bioaccessibility data. The bioavailability of arsenic (As) in the mine wastes, which is dependent, at least in part, on its oxidation state, was found to be,14%(0.9-13.5 %) for arsenite (As-III) and, 17%(3.5-16.4) for arsenate (As-V). Arsenic bioaccessibility in the mine wastes ranged from 8-36% in the stomach to 1-16 % in the intestinal phase, indicating that a small portion of the total As concentration in the mine waste was available for absorption. Asignificant correlation showed that bioaccessibility can be used as a predictor of bioavailability. The XANES results support that bioavailability and bioaccessibility results were very similar and show a strong association with the presence of ferric arsenate and As sulfides. It can be concluded that, when soil intake is adjusted for bioaccessibility, the potential health risk estimate to local residents exposed to the mine waste was significantly lower than that estimated based on a 100 % bioavailability often employed for the risk assessment.
Arsenic is ubiquitous in nature appearing in various chemical forms. The toxicity, environmental mobility and accumulation of As in living organisms depends on the form in which the element exists, thus requiring techniques which can identify specific forms whilst retaining their integrity during extraction and pre-treatment prior to measurement. Both organic and inorganic arsenic species may be present in food staples of both terrestrial and marine origin as well as natural waters, at sub ngl-1 to high mgl-1 levels. In this review, the speciation steps (sample preparation, species speciation and detection) most commonly used for the determination of As in food are described. High performance liquid chromatography separation with plasma source mass spectrometry is often the technique of choice due to its versatility, robustness and good detection limits. However, detection systems such as atomic absorption spectroscopy, and atomic fluorescence spectrometry, atomic emission spectrometry are also widely used and covered in this review, together with some less utilised techniques.
In the present work, internal standardization based on species-unspecific isotope dilution analysis technique is proposed in order to overcome the matrix effects and signal drift originated in the speciation of As in urine by HPLC-ICP-MS. To this end, 72Ge has been selected as a pseudo-isotope of As. The resulting mass flow chromatogram of the element allows the calculation of the corrected overall species concentrations without requiring any methodological calibration, providing high-throughput sample processing. The validation was carried out by analyzing a blank human urine fortified at three concentration levels and an unspiked human urine sample containing different species of arsenic. In all cases, recoveries ranging from 90 to 115% and RSD below 10% were attained with this approach. Furthermore, the proposed method provided results in excellent agreement with those obtained using standard additions and internal standard calibration, allowing a fast way to assess human exposure to arsenic species.
The formation of methylarsonous acid (MAs(III)) and dimethylarsinous acid (DMAs(III)) in the course of inorganic arsenic (iAs) metabolism plays an important role in the adverse effects of chronic exposure to iAs. High-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and hydride generation-cryotrapping-atomic absorption spectrometry (HG-CT-AAS) have been frequently used for the analysis of MAs(III) and DMAs(III) in biological samples. While HG-CT-AAS has consistently detected MAs(III) and DMAs(III), HPLC-ICP-MS analyses have provided inconsistent and contradictory results. This study compares the capacities of both methods to detect and quantify MAs(III) and DMAs(III) in an in vitro methylation system consisting of recombinant human arsenic (+3 oxidation state) methyltransferase (AS3MT), S-adenosylmethionine as a methyl donor, a non-thiol reductant tris(2-carboxyethyl)phosphine, and arsenite (iAs(III)) or MAs(III) as substrate. The results show that reversed-phase HPLC-ICP-MS can identify and quantify MAs(III) and DMAs(III) in aqueous mixtures of biologically relevant arsenical standards. However, HPLC separation of the in vitro methylation mixture resulted in significant losses of MAs(III), and particularly DMAs(III) with total arsenic recoveries below 25%. Further analyses showed that MAs(III) and DMAs(III) bind to AS3MT or interact with other components of the methylation mixture, forming complexes that do not elute from the column. Oxidation of the mixture with H2O2 which converted trivalent arsenicals to their pentavalent analogs prior to HPLC separation increased total arsenic recoveries to ~95%. In contrast, HG-CT-AAS analysis found large quantities of methylated trivalent arsenicals in mixtures incubated with either iAs(III) or MAs(III) and provided high (>72%) arsenic recoveries. These data suggest that an HPLC-based analysis of biological samples can underestimate MAs(III) and DMAs(III) concentrations and that controlling for arsenic species recovery is essential to avoid artifacts.
An improvement of current method of selective hydride generation based on pre-reduction for differentiation of tri- and pentavalent arsenicals is described, applied for the oxidation state specific speciation analysis of inorganic, mono-, di- and trimethylated arsenicals with minimum sample pretreatment using atomic absorption spectrometry with the multiatomizer. The preconcentration and separation of arsine, methylarsine, dimethylarsine and trimethylarsine is then carried out by means of cryotrapping. Presented study shows that 2% (m/v) L-cysteine hydrochloride monohydrate (L-cys) currently used for off-line pre-reduction of pentavalent arsenicals can be substituted with 1% (m/v) thioglycolic acid (TGA). Much faster pre-reduction of pentavalent arsenicals at 25°C with equal sensitivities as in the case of L-cys has been achieved with TGA. A setup for on-line pre-reduction by TGA has been optimized, with the application of segmented flow analysis for suppression of axial dispersion in the pre-reduction coil. Standard calibrations measured with or without on-line pre-reduction indicate uniform and equal sensitivities for all As forms. The possibility of standardization by water standards of single species (e.g. iAs(III)) for quantification of all other As forms in urine is demonstrated in the recovery study. Limits of detection were 100 ng·l(-1) for iAs(III), 135 ng·l(-1) for iAs(V) and 30 to 50 ng·l(-1) for methylated arsenicals.
In this paper, an on-line preconcentration system has been proposed for speciation analysis of inorganic arsenic in seawater. It is based on the selective reaction of As(III) with ammonium pyrrolidine dithiocarbamate (APDC) followed by sorption of the formed complex under a minicolumn containing polytetrafluoroethylene (PTFE). Afterward, arsenic sorbed has been eluted using a 2 mol L⁻¹ hydrochloric acid solution. The preconcentration system was optimized employing multivariate techniques. A two-level full factorial design and a Doehlert matrix were performed to determining the critical conditions of the factors: the acidity of the sample, APDC concentration, and sample flow rate. So, the procedure using the optimized conditions allows the determination of As(III) with limits of detection and quantification of 0.02 and 0.07 μg L⁻¹. Total arsenic has been determined after reduction of As(V) using thiourea in acid media and the limits achieved were 0.03 and 0.09 μg L⁻¹, for detection and quantification, respectively. The precision estimated as the relative standard deviation (RSD) was 5.3%, which was calculated using seven replicates of As(III) solution with a concentration of 0.50 μg L⁻¹. The accuracy of the method was confirmed by the analysis of the certified reference material CASS-4 seawater furnished by the National Research Council of Canada-NRCC. The system proposed was employed for speciation analysis of arsenic in five seawater samples collected from Todos os Santos Bay, Salvador, Brazil. The As(III) contents obtained varied from 0.09 to 0.51 and the total arsenic contents varied from 0.20 to 0.66 μg L⁻¹. The results are in agreement with other data reported in the literature.
The arsenic content of dried baby shrimp (Acetes sp.) was investigated as part of an independent field study of human exposure to toxic metals/metalloids among the ethnic Chinese community located in Upstate New York. The dried baby shrimp were analyzed in a home environment using a portable X-Ray Fluorescence (XRF) instrument based on monochromatic excitation. Study participants had obtained their dried baby shrimp either from a local Chinese market or prepared them at home. The shrimp are typically between 10–20 mm in size and are consumed whole, without separating the tail from the head. Elevated levels of As were detected using portable XRF, ranging between 5–30 μg g⁻¹. Shrimp samples were taken to the Cornell High Energy Synchrotron Source (CHESS) for Synchrotron Radiation μXRF (SR-μXRF) elemental mapping using a 384-pixel Maia detector system. The Maia detector provided high resolution trace element images for As, Ca, and Br, (among others) and showed localized accumulation of As within the shrimp's cephalothorax (head), and various abdominal segments. As quantification by SR-μXRF was performed using a lobster hepatopancreas reference material pellet (NRC-CNRC TORT-2), with results in good agreement with both portable XRF and ICP-MS. Additional As characterization using μX-ray Absorption Near Edge Spectroscopy (μXANES) with the Maia XRF detector at CHESS identified arsenobetaine and/or arsenocholine as the possible As species present. Further arsenic speciation analysis by LC-ICP-MS/MS confirmed that the majority of As (>95%) is present as the largely non-toxic arsenobetaine species with trace amounts of arsenocholine, methylated As and inorganic As species detected.
A method based on ion-pair reversed phase high performance liquid chromatography (HPLC) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) was developed for arsenic speciation in extract of tree moss. Under the optimal conditions, the limit of detection of eight arsenic species including arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), dimethylarsonic acid (DMA), trimethylarsinoxide (TMAO), tetramethylarsonium (Tetra), arsenocholine (AsC) and arsenobetaine (AsB) is between 0.04 and 0.07 ng/mL, with a linear range of 0.2 − 500 ng/mL. Three unknown arsenic species (Unk1, Unk2 and Unk3) and six specific arsenic species (AsIII, AsV, DMA, TMAO, Tetra and AsB) were detected in the extract of tree moss. Unk3 was identified as a kind of arsenosugars (2,3-dihydroxypropyl-5-deoxy-5(dimethylarsenoso)furanoside, arsenosugar X) by electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-qTOF-MS).
The total arsenic (As) and As species were analyzed in 19 species of wild marine organisms collected from 12 locations in Daya Bay, China; additionally, both the levels of As in the seawater and sediments and the salinity were investigated. The greatest level of As was found in crabs (13.4-35.1 μg/g), followed by shrimps (8.52-27.6 μg/g), benthic fish (3.45-28.6 μg/g), and pelagic fish (1.22-5.23 μg/g). There were significantly positive correlations between the As concentrations in the benthic fish Callionymus richardsonii/shrimp Metapenaeopsis palmensis and those in sediments, indicating that As levels in them were highly dependent on those in the sediments. Arsenobetaine (AsB) (87.3-99.8%) was the most dominant form of As found in all marine organisms. In benthic fish and shrimp, the bioaccumulation of As, especially AsB, was positively correlated with the salinity of the seawater, indicating that the salinity could control the transfer of As. The calculated hazard quotients (HQs) of the inorganic As in the marine organisms were all <1; thus, there was no apparent health hazard through the consumption of wild marine organisms.
Arsenic (As) speciation and bioaccumulation in fish muscle tissues have been intensively investigated in marine ecosystem. However, little is known about these in freshwater fish. In this study, freshwater fish including 120 specimens and 8 species were collected from the Xiang River, a typical mine-impacted river in China. Six As species including arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenocholine (AsC) and arsenobetaine (AsB) were simultaneously separated and determined using HPLC-ICP-MS. The mean (±SD) concentration of total As (tAs) in the dried fish muscle was 0.748±0.651mg·kg-1. AsB was found as the predominant As species in most of the studied fish samples, in accordance with the reports in marine fish. However, the diversity of inorganic/organic As proportion observed in the studied freshwater fish species was larger than that in marine fish species due to greater spatial variability of As contamination, mobilization and origination in the studied catchments. The percentage of AsB (AsB%) in fish muscle was irrelevant to tAs concentration, while the percentage of iAs (iAs%) decreased with tAs concentration in a hyperbolic pattern. This can be attributed to restricted assimilation and accumulation of toxic iAs with increasing tAs concentration in fish. Chronic non-carcinogenic and carcinogenic health risks were evaluated through Monte-Carlo simulation. The result indicated that consuming freshwater fish in the Xiang River could cause considerable carcinogenic risk to local inhabitants.
Freshly in situ prepared ferrite particles were used for the micro-solid phase extraction of arsenic species. When the separation was carried out at pH 8, inorganic arsenic (As(III) + As(V)) and monomethylarsonic acid (MMA) were retained in the magnetic material. A second aliquot was treated with 2,3 dimercapto propanol, leading to the retention of As(V)+MMA, while a third aliquot was first treated with sodium thiosulphate, in which case only inorganic arsenic passed to the solid phase. In all cases, the solid residue collected by a magnet was suspended in a dilute nitric acid solution containing Triton X-100 and introduced into the electrothermal atomizer to obtain the analytical signal of arsenic. The use of palladium as a chemical modifier allowed calibration to be carried out with aqueous standards. The detection limit was 0.02 µg L⁻¹ arsenic for a 10 mL sample volume. The procedure was applied to waters and herbal infusions, and its reliability was evaluated by analyzing eleven certified reference materials for which speciation data are provided.
More than 200 million people in 70 countries are exposed to arsenic through drinking water. Chronic exposure to this metalloid has been associated with the onset of many diseases, including cancer. Epidemiological evidence supports its carcinogenic potential, however, detailed molecular mechanisms remain to be elucidated. Despite the global magnitude of this problem, not all individuals face the same risk. Susceptibility to the toxic effects of arsenic is influenced by alterations in genes involved in arsenic metabolism, as well as biological factors, such as age, gender and nutrition. Moreover, chronic arsenic exposure results in several genotoxic and epigenetic alterations tightly associated with the arsenic biotransformation process, resulting in an increased cancer risk. In this review, we: 1) review the roles of inter-individual DNA-level variations influencing the susceptibility to arsenic-induced carcinogenesis; 2) discuss the contribution of arsenic biotransformation to cancer initiation; 3) provide insights into emerging research areas and the challenges in the field; and 4) compile a resource of publicly available arsenic-related DNA-level variations, transcriptome and methylation data. Understanding the molecular mechanisms of arsenic exposure and its subsequent health effects will support efforts to reduce the worldwide health burden and encourage the development of strategies for managing arsenic-related diseases in the era of personalized medicine.
Differences in the distribution, partitioning, and bioaccumulation characteristics of arsenicals between freshwater and saltwater systems remain poorly understood. To determine the characteristics of distribution and behavior of arsenicals, multimedia environmental samples including water, suspended particles, zooplankton, sediments, and porewater were collected from inner (five sites, freshwater) and outer (five sites, saltwater) regions of the estuary dike of the Youngsan River Estuary in South Korea (Nov., 2012). Six organic and inorganic forms of As were separated and measured using HPLC–ICP/MS equipped with an anion exchange column. Concentrations of arsenicals in water samples of the inner region (mean = 1.5 μg As L−1) were significantly lower than in those of the outer region (mean = 5.2 μg As L−1). Conversely, concentrations of As in suspended particles in the inner region (mean = 14 μg As g−1) were much greater than in the outer region (mean = 5.7 μg As g−1). The field-based distribution coefficient (Kd) for As depended strongly on salinity; relatively greater Kd values were found in freshwater compared with saltwater. The AsV was found to be the major form of As in all water and particle samples in both inner and outer regions. The zooplankton species were significantly distinguishable between the inner and outer regions; cladocerans were the most dominant species in freshwater and cyclopoida were predominantly found in saltwater. The As concentrations in zooplankton were shown to be particle-concentration dependent, suggesting that dietary exposure plays a substantial role in the bioaccumulation of As. Inorganic arsenicals, such as AsV and AsIII were the most dominant forms found in zooplankton. Partitioning behavior of As between porewater and sediments was similar to that in water–particle distributions. The results of the present study enhance the understanding of As biogeochemistry in river and estuarine environments.
Environmental and health studies of arsenic require the determination of arsenic species of diverse properties and toxicities. This review summarizes recent analytical advances in speciation of phenylarsenicals. Arsenic speciation techniques have taken advantage of high performance liquid chromatography (HPLC) separation with inductively coupled plasma mass spectrometry (ICPMS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection. These techniques have enabled the identification and quantitation of new arsenic species. Characterization of phenylarsenical metabolites has contributed to better understanding of the fate of phenylarsenicals and the potential risk of human exposure. Binding of trivalent phenylarsenicals to proteins has facilitated the development of analytical techniques for the capture and identification of arsenic-binding proteins.
At Jianghan Plain of central Yangtze basins where the health of >73, 000 people has been affected by long term intake of high arsenic groundwater, over 100 sediment samples from four boreholes at the field monitoring sites were collected and analyzed to delineate the distribution and speciation of As in the shallow aquifer sediment. Results showed that sediment As concentration is generally dependent on the lithological conditions, with the higher As concentration present in fine particle sediment, especially in the silty sand layers underlying clay or silty clay layers. High As concentration in the sediment mainly occurred in three different depth ranges: <5m, 15-35m, and >35m. Both the groundwater regime and redox conditions played important roles in controlling sediment As speciation. Arsenate (86%) was the dominated As species in the near surface sediment. As the redox turned to be reducing, arsenite (64%) became the dominant species in the underlying clay and silty clay layers. But in the silty sand aquifer near the boundary of unconfined aquifer and confined aquifer, arsenate (85%) became the dominant species again as results of redox potential elevation. In the deep medium to coarse sand aquifers (>35m deep), As-sulfides (49%-63%) were the main species of As. The speciation and reactivity of sediment As strongly controlled the spatial distribution of groundwater As concentration, while seasonal variation in groundwater As concentration and speciation affected the content and speciation of sediment As.
Arsenic in water is a serious problem for livings and environment. Natural waters mostly consist inorganic forms of As(III) and As(V) at concentrations below 1 ng/mL. Since the toxicity of these species is different, selective determination of trace As species in drinking water is important. Rapid speciation based on anion exchange chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS) is reported. The species were separated within 4 min with the limits of detection of 0.012 and 0.019 ng/mL for As(III) and As(V). The method was applied to spring, well, and tap water from Çankırı, Turkey. Six samples of twenty-five exceeded the permissible drinking water limit of 10 ng/mL. The results showed that As(V) was predominant, while As(III) was also present, especially in well water making up to 16% of the total As.
Arsenic speciation in seafood after several culinary treatments was performed and AsB, As(iii), DMA, MMA and As(v) species were determined by liquid chromatography hyphenated to triple-quadrupole inductively coupled plasma mass spectrometry (LC-ICP-MS/MS) using O2 as the reaction gas for the conversion of ⁷⁵As to ⁷⁵As¹⁶O. The influence of culinary treatments (boiling, frying and sautéing) with or without the addition of spices (salt, lemon juice and garlic) on the As species in blacktip shark and Asian tiger shrimp was investigated. Arsenic species were extracted by using a 30 mmol L⁻¹ HNO3 solution. Ammonium phosphate (10 mmol L⁻¹) was used as the mobile phase. The influence of pH and the addition of 1% (v/v) methanol were investigated. Oil, water, butter and the spices used during cooking were analysed to perform a close mass balance of the total As. The speciation method was also employed for a certified reference material (CRM, DORM-3), and the accuracy was evaluated by statistical comparison between the certified value and the total As concentration determined by ICP-MS after acid digestion and also by a comparison of the sum of As species with the total As. It was demonstrated that the culinary treatments practically did not influence the stability of As species in uncooked seafood. On the other hand, significant analyte losses (from 15 up to 45%) were observed for boiled seafood. The speciation analysis method presented accuracy and robustness for both raw seafood and seafood after the culinary treatments. The limits of quantification were 4, 21, 4, 9 and 18 ng g⁻¹ for AsB, As(iii), DMA, MMA and As(v), respectively. This study allowed the determination of As species in seafood after culinary treatments, thus offering additional information about the behaviour of species during cooking.
To selectively and sensitively determine the trace inorganic As species, As(III) and As(V), we developed a nanocomposite-coated microfluidic-based photocatalyst-assisted reduction device (PCARD) as a vapor generation (VG) device to couple high-performance liquid chromatography (HPLC) separation and inductively coupled plasma-mass spectrometry (ICP-MS) detection. Au nanoparticles were deposited on TiO2 nanoparticles to strengthen the conversion efficiency of the nanocomposite photocatalytic reduction. The sensitivity for As was significantly enhanced by employing the nanocomposite photocatalyst and using prereduction and signal-enhancement reagents. Under the optimal operating conditions, the analytical detection limits (based on 3σ) of the proposed online HPLC/nanocomposite-coated microfluidic-based PCARD/ICP-MS system for As(III) and As(V) were 0.23 and 0.34 μg·L(-1), respectively. The results were validated using a certified reference material (NIST SRM 1643e) and ground water sample analysis, indicating the good reliability and applicability of our proposed system for the determination of inorganic As species in natural fresh water.
In the analysis of arsenic (As) with ICP-MS, the phenomenon that methanol addition to the sample decreases the amount of ⁴⁰Ar³⁵Cl⁺ formed was observed in the previous study. To investigate the effect of methanol addition on generation of isobaric polyatomic ions and its mechanism, a diluted HCl solution and 10 μg/L As solution with varying amounts of methanol (0, 1, 2, 3, and 4 v/v%) respectively were analyzed using ICP-MS in a variety of mass spectra (m/z = 35, 47, 75, 82, 117, and 152). With addition of methanol to the sample, the signal intensity of ¹²C³⁵Cl⁺ increased 11.1-fold while that of ⁴⁰Ar³⁵Cl⁺ only increased 1.17-fold. In this regard, carbon atoms that are not ionized in the plasma (¹²C) originated from methanol seemed to convert ⁴⁰Ar³⁵Cl⁺ to ¹²C³⁵Cl⁺ through a substitution reaction. Furthermore, carbon atoms ionized in the plasma (¹²C⁺) converted ⁷⁵As into ⁷⁵As⁺ via the charge transfer reaction and thus increased signal intensity for As. At the same time, the amount of ⁴⁰Ar³⁵Cl⁺ formed in the plasma decreased additionally since the ¹²C regenerated from ¹²C⁺ during the charge transfer process can act as a reactant in the substitution reaction aforementioned.
High arsenic concentrations occur in groundwater collected from a fractured crystalline bedrock aquifer in western Quebec (Canada). Sampling and analysis of water from 59 private wells reveal that more than half of the bedrock wells exceed the Canadian guideline value of 10 μg/l for arsenic, whereas shallow wells in unconsolidated surficial deposits are not affected by the contamination. The weathering of arsenic-bearing sulfides present along the mineralized fault zone is considered to be the primary source of arsenic in groundwater. High-arsenic wells are generally characterized by mildly reducing conditions (Eh < 250 mV), weak alkaline conditions (pH > 7.4), low Ca/Na ratios, elevated dissolved Fe and Mn concentrations and high proportions of As(III). Private bedrock wells are open boreholes that likely receive groundwater from multiple contributing fractures. Hence, it is proposed that dissolved arsenic is mainly derived from the contribution to the well discharge of reducing and alkaline geochemically evolved groundwater that contains arsenic as As(III). Geochemically evolved groundwater provides favorable conditions to release arsenic by reductive dissolution of iron and manganese oxyhydroxides and alkaline desorption from mineral surfaces. Thus, high-arsenic wells would contain a high proportion of geochemically evolved groundwater, while oxidizing low-pH recharge water causes dilution and sequestration of arsenic. In relation with the chemical evolution of groundwater along the flow path, most contaminated wells are located in confined areas whereas most of the wells located in unconfined recharge areas are not contaminated. The occurrence of boreholes with high dissolved arsenic as As(V) and oxidizing conditions is attributed to extensive sulfide oxidation and alkaline desorption. This work shows that the determination of arsenic speciation provides a valuable tool to investigate the behavior of arsenic in bedrock groundwater.
The performance of a mixture of CH3F/He (1/9) as a reaction gas for the determination of As in biological fluids using a quadrupole ICP-MS instrument has been explored. A simple (dilute-and-shoot) interference-free method has been developed to quantify As concentrations at trace and ultra-trace levels in matrices with a high Cl content. As+ reacts with CH3F (through CH3F addition, followed by HF elimination) with high efficiency forming AsCH2+ as the primary reaction product, which can be monitored at a mass-to-charge ratio of 89, free from the Cl-based interferents (e.g., 40Ar35Cl+ and 40Ca35Cl+) that hamper the monitoring of 75As+. Matrix effects are overcome by the use of Te as an internal standard and the addition of 3% v/v ethanol to all samples and calibration standard solutions. The method presented was validated by analysing a set of reference materials (blood, serum and urine) and by assessing As recovery from a set of real blood samples. With this method, the limit of detection was calculated to be 0.8 ng L−1 As, favourably comparable to the vast majority of values reported in the literature, even with those obtained using more sophisticated sector-field instrumentation.
In order to better distinguish the different toxic inorganic and organic forms of arsenic (As) exposure in individuals, we have developed and validated a simple and robust analytical method for determining the following six As species in human urine: arsenous (III) acid (As-III), As
(V) acid, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine (AsB), and arsenocholine. In this method, human urine is diluted using a pH 5.8 buffer, separation is performed using an anion exchange column with isocratic HPLC, and detection is achieved using inductively coupled plasma-MS.
The method uses a single mobile phase consisting of low concentrations of both phosphate buffer (5 mM) and ammonium nitrate salt (5 mM) at pH 9.0; this minimizes the column equilibration time and overcomes challenges with separation between AsB and As-III. In addition, As-III oxidation is
prevented by degassing the sample preparation buffer at pH 5.8, degassing the mobile phase online at pH 9.0, and by the use of low temperature (–70 °C) and flip-cap airtight tubes for long term storage of samples. The method was validated using externally provided reference samples.
Results were in agreement with target values at varying concentrations and successfully passed external performance test criteria. Internal QC samples were prepared and repeatedly analyzed to assess the method's long-term precision, and further analyses were completed on anonymous donor urine
to assess the quality of the method's baseline separation. Results from analyses of external reference samples agreed with target values at varying concentrations, and results from precision studies yielded absolute CV values of 3–14% and recovery from 82 to 115% for the six As species.
Analysis of anonymous donor urine confirmed the well-resolved baseline separation capabilities of the method for real participant samples.
Feasibility of collision cell (CC) technique with the aid of a methanol modifier for the trace determination of arsenic (As) in a high-chloride-containing sample using ICP-MS was assessed to eliminate the analytical bias induced by polyatomic interference from 40Ar35Cl+ without reducing 75As+ intensity, thereby lowering the limit of detection (LOD). The signal intensity of 2% HCl measured at 75 m/z was suppressed entirely by introducing He gas into the CC at a flow rate of at least 3 mL min- 1. Results from the calibration experiments revealed that excess He gas in the CC could also decrease the 75As+ intensity. Therefore, an optimized He flow rate should be employed, which seemed to be 3 mL min- 1 in this study. To obtain greater sensitivity in the As analysis, the effect of methanol added to the sample solution in varying concentrations (0 to 5% v/v) was assessed. In accordance with previous studies, 3% methanol addition improved As sensitivity by a factor of 2.5 to 3. Also, the methanol addition seemed to decrease the formation of 40Ar35Cl+. Overall, the combined use of both strategies with optimized conditions achieved a lower LOD value of 3 ng L- 1 with a high accuracy.
Recent reports of As concentrations in certain food and drinks has garnered public concern and led to a lowering of the US guideline maximum concentration for inorganic As in apple juice and proposed limits for As in rice products. In contrast Se is an essential micro-nutrient that can be limiting when Se-poor soils yield Se-poor food crops. Rare earth element (REE) doubly charged interferences on As and Se can be significant even when initial ICP-MS tuning minimizes doubly charged formation. We analyzed NIST 1547 (peach leaves) and 1515 (apple leaves), which contain high levels of REEs, by quadrupole ICP-MS with (He) collision mode, H2 reaction mode or triple quadrupole ICP-MS (ICP-QQQ) in mass-shift mode (O2 and O2/H2). Analysis by collision cell ICP-MS significantly over-estimated As and Se concentration due to REE doubly charged formation; mathematical correction increased the accuracy of analysis but is prone to error when analyte concentration and sensitivity is low and interferent is high. For Se, H2 reaction mode was effective in suppressing Gd2+ leading to accurate determination of Se in both SRMs without the need for mathematical correction. ICP-QQQ using mass-shift mode for As+ from m/z 75 to AsO+ at m/z 91 and Se+ from m/z 78 to SeO+ at m/z 94 alleviated doubly charged effects and resulted in accurate determination of As and Se in both SRMs without the need for correction equations. Zr and Mo isobars at 91 and 94 were shown to be effectively rejected by the MS/MS capability of the ICP-QQQ.
Interference-free conditions, allowing straightforward As and Se determination, can be obtained by using CH3F (a mixture of 10 % CH3F and 90 % He) as a reaction gas in tandem ICP–mass spectrometry (ICP–MS/MS). Both target elements react via CH3F addition and subsequent HF elimination, rendering AsCH2
+ and SeCH2
+ the respective favored reaction product ions. Instrumental limits of detection were 0.2 ng L−1 for As and below 10 ng L−1 for Se, using either 77Se, 78Se, or 80Se. Neither addition of carbon to the solutions, nor admixing of additional He into the octopole reaction cell resulted in a further improvement of the LoDs, despite the increase in analyte signal intensity. By using synthetic matrices, containing elements giving rise to ions interfering at either the original mass-to-charge ratios or those of the reaction products, absence of spectral overlap could be demonstrated. This conclusion was corroborated by successful As and Se determination in a collection of reference materials from plant, animal, or environmental origin, displaying a considerable range of As and Se contents. These accurate results were obtained via external calibration using Te as an internal standard. The high efficiency reaction between As and CH3F and the possibility to use the major isotope of Se provides enhanced detection power versus other techniques, such as sector-field ICP–mass spectrometry, while the possibility to monitor at least three Se isotopes interference-free also enables isotopic analysis.
A novel pretreatment system and method for arsenic species continuous analysis of arsenite, arsenate, monomethylarsenate (MMA) and dimethylarsonate (DMA) in freshwater using liquid chromatography combined to hydride generation atomic fluorescence spectrometry (LC-HG-AFS) was designed. Arsenic species of As(III), As(V), MMA and DMA in freshwater samples can be well separated, and the analytical time using the developed method is shortened twice compared to the conventional analytical procedure. Besides, the signal of As(V) can be increased by about 50% and the sensitivity to As(V) has been enhanced. The common coexisting ions in freshwater samples have no interferences with arsenic speciation analysis. A sensitive, low cost and interference-free procedure was developed and successfully applied to arsenic speciation in freshwater with the recoveries of four arsenic species within 89.2–106.2%. LC-HG-AFS has good prospects for speciation analysis of trace and ultra trace elements allowing for hydride generation.
Different conditions of extraction using water, a methanol–water mixture and nitric acid solutions were evaluated for speciation of As(III), As(V), DMA and MMA in plant samples that previously received As(V) after being sown and emergence was investigated. Microwave-assisted extraction (MAE) using diluted nitric acid solutions was also performed for arsenic extraction from chicken feed samples. The separation and determination of arsenic species were performed using HPLC-ICP-MS. The interference standard method (IFS) using 83Kr+ as the IFS probe was employed to minimize spectral interferences caused by polyatomic species, such as 40Ar35Cl+. The extraction procedures tested presented adequate extraction efficiencies (90%), and the four arsenic species evaluated were found in plant samples. Extractions with diluted nitric acid solution at 90 °C were the most efficient strategy, with quantitative recoveries for all four As species in plant tissues. On the other hand, the methanol–water mixture was the solvent with the lowest extraction efficiency (50–60%). For chicken feed samples, MAE at 100 °C for 30 min resulted in an extraction efficiency of 97% and only As(V) was found, without any species interconversion. The IFS method contributed to improving precision and limits of detection and quantification for all tested extraction procedures. Significant improvements on accuracy were obtained by applying the IFS method and recoveries between 77 and 94%, and 82 and 93% were obtained for plant extracts and chicken feed samples, respectively.
Certified reference materials (CRM) of marine origin were characterized for arsenic-containing species. A multidimensional liquid chromatography (LC) protocol consisting of preparative anion-exchange followed by semi-preparative cation-exchange or anion-exchange high-performance liquid chromatography (HPLC) was employed to isolate, purify and identify organoarsenic species. Inductively coupled plasma mass spectrometry (ICP-MS) was employed off-line to monitor the LC effluent (1st dimension) and on-line with HPLC (2nd dimension) for mapping of key fractions. Electrospray mass spectrometry (ES MS) was employed for the analysis of arsenic-containing HPLC fractions and interpretation of collision induced dissociation spectra confirmed species identification. For minor species, whose concentrations approached the limit of detection of ES MS, high-field asymmetric waveform ion mobility spectrometry (FAIMS), a novel technique based on ion mobility spectrometry, was employed. A FAIMS device inserted between the ES source and the MS allows for the separation/focussing of ions in the gas phase and reduction of an interfering matrix. This is the first report of FAIMS being used for trace element speciation in biological tissues. The major species in all the CRMs was found to be arsenobetaine (AsB). Other species identified in the purified CRM extracts by ES MS included trimethylarsoniopropionate (TMAP), dimethylarsinic acid (DMA), monomethylarsinic acid (MMA) and arsenosugar D (As-sug D). Where ES MS was unsuccessful, ES-FAIMS-MS allowed the identification of arsenocholine (AsC+) and tetramethylarsonium ion (TMAs+). Arsenite (AsV) and arsenosugar A (As-sug A) were tentatively identified by retention time matching with standards.
Inorganic arsenic [As(V)+As(III)] and its metabolites, especially the trivalent forms [monomethylarsonous acid, MMA(III), and dimethylarsinous acid, DMA(III)], are considered the forms of arsenic with the highest degree of toxicity, linked to certain types of cancer and other pathologies. The gastrointestinal mucosa is exposed to these forms of arsenic, but it is not known what toxic effect these species may have on it. The aim of the present work was to evaluate the toxicity and some mechanisms of action of inorganic arsenic and its metabolites [monomethylarsonic acid, MMA(V), dimethylarsinic acid, DMA(V), MMA(III) and DMA(III)] in intestinal epithelial cells, using the Caco-2 human cell line as a model. The results show that the pentavalent forms do not produce toxic effects on the intestinal monolayer, but the trivalent species have a different degree of toxicity. As(III) induces death mainly by necrosis, whereas only apoptotic cells are detected after exposure to MMA(III), and for DMA(III) the percentages of apoptosis and necrosis are similar. The three forms produce reactive oxygen species, accompanied by a reduction in intracellular GSH and lipid peroxidation, the latter being especially notable in the dimethylated form. They also alter the enzyme activity of glutathione peroxidase and catalase and induce expression of stress proteins and metallothioneins. The results indicate that the trivalent forms of arsenic can affect cell viability of intestinal cells by mechanisms related to the induction of oxidative stress. Further studies are needed to evaluate how the effects observed in this study affect the structure and functionality of the intestinal epithelium.
AbstractA method for direct de termination of total in organic arsenic (III+V), arsenic (III) and dimethylarsinate (DMA) in sea water was developed by combining continuous‐flow selective hydride generation and inductively coupled plasma mass spectrometry (ICP‐MS) is presented. The principle underlying selective hydride generation is based on proper control of the reaction conditions for achieving separation of the respective arsenic species. The effects of pH and composition of reaction media on mutual interference between the arsenic species were investigated in detail. The results indicate that the appropriate media for the selective determination of total in organic arsenic, DMA and As(III) are 6 M HNO3, acetate buffer at pH = 4.63 and citrate buffer at pH = 6.54, respectively. The concentrations of total inorganic arsenic species, As(III+V), and As(III) were respectively deter mined and that of As(V) was obtained by the difference between them. As to the concentration of DMA, it was obtained after correction from the interference caused by As(III) and As(V). By following the established procedure, the detection lim its (as based on 3‐sigma criterion) for As(III+V), As(III) and DMA were 0.050, 0.009, and 0.002 ng/mL, respectively. There liability of the pro posed method was evaluated in terms of precision and spike addition. The results indicated that the precision of better than 3% and spike recovery of 95 to 105% for all the arsenic species tested in the natural sea water samples can be obtained.
Speciation of urinary arsenic is very important to know the extent of human exposure to inorganic arsenic and also from toxicity point of view. A high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) system for speciation of arsenite, arsenate, monomethyl arsonic acid (MMAA), dimethyl arsenic acid (DMAA) and arsenobetaine (AB) in a single run in urine samples has been developed. The method is based on anion exchange high performance liquid chromatography (HPLC) coupled on-line to inductively coupled plasma mass spectrometer (ICP-MS). Detection limits for the five arsenic species in urine samples are between 0.01 and 0.04 μg l−1. To validate the method, Standard Reference Material, toxic metals in freeze-dried urine SRM 2670 containing both normal and elevated levels of arsenic have been analyzed for arsenic species. Our results of arsenic species in Standard Reference Material SRM 2670 have been compared with the results of seven other laboratories. The method has been applied to determine the arsenic species in urine samples of two groups of people from two arsenic-affected villages of two districts, out of the nine affected districts of West Bengal, India. These two groups were using arsenic-contaminated water a few years ago, but are now supposed to be using safe water for drinking and cooking, as safe sources have been installed. From their urine speciation, the nature of exposure of individuals to arsenic compound could be predicted. It is concluded that, even though these groups are using safe water, they cannot avoid, from time to time, arsenic contamination as many water sources of the surrounding areas are arsenic contaminated.
A sensitive and accurate method for the differential determination of trace amounts of arsenic(III) and arsenic(V) in water samples was described. It was found that arsenic(III) was coprecipitated quantitatively with a Ni–ammonium pyrrolidine dithiocarbamate (APDC) complex at the pH range of 2–3, but arsenic(V) was hardly coprecipitated with the Ni–PDC complex in the same pH condition. The coprecipitates obtained were directly measured by electrothermal atomic absorption spectrometry (ETAAS) using the solid sampling technique. In order to determine trace amounts of total arsenic, sodium thiosulfate and potassium iodide were used to reduce arsenic(V) to the trivalent state in the sample solution before coprecipitation. The concentration of arsenic(V) in the sample solution could be calculated by the difference in concentration between arsenic(III) and total arsenic in the sample solution. The coprecipitation conditions for trace amounts of arsenic(III) and arsenic(V) in water samples by the Ni–PDC complex were investigated in detail. The concentration factor by coprecipitation was reached at about 40 000 when 2 mg of nickel as a carrier element was added to 500 ml of the water sample. The proposed method was successfully applied to the determination of trace amounts of arsenic(III) and arsenic(V) in seawater, and the detection limit for arsenic, which was defined as the concentration calculated from three times of the standard deviation of the procedural blanks, was 0.02 ng/ml for 500 ml portions of water sample in the proposed method.
Twelve commercially available edible marine algae from France, Japan and Spain and the certified reference material (CRM) NIES No. 9 Sargassum fulvellum were analyzed for total arsenic and arsenic species. Total arsenic concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion and ranged from 23 to 126 μg g(-1). Arsenic species in alga samples were extracted with deionized water by microwave-assisted extraction and showed extraction efficiencies from 49 to 98%, in terms of total arsenic. The presence of eleven arsenic species was studied by high performance liquid chromatography-ultraviolet photo-oxidation-hydride generation atomic-fluorescence spectrometry (HPLC-(UV)-HG-AFS) developed methods, using both anion and cation exchange chromatography. Glycerol and phosphate sugars were found in all alga samples analyzed, at concentrations between 0.11 and 22 μg g(-1), whereas sulfonate and sulfate sugars were only detected in three of them (0.6-7.2 μg g(-1)). Regarding arsenic toxic species, low concentration levels of dimethylarsinic acid (DMA) (<0.9 μg g(-1)) and generally high arsenate (As(V)) concentrations (up to 77 μg g(-1)) were found in most of the algae studied. The results obtained are of interest to highlight the need to perform speciation analysis and to introduce appropriate legislation to limit toxic arsenic species content in these food products.
A novel procedure was developed for the determination of arsenite (As(III)), arsenate (As(V)), monomethylarsonic (MMA) and dimethylarsinic acid (DMA) with ion chromatography-hydride generation-atomic fluorescence spectrometry (IC-HG-AFS) by employing a new gas-liquid separator (GLS). The effective separation of the four arsenic species was achieved in about 12min. With a sample loading volume of 20mul, the measurable minimum for As(III), DMA, MMA and As(V) were 0.02, 0.045, 0.043 and 0.166ng, respectively, along with relative standard deviations of 1.1, 1.1, 1.7 and 2.2% at the 100mugl(-1) level (n=6) for As(III), DMA, MMA and As(V), respectively. The present procedure was applied for the speciation of arsenic in underground water and in urine samples, and the sum of the four arsenic species by IC-HG-AFS was in good agreement with the total value by HG-AFS.
Arsenic is a metalloid whose name conjures up images of murder. Nonetheless, certain prokaryotes use arsenic oxyanions for
energy generation, either by oxidizing arsenite or by respiring arsenate. These microbes are phylogenetically diverse and
occur in a wide range of habitats. Arsenic cycling may take place in the absence of oxygen and can contribute to organic matter
oxidation. In aquifers, these microbial reactions may mobilize arsenic from the solid to the aqueous phase, resulting in contaminated
drinking water. Here we review what is known about arsenic-metabolizing bacteria and their potential impact on speciation
and mobilization of arsenic in nature.
A sensitive and robust method for the determination of seven inorganic and organic arsenic species was developed using ion exchange chromatography combined with inductively coupled plasma mass spectrometry (IC-ICP-MS). Both anion and cation exchange columns were used in a complementary fashion. Arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA(V)) and dimethylarsinic acid (DMA(V)) were selectively separated by an anion exchange column using sodium hydroxide (NaOH) gradient elution, while monomethylarsonous acid (MMA(III)), dimethylarsinous acid (DMA(III)) and arsenobetaine (AsB) were separated by a cation exchange column using 70 mM nitric acid as the mobile phase. Baseline separation, high repeatability and low detection limits (0.10-0.75 ng mL(-1)) were achieved. The spiked urine samples were analyzed with this method to evaluate the matrix effect on the method. The results suggest 1-10 dilutions should be made to urine samples before sample injection for the anion exchange analysis to minimize the matrix effect. To validate the method, a new standard reference material (NIST SRM-2670a) was also analyzed. The arsenic species in NIST SRM-2670a were determined by this method, and the sum of their concentrations agreed well with the total arsenic content certified for NIST SRM-2670a. Moreover, this method was applied to measure arsenic species in urine samples from one subject living in New Jersey who drank well water contaminated with arsenic. By this method, two key arsenic metabolites, MMA(III) and DMA(III), were found to be present in these urine samples, which has previously been rarely reported.
Speciation, mobilization, and bioaccessibility of arsenic in geogenic soil profile from Hong Kong
- J L Cui
- Y P Zhao
- J S Li
- J Z Beiyuan
- Dcw Tsang
- C S Poon
- JL Cui
Environmental arsenic exposure: from genetic susceptibility to pathogenesis
- B C Minatel
- A P Sage
- C Anderson
- R Hubaux
- E A Marshall
- W L Lam
- BC Minatel
Comparative oxidation state specific analysis of arsenic species by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry and hydride generation-cryotrapping-atomic absorption spectrometry
- J M Currier
- R J Saunders
- L Ding
- W Bodnar
- P Cable
- T Matousek
- JM Currier
Quantitative determination of arsenic species in feed using liquid chromatography-hydride generation atomic fluorescence spectrometry
- C X Liu
- Z M Xiao
- Z Jia
- J Tian
- X L Liu
- X Fan
Environmental arsenic exposure: from genetic susceptibility to pathogenesis
- Bc
- A P Sage
- C Anderson
- R Hubaux
- E A Marshall
- W L Lam