Comparison of extraction procedures for arsenic speciation in environmental solid reference materials by high-performance liquid chromatography-hydride generation-atomic fluorescence spectroscopy

Analysis of environmental pollutants using ion chromatography coupled with mass spectrometry: A review

The rise of emerging pollutants in the current environment and requirements of trace analysis in complex substrates pose challenges to modern analytical techniques. Ion chromatography coupled with mass spectrometry (IC-MS) is the preferred tool for analyzing emerging pollutants due to its excellent separation ability for polar and ionic compounds with small molecular weight and high detection sensitivity and selectivity. This paper reviews the progress of sample preparation and ion-exchange IC-MS methods in the analysis of several major categories of environmental polar and ionic pollutants including perchlorate, inorganic and organic phosphorus compounds, metalloids and heavy metals, polar pesticides, and disinfection by-products in past two decades. The comparison of various methods to reduce the influence of matrix effect and improve the accuracy and sensitivity of analysis are emphasized throughout the process from sample preparation to instrumental analysis. Furthermore, the human health risks of these pollutants in the environment with natural concentration levels in different environmental medias are also briefly discussed to raise public attention. Finally, the future challenges of IC-MS for analysis of environmental pollutants are briefly discussed.

Contribution of sedimentary organic matter to arsenic mobilization along a potential natural reactive barrier (NRB) near a river: The Meghna river, Bangladesh

Elevated dissolved arsenic (As) concentrations in the shallow aquifers of Bangladesh are primarily caused by microbially-mediated reduction of As-bearing iron (Fe) (oxy)hydroxides in organic matter (OM) rich, reducing environments. Along the Meghna River in Bangladesh, interactions between the river and groundwater within the hyporheic zone cause fluctuating redox conditions responsible for the formation of a Fe-rich natural reactive barrier (NRB) capable of sequestering As. To understand the NRB's impact on As mobility, the geochemistry of riverbank sediment (<3 m depth) and the underlying aquifer sediment (up to 37 m depth) was analyzed. A 24-hr sediment-water extraction experiment was performed to simulate interactions of these sediments with oxic river water. The sediment and the sediment-water extracts were analyzed for inorganic and organic chemical parameters. Results revealed no differences between the elemental composition of riverbank and aquifer sediments, which contained 40 ± 12 g/kg of Fe and 7 ± 2 mg/kg of As, respectively. Yet the amounts of inorganic and organic constituents extracted were substantially different between riverbank and aquifer sediments. The water extracted 6.4 ± 16.1 mg/kg of Fe and 0.03 ± 0.02 mg/kg of As from riverbank sediments, compared to 154.0 ± 98.1 mg/kg of Fe and 0.55 ± 0.40 mg/kg of As from aquifer sediments. The riverbank and aquifer sands contained similar amounts of sedimentary organic matter (SOM) (17,705.2 ± 5157.6 mg/kg). However, the water-extractable fraction of SOM varied substantially, i.e., 67.4 ± 72.3 mg/kg in riverbank sands, and 1330.3 ± 226.6 mg/kg in aquifer sands. Detailed characterization showed that the riverbank SOM was protein-like, fresh, low molecular weight, and labile, whereas SOM in aquifer sands was humic-like, older, high molecular weight, and recalcitrant. During the dry season, oxic conditions in the riverbank may promote aerobic metabolisms, limiting As mobility within the NRB.

A simple and cost-effective paper-based and colorimetric dual-mode detection of arsenic(iii) and lead(ii) based on glucose-functionalized gold nanoparticles

We report a simple and cost-effective paper-based and colorimetric dual-mode detection of As(iii) and Pb(ii) based on glucose-functionalized gold nanoparticles under optimized conditions. The paper-based detection of As(iii) and Pb(ii) is based on the change in the signal intensity of AuNPs/Glu fabricated on a paper substrate after the deposition of the analyte using a smartphone, followed by processing with the ImageJ software. The colorimetric method is based on the change in the color and the red shift of the localized surface plasmon resonance (LSPR) absorption band of AuNPs/Glu in the region of 200-800 nm. The red shift (Δλ) of the LSPR band observed was from 525 nm to 660 nm for As(iii) and from 525 nm to 670 nm for Pb(ii). The mechanism of dual-mode detection is due to the non-covalent interactions of As(iii) and Pb(ii) ions with glucose molecule present on the surface AuNPs, resulting in the aggregation of novel metal nanoparticles. The calibration curve gave a good linearity range of 20-500 μg L-1 and 20-1000 μg L-1 for the determination of As(iii) and Pb(ii) with the limit of detection of 5.6 μg L-1 and 7.7 μg L-1 for both metal ions, respectively. The possible effects of different metal ions and anions were also investigated but did not cause any significant interference. The employment of AuNPs/Glu is successfully demonstrated for the determination of As(iii) and Pb(ii) using paper-based and colorimetric sensors in environmental water samples.

Assessing arsenic redox state evolution in solution and solid phase during As(III) sorption onto chemically-treated sewage sludge digestate biochars

This work aimed to determine the arsenic redox state distribution during As(III) sorption onto chemically-modified biochars. A solid-liquid extraction protocol using phosphoric (0.3 M) and ascorbic (0.5 M) acids at 80 °C for 20 min was established to ensure a quantitative recovery and stability of As(III) during the extraction. During sorption experiments, the redox conversions of As occurred and As(III) was either stable or partially oxidized in solution. The As distribution strongly varied depending on the biochar chemical treatment performed as well as the selected washing procedures (batch versus column washings). As(III) oxidation was favored with the KOH-modified biochar washed in batch mode. This oxidation was mostly induced by the biochar solid compounds rather than by soluble compounds released in solution. The As redox state distribution of As sorbed onto the biochars was successfully assessed using the extraction procedure. Arsenic was predominantly sorbed as As(III) (76-92%) onto the biochars.

Rates and processes affecting As speciation and mobility in lake sediments during aging

Sediments from an arsenic (As) contaminated groundwater vent site were used to investigate As(III) binding, transformation and redistribution in native and iron oxide amended lake sediments using aging spiked batch reactions and a sequential extraction procedure that maintains As(V) and As(III) speciation. In the native sediments, fractionation analysis revealed that 10% of the spiked As(III) remained intact after a 32-day aging experiment and was predominantly adsorbed to the strongly sorbed (NH₄H₂PO₄ extractable) and amorphous Fe oxide bound (H₃PO₄ extractable) fractions. Kinetic modelling of the experimental results allowed identifying the dominant reaction path for depletion of dissolved As(III) to As(III) absorbed on to the solid phase, followed by oxidation in the solid phase. Arsenite was initially adsorbed primarily to the easily exchangeable fraction ((NH₄)₂SO₄ extractable), then rapidly transformed into As(V) and redistributed to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As(III) in recalcitrant fractions was less efficient. The iron oxide amendments illustrated the controls that iron oxides can have on As(III) binding and transformation rates. In goethite amended samples As(III) oxidation was faster and primarily occurred in the strongly sorbed and amorphous Fe oxide bound fractions. In these samples, 19.3μg Mn was redistributed (compared to the native sediment) from the easily exchangeable and crystalline Fe oxide bound fractions to the strongly sorbed and amorphous Fe oxide bound fractions, indicating that goethite may act as a catalyst for Mn(II) oxidation, thereby producing sorbed Mn(III/IV), which then appears to be involved in rapidly oxidizing As(III).

In vivo and in vitro methods for evaluating soil arsenic bioavailability: relevant to human health risk assessment

Arsenic (As) is the most frequently occurring contaminant on the priority list of hazardous substances, which lists substances of greatest public health concern to people living at or near U.S. National Priorities List site. Accurate assessment of human health risks from exposure to As-contaminated soils depends on estimating its bioavailability, defined as the fraction of ingested As absorbed across the gastrointestinal barrier and available for systemic distribution and metabolism. Arsenic bioavailability varies among soils and is influenced by site-specific soil physical and chemical characteristics and internal biological factors. This review describes the state-of-the science that supports our understanding of oral bioavailability of soil As, the methods that are currently being explored for estimating soil As relative bioavailability (RBA), and future research areas that could improve our prediction of the oral RBA of soil As in humans. The following topics are addressed: (1) As soil geochemistry; (2) As toxicology; (3) in vivo models for estimating As RBA; (4) in vitro bioaccessibility methods; and (5) conclusions and research needs.

Validation of an updated fractionation and indirect speciation procedure for inorganic arsenic in oxic and suboxic soils and sediments

A sequential extraction procedure (SEP) for the speciation analysis of As(III) and As(V) in oxic and suboxic soils and sediments was validated using a natural lake sediment and three certified reference materials, as well as spike recoveries of As(III) and As(V). Many of the extraction steps have been previously validated making the procedure useful for comparisons to similar previous SEP studies. The novel aspect of this research is the validation for the SEP to maintain As(III) and As(V) species. The proposed five step extraction procedure includes the extraction agents (NH₄)₂SO₄, NH₄H₂PO₄, H₃PO₄ + NH₂OH·HCl, oxalate + ascorbic acid (heated), and HNO₃ + HCl + HF, targeting operationally defined easily exchangeable, strongly sorbed, amorphous Fe oxide bound, crystalline Fe oxide bound, and residual As fractions, respectively. The third extraction step, H₃PO₄ + NH₂OH·HCl, has not been previously validated for fraction selectivity. We present evidence for this extraction step to target As complexed with amorphous Fe oxides when used in the SEP proposed here. All solutions were analyzed on ICP-MS. The greatest concentrations of As were extracted from the amorphous Fe oxide fraction and the dominant species was As(V). Lake sediment materials were found to have higher As(III) concentrations than the soil materials. Because different soils/sediments have different chemical characteristics, maintenance of As species during extractions must be validated for specific soil/sediment types using spiking experiments.

Arsenic release from arsenopyrite weathering: insights from sequential extraction and microscopic studies

At a former As mine site, arsenopyrite oxidation has resulted in formation of scorodite and As-bearing iron hydroxide, both in host rock and mine tailings. Electron microprobe analysis documents that arsenopyrite weathers along two pathways: one that involves formation of sulfur, and one that does not. In both pathways, arsenopyrite oxidizes to form scorodite, which dissolves incongruently to form As-bearing iron hydroxides. From a mass balance perspective, arsenopyrite oxidation to scorodite conserves As, but as scorodite dissolves incongruently to iron hydroxides, As is released to solution, resulting in elevated As concentrations in the headwater stream adjacent to the site. The As-bearing iron hydroxide is the dominant solid phase reservoir of As in mine tailings and stream sediment, as suggested by sequential extraction. This As-bearing iron hydroxide is stable under the aerobic and pH 4-6 conditions at the site; however, changes in biogeochemical conditions resulting from sediment burial or future remedial efforts, which could promote As release from this reservoir due to reductive dissolution, should be avoided.

Occurrence and sorption properties of arsenicals in marine sediments

The content of total arsenic, the inorganic forms: arsenite (As(III)) and arsenate (As(V)), the methylated forms: monomethylarsonic acid and dimethylarsinic acid (DMA), trimethylarsenic oxide, tetramethylarsenonium ion and arsenobetaine was measured in 95 sediment samples and 11 pore water samples from the Baltic Sea near the island of Bornholm at depths of up to 100 m. As(III+V) and DMA were detected in the sediment and As(III+V) was detected in the sediment pore water. Average total As concentration of 10.6 ± 7.4 mg/kg dry matter (DM) in the sediment corresponds to previously reported values in the Baltic Sea and other parts of the world. Existing data for on-site measurements of sorption coefficients (Kd) of arsenicals in marine and freshwater sediments show large variability from <1 to >1,000 L/kg. In this work, calculated sorption coefficients (Kd and Koc) for As(III+V) showed significant correlation with depth, dissolved oxygen (DO), salinity and sediment classification; for depths <70 m, salinity <11 %, DO >9 mg/L and sand/silt/clay sediments the Kd was 118 ± 76 L/kg DM and for depths >70 m, salinity >11 %, DO < 9 mg/L and muddy sediments the Kd was 513 ± 233 L/kg DM. The authors recommend using the found Kd value for arsenic in marine sediments when conditions are similar to the Baltic Sea. At locations with significant anthropogenic point sources or where the local geology contains volcanic rock and sulphide mineral deposits, there may be significantly elevated arsenic concentrations, and it is recommended to determine on-site Kd values.

Removal characteristics of As(III) and As(V) from acidic aqueous solution by steel making slag

This study focused on the environmental risk of steel making slag itself, arsenic removal mechanism and re-leaching possibility of arsenic to aqueous state after the adsorption. The purpose of the study is to promote the use of steel making slag as a low-cost adsorbent for arsenic in aqueous system. Calcium was easily dissolved out from the slag and become the dominant substance in the leachate. Some of the calcium could form amorphous calcium carbonate in alkaline condition, and arsenic in the aqueous solution would be removed by being co-precipitated with or adsorbed onto the amorphous calcium carbonate. Most of the amorphous calcium carbonate containing arsenic would be bound to amorphous iron oxide of the slag. When the slag was used as an adsorbent for arsenic removal, a little amount of toxic chemicals were leached from the slag itself under pH 0.8 to 13.6. Also, 70-80% of arsenic laden on the slag was bound to amorphous iron oxide which would not easily desorb unless given a reducing and complexing condition. Showing 95-100% removal efficiency near initial pH 2, the slag, therefore, could be used as an appropriate adsorbent for eliminating arsenic in acidic aqueous solution.

Fractionation and speciation of arsenic in three tea gardens soil profiles and distribution of As in different parts of tea plant (Camellia sinensis L.)

The distribution pattern and fractionation of arsenic (As) in three soil profiles from tea (Camellia sinensis L.) gardens located in Karbi-Anglong (KA), Cachar (CA) and Karimganj (KG) districts in the state of Assam, India, were investigated depth-wise (0-10, 10-30, 30-60 and 60-100 cm). DTPA-extractable As was primarily restricted to surface horizons. Arsenic speciation study showed the presence of higher As(V) concentrations in the upper horizon and its gradual decrease with the increase in soil depths, following a decrease of Eh. As fractionation by sequential extraction in all the soil profiles showed that arsenic concentrations in the three most labile fractions (i.e., water-soluble, exchangeable and carbonate-bound fractions) were generally low. Most arsenic in soils was nominally associated with the organic and Fe-Mn oxide fractions, being extractable in oxidizing or reducing conditions. DTPA-extractable As (assumed to represent plant-available As) was found to be strongly correlated to the labile pool of As (i.e. the sum of the first three fractions). The statistical comparison of means (two-sample t-test) showed the presence of significant differences between the concentrations of As(III) and As(V) for different soil locations, depths and fractions. The risk assessment code (RAC) was found to be below the pollution level for all soils. The measurement of arsenic uptake by different parts of tea plants corroborated the hypothesis that roots act as a buffer and hold back contamination from the aerial parts.

Mineralogical and geochemical controls of arsenic speciation and mobility under different redox conditions in soil, sediment and water at the Mokrsko-West gold deposit, Czech Republic

Naturally contaminated soil, sediment and water at the Mokrsko-West gold deposit, Central Bohemia, have been studied in order to determine the processes that lead to release of As into water and to control its speciation under various redox conditions. In soils, As is bonded mainly to secondary arseniosiderite, pharmacosiderite and Fe oxyhydroxides and, rarely, to scorodite; in sediments, As is bonded mainly to Fe oxyhydroxides and rarely to arsenate minerals. The highest concentrations of dissolved As were found in groundwater (up to 1141 microg L(-1)), which mostly represented a redox transition zone where neither sulphide minerals nor Fe oxyhydroxide are stable. The main processes releasing dissolved As in this zone are attributed to the reductive dissolution of Fe oxyhydroxides and arsenate minerals, resulting in a substantial decrease in their amounts below the groundwater level. Some shallow subsurface environments with high organic matter contents were characterized by reducing conditions that indicated a relatively high amount of S(-2,0) in the solid phase and a lower dissolved As concentration (70-80 microg L(-1)) in the pore water. These findings are attributed to the formation of Fe(II) sulphides with the sorbed As. Under oxidizing conditions, surface waters were undersaturated with respect to arsenate minerals and this promoted the dissolution of secondary arsenates and increased the As concentrations in the water to characteristic values from 300 to 450 microg L(-1) in the stream and fishpond waters. The levels of dissolved As(III) often predominate over As(V) levels, both in groundwaters and in surface waters. The As(III)/As(V) ratio is closely related to the DOC concentration and this could support the assumption of a key role of microbial processes in transformations of aqueous As species as well as in the mobility of As.

Extraction of arsenic species in soils using microwave-assisted extraction detected by ion chromatography coupled to inductively coupled plasma mass spectrometry

We have developed a novel microwave-assisted extraction method for determining the arsenic (As) speciation in soils that is based on extraction with phosphate solutions, including orthophosphoric acid, ammonium dihydrogen orthophosphate, and ammonium hydrogen orthophosphate. The highest extracting efficiency was obtained with 1 M ortho-phosphoric acid solution as the extractant, and this efficiency is associated with the pH of the extractant. Total As content and As species in the soil extracts were determined by inductively coupled plasma mass spectrometry (ICP-MS) alone and by the combined ion chromatography (IC) with ICP-MS, respectively. The proposed extraction procedure was applied to National Institute of Standards and Technology (NIST) standard reference material (SRM) 2711 (Montana soil) as well as to environmental soil samples collected from the agricultural lands of Bangladesh. As(V) was detected in all the soil samples, and As(III) was detected in nine soils of the 20. These results of extractable As testing indicate that the extraction of As species mainly depends on the composition of the soils. The As speciation results also indicate that As adsorption is highly dependent on the iron, aluminum, and manganese concentrations in the soil. The stability of As species in the extracts was also studied.

A comparative study of the extractability of arsenic species from silverbeet and amaranth vegetables

There is still no reliable standard extraction method for the speciation of arsenic (As) in plant tissue, and hence there is great interest in developing one for plants that are used as human food. Speciation and bioavailability are critical for accurate human health risk assessment, as As species vary in both their toxicity and bioavailability. Recent incidences of As poisoning in many countries have led to significant research into the fate and dynamics of As in the soil and water environment, including speciation. Although one of the major pathways of ingestion of As is via food, only limited research has been conducted to assess the nature and proportion of various As species present in food crops. In this study, we compared the efficacy of ammonium dihydrogen phosphate and protein extracting solution for the extractability of As from two different species of spinach (amaranth and silverbeet). We found that a microwave-assisted technique with protein extracting solution was most effective, yielding 76-114% extractability and excellent separation and speciation of all As species present in the spinach matrices. The stability test for extracted As species showed them as stable for 45 days without any significant loss or inter-conversion. Both As(III) and As(V) were identified in the shoots of amaranth and silverbeet. However, the percentage of As species varied between amaranth and silverbeet. The silverbeet shoot showed a somewhat higher percentage of As(V), while the amaranth showed a higher percentage of As(III). The samples contained mostly inorganic As, especially As(III) (>90%) in the edible part of the vegetables, a form that is more toxic and bioavailable than other organic and methylated species.

Kinetic spectrophotometric determination of Fe(II) in the presence of Fe(III) by H-point standard addition method in mixed micellar medium

The H-point standard addition method was applied to kinetic data for simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III). The method is based on the difference in the rate of complex formation between iron in two different oxidation states and methylthymol blue (MTB) at pH 3.5 in mixed cetyltrimethylammonium bromide (CTAB) and Triton X-100 micellar medium. Fe(II) can be determined in the range 0.25-2.5 microg ml(-1) with satisfactory accuracy and precision in the presence of excess Fe(III) and other metal ions that rapidly form complexes with MTB under working condition. The proposed method was successfully applied to the simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III) in spiked real environmental and synthetic samples with complex composition.

Comparison of in vivo and in vitro methodologies for the assessment of arsenic bioavailability in contaminated soils

An in vivo swine assay was utilised for the determination of arsenic (As) bioavailability in contaminated soils. Arsenic bioavailability was assessed using pharmacokinetic analysis encompassing area under the blood plasma-As concentration time curve following zero correction and dose normalisation. In contaminated soil studies, As uptake into systemic circulation was compared to an arsenate oral dose and expressed as relative As bioavailability. Arsenic bioavailability ranged from 6.9+/-5.0% to 74.7+/-11.2% in 12 contaminated soils collected from former railway corridors, dip sites, mine sites and naturally elevated gossan soils. Arsenic bioavailability was generally low in the gossan soils and highest in the railway soils, ranging from 12.1+/-8.5% to 16.4+/-9.1% and 11.2+/-4.7% to 74.7+/-11.2%, respectively. Comparison of in vivo and in vitro (Simplified Bioaccessibility Extraction Test [SBET]) data from the 12 contaminated soils and bioavailability data collected from an As spiked soil study demonstrated that As bioavailability and As bioaccessibility were linearly correlated (in vivo As bioavailability (mgkg(-1))=14.19+0.93.SBET As bioaccessibility (mgkg(-1)); r(2)=0.92). The correlation between the two methods indicates that As bioavailability (in vivo) may be estimated using the less expensive, rapid in vitro chemical extraction method (SBET) to predict As exposure in human health risk assessment.

Arsenic speciation in rice, straw, soil, hair and nails samples from the arsenic-affected areas of Middle and Lower Ganga plain

In the present study, pressurised liquid extraction and ultrasound probe sonication, for the latter in combination with a mixed enzymatic treatment in case of rice and straw samples, were applied as sample preparation prior to arsenic speciation analysis by high pressure liquid chromatography coupled to inductively coupled plasma mass spectrometric detection (HPLC-ICP-MS). A significant number of samples as different as rice, straw, soil, nail and hair, all coming from the heavily arsenic-contaminated Middle and Lower Ganga plain area, could be investigated with validated methods, supported by high speed extraction methods. For rice and paddy samples, inorganic arsenic counted up to 70-98% of the total arsenic content, being the major species As (III). The levels of arsenic obtained from straw and soil samples are significantly higher than the background levels, being the major species As (V), thus increasing human exposure to arsenic via the soil-plant-animal-human pathway. Concentrations found in hair and nails were significantly higher than their background levels: 39- and 20-fold for hair and nails, respectively. These samples contained mainly inorganic arsenic in its tri- and pentavalent forms. Results indicate that, under the local frame conditions, arsenic mainly enters into the food chain via its more problematic inorganic forms. Arsenic speciation analysis proves to be a powerful tool for a complete analytical assessment in epidemiological studies covering the endemic areas.

Analytical speciation as a tool to assess arsenic behaviour in soils polluted by mining

A study is performed to evaluate the occurrence of arsenic in polluted soils using acidic extractions and liquid chromatography-hydride generation-atomic fluorescence spectrometry (LC-HG-AFS) for speciation analysis. Seven soil samples were collected in an abandoned area polluted by mining in the Eastern Pyrenees (Spain), and two uncontaminated soils were taken for reference purposes. Moreover, the total arsenic content is evaluated in two different sieved fractions in order to obtain information on the possible particle-size-dependent association of arsenic with soil components. Soil samples were extracted with both phosphoric and ascorbic acids and the stabilities of the extracted species were studied. The arsenic species were determined by LC-HG-AFS. In addition, the ability of soil grinding to effect species change is also assessed. Arsenite and arsenate were found in the polluted soils, but only arsenate was found in the unpolluted soils. The quality of the results was assessed through a mass balance calculation and by analysing two soil Certified Reference Materials. Valuable information regarding arsenic occurrence in the studied soils is obtained from the speciation results. The presence of arsenite in the extracts can be attributed to arsenopyrite residues, whereas the presence of arsenate indicates release from weathered material.

An interdisciplinary physical-chemical approach for characterization of arsenic in a calciner residue dump in Cornwall (UK)

During the later stages of hard-rock mining in Cornwall, UK, widespread processing and refining of arsenic in purpose-built calciners resulted in severe, localized contamination of soils with arsenic. Several physical-chemical techniques were applied to characterize arsenic in a calciner residue dump: X-ray powder diffraction (XRD), sequential extraction combined with hyphenated speciation methods, and X-ray absorption spectroscopic (XAS) methods such as XANES (X-ray absorption near-edge structure) and EXAFS (extended X-ray absorption fine structure). Arsenic was predominantly present in pentavalent form, bound to amorphous or poorly-crystalline hydrous oxides of Fe (probably alpha-hematite). A small amount of a non-classified crystalline iron arsenate phase was found, viz. Fe2(As(AsO4)3). There was also evidence for the presence of some arsenate bound to quartz (alpha-SiO2). The overall results make us believe that the normally assumed relative safety, from a mobility point of view, is questionable since only a small fraction of arsenic is found in a crystalline iron arsenate form.

Evaluation of a focused sonication probe for arsenic speciation in environmental and biological samples

Arsenic speciation analysis suffers in general from high sample handling time required by sample preparation. In a previous work, ultrasonic probe has been proved to reduce sample treatment time for arsenic extraction in rice to only a few minutes. Base upon the obtained results, here several extraction media for chicken, fish and soil samples (SEAS G6RD-CT2001-00473) have been studied and evaluated employing the same technique. Chicken sample needed an enzymatic treatment in order to liberate the species linked to the protein matrix. Extraction of the major species in fish, AsB, was quantitatively achieved in water in 1 min. Also 1 min was enough to leach about 85% of species present in soils and sediments, mainly the inorganic ones, using H(3)PO(4). In all cases, no inter-conversion among As species was observed. The five species found in those samples were separated using an improved HPLC-ICP-MS method in only 11 min, with detection limits at the ng l(-1) level. The proposed methods were validated by analysing several Certified Reference Materials: SRM 1,568 a rice flour, CRM-627 tuna fish tissue, SOIL-7 soil and MURST-ISS-A1 Antarctic sediment.

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

We review recent research in the field of arsenic speciation analysis with the emphasis on significant advances, novel applications and current uncertainties.