The effect of cooking and washing rice on the bio-accessibility of As,Cu, Fe,V and Zn using an on-line continuous leaching method

A previously developed method based on continuous on-line leaching with artificial gastro-intestinal fluids was used to determine the bio-accessible fraction of As, Cu, Fe, V and Zn in brown and white rice from California by inductively coupled mass spectrometry (ICP-MS). Saliva generally accounted for the largest percentage of total element leached in comparison to gastric and intestinal juices. Arsenic speciation analysis was performed on the saliva and gastric juice leachates using ion exchange chromatography coupled to ICP-MS. The four most toxic species of As (As(III), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and As(V)), as well as Cl⁻ in the gastric juice leachate, were successfully separated within 5.5 min using a simple nitric acid gradient. While cooking rice had relatively little effect on total bio-accessibility, a change in species from As(V) and DMA to As(III) was observed for both types of rice. On the other hand, washing the rice with doubly deionized water prior to cooking removed a large percentage of the total bio-accessible fraction of As, Cu, Fe, V and Zn.     

Estimation of the bio-accessible fraction of Cr,As, Cd and Pb in locally available bread using on-line continuous leaching method coupled to inductively coupled plasma mass spectrometry

A previously developed, efficient and simple on-line leaching method was used to assess the maximum bio-accessible fraction (assuming no synergistic effect from other food and beverage) of potentially toxic elements (Cr, As, Cd and Pb) in whole wheat brown and white bread samples. Artificial saliva, gastric juice and intestinal juice were successively pumped into a mini-column, packed with bread (maintained at 37 °C) connected on-line to the nebulizer of an inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with a collision-reaction interface (CRI) using hydrogen as reaction gas to minimize carbon- and chlorine-based polyatomic interferences. In contrast to the conventional batch method to which it was compared, this approach provides real-time monitoring of potentially toxic elements that are continuously released during leaching. Mass balance for both methods was verified at the 95% confidence level. Results obtained from the whole wheat brown and white bread showed that the majority of Cr, Cd and Pb was leached by gastric juice but, in contrast, the majority of As was leached by saliva. While there was higher total content for elements in whole wheat bread than in white bread, a higher percentage of elements were bio-accessible in white bread than in whole wheat bread. Both the on-line and batch methods indicate that 40–98% of toxic elements in bread samples are bio-accessible. While comparison of total analyte concentrations with provisional tolerable daily intake values may indicate some serious health concern for children, when accounting for the bio-accessibility of these elements, bread consumption is found to be safe for all ages.     

Bioaccessibility of total arsenic and arsenic species in seafood as determined by a continuous online leaching method

A continuous leaching method coupled online with inductively coupled plasma mass spectrometry (ICP-MS) detection was used to assess the maximum bioaccessibility of arsenic (As) in seafood samples. The method simulates continuous-flow digestion by successively pumping artificial saliva, gastric and intestinal juices through a mini-column of powdered sample directly connected to the nebuliser of an ICP-MS instrument. The method allows the real-time measurement of As being released by a given reagent. Because the analyte is continuously removed from the system, in contrast to batch methods, the dissolution equilibrium is driven to the right, hence quickly providing information about the worst-case scenario. Following consecutive leaching by the digestive reagents, the leachates were subject to speciation analysis by ion-exchange chromatography with ICP-MS detection to determine the arsenic species released. Finally, the remaining residue from the mini-column was fully digested to verify mass balance. The method was used to determine the bioaccessibility of total As and As species in four certified reference materials and in several real seafood samples. The mass balance was verified in each case. Generally speaking, the non-toxic form was easily released whereas the inorganic forms were poorly bioaccessible.     

On-line coupling of an ultraviolet titanium dioxide film reactor with a liquid chromatography/hydride generation/inductively coupled plasma mass spectrometry system for continuous determination of dynamic variation of hydride- and nonhydride-forming arsenic species in very small microdialysate samples

We describe a method for continuously monitoring both hydride- and nonhydride-forming arsenic species in 10-microL microdialysate samples by coupling together on-line high-performance liquid chromatography (HPLC), a post-column UV/TiO2 film reactor, and hydride generation (HG) inductively coupled plasma mass spectrometry (ICP-MS). To maximize the signal intensities of the desired arsenic species, we optimized the photocatalytic oxidation efficiency of the analyte species and used a rapid on-line pre-reduction process to convert the oxidized species into As(III) prior to HG-ICP-MS determination. The UV/nano-TiO2 film reactor was manufactured by coating nano-TiO2 onto the interior of a glass tube. Impregnation and sol-gel methods were employed to deposit the TiO2 films, and their effectiveness for the oxidation of organic arsenicals was compared. To enhance the decomposition efficiency of organic arsenicals, we investigated the effects of the acidity and the composition of the column effluent. Because of the improved HG efficiency toward the tested arsenicals and the adoption of a segmented flow technique to retain the peak resolution in our on-line LC-UV/nano-TiO2 film reactor-HG-ICP-MS instrument, the detection limits for arseneous acid [As(III)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenic acid [As(V)], and arsenobetaine (AsB) were all in the submicrogram-per-liter range (based on 3 sigma) for 10-microL injections. A series of validation experiments--analyses of certified reference urine and rabbit serum samples--indicated that these methods can be applied satisfactorily to the continuous determination of As(III), MMA, DMA, As(V), and AsB in blood and in the extracellular space of target organs.     

Simultaneous pressurized enzymatic hydrolysis extraction and clean up for arsenic speciation in seafood samples before high performance liquid chromatography-inductively coupled plasma-mass spectrometry determination

The feasibility of pressurized conditions to assist enzymatic hydrolysis of seafood tissues for arsenic speciation was novelty studied. A simultaneous in situ (in cell) clean-up procedure was also optimized, which speeds up the whole sample treatment. Arsenic species (As(III), MMA, DMA, As(V), AsB and AsC) were released from dried seafood tissues using pepsin as a protease, and the arsenic species were separated/quantified by anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Variables inherent to the enzymatic activity (pH, temperature and ionic strength), the amount of enzyme (pepsin), and factors affecting pressurization (pressure, static time, number of cycles and amount of dispersing agent, C-18) were fully evaluated. Pressurized assisted enzymatic hydrolysis (PAEH) with pepsin can be finished after few minutes (two cycles of 2 min each one plus 3 min to reach the hydrolysis temperature of 50 °C). A total sample solubilisation is not achieved after the procedure, however it is efficient enough for breaking down certain bonds of bio-molecules and for releasing arsenic species. The developed method has been found to be precise (RSDs lower than 6% for As(III), DMA and As(V); and 3% for AsB) and sensitive (LOQs of 18.1, 36.2, 35.7, 28.6, 20.6 and 22.5 ng/g for As(III), MMA, DMA, As(V), AsB and AsC, respectively). The optimized methodology was successfully applied to different certified reference materials (DORM-2 and BCR 627) which offer certified AsB and DMA contents, and also to different seafood products (mollusks, white fishes and cold water fishes).     

Application of fast ultrasound water-bath assisted enzymatic hydrolysis--high performance liquid chromatography-inductively coupled plasma-mass spectrometry procedures for arsenic speciation in seafood materials

Enzymatic hydrolysis of seafood materials for isolating arsenic species (As(III), As(V), DMA and AsB) has been successfully performed by assisting the procedure with ultrasound energy (35 kHz) supplied by an ultrasound water-bath. The use of pepsin, as a proteolytic enzyme, under optimized operating conditions (pH 3.0, temperature 40 °C, enzyme to sample ratio of 0.3) led to an efficient assistance of the enzymatic process in a short period of time (from 4.0 to 30 min). The enzymatic extract was then subjected to a clean-up procedure based on ENVI-Carb™ solid phase extraction (SPE). An optimized anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) permitted the fast separation (less than 15 min) of six different arsenic species (arsenite, As(III); arsenate, As(V); dimethylarsinic acid, DMA; and arsenobetaine, AsB; as well as monomethylarsonic acid, MMA; and arsenocholine, AsC) in a single run. Relative standard deviations (n = 11) of the over-all procedure were 7% for AsB and DMA, 11% for As(III) and 9% for MMA. HPLC–ICP-MS determinations were performed using aqueous calibrations covering arsenic concentrations of 0, 5, 10, 25, 100 and 200 μg L⁻¹ (expressed as arsenic) for As(III), As(V), MMA, DMA and AsC; and 0, 125, 250, 500, 750, 1000 and 2000 μg L⁻¹ (expressed as arsenic) for AsB. Germanium (5 μg L⁻¹) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 96 to 105% (enzymatic digests spiked with low target concentrations), from 97 to 104% (enzymatic digests spiked with intermediate target concentrations), and from 98 to 103% (enzymatic digests spiked with high target concentrations). The developed method was successfully applied to two certified reference materials (CRMs), DORM-2 and BCR 627, which offer certified AsB and DMA contents, and also to different seafood samples (mollusks, white fish and cold water fish). Good agreement between certified and found AsB concentrations was achieved when analyzing both CRMs; and also, between certified and found DMA concentrations in BCR 627. In addition, the sum of the different arsenic species concentrations found in most of the analyzed samples was statistically similar to the assessed total arsenic concentrations after a total sample matrix decomposition treatment.     

Determination of urinary arsenic species using an on-line nano-TiO2 photooxidation device coupled with microbore LC and hydride generation-ICP-MS system

We have developed an on-line digestion device-based on the nano-TiO₂-catalyzed photooxidation of arsenic species—for coupling between microbore anion-exchange chromatography (μ-LC) and hydride generation (HG)-inductively coupled plasma mass spectrometry (ICP-MS) systems that can be used for the determination of urinary arsenic species. To maximize the signal intensities of the desired arsenic species, we optimized the photocatalytic oxidation efficiency of the analyte species and developed a rapid on-line pre-reduction process for converting the oxidized species into As(III) prior to HG-ICP-MS determination. Under the optimized conditions for the nano-TiO₂-catalyzed photooxidation-i.e., using 1 g of nano-TiO₂ per-liter, at pH 5.2, and illuminating for 3 min- As(III), monomethylarsenoic acid (MMA), and dimethylarseinic acid (DMA) can be converted quantitatively into As(V). To attain maximal hydride generation efficiency, 0.5% Na₂S₂O₄ solution, which can reduce As(V) to As(III) virtually instantaneously upon on-line mixing, was added as a pre-reductant prior to performing the HG step. In light of all the HG efficiency of tested arsenicals were improved and a segmented-flow technique was employed to avoid the loss of peak resolution when using our proposed on-line μ-LC-UV/nano-TiO₂/HG-ICP-MS, the detection limits for As(III), MMA, DMA, and As(V) were all in the range of sub-microgram-per-liter (based on 3 sigma). A series of validation experiments-analysis of neat and spiked urine samples-indicated that our proposed methods can be applied satisfactorily to the determination of As(III), MMA, DMA, and As(V) in urine samples.     

Capillary electrophoresis with inductively coupled plasma-mass spectrometric and electrospray time of flight mass spectrometric detection for the determination of arsenic species in fish samples

CE was coupled to inductively coupled plasma MS (ICP-MS) and ESI-MS to identify and quantify the arsenic species arsenobetaine (AsB), arsenite (As(III)), arsenate (As(V)), and dimethylarsinic acid (DMA). A GC-flame ionization detector (FID)-based German standard method and ICP-MS were used for validation of the data obtained for arsenobetaine and total arsenic, respectively. LODs obtained with the CE-ESI-TOF-MS method were 1.0x10(-7) M for AsB, 5.0x10(-7) M for DMA, and 1.0x10(-6) M for As(III) and As(V). For the CE-ICP-MS method, LODs were 8.5x10(-8) M for AsB, 9.5x10(-8) M for DMA, 9.3x10(-8) M for As(III), and 6.2x10(-8) M for As(V). While CE-ICP-MS provided high sensitivity and better reproducibility for quantitative measurements, CE-ESI-MS with a TOF mass analyzer proved to be valuable for species identification. With this setup, fish samples were prepared and analyzed and the obtained data were successfully validated with the independent methods.     

Total arsenic determination and speciation in infant food products by ion chromatography-inductively coupled plasma-mass spectrometry

Health risk associated with dietary arsenic intake may be different for infants and adults. Seafood is the main contributor to arsenic intake for adults while terrestrial-based food is the primary source for infants. Processed infant food products such as rice-based cereals, mixed rice/formula cereals, milk-based infant formula, applesauce and puree of peaches, pears, carrots, sweet potatoes, green beans, and squash were evaluated for total and speciated arsenic content. Arsenic concentrations found in rice-based cereals (63-320 ng/g dry weight) were similar to those reported for raw rice. Results for the analysis of powdered infant formula by inductively coupled plasma-mass spectrometry (ICP-MS) indicated a narrow and low arsenic concentration range (12 to 17 ng/g). Arsenic content in puree infant food products, including rice cereals, fruits, and vegetables, varies from <1 to 24 ng/g wet weight. Sample treatment with trifluoroacetic acid at 100 degrees C were an efficient and mild method for extraction of arsenic species present in different food matrixes as compared to alternative methods that included sonication and accelerated solvent extraction. Extraction recoveries from 94 to 128% were obtained when the summation of species was compared to total arsenic. The ion chromatography (IC)-ICP-MS method selected for arsenic speciation allowed for the quantitative determination of inorganic arsenic [As(III) + As(V)], dimethylarsinic acid (DMA), and methylarsonic acid (MMA). Inorganic arsenic and DMA are the main species found in rice-based and mixed rice/formula cereals, although traces of MMA were also detected. Inorganic arsenic was present in freeze-dried sweet potatoes, carrots, green beans, and peaches. MMA and DMA were not detected in these samples. Arsenic species in squash, pears, and applesauce were not detected above the method detection limit [5 ng/g dry weight for As(III), MMA, and DMA and 10 ng/g dry weight for As(V)].     

Identification and quantification of major species of arsenic in rice

A study was undertaken to develop a method for the chemical speciation of As in rice on the basis of current knowledge in this field for use in preparing a certified reference material (CRM). Samples of the Arborio rice variety were ground to a fine powder, which was extracted under sonication with a water-methanol mixture (1 + 1, v/v). The resulting solutions were injected into a high-performance liquid chromatograph combined on-line with a quadrupole inductively coupled plasma-mass spectrometer. This hyphenated system allowed for the quantification of As species in one analytical step. Four forms of As were detected: inorganic As (III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and inorganic As (V) at concentrations of 88.2 +/- 7.1, 50.8 +/- 5.0, 15.2 +/- 1.7, and 51.2 +/- 3.5 ng/g, respectively. The concentration of total As was 211 +/- 7 ng/g. The limits of detection (3sigma criterion) and the quantitation (10sigma criterion) were, respectively, as follows (in ng/g): As (III), 0.095 and 0.320; As (V), 0.082 and 0.273; MMA, 0.110 and 0.367; and DMA, 0.145 and 0.480. Ten hours were needed for the extraction procedure, 6 h for the evaporation, and 30 min for quantification of the analytes. This investigation was performed in the frame of a European Commission Project on the feasibility of CRMs for As and Se species.     

Determination of arsenic compounds in beverages by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

Arsenic compounds including arsenous acid (As(III)), arsenic acid (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were separated by high-performance liquid chromatography (HPLC) and detected by inductively coupled plasma mass spectrometry (ICP-MS). A Hamilton PRX-100 anionic-exchange column and a pH 8.5 K₂HPO₄/KH₂PO₄ 5.0 × 10⁻³ mol L⁻¹ mobile phase were used to achieve arsenic speciation. The separation of arsenic species provided peaks of As(III) at 2.75 min, DMA at 3.33 min, MMA at 5.17 min and As(V) at 12.5 min. The detection limits, defined as three times the standard deviation of the lowest standard measurements, were found to be 0.2, 0.2, 0.3 and 0.5 ng mL⁻¹ for As(III), DMA, MMA and As(V), respectively. The relative standard deviation values for a solution containing 5.0 μg L⁻¹ of As(III), DMA, MMA and As(V) were 1.2, 2.1, 2.5 and 3.0%, respectively. This analytical procedure was applied to the speciation of arsenic compounds in drinking (soft drink, beer, juice) samples. The validation of the procedure was achieved through the analysis of arsenic compounds in water and sediment certified reference materials.     

Mechanism of sensitivity difference between trivalent inorganic As species [As(III)] and pentavalent species [As(V)] with inductively coupled plasma spectrometry

The pentavalent inorganic arsenic (As) species [As(V)] is found to be 4% more sensitive than the trivalent species [As(III)] with inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). Although there was no sensitivity difference between As(III) and As(V) with atomic absorption spectrometry (AAS), electrothermal atomization atomic absorption spectrometry (ETAAS), X-ray fluorescence (XRF), and neutron activation analysis (NAA). The calibration solutions of As(III) and As(V) were gravimetrically prepared from the unique mother standard solution of JCSS As standard solution which is certified by Japan Calibration Service System (JCSS). Since it is essential to use the calibration solutions with exactly the same concentration of As in order to accurately compare the sensitivities between As(III) and As(V). The mechanisms of this sensitivity difference between them were investigated by ICP-MS and ICP-OES, and it elucidated that the formation rates of hydride polyatomic species of As were definitively different between As(III) and As(V) species in the plasma. This phenomenon directly affected their sensitivities with ICP-MS and ICP-OES.     

液相色谱-电感耦合等离子体质谱法测定稻米中的5种砷形态

建立了稻米中砷酸根[As（Ⅴ）]、亚砷酸根[As（Ⅲ）]、砷甜菜碱（AsB）、一甲基砷（MMA）和二甲基砷（DMA）的液相色谱-电感耦合等离子体质谱（LC-ICP-MS）检测方法。以0.3 mol/L硝酸水溶液为提取试剂,样品在石墨消解仪中于95 ℃消解1.5 h,上清液供LC-ICP-MS分析。5种砷形态采用Dionex IonPac AS19阴离子交换柱（250 mm×4 mm）分离,经ICP-MS检测。比较了4种提取液对稻米中5种砷形态的提取效率,并对提取溶剂的浓度、提取温度和提取时间等条件进行了优化。通过加标回收试验结合测定标准物质考察了方法准确度及精密度,在2个加标水平上各形态的回收率为89.6%~99.5%,RSD（n=5）不大于3.6%,大米标准物质中各形态之和的测定结果与其标准值吻合,5种砷形态的线性范围AsB和DMA为0.05~200 μg/L,As（Ⅲ）和MMA为0.10~400 μg/L,As（V）为0.15~600 μg/L,方法检出限为0.15~0.45 μg/kg。结果表明,本方法简单、灵敏、耐用,可用于稻米中5种砷形态的准确定量和风险评估。     

Determination of inorganic and organic anionic arsenic species in water by ion chromatography coupled to hydride generation-inductively coupled plasma atomic emission spectrometry

The development of an analytical methodology for the specific determination of arsenite, arsenate and the organic species monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), is described. The method is based on an ion chromatographic separation, coupled on-line to post-column generation of the gaseous hydrides by reaction with sodium tetrahydroborate in acidic medium. Detection and measurement were performed by inductively coupled plasma spectrometry operated in the atomic emission mode. Arsenic emission was monitored at 193.7 nm. Different types and sizes of anion-exchange columns, silica and polymeric, were tested using EDTA as eluent. Composition, acidity and flow-rate of the mobile phase were optimized in order to obtain the required resolution. Complete elution and resolution of the four species was achieved in about 6 min. Linear calibration curves were obtained in the 0.05-2 microg ml(-1) range for As(III), As(V) and MMA, and between 0.1 and 2.0 microg ml(-1) for DMA. The absolute limits of detection for 200-microl sample injections were in the ng range, with DMA the compound measured with less sensitivity. Results of the analyses of natural samples, such as river and ground waters spiked with the studied species, suggested that analyte recoveries might be dependent on the sample composition.     

Investigation of uranium-colloid interactions in soil by dual field-flow fractionation/capillary electrophoresis hyphenated with inductively coupled plasma-mass spectrometry

This paper deals with the study of uranium-colloid interactions in a carbonated soil. The work is focused on the immediately available fraction obtained after a leaching process, according to a normalized batch method. In order to characterize the different colloidal carriers, Asymmetrical Flow Field-Flow Fractionation (As-Fl-FFF) coupled to different detectors (UV, Multi Angle Laser Light Scattering (MALLS) and Inductively coupled Plasma-Mass Spectrometry (ICP-MS)) was used. The colloidal carriers are mainly inorganic particles (carbonated particles and clays) mixed with organic substances. Furthermore, dissolved and colloidal uranium species in the leaching solutions were monitored by Capillary Electrophoresis (CE) coupled to ICP-MS, in order to investigate the uranium/colloids interactions. According to the first results, uranium fate in this specific soil is controlled by sorption/desorption phenomena, strongly pH dependent.     

Simultaneous separation and determination of six arsenic species in rice by anion‐exchange chromatography with inductively coupled plasma mass spectrometry

The simultaneous separation and determination of arsenite As(III), arsenate As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) in rice samples have been carried out in one single anion‐exchange column run by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry. To estimate the effect of variables on arsenic (As) speciation, the chromatographic conditions including type of competing anion, ionic strength, pH of elution buffer, and flow rate of mobile phase have been investigated by a univariate approach. Under the optimum chromatographic conditions, baseline separation of six As species has been achieved within 10 min by gradient elution program using 4 mM NH₄HCO₃ at pH 8.6 as mobile phase A and 4 mM NH₄HCO₃, 40 mM NH₄NO₃ at pH 8.6 as mobile phase B. The method detection limits for As(III), As(V), MMA, DMA, AsB, and AsC were 0.4, 0.9, 0.2, 0.4, 0.5, and 0.3 μg/kg, respectively. The proposed method has been applied to separation and quantification of As species in real rice samples collected from Hunan Province, China. The main As species detected in all samples were As(III), As(V) and DMA, with inorganic As accounting for over 80% of total As in these samples.     

Speciation analysis of arsenic in Mya arenaria Linnaeus and Shrimp with capillary electrophoresis-inductively coupled plasma mass spectrometry

An improved sheath-flow interface used to couple capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) and a microwave-assisted extraction used to extract each arsenic species in seafood were developed in this work. The improved sheath-flow interface completely avoids laminar flow in CE capillary caused by the suction from ICP-MS, makes electric supply more stable in CE, and transports analyte solution to ICP-MS easily and more efficiently. CE-ICP-MS coupled with our interface have two quantitative analysis modes: continuous sample-introduction mode and collective sample-introduction mode. The collective sample-introduction technique greatly reduced the dead volume of interface to approximately zero, obviously avoided the excessive dilution of analyte, and eventually led to a much lower detection limit and a much better electrophoretic resolution. This was demonstrated by the better symmetry and narrow peak widths (10-12 s) and much lower detection limits (0.030-0.042 μg/L) of four species of arsenic determined with collective sample-introduction mode.With the help of this improved sheath-flow interface and the microwave-assisted extraction, we have successfully separated and determined four arsenic species, As(III), As(V), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in dried Mya arenaria Linnaeus and Shrimp samples using CE-ICP-MS within 10 min with a relative standard deviation of 2-4% (peak areas, n = 6) and a recovery of 96-105%.     

Speciation of arsenic by ion chromatography inductively coupled plasma mass spectrometry using ammonium eluents

A method based on ion chromatography (IC) and inductively coupled plasma MS (ICP-MS) was developed for the speciation of arsenic in water and soil extracts. An anion-exchange column (G3154A/101) was used to separate As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) with excellent resolution. Various ammonium salts, including NH4H2PO4, (NH4)2HPO4, (NH4)2CO3, and NH4HCO3, were examined as eluents to reduce matrix interference from chloride and to solve clogging problems. The best arsenic speciation was obtained within 9 min with excellent resolution and without interference from high chloride concentrations using an eluent containing 7.5 mM (NH4)2HPO4 at pH 7.9. The detection limits for the target arsenic species ranged from 0.1 to 0.4 microg/L with direct injection of sample without matrix elimination. The proposed method was effectively demonstrated by determining arsenic species in contaminated waters and soils of Bangladesh.     

Speciation of arsenic in mussels by the coupled system liquid chromatography-UV irradiation-hydride generation-inductively coupled plasma mass spectrometry

A method has been developed for the determination of seven arsenic species in mussel tissues by liquid chromatography-hydride generation-UV photo-oxidation and detection by inductively coupled plasma mass spectrometry. In order to determine the different species, two ion-exchange columns (anionic and cationic) were used with phosphate and nitric acid/ammonium nitrate as mobile phases, respectively. The optimisation of the conditions for separation, photo-oxidation and hydride generation is described. For each of these species, the limits of detection and repeatability are reported with the entire system coupling. This system was applied to the analysis of certified reference material (CRM 278) and mussels collected from Barcelona harbour. Extractions were achieved in methanol/water (1:1) using low-power focused microwaves as leaching process. As expected, arsenobetaine was the main compound extracted from both materials; the typical concentrations found were between 1 and 7 mg kg(-1). Other organoarsenical compounds, probably arsenosugars, were extracted in a concentration range of 0.3-1.5 mg kg(-1) in both cases. Amounts of dimethylarsinate (DMA) were found to be significant in the CRM 278, but very low in mussels from Barcelona harbour. The low limits of detection of the coupled system allow us to quantify low contents of other species (As(V), arsenocholine and monomethylarsonate (MMA)).     

Determination of arsenite,arsenate, monomethylarsonic acid and dimethylarsinic acid in cereals by hydride generation atomic fluorescence spectrometry

A fast, sensitive and simple non-chromatographic analytical method was developed for the speciation analysis of toxic arsenic species in cereal samples, namely rice and wheat semolina. An ultrasound-assisted extraction of the toxic arsenic species was performed with 1 mol L^− 1 H₃PO₄ and 0.1% (m/v) Triton XT-114. After extraction, As(III), As(V), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) concentrations were determined by hydride generation atomic fluorescence spectrometry using a series of proportional equations corresponding to four different experimental reduction conditions. The detection limits of the method were 1.3, 0.9, 1.5 and 0.6 ng g^− 1 for As(III), As(V), DMA and MMA, respectively, expressed in terms of sample dry weight. Recoveries were always greater than 90%, and no species interconversion occurred. The speciation analysis of a rice flour reference material certified for total arsenic led to coherent results, which were also in agreement with other speciation studies made on the same certified reference material.