Separation and sensitive determination of arsenic species (As/As) using the yeast-immobilized column and hydride generation in ICP–AES

Inorganic arsenic was separated using the yeast-immobilized column. Saccharomyces cerevisiae was covalently bonded unto the controlled pore glass, which showed selective preconcentration of As⁵⁺ over As³⁺. The effluent was directly connected to hydride generation (HG) to increase sensitivity. The optimum pH condition for the retainment of arsenic at the column was 7. As⁵⁺ and As³⁺ were completely separated in a few minutes with the flow rate of 1.5 ml min⁻¹. Three molars of nitric acid was adequate both for the elution of As⁵⁺ and hydride generation. The accuracy of the technique was tested with NIST SRMs. Quantitative analysis of arsenic species for herbicide, pesticide, and cigarette were performed, and the results showed good agreements with the suggested values. Yeast-immobilized column-HG-ICP showed a promising future for the arsenic speciation study.     

Solution Chemistry of Arsenic Anions in the Presence of Metal Cations

The interaction of arsenic(V) and arsenic(III) oxyanions with metal cations was investigated by potentiometry under temperature and ionic strength conditions approaching those prevailing in natural waters. The selection includes the major metal cations and some other ions of high environmental relevance. Ionic pairs [M(As^VO₄)]^?, [M(HAs^VO₄)] and [M(H₂As^IIIO₃)]⁺ formation is suggested for all +2 metal cations, based on the potentiometric results. These ion-pairs between arsenic anions and other metal cations are hardly ever mentioned or taken into account when arsenic speciation in natural waters is considered. These results provide the basis for studying arsenic speciation in natural aquatic systems, on which environmental fate, bioavailability and toxicity of the element depend. Some extrapolations to the conditions of the natural waters are presented as well as some insights into the adsorption process onto hydrous oxides.     

Coulometric stripping potentiometry for arsenic(III)

Calibration-free determination of As^III in the presence of As^V using coulometric stripping potentiometry is described. As^III, in the concentration range 0.01-2 mg/L, is quantitatively reduced to elemental arsenic and simultaneously dissolved in gold codeposited onto a glassy carbon substrate by electrolysis for 4 minutes at −0.50 V (vs. Ag/AgCl (0.01 MCl⁻)) in 12 μL samples containing 3 M hydrochloric acid and 10 mg/L gold(III). Selectivity between arsenic(III) and (V) is achieved by proper control of the deposition potential and by minimizing the gold(III) concentration and the time between addition of gold(III) and commencement of analysis.     

Speciation analysis of arsenic in prenatal and children's dietary supplements using microwave-enhanced extraction and ion chromatography–inductively coupled plasma mass spectrometry

A study was conducted to develop a microwave-enhanced extraction method for the determination of arsenic species in prenatal and children's dietary supplements prepared from plant materials. The method was optimized by evaluating the efficiency of various solutions previously used to extract arsenic from the types of plant materials used in the dietary supplement formulations. A multivitamin standard reference material (NIST SRM 3280) and a prenatal supplement sample were analyzed in the method optimization. The identified optimum conditions were 0.25 g of sample, 5 mL of 0.3 mol L⁻¹ orthophosphoric acid (H₃PO₄) and microwave heating at 90 °C for 30 min. The extracted arsenic was speciated by cation exchange ion chromatography–inductively coupled plasma mass spectrometry (IC–ICP-MS). The method detection limit (MDL) for the arsenic species was in the range 2–8 ng g⁻¹. Ten widely consumed prenatal and children's dietary supplements were analyzed using the optimized protocol. The supplements were found to have total arsenic in the concentration range 59–531 ng g⁻¹. The extraction procedure recovered 61–92% of the arsenic from the supplements. All the supplementary products were found to contain arsenite (As³⁺) and dimethylarsinic acid (DMA). Arsenate (As⁵⁺) was found in two of the supplements, and an unknown specie of arsenic was detected in one product. The results of the analysis were validated using mass balance by comparing the sum of the extracted and non-extracted arsenic with the total concentration of the element in the corresponding samples.     

Intake of different chemical species of dietary arsenic by the japanese,and their blood and urinary arsenic levels

We calculated the intake of each chemical species of dietary arsenic by typical Japanese, and determined urinary and blood levels of each chemical species of arsenic. The mean total arsenic intake by 35 volunteers was 195±235 (15.8-1039) μg As day^?1, composed of 76% trimethylated arsenic (TMA), 17.3% inorganic arsenic (As_i), 5.8% dimethylated arsenic (DMA), and 0.8% monomethylated arsenic (MA): the intake of TMA was the largest of all the measured species. Intake of As_i characteristically and invariably occurred in each meal. Of the intake of As_i, 45-75% was methylated in vivo to form MA and DMA, and excreted in these forms into urine. The mean measured urinary total arsenic level in 56 healthy volunteers was 129±92.0 μg As dm^?3, composed of 64.6% TMA, 26.7% DMA, 6.7% As_i and 2.2% MA. The mean blood total arsenic level in the 56 volunteers was 0.73±0.57 μg dl^?1, composed of 73% TMA, 14% DMA and 9.6% As_i. The urinary TMA levels proved to be significantly correlated with the whole-blood TMA levels (r = 0.376; P<0.01).     

Determination of the Interaction of Arsenic and Human Serum Albumin by Online Microdialysis Coupled to LC with Hydride Generation Atomic Fluorescence Spectroscopy

Study on the stoichiometry and affinity of the arsenicals bound to HSA is an important step toward a better understanding of arsenic toxic effects. After incubation of As^III or As^V with HSA at the physiological conditions (pH 7.43 and 37 °C), the free arsenicals and arsenic-HSA complexes were separated and detected by the combined techniques of microdialysis and liquid chromatography with hydride generation atomic fluorescence spectroscopy (MD–LC–HGAFS). The decrease of As^III peak response rather than As^V indicated that HSA reacted with As^III but not As^V. The binding plots indicated that the binding between HSA and As^III was in Scatchard pattern when the concentration ratios of As^III to HSA were ≤1:1. The strong binding sites (n ₁) were 1.6 and the stability constant (K ₁) was 1.54 × 10⁶ M^?1. When the concentration ratios of As^III to HSA were >1:1, the binding was in Plasvento pattern with the stability constant K ₂ ? 0 and no specific binding of As^III with HSA. On the contrary, As^V did not show binding with HSA. The results showed that As^III reacted with HSA more readily than As^V, which provides a chemical basis for arsenic toxicity.     

Ethylation of methylarsenic(III) compounds by sodium tetraethylborate

The compounds MeAsBr₂ and Me₂AsBr at concentrations of (1–5) × 10^?3 M in acetone solution are ethylated in high yield by NaBEt₄ to MeEt₂As and Me₂EtAs, as shown by ¹H NMR spectroscopy. The extents of ethylation of MeAs²⁺ and Me₂As⁺ (expressed as ions, by convention) in aqueous acid solutions [at concentrations of (5–20) × 10^?6 M ] were investigated using cold trap/AA and GC AA procedures. The species Me₂As⁺ was ethylated (to give Me₂EtAs) in good yield (88%); in contrast, MeAs²⁺ produced the volatile trialkylarsine, MeEt₂As, in poor yield (30%). No volatile trialkylarsine could be obtained on treating inorganic arsenic(III) (As³⁺) solutions with NaBEt₄.     

Determination of the Interaction of Arsenic and Human Serum Albumin by Online Microdialysis Coupled to LC with Hydride Generation Atomic Fluorescence Spectroscopy

Study on the stoichiometry and affinity of the arsenicals bound to HSA is an important step toward a better understanding of arsenic toxic effects. After incubation of As^III or As^V with HSA at the physiological conditions (pH 7.43 and 37 °C), the free arsenicals and arsenic-HSA complexes were separated and detected by the combined techniques of microdialysis and liquid chromatography with hydride generation atomic fluorescence spectroscopy (MD–LC–HGAFS). The decrease of As^III peak response rather than As^V indicated that HSA reacted with As^III but not As^V. The binding plots indicated that the binding between HSA and As^III was in Scatchard pattern when the concentration ratios of As^III to HSA were ≤1:1. The strong binding sites (n ₁) were 1.6 and the stability constant (K ₁) was 1.54 × 10⁶ M⁻¹. When the concentration ratios of As^III to HSA were >1:1, the binding was in Plasvento pattern with the stability constant K ₂ ≅ 0 and no specific binding of As^III with HSA. On the contrary, As^V did not show binding with HSA. The results showed that As^III reacted with HSA more readily than As^V, which provides a chemical basis for arsenic toxicity.

     

Application de la SAA électrothermique a Panalyse des matrices complexes: cas de l'arsenic dans les végétaux

This work shows the possibilities and the analytical limitations of ETA-SAA for arsenic determination in plants. Wet oxidation of these media is quantitative, but the direct determination of arsenic is strongly interferred with the presence of sulphuric acid and, principally, phosphorus, which is contained in plant matrix. In this case, only arsenic concentrations around 100 ng ml^?1 in solution (5 μg g^?1 in dry matter) can be directly determined.Because lower concentrations must be determined in unpolluted samples, two extraction procedures have been developed, both based on a preliminary reduction of As⁵⁺ to As³⁺ and a further extraction in toluene. NH₄I turns out as a better reducing agent than KI.In routine analysis, arsenic concentrations in the vicinity of 20ng g^?1 in dry matter can be easily determined under the adopted conditions.     

Speciation of arsenic in ground water samples: A comparative study of CE-UV, HG-AAS and LC-ICP-MS

The performance of capillary electrophoresis-ultraviolet detector (CE-UV), hydride generation-atomic absorption spectrometry (HG-AAS) and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) have been compared for the speciation of arsenic (As) in groundwater samples. Two inorganic As species, arsenite (As^III), arsenate (As^V) and one organo species dimethyl arsenic acid (DMA) were mainly considered for this study as these are known to be predominant in water. Under optimal analytical conditions, limits of detection (LD) ranging from 0.10 (As^III, AsT) to 0.19 (DMA) μg/l for HG-AAS, 100 (As^III, DMA) to 500 (As^V) μg/l for CE-UV and 0.1 (DMA, MMA) to 0.2 (As^III, As^V) μg/l for LC-ICP-MS, allowed the determination of the above three species present in these samples. Results obtained by all the three methods are well correlated (r² = 0.996*** for total As) with the precision of <5% R.S.D. except CE-UV. The effect of interfering ions (e.g. Fe²⁺, Fe³⁺, SO₄²⁻ and Cl⁻) commonly found in ground water on separation and estimation of As species were studied and corrected for. Spike recovery was tested and found to be 80-110% at 0.5 μg/l As standard except CE-UV where only 50% of the analyte was recovered. Comparison of these results shows that LC-ICP-MS is the best choice for routine analysis of As species in ground water samples.     

Speciation of arsenic trioxide metabolites in blood cells and plasma of a patient with acute promyelocytic leukemia

Arsenic trioxide (As₂O₃) has been widely accepted as the second-best choice for the treatment of relapsed and refractory acute promyelocytic leukemia (APL) patients. However, a few studies have been conducted on a detailed speciation of As₂O₃ metabolites in blood samples of patients. To clarify the speciation of arsenic, the blood samples were collected at various time points from a patient with APL after remission induction therapy and during consolidation therapy. The total amounts of arsenic in blood cells and plasma, and the plasma concentrations of inorganic arsenic and methylated metabolites were determined by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography/ICP-MS, respectively. The total amounts of arsenic in the blood cells were 4–10 times higher than those in plasma. Among all arsenic metabolites, the pentavalent arsenate (As^V) in plasma was more readily eliminated. During the drug-withdrawal period, the initial plasma concentrations of trivalent arsenic (As^III) declined more rapidly than those of methylarsonic acid and dimethlyarsinic acid, which are known as the major methylated metabolites of As^III. On the other hand, during the consecutive administration in the consolidation therapy period, the plasma concentrations of total arsenic and arsenic metabolites increased with time. In conclusion, these results may support the idea that methylated metabolites of As₂O₃ contribute to the efficacy of arsenic in APL patients. These results also suggest that detailed studies on the pharmacokinetics as well as the pharmacodynamics of As₂O₃ in the blood cells from APL patients should be carried out to provide an effective treatment protocol. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Presented at the 4th International Conference on Trace Element Speciation in Biomedical, Nutritional and Environmental Sciences, 25–29 May 2008, Munich-Neuherberg, Germany.     

Stability of arsenic peptides in plant extracts: off-line versus on-line parallel elemental and molecular mass spectrometric detection for liquid chromatographic separation

The instability of metal and metalloid complexes during analytical processes has always been an issue of an uncertainty regarding their speciation in plant extracts. Two different speciation protocols were compared regarding the analysis of arsenic phytochelatin (As^IIIPC) complexes in fresh plant material. As the final step for separation/detection both methods used RP-HPLC simultaneously coupled to ICP-MS and ES-MS. However, one method was the often used off-line approach using two-dimensional separation, i.e. a pre-cleaning step using size-exclusion chromatography with subsequent fraction collection and freeze-drying prior to the analysis using RP-HPLC–ICP-MS and/or ES-MS. This approach revealed that less than 2% of the total arsenic was bound to peptides such as phytochelatins in the root extract of an arsenate exposed Thunbergia alata, whereas the direct on-line method showed that 83% of arsenic was bound to peptides, mainly as As^IIIPC₃ and (GS)As^IIIPC₂. Key analytical factors were identified which destabilise the As^IIIPCs. The low pH of the mobile phase (0.1% formic acid) using RP-HPLC–ICP-MS/ES-MS stabilises the arsenic peptide complexes in the plant extract as well as the free peptide concentration, as shown by the kinetic disintegration study of the model compound As^III(GS)₃ at pH 2.2 and 3.8. But only short half-lives of only a few hours were determined for the arsenic glutathione complex. Although As^IIIPC₃ showed a ten times higher half-life (23 h) in a plant extract, the pre-cleaning step with subsequent fractionation in a mobile phase of pH 5.6 contributes to the destabilisation of the arsenic peptides in the off-line method. Furthermore, it was found that during a freeze-drying process more than 90% of an As^IIIPC₃ complex and smaller free peptides such as PC₂ and PC₃ can be lost. Although the two-dimensional off-line method has been used successfully for other metal complexes, it is concluded here that the fractionation and the subsequent freeze-drying were responsible for the loss of arsenic phytochelatin complexes during the analysis. Hence, the on-line HPLC–ICP-MS/ES-MS is the preferred method for such unstable peptide complexes. Since freeze-drying has been found to be undesirable for sample storage other methods for sample handling needed to be investigated. Hence, the storage of the fresh plant at low temperature was tested. We can report for the first time a storage method which successfully conserves the integrity of the labile arsenic phytochelatin complexes: quantitative recovery of As^IIIPC₃ in a formic acid extract of a Thunbergia alata exposed for 24 h to 1 mg As^v L⁻¹ was found when the fresh plant was stored for 21 days at 193 K. Figure On-line HPLC–ICP-MS/ES-MS (bottom) is the preferred method for MS determination of unstable arsenic peptide complexes in plant extracts, since this avoids fractionation and subsequent freeze-drying that are responsible for loss of arsenic phytochelatin complexes in the 2D off-line method (top) Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Estimation of palladium

Summary In presence of tartaric acid and ammonium chloride, quinaldinic acid quantitively precipitates palladium from a hot solution at a p_H range 3 to 7 whereas other ions such as arsenic (As³⁺ and As⁵⁺), mercury (Hg²⁺), cadmium, bismuth, antimony, iron, chromium, aluminium, beryllium, thorium, cerium (Ce³⁺), titanium, zirconium, uranium (UO₂ ²⁺), vanadate, molybdate, tungstate, cobalt, nickel, manganese, magnesium, calcium, barium and strontium remain in solution. The palladium complex is quite insoluble in hot water and can be dried at any temperature up to a maximum of 353° C when it decomposes.     

Simultaneous determination of mercury and arsenic by anodic stripping voltammetry

An electrochemical method for the simultaneous determinations of Hg^II concentration and total As^III and As^V concentration has been developed. The method does not require the additional preliminary step of the chemical reduction of As^V to As^III, or oxidation of As^III to As^V before stripping analysis takes place. Also, the method for the simultaneous determination of Hg^II concentration and As^III concentration is described. Measurements were performed in 0.1 M HCl using a gold-plated graphite electrode as sensor. Detection limits for both methods are below 0.4 ppb. Relative standard deviation did not exceed 15%. The possible interference by other trace metals was investigated. Analyses of natural water and industrial solutions were made using proposed methods and AAS. The t-test demonstrates that there was no significant difference between the results obtained with these methods. Proposed methods decrease the time of analysis because concentrations of the Hg^II and arsenic ions were measured simultaneously. Also, the removal of the additional step of chemical reduction of As^V to As^III or oxidation of As^III to As^V decreases analysis time, and also reduces the chance of contamination due to the use of additional reagents.     

Samarium Polyarsenides Derived from Nanoscale Arsenic

Zintl phases of arsenic and molecular compounds containing Zintl‐type polyarsenide ions are of fundamental interest in basic and applied sciences. Unfortunately, the most obvious and reactive arsenic source for the preparation of defined molecular polyarsenide compounds, yellow arsenic As₄, is very inconvenient to prepare and neither storable in pure form nor easy to handle. Herein, we present the synthesis and reactivity of elemental As⁰ nanoparticles (As⁰_Nano, d=7.2±1.8 nm), which were successfully utilized as a reactive arsenic source in reductive f‐element chemistry. Starting from [Cp*₂Sm] (Cp*=η⁵‐C₅Me₅), the samarium polyarsenide complexes [(Cp*₂Sm)₂(μ‐η²:η²‐As₂)] and [(Cp*₂Sm)₄As₈] were obtained from As⁰_nano, thereby generating the largest molecular polyarsenide of the f‐elements and circumventing the use of As₄ in preparative chemistry.     

A feasibility study on oxidation state of arsenic in cut tobacco,mainstream cigarette smoke and cigarette ash by X-ray absorption spectroscopy

This work describes the application of synchrotron-based X-ray Absorption Near-Edge Structure spectroscopy to study the oxidation state of arsenic in cigarette mainstream smoke, cut tobacco and cigarette ash. The level of arsenic in the total particulate matter of the smoke is approximately 1 ppm for the standard research reference cigarette 2R4F and its replacement 3R4F. Smoke particulate samples collected by a conventional glass-fiber membrane (commercially known as Cambridge filter pad) and a jet-impaction method were analyzed and compared. In addition smoke particulate samples were aged either at ambient temperature or at 195 K. X-ray Absorption Near-Edge Structure spectroscopy results revealed that the cut tobacco powder and cigarette ash contained almost exclusively As^V. The smoke particulate samples however contained a mixture of As^III and As^V. The As^V in the smoke particulate was reduced to As^III upon aging. Stabilizing the smoke particulate matter at 195 K by solid CO₂ slowed down this aging reaction and revealed a higher percentage of As^V. This behavior is consistent with the redox properties of the arsenic species and the smoke particulate matrix.     

Arsenic speciation in clinical samples: urine analysis using fast micro-liquid chromatography ICP-MS

Arsenic speciation is a subject that is developing all the time both from improvements in analytical techniques and from increases in toxicological understanding. Despite speciation methods being widely developed, arsenic speciation is not routinely offered as an analysis in clinical laboratory. The work in this paper describes a simple routine method for arsenic speciation that could be easily implemented in clinical laboratories. The method described, a new, fast analytical method for arsenic speciation, is reported using micro-liquid chromatography hyphenated to an inductively coupled plasma mass spectrometer (μLC-ICP-MS). The method uses a low-pressure delivery six-port valve with a 5 cm anion exchange column, which allows a fully resolved separation of five arsenic species (arsenobetaine [AB], arsenite [As³⁺], arsenate [As⁵⁺], mono-methylarsonic acid [MMA⁵⁺] and dimethylarsinic acid [DMA⁵⁺]) in urine in just 6 min. This fast analytical method offers an arsenic speciation method that is feasible for a laboratory that does not have the capability for a dedicated arsenic speciation LC-ICP-MS instrument. The micro-LC system is small, easy to install and is fully integrated with the ICP-MS software. The results reported here are from urine samples from 65 workers in a semiconductor work providing a sample for their routine biological monitoring to assess workplace exposure. Control samples from 20 unexposed people were also determined. Results show that the semiconductor workers exhibit very low levels of arsenic in their urine samples, similar to the levels in the controls, and thus are not significantly exposed to arsenic. Care must be taken when interpreting urinary arsenic species results because it is not always possible to differentiate between dietary and other external sources of exposure.     

Interference of arsenic trioxide on magnesium dependent polymerization of microtubule proteins

Prevention of microtubule polymerization is considered as one of the promising approaches towards inhibition of cell proliferation, especially in treatment of malignancies. Arsenic trioxide, As₂O₃, is being successfully used in the treatment of human lymphoma, while the mechanism of its therapeutic function is still under investigation. Experiments were designed to determine if indeed As₂O₃ interferes with polymerization of nanotube microtubule. Microtubules were extracted from sheep brain and their interaction with arsenic trioxide was examined by spectrometery. Electrical conductometry of 2 mM MgSO₄ solution containing various concentrations of As₂O₃ was studied in order to determine their possible interaction. Transmission electron microscopy was used to show microtubule structure in the presence of arsenic trioxide. Fluorometric characteristics of tubulin dimer were examined in presence of varying concentrations of arsenic trioxide. It is concluded that arsenic trioxide interacts with Mg²⁺ ion around GTPase site of β-tubulin, resulting enhancement of depolymerization of the microtubule polymer.     

Enzyme-assisted extraction and liquid chromatography mass spectrometry for the determination of arsenic species in chicken meat

Chicken is the most consumed meat in North America. Concentrations of arsenic in chicken range from μg kg⁻¹ to mg kg⁻¹. However, little is known about the speciation of arsenic in chicken meat. The objective of this research was to develop a method enabling determination of arsenic species in chicken breast muscle. We report here enzyme-enhanced extraction of arsenic species from chicken meat, separation using anion exchange chromatography (HPLC), and simultaneous detection with both inductively coupled plasma mass spectrometry (ICPMS) and electrospray ionization tandem mass spectrometry (ESIMS). We compared the extraction of arsenic species using several proteolytic enzymes: bromelain, papain, pepsin, proteinase K, and trypsin. With the use of papain-assisted extraction, 10 arsenic species were extracted and detected, as compared to 8 detectable arsenic species in the water/methanol extract. The overall extraction efficiency was also improved using a combination of ultrasonication and papain digestion, as compared to the conventional water/methanol extraction. Detection limits were in the range of 1.0–1.8 μg arsenic per kg chicken breast meat (dry weight) for seven arsenic species: arsenobetaine (AsB), inorganic arsenite (As^III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), inorganic arsenate (As^V), 3-nitro-4-hydroxyphenylarsonic acid (Roxarsone), and N-acetyl-4-hydroxy-m-arsanilic acid (NAHAA). Analysis of breast meat samples from six chickens receiving feed containing Roxarsone showed the presence of (mean ± standard deviation μg kg⁻¹) AsB (107 ± 4), As^III (113 ± 7), As^V (7 ± 2), MMA (51 ± 5), DMA (64 ± 6), Roxarsone (18 ± 1), and four unidentified arsenic species (approximate concentration 1–10 μg kg⁻¹).     

Arsenic speciation: HPLC followed by ICP-MS or INAA

Sensitivities for the measurement of four arsenic species, As^III, As^V, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), in environmental waters and rice extracts by a new neutron activation analysis (NAA) method using pre-separation of the species by liquid chromatography were determined. A manual fraction collection was used to isolate the species, followed by instrumental neutron activation analysis procedures. The sensitivities determined for arsenic species in the samples varied from 1.21 to 1.47 ng per vial or about 30 μg·L⁻¹ in sample solutions which translates to about 900 ng arsenic per gram of rice for our HPLC-NAA experiments.