Speciation Of Arsenic Compounds Research Articles

Desorption electrospray ionization mass spectrometry (DESI-MS) applied to the speciation of arsenic compounds from fern leaves

The different chemical forms of arsenic compounds, including inorganic and organic species, present distinct environmental impacts and toxicities. Desorption electrospray ionization mass spectrometry (DESI-MS) is an excellent technique for in situ analysis, as it operates under atmospheric pressure and room temperature and is conducted with no/minimal sample pretreatment. Aimed at expanding its scope, DESI-MS is applied herein for the quick and reliable detection of inorganic (arsenate--As(V): AsO4(3-) and arsenite--As(III): AsO2(-)) and organic (dimethylarsinic acid--DMA: (CH3)2AsO(OH) and disodium methyl arsonate hexahydrate: CH3AsO3·2Na·6H2O) arsenic compounds in fern leaves. Operational conditions of DESI-MS were optimized with DMA standard deposited on paper surfaces to improve ionization efficiency and detection limits. Mass spectra data for all arsenic species were acquired in both the positive and negative ion modes. The positive ion mode was shown to be useful in detecting both the organic and inorganic arsenic compounds. The negative ion mode was shown only to be useful in detecting As(V) species. Moreover, MS/MS spectra were recorded to confirm the identity of each arsenic compound by the characteristic fragmentation profiles. Optimized conditions of DESI-MS were applied to the analysis of fern leaves. LC-ICP-MS was employed to confirm the results obtained by DESI-MS and to quantify the arsenic species in fern leaves. The results confirmed the applicability of DESI-MS in detecting arsenic compounds in complex matrices.

The use of L-ascorbic acid in speciation of arsenic compounds in drinking water

Arsenic speciation, besides total arsenic content determination, is very important in analysis of water, foodstuffs, and environmental samples, because of varying degrees of toxicity of different species. For such purpose hydride generation atomic absorption spectrometry can be used based on the generation of certain types of hydride, depending on the pH value and pretreatment in different reaction media. In this study, we have investigated the effect of L-ascorbic acid as the reaction medium as well as the pre-reducing agent in speciation of arsenic by hydride generation-atomic absorption spectrometry in order to determine monomethyl arsonic acid (MMA) in the presence of inorganic forms of arsenic.

Preparation and certification of arsenobetaine reference material NMIJ CRM 7901-a

An arsenobetaine [(CH(3))(3)As(+)CH(2)COO(-)] solution reference material, NMIJ CRM 7901-a, intended for use in the speciation of arsenic compounds, was developed and certified by the National Metrology Institute of Japan (NMIJ), part of the National Institute of Advanced Industrial Science and Technology (AIST). The high-purity arsenobetaine powder was synthesized from trimethylarsine [(CH(3))(3)As], and it was dissolved in water in order to prepare 20 mg kg(-1) of arsenobetaine standard solution. The solution was bottled in 500 bottles (each containing 10 ml). Certification of the CRM for arsenobetaine was conducted by NMIJ. The concentration of As was determined by four independent analytical techniques (ICP-MS, ICP-OES, GFAAS and LC-ICP-MS), and each result was converted to the arsenobetaine concentration by applying an appropriate factor. The arsenobetaine concentration in the CRM was thus certified.

Speciation of Arsenic Compounds in Urine from Occupationally Unexposed and Exposed Persons in the U.K. Using a Routine LC-ICP-MS Method

This paper describes a routine, robust, and reproducible liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS) speciation method for five arsenic compounds [arsenobetaine (AB), arsenite, arsenate, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA)] in urine. Concentrations of these arsenic species in urine samples are reported in two sets of non-occupationally exposed controls with one set having consumed fish within 24 h (n = 31) and the other not having consumed fish for 48 h (n = 34). Arsenic species in urine samples from workers in both the timber treatment industry (n = 49) and semiconductor industry (n = 46) are also reported. The arsenic content in all of the samples was also determined using hydride-generation coupled with ICP-MS. The results show that urine samples from people not occupationally exposed to arsenic contain low levels of DMA, MMA, and AB and that only urine from smokers contained any inorganic arsenic. Consumption of seafood was seen to significantly increase the levels of AB and DMA in the unexposed persons. Urine samples from the semiconductor workers exhibited significantly higher levels of arsenite, arsenate, and DMA than the unexposed samples. The urine samples from timber treatment workers exhibited significantly higher levels of four arsenic species (not AB) than those observed in both the control groups and the semi-conductor workers.

Understanding arsenic metabolism through spectroscopic determination of arsenic in human urine

In this review we discuss a range of spectroscopic techniques that are currently used for analysis of arsenic in human urine for understanding arsenic metabolism and toxicity, especially in relation to genetics/ethnicity, ingestion studies and exposure to arsenic through drinking water and diet. Spectroscopic techniques used for analysis of arsenic in human urine include inductively coupled plasma mass spectrometry (ICP‐MS), hydride generation atomic absorption spectrometry (HG‐AAS), hydride generation atomic fluorescence spectrometry (HG‐AFS), graphite furnace atomic absorption spectrometry (GF‐AAS) and liquid chromatography mass spectrometry (LC‐MS). Advantages and disadvantages of each of these techniques are highlighted in relation to analysis of total arsenic and speciation of arsenic compounds in human urine which would be of particular benefit to those new to the field of arsenic speciation of urine samples. The review summarises our current understanding of arsenic metabolism through the analysis of urine samples and provides a list of arsenic species that have been identified in urine samples. This is done by focusing on recent published reports on arsenic metabolism and toxicity in relation to most investigated issues, i.e. genetics/ethnicity, ingestion and exposure.

Speciation of arsenic compounds in fish and oyster tissues by capillary electrophoresis‐inductively coupled plasma‐mass spectrometry

A capillary electrophoresis-inductively coupled plasma-mass spectrometric (CE-ICP-MS) method for the speciation of six arsenic compounds, namely arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine is described. The separation has been achieved on a 70 cm length x 75 microm ID fused-silica capillary. The electrophoretic buffer used was 15 mM Tris (pH 9.0) containing 15 mM sodium dodecyl sulfate (SDS), while the applied voltage was set at +22 kV. The arsenic species in biological tissues were extracted into 80% v/v methanol-water mixture, put in a closed centrifuge tube and kept in a water bath, using microwaves at 80 degrees C for 3 min. The extraction efficiencies of individual arsenic species added to the sample at 0.5 microg As/g level were between 96% and 107%, except for As(III), for which it was 89% and 77% for oyster and fish samples, respectively. The detection limits of the species studied were in the range 0.3-0.5 ng As/mL. The procedure has been applied for the speciation analysis of two reference materials, namely dogfish muscle tissue (NRCC DORM-2) and oyster tissue (NIST SRM 1566a), and two real-world samples.

Distribution of elements binding to molecules with different molecular weights in aqueous extract of Antarctic krill by size-exclusion chromatography coupled with inductively coupled plasma mass spectrometry

The distribution of silver, arsenic, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead, selenium and zinc binding to species with different molecular weight in aqueous extract of krill was studied by on-line size-exclusion chromatography (SEC)/inductively coupled plasma mass spectrometry (ICP-MS). The extract was fractionated in three fractions with different molecular weight (MW) ranges (>20,000 relative molecular mass (rel. mol. mass), 2000–20,000 rel. mol. mass and <2000 rel. mol. mass), which were further analyzed by SEC with columns having different optimum fractionation ranges in order to obtain more detailed information about the MW distribution of the elements. Various distribution profiles for the target elements among different MW ranges were observed. The results obtained indicated that manganese, zinc, silver, cadmium and lead species were mostly distributed in the higher MW range (>20,000 rel. mol. mass). In the case of chromium, iron, cobalt, arsenic and selenium, most of them bind to species with lower MW (<2000 rel. mol. mass). Only copper and nickel species was predominantly present in middle MW range (2000–20,000 rel. mol. mass). Further speciation of arsenic compounds in the small MW fraction was carried out with anion exchange chromatography (AEC) coupled with ICP-MS. The results showed that the dominant arsenic species in this fraction is As(III) (63% of extractable arsenic), while As(V) (13%) and two unknown arsenic species (19% and 5%, respectively) are present in lower amounts.

Speciation of arsenic compounds in human urine by HPLC/hexapole collision cell ICP-MS

The analytical conditions for the simultaneous determination of arsenic(As) compounds in human urine were examined using high-performance liquid chromatography (HPLC) with an ion-exchange column combined with a hexapole collision cell inductively coupled plasma mass spectrometer. The addition of 0.1 mM EDTA to the mobile phase of HPLC (a mixture of 10 mM NH4NO3 and 0.05% HNO3, pH 3.1) was necessary for good reproducibility of the peaks. The five As species {As(V), monomethylarsonic (MMA), dimethylarsinic (DMA), As(III), and arsenobetain (AB)} were separated within 14 min, however, arsenocholine(AC), trimethylarsine oxide (TMAO) and tetramethylarsonium (TeMA) were not individually separated but eluted together at about 40 min of retention time. This method was applied to urine samples from 8 male Japanese. Although As(V), MMA, DMA, and AB were detected in all urine samples, the relative amounts of these compounds were different depending on the person. The order of concentrations of arsenic compounds in urine from 4 person were AB>DMA>MMA>As(V), but those in the other samples were AB = DMA or AB<DMA, suggesting the individual difference in the eating habits of sea foods.

Ultra-Sensitive Elemental Analysis Using Plasmas. Speciation of Arsenic Compounds in Biological Samples by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry System.

Arsenic originating from the lithosphere is widely distributed in the environment. Many arsenicals in the environment are in organic and methylated species. These arsenic compounds in drinking water or food products of marine origin are absorbed in human digestive tracts, metabolized in the human body, and excreted viatheurine. Because arsenic shows varying biological a spects depending on its chemical species, the biological characteristics of arsenic must be determined. It is thought that some metabolic pathways for arsenic and some arsenic circulation exist in aqueous ecosystems. In this paper, the current status of the speciation analysis of arsenic by HPLC/ICP-MS (High Performance Liquid Chromatography-Inductively Coupled Plasma Mass spectrometry) in environmental and biological samples is summarized using recent data.

Speciation of arsenic compounds by ion-exchange HPLC-ICP-MS with different nebulizers

For the purpose of environmental biomonitoring analytical procedures for the sensitive and efficient speciation of the arsenic species As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), tetramethylarsonium ion (Tetra), arsenobetaine and arsenocholine have been optimized. The influence of different nebulizers, in particular cross flow and hydraulic high pressure, on the analytical performance and quality parameters such as limit of detection and reproducibility was investigated. LODs in the range of a few pg or even below were achieved. The HPLC-ICP-MS procedures were validated by using reference materials.

Speciation of arsenic compounds in urine by LC-ICP MS

The method validation for the speciation of five arsenic species in urine samples by liquid chromatography hyphenated to inductively coupled plasma mass spectrometry is described. Arsenic species which are identified and quantified in urine samples are the anions of arsenic(III), arsenic(V), monomethylarsonic acid and dimethylarsinic acid, and the cationic arsenobetaine. Detection limits were obtained in the range 0.3–0.4 μg As l−1 while the repeatability was in the range 3–4% (RSD) for concentrations above five times the detection limit. Urine samples could be analysed directly after a ten-fold dilution step. Arsenic compound concentrations were determined in urine samples from a volunteer who consumed a portion of tuna fish high in arsenobetaine. It was found that arsenobetaine was excreted rapidly via the urine with maximum concentrations after 12 h. Nearly complete arsenobetaine excretion was reached after 48 h. Background levels of arsenic compounds were determined in 61 urine samples from non-exposed inhabitants of The Netherlands. © 1998 John Wiley & Sons, Ltd.

Speciation of arsenic compounds by coupling high-performance liquid chromatography with inductively coupled plasma mass spectrometry

There is considerable evidence that toxicity and physiological behavior of arsenic depends on its chemical forms. Arsenic speciation became therefore the subject of increasing interest in recent years. A sensitive method for the determination of arsenic species has been developed. The proposed procedure involves the use of high-performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Six arsenic compounds were separated by anion-exchange chromatography with isocratic elution using tartaric acid as mobile phase with an elution order: arsenocholine, arsenobetaine, dimethylarsinic acid, methylarsonic acid, arsenous acid and arsenic acid. The chromatographic parameters affecting the separation of the arsenic species were optimized. Analytical characterization of the method has been realized with standard solutions. The detection limits for six arsenic compounds were from 0.04 to 0.6 μg/L as As element. The repeatability (expressed by R.S.D) was better than 7% for all investigated compounds. The HPLC-ICP-MS system was successfully applied to the determination of arsenic compounds in environmental and biological samples in μg/L level.

Speciation of arsenic compounds by using ion-pair chromatography with atomic spectrometry and mass spectrometry detection

Chromatography separation of arsenic compounds is important for chemical speciation studies; yet a complete separation of several biologically and environmentally important arsenic compounds has been difficult to achieve on a single column. We report here baseline resolution for arsenate, arsenite, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, and tetramethylarsonium ion, by using mixed ion-pair reagents containing 10 mM hexanesulfonate and 1 mM tetraethylammonium hydroxide, as mobile phase. The complete separation of these anionic, cationic and neutral arsenic species on a reversed-phase C18 column took only 12 min. Inductively coupled plasma mass spectrometry, hydride generation atomic absorption spectrometry and atomic fluorescence spectrometry systems were used for element-specific detection. The speciation technique was successfully applied to studies of urinary excretion of arsenic compounds following one-time ingestion of shrimp. Arsenobetaine ingested from the consumption of shrimp was excreted into urine in its original form; and approximately 70% of the total arsenobetaine ingested was excreted into urine within 37 h after ingestion.

Speciation of Arsenic Compounds in Drinking Water by Capillary Electrophoresis with Hydrodynamically Modified Electroosmotic Flow Detected Through Hydride Generation Inductively Coupled Plasma Mass Spectrometry With a Membrane Gas–Liquid Separator

Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride species were detected with inductively coupled plasma mass spectrometry. The HG unit utilized a microporous PTFE tube as a gas–liquid separator. The injection mode for CE was electrokinetic in conjunction with the novel use of hydrodynamically modified electroosmotic flow (HMEOF). In HMEOF, the electroosmotic flow is modified by applying hydrodynamic pressure opposite to the direction of the electroosmotic flow. HMEOF provides the capability of injecting increased quantities of analyte by offsetting the electroosmotic flow, which limits conventional electrokinetic injection. In order to correct for imprecisions in the electrokinetic injection in matrices of different ionic strength, the use of a surrogate for the injection of arsenic species was investigated. Germanium was investigated because it forms a hydride and has a low natural occurrence. The separation also utilized HMEOF, which allowed for greater freedom in buffer choice. The detection limits in distilled, de-ionized water were 25, 6, 9 and 58 ppt for the four species listed above, respectively. The detection limit was calculated from 3.14 σ n-1 of seven replicate injections and represents the precision of measuring the ratio of the area of the arsenic peaks to the area of a germanium surrogate peak. Standard addition was used to determine arsenate in drinking water samples. Recoveries of arsenite and arsenate from drinking water samples are reported using germanium as a surrogate to correct for sampling bias of the electrokinetic injection.

Speciation of Arsenic Compounds in the Urine of Rats Orally Exposed to Dimethylarsinic Acid Ion Chromatography with ICP–MS as an Element‐Selective Detector

Speciation of Arsenic Compounds in the Urine of Rats Orally Exposed to Dimethylarsinic Acid Ion Chromatography with ICP–MS as an Element‐Selective Detector

Speciation of Arsenic Compounds in the Urine of Rats Orally Exposed to Dimethylarsinic Acid Ion Chromatography with ICP-MS as an Element-Selective Detector

A combined ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP-MS) system as an element-selective detector has been used for the determination of arsenic compounds. Seven arsenic compounds were separated by cation-exchange chromatography. Subsequently, the separated arsenic compounds were directly introduced into the ICP-MS and were detected at m/z=75. Detection limits for the seven arsenic compounds ranged from 0.8 to 3.8 μg AS/l. The IC-ICP-MS system was applied to the determination of arsenic compounds in the urine of dimethylarsinic acid (DMAA)-exposed rats. DMAA was the most abundant arsenic compound detected. Arsenous acid, monomethylarsonic acid and trimethylarsine oxide were also detected.

Speciation of arsenic compounds by ion chromatography with inductively coupled plasma mass spectrometry detection utilizing hydride generation with a membrane separator

Ion chromatography (IC) was used to speciate four of the environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid, and dimethylarsinic acid. Hydride generation (HG) was used to convert the species to their respective hydrides. These hydride species were detected with ICP-MS. The gas–liquid separator for the HG unit was based on microporous PTFE tubing. Two novel features which reduce noise are incorporated into the membrane-based HG unit: firstly, gas is added to the liquid stream prior to entering the membrane, and secondly, the flow of carrier gas through the gas–liquid separator forms a ‘feedback’ loop. Absolute detection limits based on 3.14σ from 7 replicates for the four arsenic species listed above were 0.6, 3.1, 1.1, and 0.7 pg, respectively. The overall IC–HG–ICP-MS system produced RSD values of 1–6% over 30 min and 2–6% over a week for the four compounds. Two saline reference materials, NASS-4 and SLEW-2 (National Research Council of Canada), were analysed to determine concentrations of the four arsenic species, and the sum of the arsenic concentration was compared with the certified total arsenic value for each of the reference materials.

Speciation of Arsenic Compounds Using High-Performance Liquid Chromatography at Elevated Temperature and Selective Hydride Generation Atomic Fluorescence Detection

Understanding arsenic toxicity and metabolism requires quantitation of individual arsenic species. However, it has been difficult to separate many biochemically and environmentally important arsenic species on a single chromatography column. We have studied the separation of 11 arsenic compounds by using ion pair chromatography at 30, 50, and 70 °C column temperatures. The use of elevated column temperature improved separation efficiency and dramatically reduced chromatographic retention time for arsenobetaine, arsenocholine, tetramethylarsonium, and arsenosugars. On-line microwave derivatization combined with hydride generation and atomic fluorescence spectrometry (HGAFS) was used for detection, which was able to differentiate more toxic from less toxic arsenic species. The speciation technique was successfully applied to a study of metabolism of arseno sugars present in commercial seaweed products. Two uncharacterized arsenic-containing metabolites were detected in urine samples collected 20−33 h after the consumption of the seaweed product. These metabolites did not form hydride without microwave digestion. Up to 90 ng/mL of dimethylarsinic acid was detected in the urine samples collected 25−35 h after the consumption of seaweed, compared to a background level of less than 15 ng/mL in urine samples collected before the ingestion of seaweed. The combined high-temperature ion pair chromatography with selective arsenic detection provided a rapid approach to monitoring metabolism of arsenic compounds.

Speciation of arsenic compounds in some marine organisms

Speciation of arsenic compounds in some marine algae, bivalves, and crustaceans was studied by using two techniques: (i) high-performance liquid chromatography with inductively coupled plasma mass spectrometry detection and (ii) hydride generation atomic adsorption spectrometry following microwave-assisted digestion. Arsenosugars were identified as the major arsenic compounds present in marine algae, whereas arsenobetaine was the dominant arsenic species present in crab and skimp. In contrast to most previous reports, which claimed arsenobetaine as the only major arsenic species present in marine bivalves, tits study revealed the presence of arsenosugars in addition to arsenobetaine in the bivalves

Determination of arsenic species by inductively coupled plasma mass spectrometry with ion chromatography

AbstractFive arsenic species, trimethylarsine oxide, dimethylarsenic acid, monomethylarsonic acid, arsenobetaine and sodium arsenite, in urine were analysed by inductively coupled plasma mass spectrometry with ion chromatography (IC ICP MS).Since the toxicities of different arsenic compounds are different, speciation of arsenic compounds is very important in the investigation of metabolisms. In this paper, we applied ion chromatography (IC) as a separation device and inductively coupled plasma mass spectrometry (ICP MS) as a detection device. For separation of the five arsenic compounds, an anion‐exchange column and, as mobile phase, tartaric acid were used. The eluent from the IC column was introduced directly into the nebulizer of the ICP MS and analysed at 75 amu. Detection limits were from 4 to 9 pg as arsenic.