University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Dimethylarsenic

  • IUPAC Name: dimethylarsenic
  • Molecular Formula: C2H7AsO2
  • CAS Registry Number: 83636-34-4
  • InChI: InChI=1S/C2H6As/c1-3-2/h1-2H3
  • InChI Key: ZYMCGHKVJXMQRR-UHFFFAOYSA-N

@ ChemSpider@ NIST@ PubChem

Citations 10

"Determination Of Arsenic Species In Seawater By Flow Injection Hydride Generation In Situ Collection Followed By Graphite Furnace Atomic Absorption Spectrometry - Stability Of As(III)"
Anal. Chim. Acta 2000 Volume 418, Issue 1 Pages 19-31
Jean Yves Cabon and Nolwenn Cabon

Abstract: Dissolved arsenic is present in seawater at the 1 µg L-1 level in various chemical forms: mainly, As(III) and As(V) inorganic arsenic, MMA, DMA, and eventually, unknown organic compounds. The concentrations of the minor arsenic species are well below the detection limit of graphite furnace atomic absorption spectrometry (GFAAS). Therefore, a pre-concentration/separation step is generally required before their determination. In this study, arsenic species were determined in seawater by flow injection hydride generation (FI-HG), collection within the graphite furnace, followed by atomic absorption spectrometry. This protocol permitted a pre-concentration factor of about 1000 lowering the detection limit of arsenic in seawater to about 1.5 ng L-1 for a 10 mi sample volume under optimized experimental conditions. Based on the different responses of arsenic species towards hydride generation, an experimental protocol for arsenic speciation was proposed. Total arsenic could be determined after a thermal or a UV irradiation treatment in an alkaline persulfate medium after the conversion of all arsenic species to inorganic As(V). Total hydride-reactive species (As(III), As(V), monomethylarsenic (MMA) and dimethylarsenic (DMA)) could be determined for high NaBH4 and HCl concentrations because a similar analytical response was obtained for these individual species. As(III) could be determined alone by performing hydride generation in seawater at a pH of about 7-8. Non-hydride-reactive arsenic species were determined by the difference between total arsenic and hydride-reactive species. According to this analytical protocol, arsenic species were determined in reference estuarine and coastal seawaters. Hydride-reactive arsenic species were the major compounds, probably mainly As(V); this study tended also to confirm the presence of non-hydride-reactive organic species in seawater (15%). We also showed that As(III) was not stable in acidified seawater and was also slowly converted to As(V) in a coastal surface seawater at its natural pH. These results indicated that time and preservation conditions could severely modify the speciation of arsenic in seawater, particularly for the preservation of As(III).
Sea Estuarine Spectrophotometry Speciation Preconcentration Reference material Optimization

"Application Of Sample Pre-oxidation Of Arsenite In Human Urine Prior To Speciation Via On-line Photo-oxidation With Membrane Hydride Generation And ICP-MS Detection"
Analyst 2000 Volume 125, Issue 6 Pages 1215-1220
Xinyi Wei, Carol A. Brockhoff-Schwegel and John T. Creed

Abstract: A pre-oxidation procedure which converts arsenite [As(III)] into arsenate [As(V)] was investigated in urinary arsenic speciation prior to on-line photo-oxidation hydride generation with ICP-MS detection. This sample pre-oxidation method eliminates As(III) and As(V) preservation concerns and simplifies the chromatographic separation. Four oxidants, Cl2, MnO2, H2O2 and I3-, were investigated. Chlorine (ClO-(aq)) and MnO2 selectively converted As(III) into As(V) in pure water samples, but the conversion was inefficient in the complex urine matrix. Oxidation of As(III) by H2O2 was least affected by the urine matrix, but the removal of excess H2O2 at pH 10 proved difficult. The most appropriate oxidant for the selective conversion of As(III) into As(V) with minimal interference from the urine matrix is I3- at pH 7. Unlike H2O2, excess oxidant can be easily removed by the addition of S2O32-. The I3- - S2O32- treatment on a fortified sample of reconstituted NIST SRM 2670 freeze dried urine indicated that arsenobetaine (AsB), dimethlyarsinic acid (DMA), monomethylarsonic acid (MMA) and As(V) were not chemically degraded with recoveries ranging from 95 to 102% for all arsenicals. Sample clean-up involved pH adjustment prior to C-18 filtration in order to achieve efficient As(III) conversion and quantitative recoveries of AsB and DMA. The concentrations determined in NIST SRM 2670 freeze dried urine were AsB 17.2±0.5, DMA 56±4 and MMA 10.3±0.3 with a combined total of 83±5 µg L-1 (±2s).
NIST 2670 Mass spectrometry Reference material Volatile generation Speciation

"A Shipboard Method For Arsenic Speciation Using Semi-automated Hydride Generation Atomic Fluorescence Spectroscopy"
Anal. Chim. Acta 2000 Volume 409, Issue 1-2 Pages 215-226
Alison M. Featherstone, Paul R. Boult, Barry V. O'Grady and Edward C. V. Butler

Abstract: The development of a semi-automated batch HG-AFS method for the shipboard determination of As(III), As(V), MMA and DMA is described. Procedures in the analytical sequence including addition of NaBH4 to samples, cooling and heating the U-trap used for pre-concentration and separation of the arsines, and logging the AFS output are automated. Overall control of the automated tasks into a logical analytical sequence is achieved using a commercially available data acquisition and control package, WORKBENCHMAC™. Further modifications required for the method to be adapted to shipboard use, including the use of a hydrogen generator, are also detailed. This method shows a number of advantages over a previously reported manual HG-AFS method including, shorter sample throughput time, increased precision and most significantly, ease of use under shipboard conditions. The semi-automated method was operated on the RSV Aurora Australis during a Southern Ocean voyage in March 1998. Arsenic measurements from a surface transect between 42°C and 55°S along 141°30E, are presented. Application of the method to more routine laboratory use is also discussed.
Sea Fluorescence Automation Speciation Remote instrument Preconcentration Volatile generation

"Development Of Analytical Systems For The Simultaneous Determination Of The Speciation Of Arsenic [As(III), Methylarsonic Acid, Dimethylarsinic Acid, As(V)] And Selenium [Se(IV), Se(VI)]"
Anal. Chim. Acta 2000 Volume 413, Issue 1-2 Pages 13-23
Ildikó Ipolyi and Péter Fodor

Abstract: The simultaneous determination of arsenic (As(III), MMAs, DMAs, As(V)) and selenium (Se(IV), Se(VI)) species has been carried out by three instrument combinations. High performance liquid chromatography (HPLC) is coupled with two independent atomic fluorescence spectrometers (AFS) supplied with boosted discharge hollow cathode lamp (BD HCL) by high efficiency sample introduction systems. The efficiency of ultrasonic nebulisation (USN), hydraulic high pressure nebulisation (HHPN) and hydride generation (HG) was compared. The separation of the six species in one system is achieved by gradient elution programs. The HPLC-HG-AFS system provides the best detection limits, but it is not suitable for the direct determination of Se(VI). The HPLC-HG-AFS system was applied for the measurement of arsenic contaminated natural ground water samples. Absolute detection limits of 1.0, 0.5, 1.0, 0.3 and 0.7 pg for Se(IV), As(III), DMAs, MMAs and As(V), respectively, were obtained for a 100 µl injection volume using the HPLC-HG-AFS system.
Ground Fluorescence HPLC Speciation Volatile generation Method comparison

"Online Cryogenic Trapping With Microwave Heating For The Determination And Speciation Of Arsenic By Flow Injection/hydride Generation/atomic Absorption Spectrometry"
Talanta 1998 Volume 45, Issue 3 Pages 531-542
J. L. Burguera*, M. Burguera, C. Rivas and P. Carrero

Abstract: An online flow injection-hydride generation/at. absorption spectrometry method was developed for the pre-concentration and selective determination of inorganic As (As(III) and As(V)) and its methylated species. The separation of the As species was performed by an automated pH-selective arsines generation technique, using Na tetrahydroborate(III) as reductant. Each arsine was cryogenically trapped in a PTFE coil, knotted and sealed inside another wider diameter tube, through which liquid N was suctioned by negative pressure. Then, based on their different b.ps., the arsine species were selectively liberated using a heating cycle of microwave radiation, followed by atomic absorption detection. A sample solution aliquot mixed with 1% citric acid was used for the determination of As(III) alone, while a 2nd sample aliquot mixed with 2 mol/L nitric acid was used for the quant. determination of total inorganic As, monomethylarsonic acid and dimethylarsinic acid. Based on 10 mL sample, the detection limits are 20-60 ng As/L, which are sufficiently low to detect the arsines-forming species in natural waters. These values are negative affected by the reagents purity and background noise due to flame flickering, but the sensitivity can substantially be improved by increasing sample size or running several consecutive reactions.
Environmental Spectrophotometry Cold trap Speciation Microwave

"Speciation Determination Of Arsenic In Urine By High-performance Liquid Chromatography-hydride Generation Atomic Absorption Spectrometry With Online Ultraviolet Photooxidation"
Analyst 1998 Volume 123, Issue 8 Pages 1703-1710
Dimiter L. Tsalev, Michael Sperling and Bernhard Welz

Abstract: A coupled system for arsenic speciation determination based on high-performance liquid chromatography (HPLC), online UV photooxidation and continuous-flow hydride generation atomic absorption spectrometry (HGAAS) was built from commercially available modules with minor modifications to the electronic interface, the software and the gas-liquid separator. The best results were obtained with strong anion-exchange columns, Hamilton PRP X-100 and Supelcosil SAX 1, and gradient elution with phosphate buffers containing KH2PO4-K2HPO4. The online UV photooxidation with alkaline peroxodisulfate, 4% (m/v) K2S2O8-1 mol L-1 NaOH, in a PTFE knotted reactor for 93 s ensures the transformation of inorganic As(III), monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium ion to arsenate. About 32-36 HPLC-UV-HGAAS runs could be performed within 8 h, with limits of detection between 2 and 6 µg L-1 As, depending on the species. The method was applied to the analysis of spot urine samples and certified urine reference materials (CRMs). Upon storage at 4°C, reconstituted CRMs are stable for at least 2 weeks with respect to both their total arsenic content and the individual species distribution.
Urine HPLC Spectrophotometry Spectrophotometry Photochemistry UV reactor Reference material Knotted reactor Volatile generation Speciation Phase separator

"Determination Of Six Arsenic Species By High Performance Liquid Chromatography-hydride Generation-atomic Absorption Spectrometry With Online Thermo-oxidation"
Fresenius J. Anal. Chem. 1993 Volume 346, Issue 6-9 Pages 643-647
M. A. López, M. M. Gómez, M. A. Palacios and C. Cámara Contact Information

Abstract: Anion-exchange HPLC has been coupled to online thermo-oxidation and hydride generation-atomic absorption spectrometry (HG-AAS) for the speciation of As(V), As(III), MMA, DMA, AsB and AsC. The thermoreactor consists of a loop of PTFE tubing dipped in a powdered-graphite oven heated to + 140°C. Samples and persulfate solution run together into the thermo-reactor. The thermo-oxidation conditions were optimized using a FIA system. The chromatographic and chemical parameters affecting hydride generation efficiency were optimized. The overlap of the As(III) and AsB peaks made it necessary to determine AsB as the difference between absorbance in the presence and in the absence of thermo-oxidation. The thermo-conversion efficiencies were above 96%. Recoveries were around 100% and detection limits below 1 ng. The proposed method is rapid, sensitive and precise (RSD about 5%), making it suitable for online determination in environmental samples.
Environmental HPLC Spectrophotometry Interface Heated reaction Volatile generation Optimization Speciation Volatile generation

"Development Of An Automated Technique For The Speciation Of Arsenic Using Flow Injection Hydride-generation Atomic Absorption Spectrometry (FI-HG-AAS)"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 1-2 Pages 44-48
T. R. Rüde and H. Puchelt

Abstract: Sample solution (0.5 ml) was injected into a HCl carrier stream (10 ml/min) which then merged with a reagent stream (6 ml/min) containing 37 mM KBH4 in 5 mM NaOH. The mixture passed through a stripping coil to a gas-liquid separator and the AsH3 was measured by AAS at 193.7 nm. With a carrier of 4 M HCl, only As(III) reacted. Using a carrier of 0.165 M HCl, containing 1 mg/l of KMnO4, As(III) was oxidized to As(V), and hence the sum of monomethylarsonic acid (I) and dimethylarsinic acid (II) was obtained. Using a carrier of 0.025 M HCl containing 1 mg/l of KMnO4, the sum of (I) and (II) was also obtained. The individual concentrations of (I) and (II) were calculated from their different sensitivities under the two sets of conditions. Using a carrier containing 0.85 mM tartaric acid and 1 mg/l of KMnO4, all four species were determined. Detection limits were 0.2-0.5 ng/ml.
Environmental Spectrophotometry Speciation Volatile generation Volatile generation

"Determination Of Inorganic Arsenic And Its Organic Metabolites In Urine By Flow Injection Hydride Generation Atomic Absorption Spectrometry"
Clin. Chem. 1993 Volume 39, Issue 8 Pages 1662-1667
CP Hanna, JF Tyson and S McIntosh

Abstract: Urine was applied to a 1 mL Bond-Elut cartridge with HNO3/ethanol (1:10). The eluate was heated to ~120°C with solid K2Cr2O7 and concentrated HNO3 until the volume was reduced to ~1 mL and then concentrated H2SO4 was added. After heating to ~250°C for 90 min, the mixture was cooled for 1 min before H2O2 was added and the mixture reheated. After cooling, the mixture was treated with KI in HCl before flow injection AAS with mixing with HCl and sodium borohydride in NaOH solution Recovery was 108, 112, 104 and 95% for As(III), As(V), monomethylarsenic and dimethylarsenic, respectively. The detection limits were 0.1-0.2 µg/l and the RSD were 2.3-3.5%. A method has been developed for the determination of inorganic arsenic [As(III) and As(V)] and its organic metabolites (monomethylarsenic and dimethylarsenic) in urine by flow injection hydride generation atomic absorption spectrometry. The nontoxic seafood-derived arsenobetaine and arsenocholine species were first separated by a solid-phase extraction procedure. The remaining sample was digested with a mixture of nitric and sulfuric acids and potassium dichromate, followed by attack with hydrogen peroxide. The resulting As(V) was reduced to As(III) with potassium iodide in hydrochloric acid before injection into the flow injection manifold. The percentage analytical recoveries (mean±95% confidence interval) of various arsenic species added to a urine specimen at 250 µg/L were 108±2, 112±11, 104±7, and 95±5 for As(III), As(V), monomethylarsenic, and dimethylarsenic, respectively. For the determination of arsenic in Standard Reference Material 2670 (toxic metals in human urine), results agreed with the certified value (480±100 µg/L). Analyses of samples for the Centre de Toxicologie du Quebec, containing seafood-derived species, demonstrated the viability of the separation procedure. Detection limits were between 0.1 and 0.2µg/L in the solution injected into the manifold, and precision at 10 µg/L was between 2% and 3% (CV). These preliminary results show that the method might be applicable to determinations of arsenic in a range of clinical urine specimens.
Urine NIST 2670 Marine Spectrophotometry Clinical analysis Volatile generation Reference material Speciation Volatile generation

"A Flow Injection-hydride Generation-atomic Absorption Spectrometry Technique For The Online Determination Of Arsenic Species After Ion-exchange Separation And Of Total Arsenic After Microwave-assisted Digestion In Urine Samples"
Quim. Anal. 1997 Volume 16, Issue 3 Pages 165-176
Burguera, J.L.;Burguera, M.;Rivas, C.

Abstract: An online flow injection system comprising a separation column coupled to a hydride generation atomic absorption spectrometry system has been developed for the separation and sequential determination of inorganic (As(III) and As(V)) and organic (monomethylarsonic acid and dimethylarsinic acid) in 2 mL of urine samples. The separation of the arsenic species was performed with a combined cation-anion exchange column (Dowex 50W-X8 and AG 1-X8). While As(III) was not retained by the column, the following eluents: 0.006 mol L-1 trichloroacetic acid, 0.2 mol L-1 trichloroacetic acid and 5 mol L-1 NH4OH were used to eluate monomethylarsonic acid, As(V) and dimethylarsinic acid, respectively. After a cycle of the previous determinations was completed, total arsenic was sequentially determined in 0.1-2.0 mL samples after microwave assisted acidic mineralization/oxidation in a parallel and online module of the system. The continuous hydride generation for the determination of the different arsenic species was carried out by mixing downstream the acidified effluents (or digest for total arsenic) with a 15 % w/v KI + 5 % w/v ascorbic acid prereducing solution and thereafter with a 1.0% w/v sodium tetrahydroborate(III) solution The detection limits were 0.3, 0.3, 0.3, 0.5 and 0.2 ng of arsenic for As(III), As(V), monomethylarsonic acid, dimethylarsinic acid and total arsenic, respectively. The precision (relative standard deviation, RSD) of the method obtained in ten replicate anal. of urine spiked with arsenic species varied from 0.3 to 0.7%. Recovery values of the arsenic species were in the range 96-102 %. This method is applicable to the accurate determination of the arsenic metabolites and total arsenic in the urine of unexposed and exposed subjects.
Urine Spectrophotometry Volatile generation Dowex Resin Column