Oxidation Of AsIII Research Articles

Simultaneous determination of mercury and arsenic by anodic stripping voltammetry

AbstractAn electrochemical method for the simultaneous determinations of HgII concentration and total AsIII and AsV concentration has been developed. The method does not require the additional preliminary step of the chemical reduction of AsV to AsIII, or oxidation of AsIII to AsV before stripping analysis takes place. Also, the method for the simultaneous determination of HgII concentration and AsIII 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 HgII and arsenic ions were measured simultaneously. Also, the removal of the additional step of chemical reduction of AsV to AsIII or oxidation of AsIII to AsV decreases analysis time, and also reduces the chance of contamination due to the use of additional reagents.

Ultrasonic nebulization and arsenic valence state considerations prior to determination via inductively coupled plasma mass spectrometry

An ultrasonic nebulizer (USN) was utilized as a sample introduction device for an inductively coupled plasma mass spectrometer in an attempt to increase the sensitivity for As. The USN produced a valence state response difference for As. The AsIII response was suppressed approximately 20% relative to an AsV standard. This valence state response difference produced by the USN was investigated by collecting aerosol fractions and analysing these fractions by ion chromatography–ICP-MS. The analysis of these fractions indicated that AsIII could be oxidized to AsV as the aerosol traverses the USN. The fraction collected from the condenser drain of the USN was found to contain a disproportionate amount of As. The pre-nebulization oxidation of AsIII to AsVvia digestion, treatment with H2O2, and treatment with sodium hypochlorite were all investigated in terms of removing the valence state response difference of As. The treatment with 1 mg l–1 sodium hypochlorite was found to eliminate the valence state response difference for As without the need for digestion.

Osmium(VIII) oxidation of arsenic(III) in aqueous sulphuric acid

The oxidation of AsIII by OsVIII or OsVI in aqueous H2SO4 follows the rate law: $$d[Os^{IV} ]/dt = k_a K_a [oxidant][As^{III} ]/(1 + K_a [As^{III} ]).$$ An oxidant−AsIII complex first forms (equilibrium constant Ka) followed by decomposition (rate constant ka) into products. The values of ka and Ka for the OsVIII−AsIII system were found to be 0.013±0.003 s−1 and 11.0±2.0 dm3 mol−1 respectively; in the OsVI−AsIII reaction, the values were 0.030±0.003 s−1 and 22.0±4.0 dm3 mol−1.

ChemInform Abstract: KINETICS AND MECHANISM OF THE SILVER(I)‐CATALYZED OXIDATIONS OF ARSENIC(III) AND ANTIMONY(III) WITH PEROXODIPHOSPHATE IN ACETATE BUFFERS

AbstractDie Kinetik der Titelreaktionen wird durch Bestimmung von As(III) bzw. Sb(III) mit Permanganat untersucht.

Kinetics and mechanism of the silver(I)-catalyzed oxidations of arsenic(III) and antimony(III) with peroxodiphosphate in acetate buffers

A kinetic study of the silver(I)-catalyzed oxidations of AsIII and SbIII with peroxodiphosphate (pdp) was performed by estimating AsIII and SbIII with permanganate. The oxidation of AsIII was found to conform to the rate law (i) in the range pH 2.10—4.52, where K2 and K3 are the acid-dissociation –d[AsIII]/dt=[pdp][AsIII][AgI](k1K2–1[H+]2+k2[H+])/([H+]+K3)(i), constants of H3P2O8– and H2P2O82–; k1/K2 and K2 were found to be (5.0 ± 0.2)× 104 dm9 mol–3 s–1 and 38 ± 3 dm6 mol–2 s–1 at 50 °C. The oxidation of SbIII was first order in [SbIII], [pdp], and [AgI], and independent of pH, [acetate], and [tartrate]; the third-order rate was found to be 18 ± 1 dm6 mol–2 s–1 at 50 °C in the range pH 3.00—4.61. The silver(I) catalysis operates through complex formation of pdp and AgI rather than AgI/AgIII redox cycling.