Gold microelectrode ensembles: cheap, reusable and stable electrodes for the determination of arsenic (Ⅴ) under aerobic conditions

摘要

The determination of total arsenic through As(V) anodic stripping voltammetry (ASV) is, in some cases, preferable over As(Ⅲ) ASV. The As(V) ASV procedure has no chemical reduction step from As(Ⅴ) into As(Ⅲ), which results in decreased analysis time and no contamination from reducting reagents. A simple and reliable procedure of As(Ⅴ) determination is proposed. Anodic stripping determination of trace As(Ⅴ) at gold microelectrode ensembles in diluted HC1 solution in the presence of dissolved oxygen is shown. The electrode is based on a carbon black (30%)-polyethylene composite. The sensor was prepared by gold electrodeposition on the surface of the composite electrode. The given sensor is cheap, reliable and stable, especially when electrochemical activation is employed. The experimental parameters for the electrochemical determination were optimized, namely 0.005 M HO as the background electrolyte, the deposition potential -2.2 V (versus Ag/AgCl in 1 M KC1) and 180mV s~(-1) linear scan rate. Calibration curves were obtained and were linear in [As(Ⅴ)] over the 1.5-45 μgL~(-1) range, with a LOD of 0.5 μgL~(-1). The effect of common interfering species is studied. The electrochemical behaviour of As(Ⅲ) form is studied in the same experimental conditions. It was found that As(Ⅲ) is deposited at lower potentials (starting at -0.6 V) and the sensitivity of As(Ⅲ) detection is higher, but dependant on the presence of dissolved oxygen. The speciation of inorganic forms of arsenic is discussed.