Methods of the determination of inorganic arsenic species by stripping voltammetry in weakly alkaline media

Resumo

Two methods are considered for the direct determination of trace amounts of As(III) and As(V) in solutions by stripping voltammetry (SVA) using an ensemble of gold microelectrodes (Au-MEA) previously developed by the authors of this paper. In both methods, analyzing a mixture of As(III) and As(V), analysts first record an SVA signal of As(III) in a supporting Na₂SO₃ electrolyte. To record an analytical SVA signal of As(V), in the first method one should use the reduction of As(V) to As(III) on the surface of an Au-MEA catalyzed by the system Mn(II)/Mn(0) and followed by the formation of As(0) and its anode dissolution. In the second method, the photoreduction of As(V) to As(III) in a Na₂SO₃ solution is conducted under UV irradiation followed by the reduction of As(III) to As(0) and its electrooxidation on Au-MEA. The two methods are compared taking into account their performance characteristics and interfering ions. To improve the reliability of the results of analysis at an insignificant increase in its cost, we propose the consecutive use of both methods. The procedures are simple and rapid, do not require the removal of dissolved oxygen or toxic reactants, and can be used for the analysis of aqueous solutions at the place of sampling. The results of analyses of real objects, snow, river water, and process solutions are presented.