Investigation into the speciation of inorganic arsenic in weakly alkaline medium by voltammetry

The speciation of inorganic forms of arsenic was studied using anodic stripping voltammetry (ASV) at a gold microelectrode in conjunction with photoreduction of As(V). Sodium sulfite (0.1 M) and ammonium buffer (pH≥9.5) were selected as both background electrolyte and photo-reductive reagent. Oxygen was removed by radical chain reactions with sulfite. The proposed speciation method was validated for mixtures of arsenic As(III/V) at concentrations up to 1 mg L−1. The calculated LOD of As(III/V) was 0.06 µg L−1 (3σ, tdep 40 s). Any interference from nitrate anions present at up to millimolar concentration was minimized by their photoreduction.