Determination of arsenic in gold samples using matrix exchange differential pulse stripping voltammetry

A method comprising matrix exchange differential pulse stripping voltammetry (DPSV) at a gold film electrode has been proposed for the determination of small quantities of arsenic in pure gold. A wall-jet cell (WJC) and an on-line deoxygenation system were used to facilitate matrix exchange. The gold(I) cyanide complex was formed to avoid gold deposition on the electrode together with the arsenic. The pH of the sample solutions were adjusted to 3, as alkaline solutions gold(I) cyanide produced interference and the uncomplexed cyanide led to passivation of the gold film electrode. Matrix exchange electrolytes consisting of 4 mol l⁻¹ hydrochloric acid or a combination of 2 mol l⁻¹ sulphuric acid and 0.2 mol l⁻¹ hydrochloric acid could be utilised. Arsenic concentrations as low as 0.1 mg l⁻¹, could readily be detected in a gold matrix with a 60 s deposition time. While, cobalt and silver did not interfere with the arsenic determination, copper interfered even when present at similar concentrations to that of arsenic.