Determination of trace amounts of copper, lead, thallium, cadmium and zinc in pure aluminium by differential-pulse anodic-stripping voltammetry

Abstract

A method for the determination of trace amounts of copper, lead, thallium, cadmium and zinc in pure aluminium metal by differential-pulse anodic-stripping voltammetry, employing a citrate buffer of pH 4.4 as the supporting electrolyte, is described. For the determination of copper, lead + thallium and cadmium, the pre-electrolysis was carried out at –0.80 V vs. an Ag-AgCl reference electrode. The overlapping of the lead and thallium anodic peaks was overcome by shifting the reduction potential of lead(II) beyond –1.10 V by chelation with EDTA, while thallium(I) remained uncomplexed and was determined by carrying out deposition at –0.80 V. Copper and bismuth interference, if bismuth is present, can also be eliminated in the presence of EDTA, deposition of copper being carried out at –0.30 V. For the determination of zinc, the pre-electrolysis was carried out at –1.10 V. The effect of intermetallic compound formation between copper and zinc was investigated and the influence of probable impurities in pure aluminium was also studied.