Simultaneous determination of zinc, cadmium and lead in manganese sulphate electrolyte by differential-pulse anodic-stripping voltammetry

Conditions are described for the direct simultaneous determination of zinc, cadmium and lead in process manganese sulphate electrolyte by differential-pulse anodic-stripping voltammetry. The suitability of the technique in this medium is influenced by the solution pH, scan rate and pulse height. Reliable determinations of the elements are accomplished in the concentrated electrolyte at pH 4.1 with a scan rate of 8 mV s^-1 and a pulse height of 50 mV. Under these conditions, the limits of detection with a deposition time of 30 min are 0.05, 0.03 and 0.10 μg l^-1 for the three elements, respectively. The precision of the method is also satisfactory with relative standard deviations of 0.8, 1.5 and 1.2% for zinc, cadmium and lead, respectively, with 10 samples at the 1 μg l^-1 level. However, the high manganese sulphate background is inadequate for copper determination at concentrations less than 50 μg l^-1.