A study of the preconcentration and stripping voltammetry of Pb(II) at carbon electrodes

Both glassy carbon electrodes and carbon fibre microelectrodes were shown to accumulate Pb2+ ions at open circuit, the amount of Pb2+ accumulated being determined by anodic stripping voltammetry in 0.1 M HCl following the accumulation step. The mechanism of Pb2+ accumulation was investigated by studying the effects of the pH of the solution, the concentration of Pb2+ and the preconcentration time on the amount of Pb2+ accumulated. For a 5 min preconcentration time at open circuit, using a glassy carbon electrode (4 mm diameter) and a carbon fibre microelectrode (8 mm diameter), detection of around 10 nM Pb2+ was obtained for both electrodes. The pH dependence of the amount of Pb2+ accumulated suggests that the Pb2+ ions are complexed by carboxylate groups at the surface of the carbon electrodes. This conclusion is supported by results obtained using basal plane and edge plane pyrolytic graphite electrodes and by studies of the effects of electrochemical oxidation of the glassy carbon surface on the magnitude of the lead stripping peak.