Lead and copper deposition from dilute solutions onto carbon disc microelectrodes. Assessment of quantification procedures by anodic stripping voltammetry

The deposition and stripping processes of lead(II) and copper(II) ions over the concentration range 1 x 10(-3)-5 x 10(-9) M have been studied at a carbon disc microelectrode, using cyclic voltammetry (CV) and linear sweep anodic stripping voltammetry (LSASV). Both deposition and stripping processes of the analytes have been investigated in synthetic aqueous solutions containing each metal ion at various concentrations, and different supporting electrolytes as NaClO4, acetate buffer, NaCl and HNO3. The results have shown that, over the concentration range 1 x 10(-3)-1 x 10(-5) M, the reduction-stripping pattern, provided by a simple CV at low scan rate, can be employed for quantification of these analytes, while for more dilute solutions, LSASV is necessary. The LSASV behaviour for both ions depended on concentration of the analyte as well as on the time used in the preconcentration step. In particular, in a given medium, the number and position of the stripping peaks depended on whether the amount of metal deposited provided a thick (macrophase) or a thin (microphase) layer. In the former case either a single or two stripping peaks were obtained, whereas in the latter case a single peak (the less cathodic one) was recorded. The influence of stripping parameters such as deposition potential, deposition time and scan rate on the stripping responses has been examined. Particular attention has been devoted to the determination of Cu(II) in chloride solutions, where the intermediate Cu(I) can be stabilised. (C) 1998 Elsevier Science Ltd. All rights reserved.