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 studie d at a carbon disc microelectrode, using cyclic voltammetry (CV) and l inear sweep anodic stripping voltammetry (LSASV). Both deposition and stripping processes of the analytes have been investigated in syntheti c aqueous solutions containing each metal ion at various concentration s, and different supporting electrolytes as NaClO4, acetate buffer, Na Cl 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 t hese analytes, while for more dilute solutions, LSASV is necessary. Th e LSASV behaviour for both ions depended on concentration of the analy te as well as on the time used in the preconcentration step. In partic ular, in a given medium, the number and position of the stripping peak s 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 cas e a single peak (the less cathodic one) was recorded. The influence of stripping parameters such as deposition potential, deposition time an d scan rate on the stripping responses has been examined. Particular a ttention has been devoted to the determination of Cu(II) in chloride s olutions, where the intermediate Cu(I) can be stabilised. (C) 1998 Els evier Science Ltd. All rights reserved.