Automated electrochemical stripping of copper, lead, and cadmium in seawater

Abstract

Fast staircase stripping at rotating-disk, ring-disk, and split-disk electrodes has been compared with potentiometric, linear scan, and differential pulse stripping for the analysis of Cd, Pb, and Cu in seawater at the mercury film electrode using a purpose-built hard-wired instrument designed for field work. The dependence of rapid staircase stripping peak currents on the staircase parameters at short step widths (> 1 ms) was in agreement with theory for Cd and Pb but not for Cu, suggesting interference from following chemical reactions in the latter case. The technique is much faster than differential pulse stripping and can be carried out in a stirred solution making it better suited for field work. Discrimination of faradaic from capacitance currents is comparable with differential pulse in the case of Cu but is a little poorer in the case of Cd. The performance of the rapid staircase can be improved by the use of a split-disk electrode. The rapid staircase technique is not, however, suitable for use in low ionic strength waters. The performance of the potentiometric stripping technique is critically dependent on the nature of the background subtraction procedure employed.