Determination of copper, cadmium and lead in seawater by cathodic stripping voltammetry of complexes with 8-hydroxyquinoline

Abstract

Procedures are presented to determine simultaneously copper, lead and cadmium in seawater by differential pulse cathodic stripping voltammetry (DPCSV) preceded by adsorptive collection of complexes with 8-hydroxyquinoline (oxine) onto a hanging mercury drop electrode (HMDE). In preliminary experiments the optimal analytical conditions were found to be an oxine concentration of between 0.8 and 2 × 10 −5 M, a pH between 7.5 and 8, the adsorption potential at −1.1 V, and the initial scanning potential at −0.3 V. The peak heights for low levels (sub-nanomolar) of cadmium and lead increase linearly with the adsorption time between 1 and 12 min. The limits of detection for a 1 min stirred adsorption time are 0.12 n M Cd, 0.3 n M Pb and 0.24 n M Cu; these limits are reduced 10x by increasing the adsorption time to 10 min. In these conditions most seawater samples are amenable for direct voltammetric determination of copper, cadmium and lead using an HMDE.