Mutual interferences in the determination of Zn(II) and Cu(II) in seawater by anodic stripping voltammetry

Cu(II) and Zn(II) titration experiments were used to investigate the mutual interference of Zn and Cu in anodic stripping voltammetry (ASV) at the stationary, mercury-coated, glassy carbon electrode. The experiments were conducted on stored seawater with a trace metal concentration range of 10^-8-10^-7 M. It was found that both Zn(II) and Cu(II) titration curves show a characteristic beeak point, the position of which is a function of the concentration of the interfering ion. The mutual interference is attributed to the formation of an intermetallic compound (IC) with a stoichiometric formula ZnCu. The model further assumes that the rate of Zn oxidation off the amalgam is the kinetic-limiting step in the IC dissociation during the stripping cycle of the ASV analysis. Numerical simulation of the titration experiments-using the proposed model and applying experimentally derived parameters-is in good agreement with the experimental results. The model can thus be applied to correct for Zn and Cu interference in ASV.