Computer simulation of metal complex dissociation during free metal determination using anodic stripping voltammetry

Abstract

As a most widely used technique, anodic stripping voltammetry often provides overestimated results of free metal concentration or underestimated values of complexation capacity. A conceptual mode was proposed suggesting that the dissociation of the metal complex occurring in the diffusion layer close to the electrode surface during the deposition period contributes to the measurement error. A computer program was coded to simulate the transformation and mass transfer of metal ions, free ligands, and metal–ligand complexes in the diffusion layer. It was confirmed that the dissociation of the complexes within the diffusion layer causes the overestimation error for free metal determination using the anodic stripping voltammetry technique. The magnitude of the overestimation depends on the complex dissociation coefficient, concentration of the ligand, and transfer rate constant of the free metals. The results of the computer simulation were partially confirmed by experimental data based on a Cu-EDTA system.