INFLUENCE OF METAL CONCENTRATION AT THE ELECTRODE SURFACE IN DIFFERENTIAL-PULSE ANODIC-STRIPPING VOLTAMMETRY IN THE PRESENCE OF HUMIC MATTER

The influence of metal concentration in bulk solution and of depositio n time on voltammograms obtained by differential pulse anodic strippin g voltammetry in the presence of humic matter is discussed based on th e slow diffusion of complexes, adsorption of the ligand on the electro de and ligand to metal concentration ratio during the stripping step. The conditional stability parameters at pH 5, in the bulk solution and in the absorbed layer, are determined. The concentration of adsorbed sites is calculated from the saturation of the sites at the electrode surface with metal ions, estimated either from the critical deposition time or from the height of the shoulder presented in the voltammogram .