Theoretical Analysis and Determination of the Heterogeneous Stability Constant of Copper(II)-Humic Acids Complex at Chemically Modified Carbon Paste Electrode

A theory for determining the heterogeneous stability constant of a metal complex system at the surface of a chemically modified carbon paste electrode was developed. The proposed theory has been applied to the studies of a copper(II)-humic acids (Has) complex system. In an open circuit, copper(II) was accumulated from a stirred preconcentration medium onto the HAs-CMCPE. The subsequent electrochemical measurement was performed in a small volume of Britton-Robinson (B-R) buffer (pH 3.78). By means of cyclic voltammetry (CV) and anodic stripping voltammetry (ASV), the determined average heterogeneous stability constant of copper(II)-HAs complex was 4.99×109.