Stripping voltammetry of heavy metal/polyelectrolyte complexes. Part 2. Analysis in terms of polyelectrolyte theory

The association of Zn(II) and Cd(II) with polymethacrylic acid is studied by differential pulse anodic stripping voltammetry for total metal concentrations varying from 10−7 up to 10−5 mol l−1 at constant polyionic charge density. The experimentally obtained results for the ZnPMA and the CdPMA systems, expressed as normalized current/polyelectrolyte concentration curves, are satisfactorily described on the basis of a theory that combines counterion condensation and intrinsic affinity. The constancy of stability, necessary for a proper interpretation of voltammetrical complexation curves, is critically analyzed. The results are of help in setting up this type of metal speciation experiments and in establishing the fundamental interaction parameters.