Polarography and differential pulse anodic stripping voltammetry of Pb(II)/polycarboxylate complexes

Complex formation of Pb(II) with polymethacrylic acid (PMA) and polyacrylic acid (PAA) is studied by sampled direct current, normal pulse, reverse pulse, and differential pulse polarography, by cyclic voltammetry and by differential pulse anodic stripping voltammetry. The two Pb(II) systems appear to be labile on the different time scales of several techniques, and at different ligand-to-metal ratios. Voltammetric titrations of Pb(II) with partially neutralized PMA or PAA allow the precise determination of the apparent formation constants K of the complexes present in both systems. Under conditions where adsorption of Pb(II) onto the cell walls is not negligible, i.e. at low concentrations and at pH > 4.5, the application of a previously described methodology also allows the precise determination of K by introducing a correction due to adsorption. In some cases anomalous behaviour is still observed, which cannot be explained by adsorption losses.