SEMIEMPIRICAL FULL-WAVE EXPRESSION FOR INDUCED REACTANT ADSORPTION IN NORMAL PULSE POLAROGRAPHY OF LABILE METAL POLYELECTROLYTE SYSTEMS

A semi-empirical expression is proposed for the normal pulse polarographic wave of the reduction of a metal ion in a labile metal-polyelectrolyte system, in the presence of an excess of ligand, and includes both the polyelectrolytic ligand adsorption and the induced adsorption of the metal ion. This expression avoids the need to know the values of the adsorption isotherms of both the complex and the polyelectrolytic ligand as well as their time and potential dependences. A non-linear fitting procedure is performed in order to obtain the parameters of the semi-empirical expression, from which an approximate value of the stability constant of the complex can be estimated. The accuracy of this semi-empirical expression is tested by simulated curves, and it is applied to experimental results for the Cd(II)-polymethacrylate complex, in order to obtain the stability constant of the complex from experimental data in the presence of adsorption phenomena.