Journal of Electroanalytical Chemistry, Vol.375, No.1-2, 307-318, 1994
Reverse Pulse Polarography of Labile Metal Plus Macromolecule Systems with Induced Reactant Adsorption - Theoretical-Analysis and Determination of Complexation and Adsorption Parameters
A model for the interpretation of reverse pulse polarography (RPP) in metal macromolecular ligand systems is developed, including both adsorption of the macromolecule and the induced adsorption of the metal ion. The following basic assumptions are made : reversible charge transfer at a stationary planar electrode (static mercury drop electrode), labile complex, large excess of ligand compared with the total metal concentration, formation of a 1 : 1 complex and diffusion coefficients for ligand and complex species different from that of the free metal ion. Equations for the limiting current I(lim) and for the RPP full wave are deduced for both linear and Langmuirian adsorption. It is found that adsorption does not modify the expressions for I(lim) valid for the case without adsorption. Thus the stability constant K can be determined. In contrast, adsorption influences the shape and position of the RPP full wave. In the case of linear adsorption, and analytical expression has been deduced which relates the adsorption parameter K(ML)1 to DELTA(E)1/2 values, thus allowing the calculation of K(ML)1 from RPP waves. This method has been applied to experimental results obtained for the Cd(II) polymethacrylate system.
Keywords:DOUBLE POTENTIAL STEP;SIMPLE REDOX SYSTEM;POLYELECTROLYTE SYSTEMS;PRODUCT ADSORPTION;LANGMUIRIAN ADSORPTION;VOLTAMMETRY;DME;LIGANDS