DETERMINATION OF THE COMPLEXATION CAPACITY - ELECTROCHEMICAL LABILITYIN THE ABSENCE OF EXCESS OF LIGAND

Some electrochemical lability criteria are established on the basis of the solution of the mass transfer equations for a reversible charge t ransfer coupled to a previous dissociation reaction of the complex ass uming an excess of ligand species. During the course of a titration cu rve the ratio of the analytical concentration of metal to ligand chang es by several orders of magnitude, so these assumptions are not fulfil led near and before the equivalence point. Theoretical titration curve s were calculated from the analytical solution of the mass transfer eq uations obtained in excess of ligand and by solving them numerically w ithout assuming ligand excess. Comparison of the titration curves for the different parameters: electrode rotation speed and complex dissoci ation constant and rate constants allows the electrochemical lability criteria established on the basis of the analytical solution to be tes ted. One of the aims of the work is to present and discuss an alternat ive method for obtaining the complexation capacity and the conditional dissociation constant from titration curves. (C) 1997 Elsevier Scienc e S.A.