Determination of the complexation capacity. Electrochemical lability in the absence of excess of ligand

Abstract

Abstract Some electrochemical lability criteria are established on the basis of the solution of the mass transfer equations for a reversible charge transfer coupled to a previous dissociation reaction of the complex assuming an excess of ligand species. During the course of a titration curve the ratio of the analytical concentration of metal to ligand changes by several orders of magnitude, so these assumptions are not fulfilled near and before the equivalence point. Theoretical titration curves were calculated from the analytical solution of the mass transfer equations obtained in excess of ligand and by solving them numerically without assuming ligand excess. Comparison of the titration curves for the different parameters: electrode rotation speed and complex dissociation constant and rate constants allows the electrochemical lability criteria established on the basis of the analytical solution to be tested. One of the aims of the work is to prevent and discuss an alternative method for obtaining the complexation capacity and the conditional dissociation constant from titration curves.