Facilitated ion transfer reactions across oil|water interfaces.: Part I.: Algebraic development and calculation of cyclic voltammetry experiments for successive complex formation

A computational methodology to model cyclic voltammetry experiments is presented here for assisted ion transfer reactions at the interface between two immiscible electrolyte solutions. General analytical equations are given for any complexation reaction of 1:m ion-to-ligand stoichiometry, and the efficiency of the computation is demonstrated by various examples of calculated voltammograms obtained for the successive complex formation of 1:1 to 1:4 stoichiometry at the water\1,2-dichloroethane interface. The results show that the complexation reactions depend strongly on the different association constants in both phases, on the partition coefficient of the ionophore and on the initial concentrations of both the ionophore and the free metal ion. The results obtained for the formation of a unique complex are in good agreement with those performed previously by numerical simulations [Homolka et al., Electroanal. Chem., 138 (1982) 29-36 and Kakiuchi and Senda, J. Electroanal. Chem., 300 (1991) 431-445], which validates the present algebraic calculation. The methodology followed here comprises an analytical resolution of the mass balance equations at the interface. This offers the great advantage of avoiding any assumption on the phase in which the reactants are preliminarily dissolved or on the phase in which the complexation reaction occurs. Thus, the present computational method allows the analysis of any kind of assisted ion transfer reactions at an ITIES, and enables the elucidation of the mechanistic interpretation of the current waves recorded on the voltammograms. (C) 1998 Elsevier Science S.A. All rights reserved.