General theoretical treatment of simple and facilitated ion transfer processes at the most common liquid/liquid microinterfaces

Abstract

A simple theoretical approach is presented to study simple and facilitated ion transfer processes at liquid/liquid microinterfaces of the most common geometries: micropipettes, microholes, micropores and microcapillaries. A general and accurate expression is reported for the current-potential response in any voltammetric technique. The analytical solution describes the effects on the voltammetry of the (very) different mass transport conditions in each phase whatever the size and geometry of the interface and of the values of the diffusion coefficients of the ion. The theory is applied to normal pulse voltammetry and cyclic voltammety, analysing the influence of the geometry on the position and shape of the voltammograms as well as on the attainment of a steady state response. Finally, explicit analytical expressions are derived for the determination of the formal transfer potential of the ion and of the equilibrium constant of the coupled chemical equilibrium from the half-wave potential under steady state conditions.