Advances in the Study of Ion Transfer at Liquid Membranes with Two Polarized Interfaces by Square Wave Voltammetry

A general analytical expression has been deduced for the I/E response of the square wave voltammetry corresponding to ion transfer processes in systems with two liquid/liquid polarized interfaces. This expression has been evaluated through the experimental study of a series of quaternary ammonium cations and metal chloro complex anions. We have found that systems with two liquid/liquid polarizable interfaces present the striking advantage that the difference between peak potentials of square wave voltammograms of cations and anions with similar standard ion transfer potential is much greater than in systems with a single polarizable one.     

Ion Transfer Square Wave Voltammetry of Ionic Liquid Cations with a Solvent Polymeric Membrane Ion Sensor

Square wave voltammetry (SWV) with a solvent polymeric membrane ion sensor has been applied to study the ion transfer of several ionic liquid cations, from water to a poly(vinyl chloride) membrane plasticized with 2‐nitrophenyl octyl ether. The study has mainly been focused on dialkylimidazolium and alkylpyridinium cations. The experimental voltammograms obtained are in good agreement with the theoretical predictions. The standard ion transfer potentials of the ionic liquid cations have been obtained and the values found have been used to draw some conclusions on the relationship between structure and lipophilicity. Also, a relationship between the toxicity and the ion transfer potentials of dialkylimidazolium homologues has been found.