Ion-exchange voltammetry as a solid-phase microextraction analytical method: Factors influencing the mass transfer to perfluorosulfonated ionomer film-coated electrodes and some of their consequences on the current responses

A simple theoretical model of mass transfer kinetics at an electrode coated with an ion-exchange film polymer is proposed. The model takes into accoun t the analyte depletion in solution and gives the relationship between the ion-exchange voltammetric (IEV) peak current and the initial analyte concen tration in the sample matrix. The verification of the model is investigated at disposable Nafion film-coated screen-printed electrodes, using the redo x cationic (ferrocenylmethyl)trimethylammonium salt. It is shown that the t heoretical model and the experimental data fit satisfactorily insofar as th e variation of the extraction and apparent diffusion coefficients of the sa lt with the film thickness are taken into account. Indeed, the film thickne ss plays a crucial role for the optimization of the IEV sensitivity, becaus e the physicochemical properties of the recast Nafion polymer are dependent on the amount per unit area of Nafion deposited on the electrode surface.