Study of the Potentiometric Response of Glassy Carbon Electrodes Coated with the Polycationic Ionomer Tosflex

Abstract

The perfluorinated polycationic polymer Tosflex was used to modify glassy carbon electrodes in order to study the potentiometric response towards anions. The electrodes exhibited a reversible response towards all the tested analytes in the range 10−4–10−1 M, but the resulting slope was sub-Nernstian and the selectivity was very poor. If the glassy carbon surface was submitted to oxidative electrochemical pretreatment, before being coated with the Tosflex membrane, the behavior changed dramatically, since the electrode displayed a response only towards oxidizable anions, such as iodide, thiosulfate, sulfite. The electrode response was attributed to a redox process between the analytes and the oxidized sites of the graphitic oxide film produced by electrochemical anodization. The response characteristics of the activated GC/Tosflex electrode were investigated pointing out the very high selectivity towards sulfite.