Voltammetric behavior of perfluorocarboxylic acids and their corresponding ethyl esters on glassy carbon electrode: surface effects

Voltammetric responses of trifluoroacetic acid, perfluorobutyric acid, perfluorohexanoic acid, and perfluorooctanoic acid (PFOA) were studied in acetonitrile/tetra-n-butylammonium perchlorate medium on glassy carbon electrode. All the four acids gave two voltammetric waves. PFOA exhibits blocking effects. In the presence of excess water, the first cathodic peak current increases, and the second peak disappeared. Very small quantity of triethylamine (TEA; 1–2 mM) was found to be effective in suppressing the first cathodic peak. Both the peak current and peak potential values were sensitive to water and TEA content. The ester derivatives of all the four perfluorocarboxylic acids (PFCAs), however, gave well-defined cathodic reduction peak around −2.3 V. This peak appears to be the best choice for quantitative estimation of PFCAs.