SURFACTANT MODIFIED CARBON-PASTE ELECTRODE .1. ELECTROCHEMICAL AND MICROSCOPIC CHARACTERIZATION

The modification of the carbon paste electrode (CPE) with the amphiphile hexadecyl sulfonic acid (sodium salt) has permitted the development of a stable and analytically useful functionalized electrode. The electrochemical characterization of the modified electrode (potential range, background current, stability) has been investigated by cyclic voltammetry in aqueous media with different buffer compositions and in hydro-organic media and the results compared favorably with the conventional carbon paste electrode. The characterization of the sulfonated functionalities and their influence in the electrode behavior has been pointed out using linear scan and adsorptive voltammetry by studying two model compounds: promethazine and ascorbic acid. The marked influence of the pH, ionic strength, and nature of the buffer cation on the shape (potential and intensity) of the voltammetric curves confirmed the structure of the modified electrode interface, i.e., electrode bearing strong cation exchange functionalities. Scanning electron microscopy and optical microscopic observations of the CPE and modified CPE showed a higher density of graphite particles not covered by liquid paraffin at the latter.