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

The modification of the carbon paste electrode (CPE) with the amphiphi le hexadecyl sulfonic acid (sodium salt) has permitted the development of a stable and analytically useful functionalized electrode. The ele ctrochemical characterization of the modified electrode (potential ran ge, background current, stability) has been investigated by cyclic vol tammetry in aqueous media with different buffer compositions and in hy dro-organic media and the results compared favorably with the conventi onal carbon paste electrode. The characterization of the sulfonated fu nctionalities and their influence in the electrode behavior has been p ointed out using linear scan and adsorptive voltammetry by studying tw o model compounds: promethazine and ascorbic acid. The marked influenc e of the pH, ionic strength, and nature of the buffer cation on the sh ape (potential and intensity) of the voltammetric curves confirmed the structure of the modified electrode interface, i.e., electrode bearin g strong cation exchange functionalities. Scanning electron microscopy and optical microscopic observations of the CPE and modified CPE show ed a higher density of graphite particles not covered by liquid paraff in at the latter.