Electrochemical evaluation of ferrocene carboxylic acids confined on surfactant-clay modified glassy carbon electrodes:: oxidation of ascorbic acid and uric acid

We report on the electrochemical behavior of chemically modified glassy carbon (GC) electrodes by using surfactant/clay films, [cetyltrimethylammonium bromide (CTAB)/hydrotalcite-like], containing ferrocenecarboxylic (FC) or ferrocenedicarboxylic (FDC) acid. The results show that the surfactant molecules incorporated into the clay could increase the permeability and the positive surface of the film. The FDC-CTAB-clay-GC modified electrode showed greater stability and redox electroactivity than the FC-CTAB-clay-GC modified electrode. Low concentrations of ascorbic acid (H(2)A) and uric acid (UA) in aqueous solution were easily oxidized on the FDC-surfactant-clay-GC modified electrode. The kinetic of the catalytic reactions were investigated by using cyclic voltammetry and rotating disk electrode. The results suggest that the oxidation of HA on FDC-CTAB-clay-GC electrode is limited by kinetics while the oxidation of UA is mass transport-limited. The FDC-CTAB-clay-GC modified electrode allows to determine H(2)A in presence of UA, and shows good anti-fouling properties towards surface active materials. (C) 2004 Elsevier Ltd. All rights reserved.