Electrocatalytic oxidation of ascorbate at glassy carbon electrodes modified with electrodeposited films derived from dihydroxybenzaldehyde isomers

The electrocatalytic oxidation of ascorbate at glassy carbon electrodes mod ified with electrodeposited films derived from dihydroxybenzaldehyde (DHB), in particular 2,3-DHB, 2,5-DHB and 3,4-DHB, has been examined. NADH can al so be electrocatalytic oxidized at 2,3-DHB and 3,4-DHB modified electrodes. However, 2,5-DHB modified electrodes catalyzed preferentially ascorbate, w hile the oxidation of NADH is unaffected. In addition, we have carried out studies of the kinetics of the catalytic reaction, as well as permeability studies. The effect of increasing concentrations of ascorbate on the ampero metric responses of 2,5-and 3,4-DHB modified electrodes was investigated. C atalytic currents are proportional to the concentration of ascorbate over t he range of 0.2 to 3.0 mM. The detection limit was 0.16 and 0.05 mM for fil ms derived from 2,5-DHB and 3,4-DHB, respectively. Selectivity was illustra ted by the analysis of ascorbate at 2,5-DHB modified electrodes in the pres ence of NADH or 4-acet amidophenol. (C) 2000 Elsevier Science B.V. All righ ts reserved.