Electrochemical oxidation of NADH on sol–gel derived, surface renewable, non-modified and mediator modified composite-carbon electrodes
Published on Apr 1, 1998in Advances in Carbohydrate Chemistry and Biochemistry2.43
· DOI :10.1016/S0022-0728(97)00547-0
The electrochemical oxidation of the cofactor, dihydronicotinamide adenine dinucleotide was studied on sol–gel derived, polishable, ceramic-carbon electrodes (CCEs), in phosphate buffer of pH 7.3. NADH was found to undergo an apparently irreversible, two-electron oxidation in the available range of potentials. Cyclic voltammetric studies at high sweep rates revealed a prewave due to the adsorption of the oxidation product, NAD+. The prewave was found to be suppressed when the surface was adsorbed with NAD+, prior to initiating the voltammetric scan. Steady state sensing of the cofactor at high overpotentials of 0.3 and 0.5 V was complicated by the adsorption process. However, CCEs have the advantage of sensing NADH at low potentials of 0.15 V vs. Ag|AgCl|KCl (satd.) where the interferences due to adsorption were found to be greatly minimized. A comparison of glassy carbon and CCEs reveals a shift of the onset potential of oxidation by more than 0.3 V and higher sensitivity of the CCE. Bulk modification of the CCEs by incorporation of Meldola's blue into the sol–gel precursors was found to reduce the overpotential needed for NADH sensing to −0.2 V. Stability of the signal at low overvoltages in the continuous operation mode was found to be good. The surface renewability of the CCEs by mechanical polishing revealed less than 8% relative standard deviation for successive surface renewals of the blank and mediator modified electrodes.