Electrochemical oxidation of NADH at a bare glassy carbon electrode in different supporting electrolytes

Abstract The electrochemical oxidation of NADH at a bare glassy carbon electrode was studied as a function of the supporting electrolyte using differential pulse voltammetry. NADH forms adducts with phosphate anions via nicotinamide and adenosine groups in the NADH molecule. The adduct, oxidised at potentials ca. 0.200 V higher than the original molecule, catalyses the co-factor decomposition with production of the adenine–phosphate adduct as major decomposition product. The last one is oxidised at applied potentials higher than 0.9 V and the strongly adsorbed oxidation products block the electrode surface. Anions present in the supporting electrolyte can be adsorbed on the electrode surface and block the NADH oxidation. The best buffer system used was piperazine– N , N ′-bis [2-ethanesulphonic acid] exhibiting a linear relationship between oxidation currents and NADH concentrations in the 0.015–0.81 mM range with a detection limit of 0.0082 mM.