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

The electrochemical oxidation of NADH at a bare glassy carbon electrode was studied as a function of the supporting electrolyte using differential pul se voltammetry. NADH forms adducts with phosphate anions via nicotinamide a nd adenosine groups in the NADH molecule. The adduct, oxidised at potential s ca, 0.200 V higher than the original molecule, catalyses the co-factor de composition with production of the adenine-phosphate adduct as major decomp osition product. The last one is oxidised at applied potentials higher than 0.9 V and the strongly adsorbed oxidation products block the electrode sur face. Anions present in the supporting electrolyte can be adsorbed on the e lectrode surface and block the NADH oxidation. The best buffer system used was piperazine-N,N'-bis [2-ethanesulphonic acid] exhibiting a linear relati onship between oxidation currents and NADH concentrations in the 0.015-0.81 mM range with a detection limit of 0.0082 mM. (C) 1999 Elsevier Science B. V. All rights reserved.