Mediatorless catalytic oxidation of NADH at a disposable electrochemical sensor

We report here a simple, selective and sensitive method for the determination of NADH in neutral aqueous solution by using an electrochemically preanodized screen printed carbon electrode (SPCE*) without the addition of any redox mediator. The preanodization procedure makes the SPCE more electroactive towards NADH oxidation with a decrease of similar to 300 mV in the overpotential without electrode fouling. It is proposed that surface reorientation to generate more edge plane sites during the preanodization procedure, as confirmed by a distinctive Raman band at similar to 1360 cm(-1), is the main cause for the facilitated electron transfer for the oxidation of NADH. Presence of large excess of ascorbic acid does not interfere the detection of NADH and the SPCE* shows individual voltammetric peaks for ascorbic acid and NADH. Under optimized conditions, the obtained calibration plot shows a linear range up to 100 mu M with a detection limit (S/N = 3) of 157 nM by flow injection analysis. (C) 2006 Elsevier B.V. All rights reserved.