Electrochemical determination of NADH using screen printed carbon electrodes modified with reduced graphene oxide and poly(allylamine hydrochloride)

We describe a new type of NADH sensor based on a screen-printed electrode (SPE) modified with reduced graphene oxide (RGO) and poly(allylamine hydrochloride) (PAH). A mixture of graphene oxide (GO) and PAH was deposited on the surface of a carbon working electrode, and RGO was prepared in-situ by electrochemical reduction of GO. The oxidation peak of NADH was recorded at +450 mV (vs. silver pseudo-reference). Under optimized conditions, the electrode exhibits high electrocatalytic activity toward NADH oxidation, expressed by a high rate constant and a stable response up to 0.8 mM concentrations. The sensitivity is 108.6 mu A center dot mM(-1)center dot cm(-2), the response time is 20 s (for 95 % of the steady state current), and the detection limit is 6.6 mu M (at an S/N ratio of 3). A peak separation of about 300 mV was achieved in differential pulse voltammetric determination of NADH in the presence of ascorbic acid. This makes the new sensor a useful tool with potential analytical application in different dehydrogenase based systems.