Electrocatalytic Oxidation of NADH Using a Pencil Graphite Electrode Modified with Hematoxylin

In the present study, the electrocatalytic oxidation of reduced p-Nicotinamide Adenine Dinucleotide (NADH) was investigated using a pencil graphite electrode modified with hematoxylin (PGE/HMT). The PGE/HMT was prepared by adsorption of HMT on the PGE via immersion of bare PGE into 1.0 mM HMT solution (in methanol) for 60 s at room temperature. Cyclic voltammetric studies show that the peak potential of NADH oxidation shifts from +450 mV at bare PGE to +200 mV at PGE/HMT. The electrocatalytic currents obtained from the amperometric measurements at +200 mV versus Ag/AgCl/KClsat and pH 7.0 phosphate buffer solution containing 0.1 M KCl were linearly related to the concentration of NADH. The calibration graph consisted of two linear segments of 0.5-10 mu M and 10-300 mu M with a detection limit of 0.2 mu M (based on 3s(b), s(b) is the standard deviation of the blank response). The amperometric measurements exhibited that the response of the modified PGE/HMT towards the oxidation of NADH is reproducible, fast, sensitive and stable. Finally, the results obtained in the present study conclusively show that PGE modified with HMT can be effectively used to detect NADH.