Determination of dihydronicotinamide adenine dinucleotide (NADH) using a carbon paste electrode modified with graphite nanoparticles and modifier

The electrochemical oxidation of dihydronicotinamide adenine dinucleotide (NADH) to the corresponding oxidized form (NAD+) in aqueous solution has received considerable attention .However, direct electrochemical oxidation of NADH at a bare platinum electrode requires a high ( 1 V) overpotential. The overpotential for NADH oxidation could be reduced by using a mediator [1-3]. In this present work, we prepared a modified carbon paste electrode by using 2((7-(2, 5dihydrobenzylideneamino) heptylimino) methyl) benzene-1, 4-diol (DHB) modifier and graphite nanoparticles for NADH detection. Modifier synthesized in our laboratory and characterized by spectroscopy techniques. The Electrochemical behavior of DHB was investigated. The anodic and cathodic peak potentials appeared at 0.185 and 0.132 V (vs Ag/AgCl/KCl 3.0 mol/L), respectively, and ΔEp was 0.053 V. The electrochemical response characteristics of the modified electrode toward NADH were investigated by cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV) techniques. All the optimum condition, the concentration of NADH in 0.1M phosphate buffer solution at pH=7 was performed. Based on CV method the redox properties of the modified electrode at various scan rates were investigated. The affecting parameters such as pH, amount of modifier and nanoparticles content were optimized. The dynamic linear ranges, current sensitivity and detection limit for NADH were obtained by DPV technique. Under the optimized conditions, the oxidation peak current of NADH showed linear dynamic range (12.0-5000.0 μmol /L) with a detection limit of 6.0 μmol /L. The advantages of this fabricated sensor include a low detection limit, good stability and reproducibility.