Electrochemical investigations of the reaction mechanism and kinetics between NADH and redox-active (NC)_2C_6H_3-NHOH/(NC)_2C_6H_3-NO from 4-nitrophthalonitrile-(NC)_2C_6H_3-NO_2-modified electrode

摘要

A simple and sensitive method for the electrocatalytic detection of NADH on a carbon paste electrode modified with a redox-active (NC)(2)C6H3-NO/(NC)(2)C6H3-NHOH (NOPH/NHOHPH) electrogenerated in situ from 4-nitrophthalonitrile (4-NPHN) is presented. The electrode modified with 4-NPHN showed an efficient electrocatalytic activity towards the oxidation of NADH with activation overpotential of 0.12 V vs. Ag/AgCl. The formation of all intermediate charge transfer complex is proposed for the charge transfer reaction between NADH and the 4-NPHN-resulting system. The second-order rate constant for electrocatalytic oxidation of NADH, kappa(obs), and the apparent Michaelis-Menten constant K-M, at pH 7.0 were evaluated with rotating disk electrode (RDE) experiments, giving 1.0 x 10(4) mol(-1) Ls(-1) and 2.7 x 10(-5) mol L-1, respectively. Employing the Koutecky-Levich approach indicated that the NADH oxidation reaction involves two electrons. The sensor provided a linear response range for NADH from 0.8 up to 8.5 mu mol L-1 with sensitivity, detection, quantification limits and time response of 0.50 mu A L mu mol(-1), 0.25 mu mol L-1, 0.82 mu mol L-1 and 0.1 s. respectively. The repeatability of the measurements with the same sensor and different sensors. evaluated in terms of relative standard deviation, were 4.1 and 5.0%, respectively, for n = 10. (C) 2008 Elsevier B.V. All rights reserved.