Study of the electrochemical behavior of Disperse Blue 1-modified graphite electrodes. Application to the flow determination of NADH

摘要

The preparation and the electrochemical study of Disperse Blue 1-chemically modified electrodes (DB1-CME), as well as their efficiency for the electrocatalytic oxidation of NADH is described. The proposed mediator was immobilized by physical adsorption onto graphite electrodes. The electrochemical behavior of DB1-CME was studied with cyclic voltammetry. The electrochemical redox reaction of DB1 was found to be reversible, revealing two well-shaped pair of peaks with formal potentials 152 and -42 mV, respectively, (vs. Ag/AgCl/3M KCl) at pH 6.5. The current I-P has a linear relationship with the scan rate up to 800 mV s(-1), which is indicative for a fast electron transfer kinetics. The dissociation constants of the immobilized DB1 redox couple were calculated pK(1) = 4 and pK(2) = 5. The electrochemical rate constants of the immobilized DB1 were calculated k(1)degrees = 18s(-1) and k(2)degrees = 23s(-1) (Gamma = 2.36 nmol cm(-2)). The modified electrodes were mounted in a flow injection manifold, poised at + 150 mV (vs. Ag/AgCl/3M KCl) and a catalytic current due to the oxidation of NADH was measured. The reproducibility was 1.4% RSD (n = 11 for 30 muM NADH) The behavior of the sensor towards different reducing compounds was investigated. The sensor exhibited good operational and storage stability.