Electrochemical properties of violuric acid and oxidase biosensor preparation

The electrochemical properties of violuric acid (VA) have been investigated at pH 4.0-10.0 by using cyclic voltammetry on a glassy carbon electrode. T he peak current was proportional to the square root of the potential scan r ate. The calculated diffusion coefficient was 2.0 +/- 0.7 x 10(-6) cm(2) s( -1). The formal oxidation-reduction potential of VA was 0.63 V versus SCE a t pH 7.0. The kinetics of VA interaction with reduced glucose oxidase (GO) was explored in the electrocatalytical system. A typical electrocatalytical wave was generated in the presence of the VA and glucose. An apparent k(ox ) calculated by using the Nicholson-Shain function was 1.85 x 10(6) M-1 s(- 1) at pH 7.0 and 25 degrees C. Glucose and L-lactate bioelectrodes were pre pared by adsorbing the GO and L-lactate oxidase (LO) onto the VA-modified g raphite electrode. The electrode was poised at 0.6 V versus SCE and Linear response was obtained over the range of 4-20 mM glucose and 2-12 mM L-lacta te, respectively. (C) 2000 Elsevier Science S.A. All rights reserved.