Multianalyte sensor for the simultaneous determination of hypoxanthine, xanthine and uric acid based on a preanodized nontronite-coated screen-printed electrode

Simultaneous determinations of purine bases of hypoxanthine (Hx), xanthine (X), and uric acid (UA) were demonstrated on preanodized nontronite-coated screen-printed carbon electrodes (NSPEs*). Good enhancement in the electrochemical sensitivity was noticed upon preanodization at 2.0 V versus Ag/AgCl. The measured interaction parameter "r" reveals a strong attractive force of the purine bases to the NSPE*. Cyclic voltammetric studies show different charge transfer behavior among the purine bases on the NSPE*. The experimental parameters were systematically optimized for each analyte of Hx, X, and UA. The calibration curves were all linear in the range of 4-30, 2-40. and 2-40 muM with detection limits (S/N = 3) of 0.34, 0.07, and 0.42 muM for Hx. X, and UA, respectively. The analytical performance of the NSPE* was demonstrated for the simultaneous determination of Hx, X. and UA in blood plasma and urine samples. The estimation of the fish freshness by monitoring the Hx content was also established with very good reproducibility. (C) 2002 Elsevier Science B.V. All rights reserved.