Modified Carbon Paste Electrode for Kinetic Investigation and Simultaneous Determination of Ascorbic and Uric Acids

The present work explores, for the first time, the electrocatalytic oxidation of ascorbic acid (AscH(2)) and its determination in the presence Of Uric acid (UA) on the in situ activated 4-nitrophthalonitrile modified carbon paste electrode. The kinetic constant kappa for the catalytic reaction for the electrocatalytic oxidation of ascorbic acid, evaluated by cyclic voltammetry, chronoamperometry and RDE voltammetry provided values around 10(6) L mol(-1) s(-1). The sensor provided a linear response range for AscH(2) and UA from 5.0 up to 120.0 mu mol L-1 with detection limits of 1.6 mu mol L-1 and 1.3 mu mol L-1, respectively. The sensor was applied for the Simultaneous determination of AscH(2) and UA in urine samples and the average recoveries for these samples were 99.8 (+/- 3.1)% and 99.9 (+/- 2.1)%, respectively.