Amperometric detection of uric acid and hypoxanthine with Xanthine oxidase immobilized and carbon based screen-printed electrode. Application for fish freshness determination.

Carbon-based screen-printed electrodes are suitable for uric acid detection. Xanthine oxidase (XO) was immobilized either directly on the surface of the electrode or in a reactor with CPG aminopropylsilane in a FIA assembly. Higher reproducibility and lifetime was obtained with the reactor. Optimum conditions were found for the determination of Hypoxanthine (Hx), Inosine (HxR) and Inosine monophosphate (IMP). Calibration curves for IMP, HxR and Hx are linear up to 50 muM with detection limit of 1 muM for 50 mul injection. One assay is completed within 30 s. The reproducibility of 20 muM of Hx was obtained with CV 2%.