SIMULTANEOUS VOLTAMMETRIC DETERMINATION OF URIC AND ASCORBIC ACIDS INURINE

Anodic voltammetric method for simultaneous determination of uric acid (UA) and ascorbic acid (AA) in urine has been developed with the use of a commercial working rotating glassy carbon electrode. UA may be de termined in a sample diluted by the buffer supporting electrolyte (HOA c + NH4OH; pH 5.1-5.2) approximate to 100 times, and AA-in a sample di luted not similar or equal to 20 times. Before obtaining the analytica l signal the electrode should be maintained in the diluted sample duri ng 3 min at potential 0 V and the working electrode rotating 100 rpm, for achievement of the adsorption equilibrium of inhibitors from the u rine matrix. For UA the electron transfer is close to reversible, for AA it is an irreversible one. Optimal voltammetric techniques are the square-wave for UA and the differential pulse for AA. Calibration curv es, detection limits and recoveries for both determinations were evalu ated as satisfactory. (C) 1997 Elsevier Science B.V.