SQUARE-WAVE VOLTAMMETRIC DETERMINATION OF URIC-ACID BY CATALYTIC-OXIDATION AT A PERFLUOROSULFONATED IONOMER RUTHENIUM OXIDE PYROCHLORE CHEMICALLY-MODIFIED ELECTRODE

A Nafion/ruthenium oxide pyrochore (Pb2Ru2-xPbxO7-y) chemically modified electrode (CME) for the determination of uric acid by Osteryoung square-wave voltammetry (OSWV) is described. Compared to the glassy carbon electrode, the CME exhibits a 150 mV shift of the oxidation potential of uric acid in the cathodic direction and a marked enhancement of the current response, The best instrumental settings for OSWV are 50 Hz modulation frequency, 20 mV modulation amplitude, and 2 mV step height. Linear calibration curves are obtained over the 7.5 x 10(-5)-5 x 10(-7) M range in pH 1 buffer solution. The detection limit (3 sigma) is 1.1 x 10(-7) M. Ascorbic acid in less than 10-fold excess does not interfere. The practical analytical utility is illustrated by selective measurements of uric acid in human urine and serum without any preliminary treatment.