EFFECT OF THIOUREA ON THE ACTIVITY OF THE POLYPYRROLE URICASE ELECTRODE AND DETERMINATION OF THIOUREA

An inactive polypyrrole uricase electrode can be activated by thiourea and reused for determining the concentration of uric acid. We have ob served an interesting reaction in which the oxidation of thiourea is c atalyzed by the uricase immobilized on a polypyrrole film in the absen ce of uric acid. The reaction rate of the enzyme electrode with respec t to thiourea decreases with increasing pH value and increases with in creasing applied potential and temperature. The activation energy of t he enzyme-catalysed reaction for the thiourea is 42.2 kJ mol-1. The re sponse current of the enzyme electrode in the absence of uric acid inc reases linearly with increasing concentration of thiourea in the range below 2.0 mmol dm-3. Thus the polypyrrole uricase electrode can be us ed to determine the concentration of thiourea.