Amperometric Determination of Hypoxanthine and Inosine by Use of Enzyme Sensors Based on a Clark-Type Hydrogen Peroxide or Oxygen Electrode

A hypoxanthine sensor was constructed using a polarographic electrode in combination with immobilized xanthine oxidase [E.C. 1.2.3.2.]. Electrodes for the determination of both the generated hydrogen peroxide and the consumed oxygen were tested. Xanthine oxidase was immobilized via glutaraldehyde activation on a polycarbonate membrane which was subsequently mounted on the tip of the electrodes. A linear response of the sensor in the range 2.5 – 375 × 10−6 M hypoxanthine was observed. An inosine sensor containing xanthine oxidase and nucleoside phosphorylase [E.C. 2.4.2.1.] was also developed using the same principles. This sensor responded linearly to inosine concentrations in the range 2.5 – 500 × 10−6 M. The determination of hypoxanthine and inosine concentrations is of importance in fish freshness estimations.