AMPEROMETRIC CHOLINE SENSOR WITH ENZYME IMMOBILIZED BY GAMMA-IRRADIATION IN A BIOCOMPATIBLE MEMBRANE

An amperometric choline biosensor was constructed using choline oxidase immobilized on poly(2-hydroxyethylmethacrylate) membranes obtained by gamma radiation-induced polymerization at low temperature. The measurements were carried out by Clark-type oxygen or hydrogen peroxide electrodes. Calibration curves were linear in the 10-200 mu mol.l(-1) range for the oxygen probe and 5-250 mu mol.l(-1) for the H2O2-based probe. Temperature and pH effects on the activity of immobilized enzyme are described and the response characteristics of the sensor are summarized The immobilized enzyme membranes stored in glycine buffer or in a dry state were very stable and no significant decrease in the electrode response was observed after three months. The biosensor was employed also to analyse a choline-containing pharmaceutical product and the results were compared to those obtained by enzymatic-spectrophotometric detection.