INVESTIGATIONS OF PLATINIZED AND RHODINIZED CARBON ELECTRODES FOR USEIN GLUCOSE SENSORS

Graphite electrodes were modified by the electrodeposition of either p latinum or rhodium, using cyclic voltammetry. Following only brief per iods nf treatment, plantinized carbon electrodes were able to directly oxidize glucose at a potential of +350 mV (vs. Ag/AgCl). By narrowing both the potential range of deposition (-450 to -500 mV) and cycling period (50 seconds at a scan rate of 10 mV s(-1)), the effects of dire ct glucose oxidation could be significantly: reduced. Detection of H2O 2 at +400 mV was possible; glucose enzyme electrodes were constructed, with glucose oxidase immobilized in hydroxyethylcellulose and operate d at this potential. These sensors had a linear range of 0.1 to 25 mM glucose and a slope of 8 nA/mM. Other electrodes were prepared by the electrodeposition of rhodium. These base electrodes proved to be insen sitive to glucose and produced higher currents (compared to low platin um electrodes) to H2O2. Glucose sensors were constructed using rhodini zed electrodes. Again operating at +400 mV, these sensors had a linear range from 0.1 to 20 mM and a slope of 21 nA/mM glucose.