A NEW PRINCIPLE FOR AN ELECTROCHEMICAL OXYGEN SENSOR

An electrochemical oxygen sensor using a smooth glassy carbon electrod e for continuous monitoring of oxygen has been developed, which can fi nd a wide range of application. Two different potential levels of pres et durations are imposed on the sensing electrode in a cyclic manner. The current flow due to O-2 reduction at a negative potential is integ rated after a time lag. The charge is proportional to the oxygen conce ntration. The electrode is then held at a positive potential for a lon ger period before repeating the cycle. Thus, oxygen is consumed only d uring the short pulse duration. This sensor principle is unique, since the sensing electrode operates without a covering membrane. This is p ossible because of the low electrocatalytic activity of glassy carbon. The response is immediate and reproducible even at a low consumption of oxygen. The long-term response is stable over 60 h and sensitive to a change of about 0.5 hPa partial pressure of oxygen in saline soluti on. Measurements with the sensor in bovine serum demonstrated the negl igible influence of other substances on the response to oxygen. The se nsor has been tested in animal experiments, and shows a good response in blood as well as in tissue.