In vitro measurements with electrocatalytic glucose sensor in blood.

The principle of measurement with electrocatalytic glucose sensor is based on the direct electrochemical oxidation of glucose at an active and membrane-covered noble metal electrode. The objective is to measure glucose in the range of diffusion limiting current, since the glucose concentration in front of the membrane is proportional to the oxidative current. The determination of glucose concentration is realized by considering the electrode processes taking place at different potentials, and by measuring the impedance of the electrode/membrane system using the conventional three-electrode arrangement. Performance and long-term stability of the sensor are mainly dependent on the properties of the membrane and on the poisoning reactions at the electrode. Using this method, measurements were carried out in defibrinated sheep blood at 37 degrees C. After reproducible in vitro measurements could be made with the sensor over up to 3 weeks with an error of 20%, experiments were conducted in sheep using an extracorporeal circulation system. The correlation between the electrode signal and the glucose concentration in blood could be confirmed during glucose tolerance tests.