AMPEROMETRIC GLUCOSE BIOSENSOR WITH EXTENDED CONCENTRATION RANGE UTILIZING COMPLEXATION EFFECT OF BORATE

Borate buffer strongly decreases amperometric response of a glucose oxidase linked pO2 or H2O2 sensing electrode, extending substantially its linear calibration range. With increasing pH and concentration of the buffer the upper limit for glucose can be varied between 1 and 30 mmol l-1 glucose. The effect of borate ion is explained by the rapid complexation of glucose decreasing the equilibrium concentration of free beta-anomer, the specific substrate of glucose oxidase. The high loading of cross-linked enzyme inside the sensor membrane is necessary for the measurement to ensure an almost constant response factor (DELTA(i) per 1 mmol l-1) between pH 5 and 1 0. Analysis in stirred solution and in a flow-through system has been employed for the measurement of elevated glucose levels in heparinized human blood or plasma samples.