Amperometric glucose biosensor with extended concentration range utilizing complexation effect of borate

Borate buffer strongly decreases amperometric response of a glucose oxidase linked pO 2 or H 2O 2 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 1 −1 glucose. The effect of borate ion is explained by the rapid complexation of glucose decreasing the equilibrium concentration of free β-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 (Δ i per 1 mmol 1 −1) between pH 5 and 10. Analysis is 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.