A glucose biosensor with enzyme-entrapped sol–gel and an oxygen-sensitive optode membrane

Abstract

An optical biosensor for the continuous determination of glucose in beverages based on the canalisation of glucose oxidase into a sol–gel is presented. The enzyme was entrapped within a glass matrix by the sol–gel method. The matrix was ground to a powder form and packed into a laboratory-made flow cell. This minireactor was positioned in a spectrofluorimeter connected to a continuous sample flow system. An oxygen-sensitive optode membrane was fabricated from tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) didodecyl sulfate adsorbed on silica gel particles and entrapped in a silicone-rubber film. The membrane was situated against the wall of the flow cell to sense the depletion of oxygen content upon exposure to glucose. The change of the luminescence intensity of the optode membrane can be related to glucose concentration. The effects of temperature and pH on the response of the biosensor were investigated. Storage, stability and repeatability of the biosensor were also studied in detail. The analytical range of the biosensor was from 0.06 to 30 mmol dm−3 glucose and the time taken to reach a steady signal in a flowing solution was 5–8 min. The detection limit was found to be 6 μmol dm−3. Common matrix interferents such as fructose, galactose, lactose, raffinose, rhamnose, stachyose, sucrose and other components in beverage samples showed no interference. The glucose biosensor has been successfully applied to the determination of glucose contents of beverage samples.