Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Two kinds of biosensors for the determination of pyranose oxidase substrates were developed, based on the detection of evolving hydrogen peroxide on a platinum or platinized graphite electrode at +650 or +400 mV, respectively. The membranes consisted of enzyme immobilized by covalent bonds on nylon net and were stable for 8 months of dry storage at 4 °C. In addition to D-glucose, low concentrations of D-xylose, D-galactose and L-sorbose can also be measured with the biosensor. The shift of the optimum pH of the immobilized enzyme to the alkaline region (8.0 - 9.5) is convenient for the borate buffer medium which extends the linear concentration region of the biosensor to 15 mmol l^-1 for D-galactose, 30 mmol l^-1 for D-xylose and 30 mmol l^-1 for maltose. L-Sorbose provides no response up to a concentration of 10 mmol l^-1 in 0.05 M borate and up to a concentration of 30 mmol l^-1 in 0.2 M borate at pH 9.2. Interfering D-glucose was eliminated up to 2.5 mmol l^-1 by means of an enzyme pre-membrane with immobilized hexokinase. The effect of ascorbate was eliminated, up to 75 mmol l^-1, by using a cellulose acetate electrostatic barrier. D-Galactose, however, decreases the sensor response to D-glucose.