Glucose concentration measurement using immobilized glucose oxidase

Abstract

A reactor with an immobilized glucose oxidase layer on a magnetic disc impeller for routine determination of the glucose concentration in biological samples was designed and studied both experimentally and theoretically. The rate of oxygen concentration decrease in the reacting mixture (consisting of ca. 200 μl of buffer solution, pH 5.5, saturated with air, with 1 to 20 μl of a sample solution of 0.026 M glucose) was measured with an oxygen probe under conditions of external diffusion of the glucose to the enzyme layer surface as the controlling process. The calibrations found for this arrangement were linear up to a glucose concentration of 1 m M in the reacting mixture. They were independent of the enzyme layer activity (and, therefore, permanently stable) when some minimum enzyme activity had been used, of the presence of catalase, of the impeller speed, and of the initial oxygen concentration. The slope of the calibration line was only slightly dependent on the temperature. The standard deviation of the experimental points from the calibration line was 0.7% of the concentration range. The short duration of the measurement cycle (32 s) and the elimination of the necessity of frequent recalibration suggests the use of the proposed method for rapid and accurate routine measurements in clinical practice.