AN ELECTROCHEMICAL CAPILLARY FILL DEVICE FOR THE ANALYSIS OF GLUCOSE INCORPORATING GLUCOSE-OXIDASE AND RUTHENIUM(III) HEXAMINE AS MEDIATOR

This article describes a coulometric measurement device for glucose based on thin-layer bulk electrolysis. The analysis is carried out in a specially constructed cell, the electrochemical capillary fill device, which has a total volume of less than 20-mu-l. Once the sample enters the cell by capillary action, the freeze-dried assay components (glucose oxidase, ruthenium (III) hexamine, buffer salts, etc.) become solubilized and quickly disperse throughout the volume of the cell. After a period of one min, the time taken for the enzyme catalyzed oxidation of glucose to gluconic acid to reach completion, a potential step is applied and the current transient, resulting from the oxidation of reduced mediator at the working electrode, integrated over a period of 60 s. From the resultant charge value, the concentration of glucose in the sample can be unambiguously determined. The response of the sensor is both linear and accurate over the range 2-30 mM, which covers the normally accepted range for blood glucose levels in diabetic patients. The second order rate constant for the reaction between reduced glucose oxidase and ruthenium (III) hexamine was evaluated by conducting a numerically based analysis that was designed to separate the diffusional and catalytic components of current transients.