DETERMINATION OF GLUCOSE IN DILUTED BLOOD WITH A THERMAL FLOW-INJECTION ANALYSIS BIOSENSOR

The glucose concentration in diluted whole blood has been measured, us ing a miniaturized thermal biosensor based on the enzyme thermistor pr inciple. The biosensor is a small flow injection system. A sample volu me of 20 mu l is injected into a flow of 50 mu l/min. The heat produce d when the sample passes the enzyme column is measured with a thermist or connected to a Wheatstone bridge. The enzyme column contains glucos e oxidase and catalase co-immobilized on a solid support material. Sam ples of whole blood usually cause problems in flow-systems. The blood cells tend to block the enzyme column and the back pressure increases. We have tested a superporous agarose material as enzyme support mater ial using tenfold diluted samples of whole human blood. The blood was collected from the finger-tip and diluted with buffer containing an an ticoagulant and sodium fluoride. The number of samples possible to inj ect and the accuracy compared to the Boehringer Mannheim Reflolux have been determined. At least 100 ten-fold diluted blood samples could be injected on a micro-column of superporous agarose. The obtained gluco se concentration correlated well with the one obtained with the refere nce instrument.