An immobilized-enzyme flow-enthalpimetric analyzer: application to glucose determination by direct phosphorylation catalyzed by hexokinase.

A novel flow-enthalpimetric analyzer is described and its use demonstrated by an analysis in which glucose is determined by its hexokinase-catalyzed phosphorylation reaction. The method depends on measurement of the temperature differential across a column packed with glass-supported immoblized enzyme. Sample volumes of 120 mul can be used to obtain a calibration curve that is linear up to 25 mmol of glucose per liter. A precision (within-day) of 5% is generally observed in the optimum concentration range where glucose is quantitatively phosphorylated. Results by the technique correlate reasonably with those by the o-toluidine and the hexokinase/glucose-6-phosphate dehydrogenase methods: Other sugars--including fructose, glucosamine, and mannose--will interfere; galactose does not. The technique is amenable to both routine and emergency analyses.