Spectrophotometric determination of glucose in foods by flow injection analysis with an immobilized glucose oxidase reactor

A stopped-flow injection analysis system for the determination of glucose is described, based on the iodometric measurement of hydrogen peroxide generated in a glucose oxidase reactor. The detection of the iodine–starch complex was carried out spectrophotometrically. The calibration curve was linear up to 2 mmol l-1 glucose, with a correlation coefficient, r, of 0.9996. The relative standard deviation was 1.6% (n=5) for 1.0 mmol l-1 glucose. A sample frequency of 25 samples h-1 was achieved. This method was applied to the determination of glucose in fruit products and the results obtained using this method were in good agreement with those of a routine enzymatic method. A high dilution of the sample avoided interference from ascorbic acid. The enzyme reactor was stable for 1 month after 200 measurements with no loss of activity.