IMPROVEMENT OF THE SELECTIVITY OF AN FIA AMPEROMETRIC BIOSENSOR SYSTEM FOR GLUCOSE

A flow injection analysis (FIA) biosensor system has been developed fo r the determination of glucose from urine, blood plasma and foodstuffs . Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an enzyme column. The hydrogen p eroxide released from the conversion of glucose to gluconic acid was m onitored by a platinum electrode vs. silver/silver chloride poised at +700 mV. As a novel aspect to the improvement of the selectivity of th e biosensor system, an anion exchange column was placed upstream to re move uric acid, ascorbic acid or acetaminophen, three major electroact ive interfering substances which usually occur in urine and blood plas ma. Among several resins tested, the effective adsorption of uric and ascorbic acids could be accomplished using an acetate anion exchanger, and the selectivity coefficient was pH dependent. The binding of acet aminophen to the resin was much less efficient and, in all cases, the selectivity coefficient was independent of the operating temperature u p to 37-degrees-C. When applied to real samples, the data obtained by the biosensor system compared well with those of the standard hexokina se assay. The immobilized glucose oxidase could be reused for at least 2000 repeated analyses without loss of its original activity.