Use of a reversibly immobilized enzyme in the flow injection – amperometric determination of picomole glucose levels
A reversibly immobilized enzyme (glucose oxidase EC 1. 1. 3. 4) reactor coupled to a continuous flow system is used in the determination of serum glucose. The soluble enzyme is first covalently attached to an antibody. This conjugate is then introduced into a microreactor containing an immobilized antigen. The resulting immunological reaction produces an immobilized enzyme. Injection of glucose yields hydrogen peroxide, which is detected electrochemically. The reactor can be regenerated in the event of a loss of enzyme activity to within ± 3% of the original reactor activity in > 30 min by eluting the immobilized enzyme and reacting a fresh aliquot of the enzyme-labelled antibody with the same reactor. The lifetime of the reactor is more than one year, during which time the antigen remains active in binding. The sample throughout is ca. 20–30 samples per hour and the accuracy is in the order of ± 3%. The linear dynamic range for glucose is 0.01–10 mg cm–3 for a sample size of 20 mm3.