CHEMICALLY MODIFIED ELECTRODES AS BIOSENSORS: AMPEROMETRIC GLUCOSE SENSOR FOR FLOW INJECTION ANALYSIS

Abstract

An amperometric biosensor was constructed for glucose blood serum determinations with flow injection analysis. A platinized, reticulated vitreous carbon (RVC) electrode is used as an enzyme support, reactor, and detector. A partial platinum coating provided an increased current response from the oxidation of hydrogen peroxide, as compared with a bare RVC electrode. It also allowed the electrode to operate at a much lower potential (+0.6 vs +0.9 volts vs SCE), thus resulting in an increased signal to noise ratio. However, carbonaceous sites were still available for enzyme immobilization. Glucsseloxidase (E.eC2 1T.1IE 3.4) is immobilized on the surface of the RVC electrode to provide selectivity for glucose and to produce an electroactive product, hydrogen peroxide. The enzyme is immobilized by either covalent attachment with carbodiimide or cross-linking with glutaraldehyde. The enzyme remained active for over three months with almost daily use. An electropolymerized film of 1,2-diaminobenzene was incorporated on the sensor to eliminate the effects of electrochemically active interferences present in serum samples. The polymer film also virtually eliminated electrode fouling caused by large proteins. The working lifetime of the sensor, as well as, the thermal stability of the immobilized glucose oxidase were increased by the polymer film.