AMPEROMETRIC GLUCOSE-SENSING ELECTRODE BASED ON CARBON-PASTE CONTAINING POLY(ETHYLENE GLYCOL)-MODIFIED GLUCOSE-OXIDASE AND COBALT OCTAETHOXYPHTHALOCYANINE

An amperometric enzyme electrode for glucose was prepared by incorpora ting poly (ethylene glycol)-modified glucose oxidase and cobalt octaet hoxyphthalocyanine [CoPc(OEt)(8)], a new mediator, into a carbon paste matrix. The polymer-modified enzyme exhibited a higher activity than the native enzyme in the hydrophobic carbon paste medium. CoPc(OEt)(8) could oxidize the enzyme at more negative potentials than unsubstitut ed cobalt phthalocyanine (CoPc). Further, the CoPc(OEt)(8)-mediated en zyme electrode showed a high stability: the electrode response to gluc ose did not decrease for at least 4 weeks (or for 700 assays), whereas the glucose response from a CoPc-mediated enzyme electrode fell to ha lf of the initial value within 2 weeks (or after 300 assays). CoPc(OEt )(8), a paraffin-oil soluble derivative of CoPc, incorporated in the b ulk of carbon paste, diffused towards the electrode surface so as to r enew continuously the electrode surface, which resulted in the high st ability of the new mediator-based enzyme electrode.