SURFACE MODIFICATION OF ELECTRODES FOR AMPEROMETRIC BIOSENSORS IN ANALYTICAL-CHEMISTRY

Amperometric biosensors based on surface modifications of electrodes are described. Cobalt porphyrins modified on glassy carbon and carbon fiber electrodes can greatly decrease the overpotential and increase the sensitivity of detection due to EC electrocatalysis. Cation exchange polymer films, Nafion and Eastman Kodak AQ, as well as poly(1,2-diaminobenzene) film, were used as membrane barriers; they can avoid the interference from ascorbic acid and uric acid. Simple ferrocene without any substitutes was incorporated in Nafion film for preparation of glucose sensor; it shows long term stability because of two domains (hydrophilic and hydrophobic) existed in the film. By using ferrocene derivatives as mediator, amino acid enzyme electrode was fabricated with double-enzymes. Dehydrogenase (lactic acid, alcohol and malic acid dehydrogenase) enzyme electrodes were prepared with double-mediators. This kind of biosensor can overcome the disadvantage of poor selectivity and reproducibility by using the mediators for direct determination of NADH.