A CRITICAL-EVALUATION OF A GLUCOSE BIOSENSOR MADE BY CODEPOSITION OF PALLADIUM AND GLUCOSE-OXIDASE ON GLASSY-CARBON

The preparation of a glucose biosensor by the electrochemical codeposi tion of palladium and glucose oxidase (GOx) on a glassy carbon electro de is described. The Pd/GOx electrode system allowed a low working pot ential of +0.3 V vs. Ag\AgCl which is ca. 0.3 V lower than that report ed for equivalent Pt/GOx systems. The sensor required no special pretr eatment to suppress interference from galactose. It is demonstrated th at the pH of the plating solution has a critical effect on the success ful codeposition of palladium and GOx. In addition, the results of a s ystematic study demonstrated that the deposition time as well as the c oncentration of the palladium salt and the enzyme level strongly affec t the sensitivity of the resulting electrode. During a test period of 50 days the electrode lost approximately 50% of its sensitivity within the first 20 days, after which the response was essentially constant. The morphology of the electrode surface was characterized by scanning electron microscopy.