Amperometric glucose sensors fabricated by electrochemical polymerization of phenols on carbon paste electrodes containing ferrocene as an electron transfer mediator

A non-conducting polymer film of phenol and its derivatives, in which glucose oxidase (GOx) was immobilized, has been prepared on a car bon paste electrode containing ferrocene by electrochemical polymerization. Five phenol derivatives (phenol, 3-aminophenol, 3-methylphenol, 3-nitrophenol, and 1,3-dihydroxybenzene) were examined; 3-aminophenol was found to be the most suitable monomer for the fabrication of amperometric glucose sensors. The maximum current Delta i(max) obtained from the Eadie-Hofstee form of the Michaelis-Menten equation decreased with increasing the substituent constant sigma(m); a plot of Delta i(max) vs. sigma(m) gave a straight line except for S-aminophenol. In the case of 3-aminophenol, both hydroxyl and amino groups participated in the electropolymerization and consequently larger amounts of GOx; may be immobilized in this polymer film. This behavior resulted in the higher sensitivity to glucose. The response currents of Fc,CP/GOx/PAPO, which was fabricated by cycling between 0.20 and 1.40 V vs. Ag/AgCl for the electropolymerization of 3-aminophenol, changed little within a period of 40 d. In addition, this glucose sensor could minimize contributions from the easily oxidizable compounds, uric acid and L-ascorbic acid.