Glucose sensor based on carbon paste electrode incorporating poly(ethylene glycol) -modified glucose oxidase and various mediators

Amperometric bioelectrodes constituted of carbon paste electrode incorporating poly(ethylene glycol)-modified glucose oxidase and mediators are studied. Influences of the nature of the mediators (anthraquinone, methylene blue, 2,6-dichloro-phenolindophenol, tetracyanoquinodimethane, 1,1ʹ-dimethylferrocene) on the characteristics (potential window, apparent Michaelis constant, response time, stability) of the bioelectrodes are investigated. It is possible to show that the behaviour of the mediator is influenced by the pasting liquid contained in the carbon paste. Moreover, the water solubility of the mediator is the cause of a decrease of the apparent Michaelis constant in the case of methylene blue. A comparison between the stability of a low water soluble mediator (tetracyanoquinodimethane) and a more water soluble mediator (methylene blue) shows that the leakage of mediator from the carbon paste is not the cause of the lack of stability of such bioelectrodes. Among the various mediators tested, tetracyanoquinodimethane seems the most appropriate for the construction of a bioelectrode.