Mixed ferrocene-glucose oxidase-carbon-paste electrode for amperometric determination of glucose

The simultaneous incorporation of ferrocene derivatives and glucose oxidase into a carbon-paste matrix results in an effective microelectrode for sensing glucose. The close proximity of the enzymatic, redox mediating and sensing sites offers extremely short response times (t_95%=18 s) compared with early ferrocene-based glucose sensors. Several ferrocene derivatives are evaluated, with 1,1′-dimethylferrocene yielding the best results. The influence of the paste composition, operating potential, glucose concentration and other variables is described. The incorporation of stearic acid into the enzyme-containing paste greatly reduces the interference due to ascorbic acid. The microelectrode is easily fabricated, as time-consuming multi-step immobilization schemes are eliminated. Flow-injection measurements at a rate of 90 samples per hour and relative standard deviations of 3% are also reported.