GLUCOSE-OXIDASE ELECTRODE BASED ON GRAPHITE AND METHYLTHIO TETRATHIAFULVALENE AS MEDIATOR

A glucose sensor based on glucose oxidase and a new mediator - 4,5-dimethyl-4'-methylthio-DELTA 2,2'-bi-1,3-dithiole (MTTTF) is described. The background for sensor action is the effective MTTTF cation interaction (apparent bimolecular constant (2.0+/-0.5)*10(6) M-1 s-1 at 25-degrees-C and pH 7.0) with reduced glucose oxidase and the high electrochemical rate of mediator transformation. A glucose sensor was prepared by adsorbing mediator (MTTTF and glucose oxidase on graphite rods. The sensor responds to glucose at electrode potentials higher than 50 mV vs SCE, but the maximal activity is obtained at a potential of 250 mV. In air saturated solution the electrode shows a non-linear calibration curve with a half-saturation concentration 10.4 mM and Hill coefficient 2.08 at 250 mV. Sensor response changes little at pH 6.5-8.0. The energy of activation of the sensor response calculated from the Arrhenius equation was 64.5 kJ /mol and the temperature coefficient at 25-degrees-C was 9.2 %.