Characterization of tyrosinase-Teflon/graphite composite electrodes for the determination of catechol in environmental analysis

Amperometric biosensors incorporating tyrosinase into Teflon/graphite composite were developed for the detection of catechol. The homogeneity of Teflon/graphite was elucidated by means of chronoamperometry (using ferricyanide) and the calculation of the electrochemically active and total surface area of the electrodes. The homogeneity of composite is increased when working with the frozen Teflon. The mechanical strength, sensitivity, apparent Michaelis-Menten constant, maximum currents, and the compatibility with methanol and acetonitrile of the bioelectrodes were investigated. It was found that 10-30% of graphite in Teflon were suitable for the preparation of electrodes of high mechanical strength and low electrical resistivity. The sensitivity was found to be dependent on the ratio of Teflon/graphite where higher percentage of graphite gave the highest sensitivity. Electrode responses for catechol decreased 5% during one hour of its operation in buffer solution containing 10% methanol.