An inhibition type amperometric biosensor based on tyrosinase enzyme for fluoride determination.

In this study, a new biosensor based on the inhibition of tyrosinase for the determination of fluoride is described. To construct the biosensor tyrosinase was immobilized by using gelatine and cross-linking agent glutaraldehyde on a Clark type dissolved oxygen (DO) probe covered with a teflon membrane which is sensitive for oxygen. The phosphate buffer (50mM, pH 7.0) at 30 degrees C were established as providing the optimum working conditions. The method is based on the measurement of the decreasing of dissolved oxygen level of the interval surface that related to fluoride concentration added into reaction medium in the presence of catechol. Inhibitor effect of fluoride results in decrease in dissolved oxygen concentration. The biosensor response depends linearly on fluoride concentration between 1.0 and 20 microM with a response time of 3 min. In the characterization studies of the biosensor some parameters such as reproducibility, substrate specificity and storage stability were carried out. From the experiments, the average value (x), Standard deviation (S.D) and coefficient of variation (C.V %) were found as 10.5 microM, +/-0.57 microM, 5.43%, respectively for 10 microM fluoride standard.