Sensitive mediator-free tyrosinase biosensor for the determination of 2,4-dichlorophenol

A novel tyrosinase-based biosensor was developed for the determination of 2,4-dichlorophenol (2,4-DCP) by immobilizing tyrosinase on multi-walled carbon nanotubules (MWNTs) and polydiallyldimethylammonium chloride (PDDA) modified glassy carbon electrode. The biosensor showed a sensitive electrochemical response to 2,4-DCP in the presence of oxygen in solution. The effects of pH, adsorption time of PDDA, amount of tyrosinase immobilized on the enzyme electrode, and the volume of the MWNTs solution during the preparation of the sensor on the amperometric response of the electrode were explored for optimum analytical performance. The biosensor exhibited a fast amperometric response (less than 7 s), a high sensitivity and good storage stability for monitoring 2,4-DCP. The method showed good linearity in the range from 2 mu m to 100 mu m 2,4-DCP with a correlation coefficient of 0.997 and a detection limit of 0.66 mu m. The response of the electrode showed Michaelis-Menten behavior at lower 2,4-DCP concentrations. The K-m(app) value of immobilized tyrosinase on the modified electrode was calculated to be 66.3 mu m using 2,4-DCP as the substrate.