Immobilization of Tyrosinase on (3-Aminopropyl)triethoxysilane-Functionalized Carbon Felt-Based Flow-Through Detectors for Electrochemical Detection of Phenolic Compounds

Tyrosinase (TYR) was covalently immobilized onto amino-functionalized carbon felt (CF) surface via glutaraldehyde (GA). Prior to the TYR-immobilization, primary amino group was introduced to the CF surface by treatment with 3-aminopropyltriethoxysilane (APTES). The resulting TYR-immobilized CF was used as a working electrode unit of an electrochemical flow-through detector for monoand di-phenolic compounds (i.e., catechol, p-cresol, phenol and p-chlorophenol). Additionally, flow injection peaks based on electroreduction of the enzymatically produced o-quinone species were detected at −0.05 V vs. Ag/AgCl. The resulting TYR/GA/APTES/CF biosensor responded well to all compounds tested with limits of detection range from 7.5 to 35 nmol−1 (based on three times S/N ratio). Moreover, such modified electrode exhibits good stability and reproducibility for catechol. No serious degradation of the peak current was found over 30 consecutive injections.