Electrochemical detection of phenolic compounds using composite film of multiwall carbon nanotube/surfactant/tyrosinase on a carbon paste electrode

A new tyrosinase-based biosensor was developed for detection of phenolic compounds using composite film of multiwall carbon nanotube (MWCNT)/dimethylditetra-decylammonium bromide (DTDAB)/tyrosinase (Tyr) on a Nafion-incorporated carbon paste electrode. The biosensor showed a sensitive electrochemical response to the reduction of the oxidation products of different phenolic compounds (phenol, catechol, p-cresol, and p-chlorophenol) by dissolved O-2 in the presence of the immobilized enzyme. The effects of pH, operating potential, MWCNT concentration, and the DTDAB/Tyr ratio on electrochemical response were explored for optimum analytical performance. The biosensor exhibited a linear response range of 1.5-25.0, 2.0-15.0, 2.0-15.0, and 2.5-25.0 mu M and sensitivity of 2,900, 3,100, 3,100, and 1,500 mu A/mM for phenol, catechol, p-cresol, p-chlorophenol, respectively. In addition, the response of the enzyme electrode showed Michaelis-Menten behavior at concentrations of the phenolic compounds higher than 5.0 mu M. The stability and the application of the biosensor were also evaluated.