An amperometric biosensor was constructed by entrapment of enzyme, tyrosinase, also known as poly phenol oxidase (PPO) in an electrochemically prepared p-toluene sulfonate ion-doped polypyrrole film on a glassy carbon plate. The enzyme, tyrosinase, retains its bioactivity well within the polymer film. Phenolic compounds were quantitatively estimated in aqueous medium by the direct electrochemical reduction of enzymatically liberated quinone species at 0.05 V vs. Ag/AgCl, The results of amperometric response measurements conducted on enzyme electrode show sensitivity of 17.1, 70.2 and 24.3 muA/mM, and a linear response range of 3.3-220.3, 5.6-74.3 and 3.8-85.6 muM for phenol, catechol and p-chlorophenol, respectively. The limit of detection and a response time of the enzyme electrode are ranges from 0.8 to 2.4 muM and 40 to 75 s, respectively for these phenolic compounds. The enzyme electrode is stable for 3 months at about 4 degreesC. (C) 2004 Elsevier B.V. All rights reserved.