Amperometric catechol biosensor based on polyaniline–polyphenol oxidase

A novel catechol biosensor was described based on the immobilization of polyphenol oxidase (PPO) into polyaniline (PANI), which was easily constructed by direct electropolymerization of aniline in a solution containing ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES). The developed biosensor for the detection of catechol has a linear range of 1.25–150 μmol dm−3. The maximum response current (Imax) and the Michaelis–Menten constant (k′m)(k′m) are 0.62 μA and 146 μmol dm−3, respectively. The activation energy (Ea) of the PPO catalytic reaction is 31.1 kJ mol−1 in the B–R buffer. The biosensor shows good reproducibility (a relative standard deviation of 3.1% was obtained) and remarkable long-term stability (it retains 75% of the original activity after four months). The effects of potential and pH on the response current of the biosensor are also described.