Silica sol–gel immobilized amperometric biosensor for the determination of phenolic compounds

An amperometric enzyme electrode for phenolic compounds was developed via an easy and effective immobilization method using the sol–gel technique. The enzyme electrode comprises tyrosinase immobilized by the thin silica sol–gel layer on a carbon-paste electrode. The tyrosinase retains its bioactivity when being immobilized by the sol–gel film. Phenolic compounds were determined by the direct reduction of biocatalytically liberated quinone species at 0 mV vs. Ag/AgCl (sat. KCl). The process parameters for the fabrication of the enzyme electrode were optimised. The influence of various experimental variables was explored for optimum analytical performance of the enzyme electrode. The effect of oxygen on the response of the enzyme electrode was evaluated. The sensitivities of the enzyme electrode for catechol, phenol, p-cresol, m-cresol, o-cresol and 2-chlorophenol were 1.53, 1.28, 1.05, 0.687, 0 and 0 A M−1, respectively. The enzyme electrode retained ca. 50% of its activity after 15 days of storage in a phosphate buffer solution at 4°C.