A polypyrrole-bienzyme electrode (salicylate hydroxylase-polyphenol oxidase) for the interference-free determination of salicylate

Th, electrochemical immobilization of salicylate hydroxylase (SH) within po ly(amphiphilic pyrrole ammonium) films electrogenerated on carbon electrode is described. The amperometric determination of salicylate, is carried out at 0.4 V (vs. Ag/AgCl) via the oxidation of the enzymically generated cate chol. The detection limit and the sensitivity of the polypyrrole-SH electro de were 3 x 10(-9) M and 1.7 AM(-1) cm(-2) respectively. Moreover, the co-e ntrapment of SH and polyphenol oxidase (PPO) in such polypyrrole, films pro vides a bienzyme electrode also for the determination of salicylate. Contra ry to the monoenzyme electrode, the functioning principle of the bienzyme e lectrode is based on the reduction of o-quinone enzymically generated from catechol. Consequently, the amperometric detection of salicylate, was, perf ormed at -0.2 V without interferences from easily oxidizable compounds. The calibration range for salicylate, measurement and the biosensor sensitivit y were 5 x 10(-8)-3 x 10(-6) M and 0.25 A M-1 cm(-2), respectively.