Flow-injection analysis with electrochemical detection for determination of salicylic acid in pharmaceutical preparations

Abstract An enzyme-based flow-injection system with electrochemical detection suitable for the determination of salicylic acid in pharmaceuticals is described. The method makes use of the enzyme salicylate hydroxylase (EC 1.14.13.1), which is covalently bound to glass beads and put into the reactor of a flow system. The enzyme catalyses the stoichiometric conversion of salicylic acid to catechol, which can then be detected amperometrically at +0.45 V (vs. Ag/AgCl/KCl sat. ). The electrode response is linearly proportional to the concentration of salicylic acid between 5 and 150 μg ml −1 . The detection limit is 0.4 μg ml −1 . This method is simple, rapid and specific. The assayed samples yielded relative standard deviations between 0.5 and 2.0% and recoveries between 93 and 98%.