Determination of salicylate in beverages and cosmetics by use of an amperometric biosensor.

A fast and selective enzymatic method for the determination of salicylate in beverages and cosmetics has been developed. The enzyme salicylate hydroxylase was immobilised covalently onto a glassy carbon working electrode of a wall-jet cell coupled with a flow-injection analysis system. The salicylate is enzymatically converted to catechol, which can be detected amperometrically on the glassy carbon electrode at +0.45 V. The response of the biosensor is linearly proportional to the concentration of salicylate between 725 nmol/l and 700 micromol/l. A high sample throughput (60 h(-1)) is possible, and the biosensor is stable for more than three months. Sample pretreatment for beverages and hair lotions is easy and fast. For creams, an extraction of salicylate is necessary. Relative standard deviations are less than 5.5% and the recoveries are between 95 and 105%.