ENZYMATIC SENSOR COUPLED TO A FLOW-INJECTION ANALYSIS SYSTEM FOR THE DETERMINATION OF SALICYLATE

A quick and reliable enzymatic method for the direct determination of salicylate in pharmaceuticals after appropriate dilution is described. The enzyme salicylate hydroxylase was attached directly onto a platin um working electrode of a wall-jet cell coupled with a flow-injection analysis system. Therefore, the platinum electrode was oxidized, silan ized and derivatized with p-tetrachloroquinone, then the enzyme was co valently bound to the quinone and afterwards crosslinked with glutardi aldehyde. The enzymatic conversion of salicylate to the electrochemica lly detectable catechol is about 25%. It can mainly be influenced by t he amount of coenzyme added and by the flow velocity. The response of the biosensor is linearly proportional to the concentration of salicyl ate between 7.25 mu M and 4.35 mM. A high sample throughput (60 h(-1)) is possible, and the biosensor is stable for at least three months. T he assayed samples yielded relative standard deviations between 1.7 an d 4.3% and recoveries between 83 and 104%.