DETERMINATION OF BETA-2-RECEPTOR AGONISTS IN BOVINE URINE AND LIVER BY GAS-CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY

Abstract

A highly specific and sensitive method for the simultaneous detection of seven beta-2-receptor agonists in bovine liver homogenates and urine was developed. A 10-g amount of liver was homogenized and treated with Subtilisin A(R). The resulting enzymatic digest was extracted with tert.-butanol-ethyl acetate (3:7) and the crude extract was purified on a 6-ml Bakerbond(R) alumina neutral disposable extraction column. Subsequently, the hydrous eluate from the alumina column was buffered at pH 6 and loaded on top of a preconditioned 3-ml Bond-Elut Certify(R) column. Urine was buffered and loaded onto a 3-ml Certify column without pretreatment. The analytes were eluted with dichloromethane-isopropanol (8:2) containing 2% ammonia. The extract obtained was trimethylsilylated and analysed by gas chromatography-tandem mass spectrometry using multiple selected reaction monitoring. The limits of detection for the beta-2-receptor agonists evaluated were between 0.5 and 5 ppb.