Multi-residue analysis for β-agonistic drugs in urine of meat-producing animals by gas chromatography—mass spectrometry

Abstract

Two reliable gas chromatographic-mass spectrometric (GCMS) procedures for the unequivocal determination of β-agonists in urine of meat-producing animals are described. The β-agonistic drugs are extracted using disposable mixed solid-phase extraction columns. The urine sample (10 ml) is buffered (pH 6.0) and applied to a Clean Screen DAU cartridge. The analytes are eluted with ethyl acetate containing 3% (v/v) of concentrated (32%) ammonia solution. The extracted analytes are derivatized to either their trimethylsilyl (TMS) or cyclic 2-(dimethyl)silamorpholine (DMS) derivatives and analysed by GCMS under electron impact (EI) and positive-ion chemical ionization (PCI) conditions. Cyclic DMS derivatives proved to be useful for screening for or confirming the presence of clenbuterol analogues in the EI mode. If necessary, they could also be confirmed in the PCI mode using ammonia as reagent gas. With regard to TMS derivatives, their use provided a rapid and efficient method for screening for (EI) and confirming (PCI) the presence of at least thirteen β-agonists at the low ng ml −1 level.