Determination of trenbolone and zeranol in bovine muscle and liver by liquid chromatography–electrospray mass spectrometry

A sensitive and selective method using liquid chromatography (LC)–electrospray mass spectrometry for the determination of growth promoters, trenbolone and zeranol, in bovine muscle and liver has been developed. The LC separation was performed on a Zorbax XDB-C18 column (150×2.1 mm I.D.) using 0.005% acetic acid–acetonitrile (60:40, v/v) as the mobile phase at a flow-rate of 0.2 ml/min. The positive ionization produced typical (M+H)+ molecular ions of α-trenbolone and β-trenbolone. On the other hand, the negative mode produced (M−H)− ion of zeranol. The calibration graphs for α-trenbolone, β-trenbolone and zeranol were rectilinear from 2.5 pg to 1.0 ng with selected ion monitoring. The drugs were extracted with 0.2% metaphosphoric acid–acetonitrile (6:4, v/v), and the extracts were cleaned up on a OASIS HLB (60 mg) cartridge. The recoveries of the hormones from bovine muscle fortified at 2 ng/g were 82.3–85.1%, and detection limits were 0.5 ng/g for each drug.