Feed additives in animal nutrition: Quantification of a new adrenergic drug by hyphenated techniques

Zilpaterol, (+/-)-trans-4,5,6,7-tetrahydro-7-hydroxy-6-(isopropylamino) imidazo [4,5,1-jk]-[1]benzazepin-2(1H-one, is an adrenergic agonist drug licensed in Mexico and South Africa as feed additive for cattle at slaughter age. In contrast, the EU legislative framework prohibits the use of beta-agonists as growth promoters to produce lean meat. In this study, the compound was quantified as its TMS derivative both by gas chromatography-mass spectrometry (GC-MS) with a quadrupole detector (QUADR) and by GC-MS/MS with an ion trap detector (ITD), in Electron Impact (El) ionization. Subsequently, an extraction and clean-up procedure for the identification of Zilpaterol in commercial feeds was set up. Different extraction solvents and matrices were considered for their influence on Zilpaterol yield. The analytical method led to good recoveries and limits of detection and quantification in feeds well below the 5-20 mug/g dose proposed for animal nutrition.