Abstract: : A new method has been developed using a hybrid triple-quadrupole linear ion trap (QTrap) mass spectrometer for the fast detection and identification of nine β-agonists, clenbuterol, salbutamol, ractopamine, ritodrine, terbutaline, isoxsuprine, tulobuterol, cimaterol and bambuterol, in one single liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The homogenized tissue samples were purified with liquid-liquid extraction after enzymatic hydrolysis by β-glucuronidase/aryl sulfatase. After gradient elution separation on C18 LC column using acetonitrile and formic acid aqueous solution as the mobile phases, a multiple reaction monitoring (MRM) scan as survey scan and an enhanced product ion (EPI) scan as dependent scan were performed in an information dependent acquisition (IDA) experiment. Finally, the identification of the drugs was carried out by library search with a newly developed MS/MS library based on EPI spectra at three different collision energies in positive mode. The analytical method in the present study was well validated and good results were obtained with respect to precision, repeatability and spiked recovery. The limits of detection of residues were 0.1-0.2 μg/kg for β-agonists, and with a linear range from 0.1 to 50.0 μg/L. Three concentration levels of 0.5, 1.0 and 5.0 μg/kg were spiked in pig tissues, and the overall recoveries were between 72.0% and 95.1% with the relative standard deviations (RSDs) between 3.1% and 12.1%. The real sample test showed that this method could be used for sensitive and accurate determination of β-agonist residues in pig tissues.

Key words: β-agonists, pig tissue, spectral library, liquid chromatography-tandem mass spectrometry (LC-MS/MS)