Simultaneous determination of 18 β -agonist residues in feed using QuEChERS sample preparation and high performance liquid chromatography-tandem mass spectrometry

A multi-residue method was developed for the simultaneous determination of 18 β-agonist residues (clenbuterol, ractopamine, penbutolol, tulobuterol, etc) in feed by using QuEChERS sample preparation and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The feed samples were dispersed by water, then the analytes were extracted with acetonitrile containing 4% (v/v) ammonia and cleaned up by QuEChERS method with 25 mg octadecylsilyl (C18) and 50 mg primary secondary amine (PSA) adsorbents. The separation of compounds was carried on an Agilent ZORBAX Eclipse XDB-C,8 column (50 mm x 4. 6 mm, 1. 8 μm) by a gradient elution using methanol-0. 1% (v/v) formic acid aqueous solution as mobile phase. The analytes were detected by tandem mass spectrometry under multiple reaction monitoring (MRM) mode with positive electrospray ionization (ESI+) and quantified by the matrix-matched external standard method. The results showed that the calibration curves of the 18 β-agonists were linear in the range of 5 - 200 μg/L with correlation coefficients of 0. 9912-0. 9995. The average recoveries of the 18 analytes at three spiked levels of 0.05, 0.1 and 0. 5 mg/kg ranged from 78. 4% to 107. 1% with the relative standard deviations (RSDs) of 3.5%-12.3%. The limit of quantification (LOQ, S/N≥10) was 0. 05 mg/kg for each analyte. The developed method is simple and sensitive, and can be applied as a screen and confirmatory method for the analysis of β-agonists in feed.