An effective analytical strategy was developed for simultaneous determination of seven cyclopolypeptide antibiotics (vancomycin, polymyxin B, polymyxin E, teicoplanin A2, bacitracin A, daptomycin and virginiamycin M1) in feed using liquid chromatography-tandem mass spectrometry. The extraction of sample was based on acidified methanol-aqueous solution, followed by a simply dispersive solid-phase extraction for further purification with primary secondary amine as an adsorbent. The method showed good linearity for target analytes in the experimental concentration ranges. At three spiked concentration levels of 50, 100 and 200 μg/kg, the average recoveries for target compounds were in the range of 63.1%-107.5% with the relative standard deviations less than 14.7%. Matrix effects in different feeds were evaluated and the strong signal suppression (>50%) was observed. Compared with the corresponding methods in literature, the developed method is more economical, more sensitive and involves the detection of authorized/banned cyclopolypeptides in animal feed. The proposed method was successfully applied to the routine supervision and rapid screening of cyclopolypeptide antibiotics in complete and premix feed.
Keywords: Cyclopolypeptide antibiotics; Dispersive solid-phase extraction; Feed; Liquid chromatography–tandem mass spectrometry.
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