Sensitive Determination of Four Polypeptide Antibiotic Residues in Milk Powder by High Performance Liquid Chromatography-Electrospray Tandem Mass Spectrometry

Polypeptide antibiotics abuse can lead to antibiotic residues in food products and have unwanted effects on human health. A selective, accurate, and sensitive analytical method for the simultaneous determination of four polypeptide antibiotics (gramicidin S, bacitracin, polymyxin B, and polymyxin E) in infant formula powder was developed using solid-phase extraction (SPE) combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The samples were extracted with acidified methanol, deproteinized with acetonitrile, and degreased with n-hexane before SPE. After cleanup with 0.1% formic acid and methanol (3:1, v/v) in Oasis HLB cartridges, the extracts were analyzed by HPLC-MS/MS with electrospray ionization (ESI) source and time-scheduled multiple reaction monitoring (MRM). Linearity was assessed by using matrix-matched standard calibration and good determination coefficients (r(2) > 0.995) were obtained. The average recoveries for blank sample at three spiked concentration levels were in the range of 82.8-101.2%. The limits of detection (LODs) and limits of quantitation (LOQs) of all analytes were in the range of 5-15 mu g kg(-1) and 20-50 mu g kg(-1), respectively. The intra-day and inter-day precisions were lower than 10%. The results of method validation demonstrated that the developed method is accurate and reliable, and it can be applied for screening and quantitation of target polypeptide antibiotics in food. Graphic