Detection of residual bacitracin A, colistin A, and colistin B in milk and animal tissues by liquid chromatography tandem mass spectrometry.
Liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the determination of residual bacitracin A, colistin A, and colistin B in milk and animal tissue samples. Prior to instrumental analysis, samples were subjected to acid extraction followed by solid-phase cleanup using Strata-X cartridges. Mass spectral acquisitions were performed under selective multiple reaction monitoring (MRM) mode at m/z 199 and 670 from triply charged precursors of bacitracin A (m/z 475); m/z 385 and 379 from triply charged precursors of colistin A (m/z 391); and m/z 380 and 374 from triply charged precursors of colistin B (m/z 386). Method precision was evaluated from spike recovery of samples fortified at concentrations corresponding to 2/5 of the maximum residue limits (MRLs) for each of the analytes under study. Intra-day and inter-day variations were found to range from 90.9 to 104% with relative standard deviation (RSD) <6.5%, and from 90.1 to 106% with RSD <9.1%, respectively. Limits of quantification (LOQs) were defined as the spiking concentrations at 2/5 MRL, and limits of detection (LODs) were 10-47 microg kg(-1) for bacitracin A, 1-16 microg kg(-1) for colistin A, and 6-14 microg kg(-1) for colistin B in milk and animal tissues. The presented method has good precision and high sensitivity and was applied as a fast screening protocol and a quantitative tool for monitoring of the concerned polypeptides in foods as part of a surveillance program.
Analytical and Advisory Services, Government Laboratory of the Hong Kong Special Administrative Region (HKSAR), Homantin Government Offices, Hong Kong, China.
Eric Chun-hong
EC
Wan
Clare
C
Ho
Della Wai-mei
DW
Sin
Yiu-chung
YC
Wong
D000818:Animals; D001414:Bacitracin / Q000032:analysis*; D002417:Cattle; D002853:Chromatography, Liquid / Q000379:methods*; D003091:Colistin / Q000032:analysis*; D004350:Drug Residues / Q000032:analysis*; D008099:Liver / Q000737:chemistry; D008892:Milk / Q000737:chemistry*; D015394:Molecular Structure; D018482:Muscle, Skeletal / Q000737:chemistry; D011200:Poultry; D013552:Swine; D053719:Tandem Mass Spectrometry / Q000379:methods*
D001414:Bacitracin; C026461:bacitracin A; D003091:Colistin