A multi-residue method for the determination of seven polypeptide drug residues in chicken muscle tissues by LC-MS/MS

A new multi-residue method for the determination of seven polypeptides, namely, polymixin B1, polymixin B2, polymixin E1 (colistin A), polymixin E2 (colistin B), enduracidin A (enramycin A), enduracidin B (enramycin B), and bacitracin A, in food of animal origin was developed and validated for chicken muscle tissue. Chicken muscle tissue was extracted with acidified methanol (1 % TFA). After homogenization, shaking, and centrifugation, the acidified methanol extract was decanted. A second extraction was performed with methanol (1 % TFA) and formic acid (1 %) 25:75, v/v. The pooled extract was cleaned up and concentrated on a solid-phase extraction cartridge. The retained analytes were eluted with methanol/acetonitrile. The extract was evaporated to dryness, reconstituted in mobile phase, filtered, and quantified by LC-MS/MS under ESI conditions. The method has a LOQ of 50.0 μg/kg for polymixin E2 (colistin B), 39.0 μg/kg for polymixin E1 (colistin A), 74.0 μg/kg for polymixin B1, 71.0 μg/kg for polymixin B2, 66.0 μg/kg for enduracidin A, 50.0 μg/kg for enduracidin B, and 30.0 μg/kg for bacitracin A in chicken muscle tissues. This is the first sensitive, suitable, multi-residue method reported for the seven polypeptide drug residues in chicken muscle tissue.