It is significant to develop a method for the simultaneous determination of multiple polypeptide antibiotics residues in lake water because of the emergence of multidrug-resistant microorganisms in water. A sensitive, eco-friendly and simple method was developed for the determination of multiple polypeptide antibiotics, including vancomycin, teicoplanin, polymyxin B, colistin and bacitracin A in lake water using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Water samples were lyophilized to enrich them after adjusting the pH to 3. Then, 80% methanol in water containing 0.1% formic acid was used to reconstitute the residues for LC-MS/MS analysis. The results showed that target compounds were well separated and detected under the optimum instrumental conditions. The limits of detection and the limits of quantification of polypeptide antibiotics were in the range of 0.01 - 0.1 and 0.02 - 0.2 ng mL-1, respectively. The matrix-matched calibration curves of all compounds were linear in the calibration range of 1 - 200 ng mL-1. At three spiked levels of 0.2 (0.04), 0.4 (0.1) and 1.0 (0.2) ng mL-1 in lake water, the average recoveries of analytes were higher than 70%, except for teicoplanin, with relative standard deviations of less than 20%. Compared with other common sample pretreatment methods, the lyophilization process is simpler and more eco-friendly, achieving the simultaneous detection of multiple polypeptide antibiotics in lake water. The developed method is successfully applied to the routine monitoring of polypeptide antibiotics residues in lake water.
Keywords: Polypeptide antibiotics; lake water; liquid chromatography–tandem mass spectrometry; lyophilization.