Detection of residual bacitracin A, colistin A, and colistin B in milk by TSQ Discovery.pdf

A method based on liquid chromatography tandem mass spectrometry for simultaneous determination of residual bacitracin A, colistin A, and colistin B in milk and animal tissues was described. Validation data including precision, in terms of intra-day and inter-day recoveries, LOQ, LOD, and quality control measures were discussed in detail. Sample cleanup using a more efficient SPE cartridge resulted in comprehensive removal of the interfering substances that had been found to cause ion signal suppression during mass detection in a previous study. The method offers broad application in detecting the residual polypeptides in poultry and porcine; and allows the employment of calibration standards, instead of matrix spikes, for quantification purpose with improved detection limits, accuracy, and precision. Furthermore, by using a one-point control approach, the method provides a rapid and high-throughput method for surveillance exercises. Notwithstanding the above, the previous method [17] could still be used to quantify bacitracin A and colistin A in bovine milk and offal samples; and also it might be used, if appropriate, as a cross-checking technique with the present method for the presence of the concerned analytes in bovine samples.