Simultaneous detection of flumethasone, DL-methylephedrine, and 2-hydroxy-4,6-dimethylpyrimidine in porcine muscle and pasteurized cow milk using liquid chromatography coupled with triple-quadrupole mass spectrometry

A simple analytical method based on liquid chromatography coupled with triple-quadrupole mass spectrometry was developed for detection of the veterinary drugs flumethasone, DL-methylephedrine, and 2-hydroxy-4,6-dimethylpyrimidine in porcine muscle and pasteurized cow milk. The target drugs were extracted from samples using 10mM ammonium formate in acetonitrile followed by clean-up with n-hexane and primary secondary amine sorbent (PSA). The analytes were separated on an XBridge (TM) hydrophilic interaction liquid chromatography (HILIC) column using 10mM ammonium formate in ultrapure water and acetonitrile. Good linearity was achieved over the tested concentrations in matrix fortified calibrations with correlation coefficients (R-2) >= 0.9686. Recovery at two spiking levels ranged between 73.62-112.70% with intra- and inter-day precisions of <= 20.33%. The limits of quantification ranged from 2-10 ng/g in porcine muscle and pasteurized cow milk. A survey of market samples showed that none of them contained any of the target analytes. Liquid-liquid purification using n-hexane in combination with PSA efficiently removed the interferences during porcine and milk sample extraction. The developed method is sensitive and reliable for detection of the three target drugs in a single chromatographic run. Furthermore, it exhibits high selectivity and low quantification limits for animal-derived food products destined for human consumption. (C) 2016 Elsevier B.V. All rights reserved.