Residual detection of buparvaquone, nystatin, and etomidate in animal-derived food products in a single chromatographic run using liquid chromatography-tandem mass spectrometry

A reliable and highly sensitive screening method based on liquid chromatography coupled with triple-quadrupole electrospray tandem mass spectrometry (LC-MS/MS) analysis has been developed for the detection and quantification of three veterinary drugs, including buparvaquone, nystatin, and etomidate impurity B CRS. The tested drugs were extracted from samples of porcine muscle, pasteurized whole milk, and eggs using 10 mM ammonium formate in acetonitrile followed by liquid-liquid purification with n-hexane. Chromatographic separation was achieved on a Phenomenex Luna C18 analytical column using 0.1% formic acid in ultrapure water (A) and acetonitrile (B) as mobile phases. All the matrix-matched calibration curves were linear (R-2 >= 0.9756) over the concentration levels of the drugs tested. Recovery at two spiking levels (equivalent to the limit of quantification (LOQ) = 5 ng/g and 2 x LOQ) ranged from 72.88% to 92.59% with intra-and inter-day precisions <17%, except for porcine muscle spiked with 5 ng/g nystatin (RSD = 25.15%). Samples collected from markets located in Seoul, Republic of Korea, tested negative for all the drugs analyzed. In summary, this method is suitable for screening and quantifying the selected drugs in a single chromatographic run and with high selectivity in animal-derived food products meant for human consumption. (C) 2017 Elsevier Ltd. All rights reserved.