Simple extraction method for quantification of phenothiazine residues in pork muscle using liquid chromatography-triple quadrupole tandem mass spectrometry

In this study, an analytical method was developed for quantification of residues of the anthelmintic drug phenothiazine (PTZ) in pork muscle using liquid chromatography-tandem mass spectrometry. Muscles were extracted using 0.2% formic acid and 10mm ammonium formate in acetonitrile, defatted and purified using n-hexane. The drug was well separated on a Waters XBridge C-18 analytical column using a binary solvent system consisting of 0.2% formic acid and 10mm ammonium formate in ultrapure water (A) and acetonitrile (B). Good linearity was achieved over a six-point concentration range in matrix-matched calibration with determination coefficient =0.9846. Fortified pork muscle having concentrations equivalent to and double the limit of quantification (1ng/g) yielded recovery ranges between 100.82 and 104.03% and relative standard deviations <12%. Samples (n=5) collected from large markets located in Seoul City tested negative for PTZ residue. In conclusion, 0.2% formic acid and ammonium formate in acetonitrile can effectively extract PTZ from pork muscle without solid-phase extraction, a step normally required for cleanup before analysis and the validated method can be used for routine analysis to ensure the quality of animal products.