Simultaneous determination of lincomycin and virginiamycin M1 in swine muscle, liver and kidney by liquid chromatography– electrospray ionization tandem mass spectrometry

A simple, selective and sensitive method for simultaneous determination of lincomycin (LCM) and virginiamycin M1 (VGM) in swine muscle and organs using liquid chromatography with electrospray ionization tandem mass spectrometry is presented. Acetonitrile was used to extract the analytes from the samples. Lipids in the extracts were removed by liquid–liquid partition with n-hexane. Analytes in the purified acetonitrile extracts were separated by liquid chromatography with a reversed-phase Hypersil BDS C18 column (250 mm × 2.1 mm, 5 (mu)m) under gradient elution of an ammonium formate buffer (saturated ammonium formate:formic acid:acetonitrile:water, 1:5:50:950, v/v) and 0.1% formic acid in acetonitrile at 0.2 mL min^-1. Identification was performed by monitoring two pairs of multiple reaction monitoring ions from the parent ions (m/z 407.2(right arrow)126.1 and 407.2(right arrow)359.2 for LCM, respectively, and m/z 526.3(right arrow)508.3 and 526.3(right arrow)355.1 for VGM, respectively) at the defined retention time windows and by matching of the specific tolerance of relative abundance of major ions as stated in the European Union Commission Decision 2002/657/EC. Quantification was based on the relative ratios of the sum of peak areas of major ions of the analytes to those of clindamycin (internal standard) with reference to the respective ratios of the calibration standards. The method was validated by determining and evaluating the accuracy and precision of the intra-day and inter-day repeatability at two independent spike levels and the trueness of measurements on analysis of quality check samples. The limits of detection in different matrices were found ranging from 0.6 to 1.5 (mu)g kg^-1 and 1.9 to 4.3 (mu)g kg^-1 for LCM and VGM, respectively.