Abstract: An accurate method was described for the determination of chloramphenicol (CAP) in pork. The analyte was quantified by isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) operating in negative ion multiple reaction monitoring (MRM) mode. The sample was treated by liquid-liquid extraction with ethyl acetate followed by a clean-up step on an HLB solid-phase extraction cartridge. Chloramphenicol-D5 (CAP-D5) was added as an isotope internal standard. Under the optimized conditions, the calibration curve showed a good linearity in ranging from 0.01 to 0.5 ng/g CAP. The correlation coefficient r2 was 0.9998. The limit of detection and the limit of quantification were 0.004 and 0.02 ng/g, respectively. The average recoveries of CAP at 0.02 ng/g and 1.0 ng/g spiked levels ranged from 95.2%~109.1%, 99.7%~102.5%, respectively. The relative standard deviations (RSDs) of intra-day and inter-day were less than 2%. Meanwhile, matrix effect factors k of CAP and CAP-D5 were determined under different mobile phases and the sample solvent composition, the k was in the range of 0.950~1.015. The method can be used as a confirmed method for the determination of CAP in pork.

Key words: chloramphenicol, liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS), matrix effect, pork, isotope dilution