Rapid detection of chloramphenicol in animal products without clean-up using LC-high resolution mass spectrometry

A rapid confirmatory and quantitative method using liquid chromatography-high resolution mass spectrometry (LC-HRMS) was developed to determine sub-µg/kg levels of chloramphenicol (CAP) in meat products. The sample plus deuterated chloramphenicol internal standard was homogenised, extracted with ethyl acetate, centrifuged and the supernatant evaporated to dryness. The residue was re-dissolved in methanol/5% ammonium acetate solution (20:80, v/v), defatted with hexane and directly injected into the LC-MS. Chromatographic separation was performed on a C(18) column using methanol/water (60:40, v/v) as the mobile phase. CAP was detected using selected ion monitoring of the high accurate mass of the molecular ion [M-H](-) of CAP using a LTQ-Orbitrap mass spectrometer in negative electrospray ionisation mode (ESI(-)). The limit of quantification of the method was 0.1 µg/kg using isotope internal standard. Recoveries of CAP spiked at levels of 0.1-1.0 µg/kg ranged from 73 to 99%, and the relative standard deviation ranged 3.9-8.1%.