Simultaneous determination of residual thiamphenicol and florfenicol in foods of animal origin by HPLC/electrospray ionization-MS/MS.

A simple and reliable method using HPLC/MS/MS has been developed for determination of thiamphenicol and florfenicol in foods of animal origin, such as pork, porcine liver, porcine kidney, beef, bovine liver, fish, and chicken. The HPLC separation was performed on a Waters XTerra phenyl column (100 x 2.1 mm, 3.5 microm) with a gradient mobile phase system of 0.1% formic acid-methanol at a flow rate 0.35 ml/min. Negative ionization produced the molecular ions at m/z 354 and 356 for thiamphenicol and florfenicol, respectively. Two characteristic transition reactions (m/z 354-->185, 290 and m/z 356-->336, 185) in the selected reaction monitoring mode were tested for detection and confirmation of thiamphenicol and florfenicol simultaneously. The analytes were extracted with ethyl acetate and defatted with n-hexane by liquid-liquid extraction. The recoveries of thiamphenicol and florfenicol by the developed method were 72.5-97.6%. The limits of determination were 1.0 ng/g (ppb) for both compounds.