Detection of Residual Chloramphenicol, Florfenicol, and Thiamphenicol in Yellowtail Fish Muscles by Capillary Gas Chromatography−Mass Spectrometry

Chloramphenicol (CAP), florfenicol (FF), and thiamphenicol (TAP) were extracted from yellowtail muscles with ethyl acetate, and the extract was evaporated. The residues was dissolved with sodium chloride solution and partitioned with n -hexane to remove lipids, and then the drugs were extracted with ethyl acetate. After evaporation of ethyl acetate extract, the residue was dissolved with n -hexane followed by ethyl ether and applied to a Sep-Pak Florisil cartridge successively. The drugs were eluted from the cartridge with methanol−ethyl ether (3:7), and eluate was evaporated to dryness. After acetonitrile and BSA were added to the residues, the drugs were derivatized at 50 °C for 10 min. After the solvent was evaporated, the residue was dissolved with ethyl acetate and applied to gas chromatography−mass spectrometry. The drugs were separated by a capillary column coated with 5% phenyl methyl silicone, and SIM was performed at m / z 208 and 225 for CAP, at m / z 257 for FF, and at m / z 242, 257, and 330 for TAP. Recoveries of each drug from yellowtail muscle fortified at 0.1 ppm were more than 65%, and detection limits were 5 ppb.