Objectives To develop an analytical method for simultaneous determination of the residues of 4 quinolones (norfloxacin, enrofloxacin, ofloxaxin and ciprofloxacin) in fish by high performance liquid chromatography/electrospray tandem mass spectrometry (HPLC-MS/MS).

Methods Samples were extracted with acetonitrile in McⅡvaine buffer, and then purified by solid phase extraction cartridge (HLB), separated on a ShimpackXR-ODSⅢ C18 column, and gradient eluted with 0.1% formic acid aqueous solution and methanol. The quantification of four quinolones was achieved under a multiple reaction monitoring (MRM) mode by positive electro spray (ESI⁺).

Results There was a good linearity in the range of (0.5~100) ng/g for four quinolones, with a linear correlation coefficient of >0.995. The limit of detection for norfloxacin, enrofloxacin, ofloxaxin and ciprofloxacin were 0.7, 0.15, 0.15 and 0.7 ng/g, respectively. The limit of quantification for norfloxacin, enrofloxacin, ofloxaxin and ciprofloxacin were 2.5, 0.5, 0.5 and 2.5 ng/g, respectively. The recovery rates spiked at 5, 10 and 50 ng/g were in the range of 80.4%~104% with a relative standard deviation (RSD) of 3.2%~9.5%.

Conclusions This method was reliable with high sensitivity, good recovery and repeatability. It was suitable for the determination of quinolones residues in fish.