| A high performance liquid chromatography- tandem mass spectrometric(HPLC- MS/MS) method was developed for the determination of cefquinome residues in animal tissues,such as beef,pork,chicken,fish and loach.The sample was extracted with acetonitrile -water(4∶1) and cleaned up with Sephadex LH-20 gel column(16 mm i.d.×320 mm).The separation of cefquinome was performed on a CAPCELL PAK MG C18(100 mm ×2.0 mm,3 μm) column using a mobile phase of 0.1% formic acid- methanol by gradient elution at a flow rate of 0.2 mL/min.The electrospray was operated in the positive ionization mode and cefquinome was identified under selective reaction monitoring(SRM) mode.The ion pairs,m/z 529.1/134.2,529.1/396.1 and 529.1/125.1 were selected as the qualitative ion pairs,and m/z 529.1/134.2 was used as the quantitative ion pair.Under the optimal conditions,the calibration curve showed a good linearity in the range of 5.0-200 μg/L for cefquinome with a correlation coefficient of 0.999 1.The limit of detection(LOD,S/N≥3) for cefquinome was 1.0 μg/kg and the limit of quantitation(LOQ,S/N≥10) was 3.0 μg/kg.The recoveries of cefquinome at four spiked concentration levles of 3.0,10,50 and 100 μg/kg ranged from 75% to 105%,with relative standard deviations(RSDs,n=6) of 2.4% - 11.9%.With the advantages of high cleanup effectiveness,good reproducibility and high sensitivity,the method could meet the requirements for the determination of cefquinome residues in animal tissues. |