Simultaneous Determination of Clenbuterol£¬Chloramphenicol and Diethylstilbestrol in Bovine Milk by Isotope Dilution Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

KeyWord:clenbuterol  chloramphenicol  diethylstilbestrol  liquid chromatography-tandem mass spectrometry  isotope dilution  bovine milk  residue

Abstract:

      A method for the determination of clenbuterol£¬chloramphenicol and diethylstilbestrol in bovine milk was developed by isotope dilution ultra high performance liquid chromatography-tandem mass spectrometry.Samples were directly purified through HLB cartridge with 5 mL water and 5 mL hexane as washing solution.The analytes were eluted with 15 mL ethyl acetate.Then the eluate was evaporated to dryness at 40 ¡æ under nitrogen and redissolved with 5 mmol?L-1 of ammonium acetate solution-acetonitrile£¨90¡Ã10£¬by volume£©.The analytes were analyzed by LC-MS/MS on an Acquity UPLC¡k BEH C18 column using acetonitrile -5 mmol?L-1 ammonium acetate as mobile phase by gradient elution.The mass spectrometer was operated under multiple reaction monitoring£¨MRM£© mode.The samples were quantified by the internal standards labeled with stable isotopes.The calibration curves of clenbuterol£¬chloramphenicol and diethylstilbestrol were linear in the ranges of 0.2-20£¬1.2-100,2.0-200 ¦Ìg?L-1£¬respectively£¬with correlation coefficients more than 0.998 5.The limits of detection of clenbuterol£¬chloramphenicol and diethylstilbestrol were 0.009£¬0.007,0ª±04 ng?g-1£¬respectively.The recoveries of three drugs in bovine milk sample at the fortified levels of 0.05-0.10£¨clenbuterol£©£¬0.30-0.60£¨chloramphenicol£©£¬0.50-1.0 ng?g-1£¨diethylstilbestrol£© were in the range of 94%-107% with RSDs less than 10%.The method was suitable for the determination of clenbuterol£¬chloramphenicol and diethylstibestrol residues in bovine milk.