Simultaneous determination of 14 estrogens and progesterones residues in dairy by liquid chromatographytandem mass spectrometry

A multi-residue method for the simultaneous determination of 8 estrogens and 6 progesterones in dairy by liquid chromatography-tandem mass spectrometry(LC-MS/MS) was developed.The powdered milk was dissolved in water,hormones were extracted with methanol(the analytes in liquid milk were extracted by methanol directly),and the lipids in extract solution were removed by acetonitrile saturated n-hexane.The purification was carried out on a hydrophilic-lipophilic solid phase extraction column and separation was performed using a ZORBAX Extend-C18 column by gradient elution.Electrospray ionization mass spectrometry was operated in the positive or negative mode using multiple reaction monitoring(MRM) for the analytes.Acetonitrile and water with 0.2%(V/V) formic acid were used as the mobile phase in the positive mode.Acetonitrile and water with 0.1%(V/V) ammonia hydroxide were used as the mobile phase in the negative mode.The correlation coefficients of linear calibration curves were over 0.99 in the corresponding concentration range.The average recoveries varied from 61.6% to 125.1%,and the relative standard deviations(RSDs) were 1.9%~20%.The limits of detection(LOD,S/N=3) and quantification(LOQ,S/N=10) were 0.1~1.5 μg/kg and 0.3~5.0 μg/kg,respectively.