Abstract:A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of four estrogens residues (estrone, 17 β-estradiol, 17α-estradiol, estriol) in milk samples. The milk samples were extracted by oscillation with acetonitrile, dehydrated with NaCl and defatted under freezing condition, and then purified by solid-phase extraction using C18 cartridges. The analytes were separated using Hydrosphere C18 chromatographic column with gradient elution of acetonitrile/water. Finally, the eluents were qualitatively and quantitatively determined by mass spectrometer with electrospray ionization in negative multiple reaction monitoring mode. The parameters of the liquid chromatography (mobile phase, flow rate, temperature of column) and mass spectrometry were also optimized to enhance detection sensitivity. Using matrix matched external standard method, good linearity in response could be obtained with correlation coefficients larger than 0.999. All quantification limits of estrone, 17β-estradiol, 17α-estradiol and estriol were 0.2 μg/kg. At the spike levels of 0.2 μg/kg, 0.4 μg/kg and 1.0 μg/kg for each estrogen, the recoveries of estrogens were within the range of 69.7%~108.0%, and the relative standard deviation were from 4.3% to 10.5%. The above results showed that the method was accurate and reliable, and suitable for the determination of estrogens residues in milk samples.
