Evaluation of the combination of a dispersive liquid–liquid microextraction method with micellar electrokinetic chromatography coupled to mass spectrometry for the determination of estrogenic compounds in milk and yogurt

In this work, the suitability of a methodology based on dispersive liquid–liquid microextraction (DLLME) has been evaluated for the extraction of four endoestrogens (estriol, 17α‐estradiol, 17β‐estradiol, and estrone), an exoestrogen (17α‐etynylestradiol), and a mycotoxin (zearalenone), together with some of their major metabolites (2‐methoxyestradiol, α‐zearalanol, β‐zearalanol, α‐zearalenol, and β‐zearalenol) from different types of milk (whole and skimmed cow milk and semiskimmed goat milk) and whole natural yogurt. The methodology includes a previous protein precipitation with acidified ACN and a defatting step with n‐hexane. Separation of the analytes, determination, and quantification were developed by MEKC coupled to ESI‐MS using a BGE containing an aqueous solution of ammonium perfluorooctanoate as MS friendly surfactant. Calibration, precision, and accuracy studies of the described DLLME‐MEKC‐MS/MS method were evaluated obtaining a good linearity and LODs in the low micrograms per liter range.