Microdetermination of Catechol Estrogens by Liquid Chromatography-Electrospray Ionization Tandem Mass Spectrometry Combined with Picolinyl Derivatization

Abstract

A simultaneous method for quantification of four catechol estrogens, namely, 2-hydroxyestrone, 2-hydroxyestradiol, 4-hydroxyestrone, and 4-hydroxyestradiol by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was developed in a positive mode for analyzing a simple picolinyl derivatization. Reaction of these estrogens with picolinyl derivatization reagent resulted in the formation of di- or tri-picolinyl derivatives, and the derivatives exhibited single charged protonated molecules as base peaks in a positive mode in electrospray ionization/mass spectrometry (ESI-MS). Picolinyl derivatives of these catechol estrogens provided approximately 10 times greater ESI responses in LC-ESI-MS/MS (selected reaction monitoring) compared with those of underivatized molecules in a negative mode. The use of picolinyl derivatizatives, solid-phase extraction, and a 13C-labeled internal standard helped us in determining these catechol estrogens whose quantification limit was 20 pg for every sample. The present method was applied for quantifying these catechol estrogens in a biological sample.