Simultaneous determination of the 18 steroids in hypotha-lamic pituitary gonadal axis based on UPLC–MS/MS with multimode ionization

To objectively quantify changes in steroid hormones in organisms caused by adverse environmental loads, we developed a simple and sensitive UPLC-MS/MS (ultra-performance liquid chromatography triple quadrupole mass spectrometry) method for the simultaneous determination of 18 steroid hormones on the HPG axis. This analytical method was based on liquid extraction and a multimode electrospray and atmospheric pressure chemical ionization (ESCi) source, which was optimized by mass spectrometry, liquid phase and pretreatment for the quantification of cholesterol (CH), aldosterone (A), cortisone (E), hydrocortisone (F), 21-deoxycortisol (21-DF), corticosterone (B), 11-deoxycortisol (11-DF), androstenedione (A