Hydroxyl Group Derivatization of Steroid Environmental Endocrine Disrupting Chemicals

The derivatization of hydroxyl groups of steroid environmental endocrine-disrupting chemicals, such as estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2), with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as derivatization reagent followed by gas chromatography–mass spectrometry (GC-MS) was studied. The effects of the amount of BSTFA, derivatization temperature and time on the derivatization of target compounds; the stability of steroid derivatives; calibration curves; and instrumental quantification limits were systematically investigated. The cleavage mechanism of steroid derivatives and characteristic fragment ions was also interpreted. Better derivatization results were obtained when the amount of BSTFA was 25 μl for 100 μl steroids standard mix solution at 0.01 g l−1 and when the steroids were derivatized with BSTFA at room temperature (20 °C) for 10 min without heating, which was different from nearly all the previous studies. The derivatives of target compounds were stable because their relative response factors had no observable change when deposited at −20 °C for 48 h. Under the optimal conditions, good linear correlation was obtained, and the instrumental quantification limit was 0.3 μg l−1 for E1 and E2 and 5 μ g l−1 for EE2 and E3.