Stir bar sorptive extraction with in situ derivatization and thermal desorption–gas chromatography–mass spectrometry in the multi-shot mode for determination of estrogens in river water samples

A novel method for the trace analysis of natural and synthetics estrogens, such as estrone (E1), 17β-estradiol (E2) and 17α-ethynylestradiol (EE), in river water sample was developed, which involved stir bar sorptive extraction (SBSE) with in situ derivatization followed by thermal desorption (TD)–gas chromatography–mass spectrometry (GC–MS). The derivatization conditions with acetic acid anhydride and the SBSE conditions such as sample volume and extraction time were investigated. In addition, the single and multi-shot modes in TD were investigated. The detection limits of E1, E2 and EE in river water sample were 0.2, 0.5 and 1 pg ml−1 (ppt), respectively, in the multi-shot mode using five stir bars. The calibration curves for E1, E2 and EE were linear and had correlation coefficients >0.99. The average recoveries of E1, E2 and EE from all sample volumes were higher than 90% (R.S.D. < 10%) with correction using an added surrogate standard such as estrone-13C4, 17β-estradiol-13C4 or 17α-ethynylestradiol-13C4. This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of estrogens in water samples.