Determination of estrogens and estrogen mimics by solid-phase extraction with liquid chromatography-tandem mass spectrometry

An analytical method has been developed and validated for the determination of six estrogens and estrogen mimics, namely estriol (E3), bisphenol A (BPA), 17β-estradiol (E2), estrone (E1), ethynyl estradiol (EE2) and dienestrol (DIE), with frequent occurrence in the natural environment. Solid phase extraction coupled with liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) using electrospray ionization (ESI) in a negative mode was applied to concentration, identification, and quantification of estrogens and estrogen mimics. The SPE conditions were optimized as the selection of C18 as cartridges and MeOH as an eluent, and the control of solution pH at 9.0. The method was validated by satisfactory recoveries (80–130%) and intra-day and inter-day precision (<18.4%, as relative standard deviation), and excellent linearity for calibration curves (R² > 0.996). The limits of detection (LODs) for six target estrogenic compounds ranged between 2.5 and 19.2 ng/L. The effects of matrix background on the determination were evaluated in terms of LODs, LOQs, analyte recovery, and slopes of calibration curves in five different water matrices. Matrix effects by tap water were negligible. However, both matrix suppression and enhancement (i.e., E3, E1, DIE) were observed in surface water and wastewater. The positive correlation between LODs and TOC in various water matrices indicated the negative effect of organic pollutants on the method sensitivity. The sum of target estrogenic compounds in environmental samples were within 17–9462 ng/L.