Development and validation of an UHPLC-ESI-MS/MS method to quantify estrogenic compounds as pyridine-3-sulfonyl derivatives in aqueous matrices

Natural estrogens (estrone: E1, 17-β-estradiol : E2, estriol : E3) and synthetic estrogen (17-α-ethinylestradiol: EE2) are powerful endocrine disruptors. They may have deleterious effects on aquatic wildlife and also humans even at extremely low concentrations. For this reason, these molecules have been included in a watch list from the European Commission regarding emerging aquatic pollutants. The maximum detection limits are set at 0.035 and 0.4 ng/L for EE2 and E1, E2 respectively. Reaching such low levels of concentration of estrogenic compounds is a challenge, even using state-of-the-art analytical methods. In this study, we developed a UHPLC-ESI-MS/MS (ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry) method allowing the quantification of E1, E2, E3 and EE2 residues in aqueous matrices. Studies commonly used ESI in negative mode, albeit the poor ionization efficiency of native estrogenic compounds in this mode. In this study, the molecules were derivatized using a sulfonyl chloride reagent: pyridine-3-sulfonyl (P-3-S). The resulting response in the positive mode was significantly enhanced. Similarly to other dansyl derivatives, the product ion spectra of the P-3-S derivatives indicate ions originating from the derivatization reagent moiety (Zhang et al. 2004). Moreover, several other ions were included in the product ion spectra of the P-3-S. Their specificity was assessed by a qualitative approach implying the analysis of different types of water samples (groundwater, surface water). Some product ions were found to be noticeably better for quantification and confirmation of the analytes. The developed analytical method was validated according to the NF T90-210 norm which is suitable to assess the performances of a method in the water quality field. The limits of detection were 0.012, 0.015, 0.030 and 0.006 ng/L in groundwater and 0.267, 0.237, 1.33 and 0.087 ng/L in surface water for E1, E2, E3 and EE2 respectively