Development and validation of methods using UHPLC ESI MS/MS for the quantification of estrogenic compounds at ultra trace levels in different types of water

Natural estrogens (estrone: E1, 17-β-estradiol: E2, estriol: E3) and synthetic estrogen (17-α-ethinylestradiol: EE2) belong to the group of endocrine disrupting compounds (EDCs) harmful for wildlife and human. The European Union published a watch-list of substances including these estrogenic compounds and specified maximum acceptable method detection limit of 0.035 ng/L for EE2 and 0.4 ng/L for E1 and E2. These extremely low LODs are difficult to reach even using up-to-date analytical methods. LC-ESI-MS/MS characterized by a high sensitivity and specificity was the selected method. In the literature, ESI(-) mode was more commonly used. However, the target analytes are characterized by a low ionization efficiency in ESI(-) mode. To deal with this issue, analytes were derivatized and were analyzed in the opposite mode ESI(+). Pyridine-3-sulfonyl chloride was selected as derivatization reagent as it allowed a fast derivatization reaction, significantly increased the response of estrogenic compounds and led to specific fragments in MS/MS. The specificity of the product ions was studied by evaluating signal-to-noise ratios, chromatographic interferences and ion ratios in ground and surface water. A method with one SPE extraction was validated on mineral drinking water. The application of the method was then extended to surface water.