Simultaneous determination of isoflavones and lignans at trace levels in natural waters and wastewater samples using liquid chromatography/electrospray ionization ion trap mass spectrometry

A high-performance liquid chromatography/electrospray ionization ion trap mass spectrometry (HPLC/ESI-MSn) method has been developed for the trace determination of phytoestrogens in aquatic environmental samples. The method includes solid-phase extraction (SPE) and analysis using liquid chromatography/electrospray ionization ion trap mass spectrometry. The aquatic environmental samples, influent of a wastewater treatment plant (WWTP) and creek water, were adjusted to pH approximately 5 before extraction. The analyzed phytoestrogens were identified by an MSn method and quantified against a deuterated internal standard (genistein-3',5',6,8-D4). In negative ion mode, 0.1% formic acid was employed in acetonitrile/water mobile phase. The method detection limits ranged from 0.5 to 10 ng/L in WWTP influent and from 0.1 to 5 ng/L in creek water. Average SPE recoveries for the analyzed phytoestrogens ranged from 85 to 95%, with a relative standard deviation (RSD) (%) ranging from 3.9 to 6.5. The concentrations of the six analyzed phytoestrogens varied from 0.2 to 600 ng/L with high levels of enterolignans (enterolactone and enterodiol) found in the collected wastewater. The method is shown to be suitable for the determination of phytoestrogens in aquatic environmental samples at nano- and sub-nanogram per liter levels.