Rapid activity-directed screening of estrogens by parallel coupling of liquid chromatography with a functional gene reporter assay and mass spectrometry

• A platform for the identification of newly emerging estrogenic compounds.
• LC, nanofractionation, bioassay testing and high resolution MS combined.
• The platform enables the reconstruction of bioassay chromatograms.
• MS and bioassay chromatograms can be overlaid for rapid pinpointing of bioactives.
• Identification via accurate mass database searching and isotope pattern fitting.

In this study we developed a new LC nanofractionation platform that combines a human cell (BG1.Luc) gene reporter assay with a high resolution mass spectrometer for the detection and identification of estrogenic and anti-estrogenic compounds in environmental waters. The selection of this assay was based on its high sensitivity and selectivity, which is required for environmental trace level detection. We modified an autosampler and controlled it with in-house developed software to collect fractions in the low second range in microtiter plates. This ensured that chromatographic separation was maintained and allowed straightforward hyphenation with the bioassay. After bioassay testing, bioassay chromatograms were reconstructed and directly correlated with MS chromatograms that were obtained in parallel. This enabled to pinpoint bioactives in the MS chromatogram within a single fractionation cycle and results in a significant increase in throughput compared to traditional EDA studies. The sensitivity of the platform was low enough for environmental waters (80 nM for bisphenol A and 320 pM and 3.2 nM for estradiol and estriol, respectively). In addition, the ability of the platform to detect anti-estrogens was successfully demonstrated as well. Finally, real samples were analysed.