S1 Supporting Information 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Estrogenic Activity Measurements in Water Using Diffusive Gradients in Thin-film Coupled with an Estrogen Bioassay Wei Guo, †, ‡, a Kersten Van Langenhove, †,a Michael S. Denison, § Willy Baeyens, † Marc Elskens, † Yue Gao * ,† † Analytical, Environmental and Geo-Chemistry (AMGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussel, Belgium ‡ School of Environmental Science and Engineering, North China Electric Power University, Beijing, 102206, China § Department of Environmental Toxicology, University of California, Davis (UC Davis), One Shields Avenue, Davis, CA 95616, USA Table of contents The extraction procedure of aqueous samples The extraction procedure of XAD 18 resin VM7Luc4E2 cells cultivation, seeding and dosing in 96 well plates Diffusion Boundary Layer (DBL) measurements Figure S1. The uptake characteristics of E2 on XAD 18 resin gel at different E2 concentrations. Figure S2. DGT deployments in the laboratory and in the field (Sampling station GBD- 2 in Gaobeidian sewage treatment plant in Beijing). 1/mass of E2 on XAD 18 resin gel is plotted versus the diffusive layer thickness. 28 29