A multi-analyte stock solution contained endogenous human metabolites (145 analytes) at 50 µM (median of 9300 ng/mL) and xenobiotics, including estrogenic compounds and human estrogens (106 analytes) at a concentration between 5 -5000 ng/mL (median 100 ng/mL) and was prepared in ACN/water (50/50; v/v) (Figure ). In the context of this paper, the estrogens are evaluated together with the xenobiotic substances and mentioned accordingly. In addition, 15 different isotopically labelled standards of xenobiotics and a separate 13 C-labelled yeast extract (ISOtopic solutions, Vienna) were used as internal standards. A complete list of all analytes is available in the Supporting Information (Table ). A 24 h pooled urine sample obtained from a healthy female volunteer collected on one day after three days of a low xenoestrogen/polyphenol diet was chosen as a model matrix in this study since urine is frequently used for assessing chemical exposure. Moreover, as a second model matrix, pooled human Li-Heparin plasma was acquired from Innovative Research (Novi, USA). Arylsulfatase/β-glucuronidase from Helix pomatia was purchased from Sigma-Aldrich (Vienna, Austria). All materials were stored at -80°C prior to extraction. The concentrations of all analytes (xenoestrogens, mycotoxins, endogenous estrogens and other endogenous metabolites) in the calibration standards (8 levels) are listed in the Supporting Information (Table ).