3 4 hydroxy 3 methoxyphenyl propionic acid

We gathered fragmentation data from the QC sample $\sim 2.5$ y after the initial untargeted analysis. Where available, we used commercial standards to check putative metabolite identifications. Standards purchased included 3-(4-hydroxy-3-methoxyphenyl)propionic acid (Sigma-Aldrich, CAS 1135-23-5; putative identification for metabolite 1), ethyl 2,4-dihydroxy-6-methylbenzoate (Sigma-Aldrich, CAS 2524-37-0; putative identification for metabolite 1), argininosuccinic acid disodium salt hydrate (Sigma-Aldrich, CAS 918149-29-8 anhydrous; putative identification for metabolite 2), bergenin (Chromadex, CAS 477-90-7; putative identification for metabolite 2), and lignoceric acid (Sigma-Aldrich, CAS 557-59-5; putative identification for metabolite 3). Fragmentation data were gathered for each of the seven metabolites associated with paraben exposure and for a standard if it was detected using the same liquid chromatography–mass spectrometry (LC-MS) methods and instrument as in the untargeted analysis, with ramping from 10 to 40 eV (see Supplemental Excel File for fragmentation data). Fragmentation patterns were compared with those of commercial standards and data in public libraries using the SIRIUS and CFM-ID (Competitive Fragmentation Modeling-Identification) software.^{59 (link)–61 (link)}