Suspect Screening Using Spectral Libraries

Suspect screening was conducted using the Agilent MassHunter Qualitative Analysis software (version B.07) by applying the “Find by Formula” workflow following the method described in Moschet et al. (2017)^{28 (link)}. Two curated spectral libraries, Agilent Forensic Toxicology Personal Compound Database and Library (PCDL) and Agilent Water Contaminant LC/MS PCDL, containing 8,000 and 1,450 compounds with MS/MS spectra were used. Briefly, compounds for which a chromatographic peak was found for their main adduct (mass accuracy: ±10 ppm) and for which the isotope pattern gave a good match (score > 70/100)^{28 (link)} were selected (see SI-3.2 for details). Next, the exact masses from the five main fragments in the PCDL’s MS/MS library spectra (CE 10, 20, 40) were searched in the high energy scans by the software. If one or more fragments were present and co-eluting with the parent (determined based on a coelution score in the software), the compound was automatically flagged as “qualified”. Compounds “qualified” in at least five out of the 38 samples and for which the intensity was higher than ten times the intensity in the method blank were manually inspected. If possible, a reference standard was purchased for these tentatively identified compounds (confidence level 2^{30 (link)}) for unambiguous confirmation.