Identifications were considered Level 1 when the match between the standard and tentative candidate (in the CSF) yielded a SpectrumSimilarity score ≥ 0.7 and the retention time (RT) shift was <1 min. OrgMassSpecR was used to calculate spectral similarity. Xcalibur Qual Browser (version 4.1.31.9) was used to check the RT and to extract the MS/MS information.