From Single Injection to Dual Insights: Integrating EAD and CID Acquisition for Spectral Library Generation and EAD-CID Spectral Matching.

Mass spectral MS/MS libraries are essential in nontargeted metabolomics as they facilitate metabolite annotation and provide the basis for in silico annotation tools and fragmentation rules. While significant progress has been made toward more comprehensive MS/MS libraries, those efforts have focused mainly on collision-induced dissociation (CID)- and higher-energy collisional dissociation (HCD)-based approaches. In this work, we introduce a flow injection-high-resolution targeted MS/MS-based acquisition strategy that acquires electron-activated dissociation (EAD) and CID across a wide range of fragmentation energies within a single injection. The workflow supports both nontargeted and targeted analysis, through efficient library generation and MS/MS parameter optimization, respectively. We apply the workflow via a set of 45 steroid standards, known for their important role in human health, disease, and doping, expanding the coverage of public libraries for both CID and EAD. Finally, we utilize public MS/MS libraries and raw data to reveal that EAD MS/MS spectra can, to some extent, be annotated via existing MS/MS libraries, governed by CID and HCD, and show that the acquired CID library enables novel annotations in publicly available clinical data, demonstrating its utility for biological studies.