A Dual-Ion Source GC-HRMS Nontargeted Screening Strategy for Comprehensive Profiling of G-Series Nerve Agents and Related Chemicals

The practical verification analysis of chemical warfare agents, notably the G-series organophosphorus nerve agents, and their related chemicals─including precursors, byproducts, and degradation products─is critical not only for attributing the use of chemical weapons but also for retrospection of illicit production networks and gathering crucial forensic evidence. However, this task is significantly challenged by the vast "chemical space explosion" of potential analogues and the limitations of conventional database-dependent methods, necessitating high-throughput nontargeted screening approaches. In this study, following systematic characterization of fragmentation pathways and characteristic ions through integration of mass spectral libraries and clustering analysis, an integrated dual-ion source nontargeted screening strategy based on gas chromatography high-resolution mass spectrometry was established for the identification of unknown nerve agents and their related chemicals. Under electron ionization mode, a set of 52 specific "Alerting Ions" and 12 types of structures was established and applied for the rapid screening and classification of millions of suspected compounds. These candidates, after being located via retention index, were further verified under chemical ionization mode through Kendrick Mass Defect analysis of their molecular ions. Plausible structures were proposed through comprehensive spectral interpretation, and the candidate list was significantly refined using an RI prediction model. Final confirmation was achieved by comparison with reference standards. This strategy was validated using 73 home-synthesized compounds and exhibited a low limit of detection of 10-50 ng/mL. It was successfully applied to the analysis of environmental authentic samples from the Organization for the Prohibition of Chemical Weapons.