Chromatography-free high throughput analysis by matrix assisted laser desorption ionization mass spectrometry,...

Analyzing and understanding the impurity profile and the Chemical Attribution Signature (CAS) of chemical warfare agents (CWAs) can provide valuable chemical forensic insights. Determining the synthetic route enables the forensic linking of the use of a given chemical and its origin to support investigations. Previously, we demonstrated the feasibility to use untargeted mass spectrometry-based strategies to differentiate synthesis routes based on chemical profiling of crude chlorpyrifos samples taken as a first use-case by ultra-high-performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). In this proof of principle study, we investigated Matrix Assisted Laser Desorption Ionization (MALDI) coupled to HRMS to screen impurities resulting from the synthesis of chlorpyrifos. Data from our approach were assessed to ensure that they provide sufficient discriminatory power to unambiguously identify the synthesis route employed. Additionally, unknown samples were also analyzed in MALDI-HRMS to assess method performance. The use of and Trapped Ion Mobility Spectrometry (TIMS) enabled decreasing the limit of detection (LOD) for the majority of relevant compounds, improved peak resolution and accurate mass assignment. The acquisition of MS/MS spectra allowed confirmation of impurity identifications. The suspect screening approach employed with a list of discriminating impurities allowed the determination of the synthetic pathways of unknown samples using unsupervised statistical analysis. For high throughput analyses, MALDI-IM-HRMS analysis offers tenfold time saving compared with conventional UHPLC-HRMS approaches.