Green_2025_Forensic.Sci.Int_377_112641

The ongoing use of chemical warfare agents (CWAs) in conflicts, assassinations, and terrorist attacks means that the detection and identification of these compounds are crucial. The forensic identification of organophosphorus nerve agents (OPNAs) and their precursors and degradation products remains challenging due to the destructive nature and extensive preparation required for conventional chromatographic methods. In this study, we characterise precursor and degradation products of Novichok analogues, including 1,1,3,3-tetramethylguanidine, N,N-diethylpentanimidamide, N,N-dipropylbutanimidamide, using 2D 1H-13C heteronuclear multiple quantum coherence (HMQC) NMR. We further investigate mixtures of phosphonate compounds [dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate (DIMP), diethyl 2,2-diethoxyethylphosphonate (DEOP), and dibutyl butylphosphonate (DBBP)] and a fully degraded VX sample using H diffusion-ordered spectroscopy (DOSY) and 3D 1H-13C DOSY-HMQC NMR. The 1H DOSY experiments successfully separated components of both amine and phosphonate mixtures, while analysis of the degraded VX sample revealed key degradation products, including ethyl methylphosphonic acid and bis-2-(diisopropylaminoethyl)disulfide. The 3D DOSY-HMQC method provided improved resolution of overlapping signals compared to 2D approaches, representing the first application of this experiment to CWA-related compounds. These results demonstrate that DOSY-based NMR can virtually separate complex mixtures non-destructively, providing complementary capability to GC-MS and LC-MS in forensic CWA investigations.