Position specific isotope analysis of diethylamine by 2H and 13C NMR – Dual nucleus analysis in forensic investigation of illegal use of chemical weapons

Diethylamine (DEA) is a known precursor to some of the most toxic chemical warfare agents (CWA) as both V-agents and Fourth Generation Agents (FGAs) contain the dialkylamine functionality. DEA is also a readily available commercial substance with extensive use in the chemical industry for legitimate purposes. Because of this potential dual use, it is desirable to develop methods to trace the origin of dialkylamines if they are used for illicit purposes. We herein demonstrate that it is possible to differentiate six commercial batches of DEA using position-specific isotope analysis (PSIA) by both ²H and ¹³C NMR. Using a high-field NMR spectrometer together with a cryogenic ²H probe, we have produced ²H-{¹H} NMR data with high accuracy and precision. The PSIA by NMR results show that the intramolecular ²H ratios of all six DEAs are significantly different while two of the six DEAs have unique ¹³C ratios. Further, the intramolecular isotopic variations can be used to link the DEAs to different suppliers. The two nuclei separately contribute to isotopic profiles of the DEAs. However, combining the two techniques provides a higher-resolved isotopic profile that can differentiate all DEAs and thus be useful in forensic investigations of illegal use of chemical weapons.