Chemical impurity profiling: Linkage of starting materials and an intermediate synthesis product of a carbamate chemical warfare agent

Establishing links between starting materials and products is highly valuable in the investigation of the use of toxic chemicals for illicit purposes. In this study, impurity profiling was performed on starting materials and their synthesis product, 2-([dimethylamino]methyl)pyridin-3-yl dimethylcarbamate, an intermediate compound in the production route for the carbamate class of Chemical Warfare Agents. The aim was to link the five commercial starting materials to the correct synthesis products. Initially, the intermediate compound was synthesized using different batches of the two starting materials (2 plus 3 batches), producing six unique combinations. All synthesis batches and the different starting materials were analysed by gas chromatography-high resolution mass spectrometry (GC-HRMS). Chemometrics analyses were conducted with principal component analysis and orthogonal projections to latent structures discriminant analysis to extract chemical impurity profiles and to build supervised classification models.

Additionally, 12 test set samples, produced using the same starting materials by two different chemists in another laboratory, were analysed by GC-HRMS. A classification model able to distinguish all supplier combinations was successfully created and used to link the test set samples to their corresponding starting material.

Furthermore, a new set of synthesis samples was extracted with a work-up procedure before analysis to investigate the effect of higher sample purity on the classification model. The results show that linking the synthesis products to their starting materials was successful for one of the starting materials, despite the purification procedure.