The identification of VX chemical attribution signatures from different synthetic routes

Despite it being banned under the Chemical Warfare Convention, VX is still being used, as demonstrated in 2017 with the assassination of Kim Jong Nam in Malaysia. In addition to conducting the typical forensic investigations, incidence of the deliberate use of chemical warfare agents (CWA) such as VX could also include undertaking chemical forensics to address questions including method of production, precursor-product-matching and batch-matching. The identification of residual impurities in VX, known as chemical attribution signatures (CAS), that allow for these questions to be addressed, would be beneficial to agencies undertaking these investigations. To increase the knowledge pool regarding CAS specific to a particular production method, five synthetic routes of VX formation were chemically profiled and subjected to multivariate analysis. In total, forty-one impurities of interest were identified that could be attributed to a production method. The structures of thirty-four were confirmed through a combination of database matching, accurate mass measurement, literature analysis and comparison with authentic standards. Several of these impurities were identified as candidate CAS for method attribution. Additionally, the longevity of the CAS was assessed by analysing samples after storage for 18 months at room temperature. While samples could not be classified (via MVA) to a specific production method, nineteen candidate CAS were still able to be identified. These results are suggestive that VX method of production may still be able to be elucidated on long term storage.