Impurity Profiling to Match a Nerve Agent to Its Precursor Source for Chemical Forensics Applications

• Published in: Analytical chemistry (Washington) 2011-12, Vol.83 (24), p.9564-9572
• Main Authors: Fraga, Carlos G, Pérez Acosta, Gabriel A, Crenshaw, Michael D, Wallace, Krys, Mong, Gary M, Colburn, Heather A
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemical Warfare Agents - analysis; Chemical Warfare Agents - chemical synthesis; Chemistry; Chromatographic methods and physical methods associated with chromatography; Cluster Analysis; Direct current; Exact sciences and technology; Forensic chemistry; Forensic engineering; Forensic Medicine; Gas chromatographic methods; Gas Chromatography-Mass Spectrometry; Impurities; Mass spectrometry; Nerves; Organophosphorus Compounds - analysis; Organophosphorus Compounds - chemical synthesis; Precursors; Profiling; Raw materials; Sarin; Sarin - analysis; Sarin - chemical synthesis; Spectrometric and optical methods; Toxicology
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac202340u

Chemical forensics is a developing field that aims to attribute a chemical (or mixture) of interest to its source by the analysis of the chemical itself or associated material constituents. Herein, for the first time, trace impurities detected by gas chromatography/mass spectrometry and originating from a chemical precursor were used to match a synthesized nerve agent to its precursor source. Specifically, six batches of sarin (GB, isopropyl methylphosphonofluoridate) and its intermediate methylphosphonic difluoride (DF) were synthesized from two commercial stocks of 97% pure methylphosphonic dichloride (DC); the GB and DF were then matched by impurity profiling to their DC stocks from a collection of five possible stocks. Source matching was objectively demonstrated through the grouping by hierarchal cluster analysis of the GB and DF synthetic batches with their respective DC precursor stocks based solely upon the impurities previously detected in five DC stocks. This was possible because each tested DC stock had a unique impurity profile that had 57% to 88% of its impurities persisting through product synthesis, decontamination, and sample preparation. This work forms a basis for the use of impurity profiling to help find and prosecute perpetrators of chemical attacks.