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Title: Stable-Carbon Isotope Ratios for Sourcing the Nerve-Agent Precursor Methylphosphonic Dichloride and Its Products

The ability to connect a chemical threat agent to a specific batch of a synthetic precursor can provide a fingerprint to contribute to effective forensic investigations. Stable isotope analysis can leverage intrinsic, natural isotopic variability within the molecules of a threat agent to unlock embedded chemical fingerprints in the material. Methylphosphonic dichloride (DC) is a chemical precursor to the nerve agent sarin. DC is converted to methylphosphonic difluoride (DF) as part of the sarin synthesis process. We used a suite of commercially available DC stocks to both evaluate the potential for δ 13C analysis to be used as a fingerprinting tool in sarin-related investigations and to develop sample preparation techniques (using chemical hydrolysis) that can simplify isotopic analysis of DC and its synthetic products. We demonstrate that natural isotopic variability in DC results in at least three distinct, isotope-resolved clusters within the thirteen stocks we analyzed. Isotopic variability in the carbon feedstock (i.e., methanol) used for DC synthesis is likely inherited by the DC samples we measured. Here, we demonstrate that the hydrolysis of DC and DF to methylphosphonic acid (MPA) can be used as a preparative step for isotopic analysis because the reaction does not impart a significant isotopicmore » fractionation. MPA is more chemically stable, less toxic, and easier to handle than DC or DF. Further, the hydrolysis method we demonstrated can be applied to a suite of other precursors or to sarin itself, thereby providing a potentially valuable forensic tool.« less
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  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0039-9140; PII: S0039914018303667
Grant/Contract Number:
AC05-76RL01830; HSHQPM-15-X-00055
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Name: Talanta; Journal ID: ISSN 0039-9140
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
Country of Publication:
United States
07 ISOTOPE AND RADIATION SOURCES; chemical attribution signature; chemical forensics; sarin; isotope ratio mass spectrometry; methylphosphonyl difluoride
OSTI Identifier: