Better sleuthing through chemistry

New tool can tell where, when or how a chemical warfare agent originated

SAN FRANCISCO — Finding out whodunit in chemical warfare cases may be aided by scientists focused on the howdunit.

Researchers have developed a technique to ascertain the chemical fingerprint of compounds such as mustard gas, rat poison and nerve agents such as VX. Figuring out the details of how these compounds were created in the first place could provide vital clues to law enforcement agencies aiming to catch chemical warfare criminals and help guide first responders as they gather evidence.

Chemical forensics typically focuses on identifying the compound in question, but chemist Audrey Martin and her colleagues at Lawrence Livermore National Laboratory in California wanted to take these analyses a step further. “If we already know this was a chemical attack using mustard gas, now we want to know who made it,” said Martin, who presented the research March 22 in a poster session at a meeting of the American Chemical Society held in San Francisco. “We’re looking at the next step — where did this come from?”

The technique relies on the fact that there are often many routes to the same chemical — for example there are 12 different ways of making sulfur mustard gas. Depending on the route and the ingredients, there are various chemical by-products, impurities and unreacted ingredients in the final product. The presence and proportions of these molecules can provide clues to how the compound was made, said Martin. In some cases, such as with the rat poison tetramine, one synthetic route might be ruled out entirely by the presence of a particular ingredient. Signatures of the reaction conditions, such as temperature and pressure, may also be hidden in the final product.

So far, the Lawrence Livermore team has determined these various chemical signatures for a handful of compounds, including Sarin gas and the toxic nerve agent VX. The team is also documenting how these chemicals evolve over time, so scientists can tell if something has been sitting around for five minutes, 20 minutes or a week. Martin has developed a computer application that she can feed these signatures into, minimizing time spent manually comparing chemical profiles. The researchers are also investigating how such agents interact with food and surfaces such as tile, plastic and metal. This information could help guide first responders charged with sampling a contaminated area, said Martin.

“It’s not a smoking gun,” she cautions. But if a suspect was seen purchasing a particular ingredient, or has a telltale residue on a shirtsleeve, the method might help clinch a case.  

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