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Fraga and colleagues at PNNL and Battelle Memorial Institute in Columbus, Ohio, recently used impurity profiling to link samples of sarin they synthesized to the specific batches of its precursor, methylphosphonic dichloride. They found they could tell what commercial manufacturer supplied the precursor and even what chemical lot it came from (Anal. Chem., DOI: 10.1021/ac202340u). “We were able to show that most of the impurities that were in the precursor transferred over into the product,” Fraga explains. “I was pretty surprised by that because there’s a distillation step that’s done, two solvent extraction steps, and we still found these impurities.”
Saphon Hok, a chemist at Lawrence Livermore National Laboratory (LLNL), in collaboration with the Swedish Defence Research Agency, has been using impurity profiling to link chemical threat agents to the method used to make them. At the American Chemical Society national meeting in Denver last fall, Hok reported that he could differentiate among four production routes to make the nerve agent known as Russian VX. He has done similar work on sarin, VX, and the blister agent sulfur mustard.
“I go through all the possible ways an agent can be synthesized, and then I go into the laboratory and make these compounds on a small scale as crudely as possible,” Hok explains. “We try to mimic someone who is trying to do this synthesis in their backyard or in their garage.” He then analyzes the compounds using liquid chromatography/mass spectrometry, gas chromatography/mass spectrometry (GC/MS), and nuclear magnetic resonance (NMR) spectroscopy. The data, he says, reveal different signatures that pinpoint the production method used.