Monday, February 6, 2012

That's some hairy chemistry

""Did YOU possibly THINK that my picture wouldn't show
up here? I'm a biochemist! I drive a Volvo!"
Photo credit: thumbpress.com
Also in this week's Chemical and Engineering News, Bethany Halford looks at the forensic chemistry of chemical weapons:
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.
I don't think I have the technique required for this kind of chemistry. Good on them. 

10 comments:

  1. That's really interesting. It reminds me of similar methods used to trace sources of radioactive material. I remember reading that they could trace the polonium-210 used to kill Alexander Litvinenko back to a Russian reactor (and therefore implicate the ex-KGB) by analyzing the precise and unique mixture of isotopic impurities that the polonium contained.

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    1. There's a wonderful passage in "The Sum of All Fears" by Tom Clancy where a NEST member and a naval officer have a conversation about radioisotopes in tracking a terrorist weapon.

      I'm always struck, that with these forensic techniques, they're all about tracking the origins of the figurative fired bullet or exploded bomb. Closing the barn door?

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    2. One of he best nuclear forensics was done with atmospheric sampling of radioactive fallout from nuclear explosions - it turns out that the isotopic signature is highly sensitive to the type of nuclear weapon used, it could unambiguously identify both the fissile and non-fissile materials used in the design, it can tell you what compression/temperatures were achieved = how effective was the implosion design, if tritium boosting was used etc. US was ahead in this forensics, US could tell from air sampling that the first USSR bomb was pretty much a replica of the Nagasaki bomb, or that Soviet thermonuclear warheads were using an earlier design that had a fatal flaw (it could be ruined by nuclear-armed interceptor blowing up miles afar) and they could tell that this flaw was fixed in later tests. Russians analyzed the fallout from the Mike test and realized that US must have a far more efficient thermonuclear design than USSR Russians best design was "Alarm Clock" aka Sloika), and this let them to search for it and come up with their own Ulam-Teller design rediscovery.

      So moving the nuke testing underground was just as practical design concealment measure as it was a political one (to minimize the fallout affecting the world population)

      Incidentally, the early atmospheric sampling schemes greatly contributed to UFO sightings (baloons from silverized Mylarsuper-thin foil, many of them getting blown by air currents all over the world) and US Air Force was thankful for the cover that the UFO news provided.

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    3. Yeah, that's what they wanted you to think! ;-)

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    4. @milkshake Is there a book you are getting this info from? It sounds like it would make for some great summer reading to go along with the John le Carre kick I am currently on.

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    5. I don't know milkshake's source, but the Richard Rhodes book "The Making of the Atomic Bomb" and the followup, "Dark Sun" are excellent reading.

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    6. There is "Brotherhood of The Bomb" from Gregg Herken - It is highly informative if sometimes dry read about Oppenhaimer, Lawrence and Teller. It is quite big on the declassified espionage and counterespionage info. Some other stuff was collected from The Nuclears Weapon Archive, The Garwin Archive and Bulletin of the Atomic Scientists (the past issues used to be free access until recently, but not anymore)

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  2. This just reminds me too much of CSI..."I found this impurity in the carpet fiber - it was made by XYZ fabrics, on their old 58mm extruder, and Bob R. was the operator that night because he always like to keep the temperature in zone 3 a little hotter than the days guys do..."

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  3. When you say "I don't think I have the technique required for this kind of chemistry" are you talking about handling nerve agents/chemical weapons or the forensic aspects? I have known a few chemists who have spent time in the chem/bio-weapons field (counter-agents) and energetic/explosives research/manufacture. Not sure comes down so much a matter of technique as having appropriate equipment and strong sense of precaution/preservation (which seems some garage labs likely would lack). Although I do doubt I would be inclined to try to test this in practice myself.

    On the other hand tracing back to specific sources of manufacturer and even lots, plus deciphering how supplier likely makes the materials, is much in the realm of process development and process validation. How often are process chemists called on the ID impurities then figure out origin or means to remove/control and on occasion make authentic samples to confirm structures? Certainly one of the biggest real-time problems is to sort out why a previously unknown or always low level peak is now visible in the product analysis. I don't see that as dissimilar from the statements above if one does switch the context of types of compounds (which can be dangerous but perhaps less chemical complex).

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    1. Yes, I was meaning that I would be terrified of getting Sarin on my pants and bringing it home with me, etc., etc.

      I suppose you're right about impurity ID, though. It's an important part of process chemistry, for sure.

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