The PETN detection universe

29 December 2009 - Counter terrorism

klik hier voor de afbeelding op ware grootteAs the son of a high ranking Nigerian banking official suspected terrorist Abdulmutallab of course carried a diplomatic passport while boarding Northwest Airlines Flight 253, at Schiphol Airport all regular personnel was replaced by inexperienced temporary staff on account of Christmas, even the bomb dog was having a day off and the so-called 500,000 TIDE list is so severely polluted and outdated that no one is supposed to look at it. Questions for this blog however are strictly chemistry related. Would 80 grams of PETN have done the job and what does it take to detect the explosive before it gets on board?.

With regards to the first question missile and explosives expert Herman Schöyer in an interview to NRC thinks not unless Abdulmutallab "placed the PETN in a box against a wall" first. Detonating a quantity of loose powder will definitely not work. This blog realises it is never smart to give terrorists free advice (like Hermann just did) but as PETN dissolves very well in acetone how about impregnating your clothing with the stuff and then stuff it the box!. By the way, the news reports continue to mention a syringe with which the explosive was somehow activated. From a chemistry point of view this does not make sense as there is no apparent two-component mechanism at work.

With regard to the second question - how to detect PETN at the airport - the general complaint according to the news media is the lack of sophisticated and very expensive backscatter X-ray equipment. Problem is that this equipment would detect powder in a condom hidden on a body but not the hypothetical PETN impregnated clothing. Backscatter X-ray primarily scans objects, it does not detect chemicals. On the other hand the radiation analyzed is sensitive to the low atomic number elements (C,N,O) and it therefore makes organic materials stand out compared to metals. If backscatter equipment exists ultra sensitive to nitrogen is another matter. In one report at least (DOI) with a lot of more free advice on how not to smuggle illicit goods, a backscatter image identifies a parcel of plastic explosive in a batch of chocolate parcels.

An alternative to backscatter X-ray and sometimes found in US airports is the puffer machine: a puff of air flushes out any airborne chemical on a passenger and the chemicals are then tested inside a mass spectrometer. Now this machine can actually tell if someone has been in contact with PETN which only leaves the job of excluding any medical personnel because very inconveniently PETN is also a cardiac drug.

Third option overlooked thus far by the media is the good old fashioned bomb sniffing dog. Here is some free advice for Schiphol Airport Security: bombdog4sale. Dog Miya has degrees in TNT, RDX and PETN and does not mind working irregular shifts.

See also: the chemists working on the other side of the fence

Update (30-12): explosives expert Jimmie C. Oxley in the NYT(link) is also clueless on the syringe: according to Oxley PETN itself does not detonate very easily the reason why in the 2001 shoe bomb plot the detonator for the PETN was TATP. However as TATP is again a solid this does still not explain the syringe.

Update (13-01-2010): Thanks to reader M. for interesting comments. The primary interest of this blog is the way the media have been reporting on this incident with respect to the technology involved. Do the body scanners that Schiphol Airport plans to have installed really detect explosive powders or just powders? With respect to the mystery syringe the relevant question is: was the suspected terrorist actually capable with chemicals?.
Also thanks to reader D. Yes, Dr Oxley was not exactly clueless, she did have a theory but told the NYT reporter but I'm not going to tell you - no free advice there.