Path: utzoo!utgpu!watserv1!watmath!att!cbnews!military
From: djm@castle.ed.ac.uk (D Murphy)
Newsgroups: sci.military
Subject: Explosives detector
Message-ID: <1990Aug2.042232.2843@cbnews.att.com>
Date: 2 Aug 90 04:22:32 GMT
Sender: military@cbnews.att.com (William B. Thacker)
Organization: Edinburgh University Chemistry
Lines: 29
Approved: military@att.att.com



From: D Murphy <djm@castle.ed.ac.uk>

I suppose this might really go into `sci.antiterrorism' :-) but..

An article in `The Scotsman' newspaper today (01-08-90) says that a device
has been developed which is capable of detecting small quantities of
explosives, including TNT, nitroglycerine and `semtex'.

It consists of a handheld, battery operated `sniffer' which passes air sucked
from the object being tested into a gas chromatograph. The standardised 
conditions inside the chromatograph allows the identification of vapours
around the object by the time they are retained in the machine. Different
retention times both separate components and can identify them by comparison
with known values of a `genuine' sample. Israel is said to have bought a
couple of the machines for an estimated 200,000 pounds (ca. US$300,000).

This is important in combatting the use of `semtex' plastic explosives
which do not show up on conventional x-ray scanners. The article did not
say whether the `semtex' standard used to allow identification checked for
the presence of RDX (hexogen - the explosive constituent of the military
semtex-H which caused the Lockerbie disaster) or the plasticising agent which
would presumably allow detection of a wide variety of plasticised explosives.
It is more likely, however, that the signatures used in identification are
mixtures of different components, and that a `likelyhood' criterion is
used by the equipment for giving a warning.

Murff... djm%ed.castle@nsfnet-relay.ac.uk