Penning an answer to terrorism

Israeli researchers have designed a portable tester that can identify improvised explosives commonly used by terrorists.

The Peroxide Explosive Tester (PET) resembles a thick three-coloured pen and responds to tiny traces of the substance triacetone triperoxide (TATP). TATP is easy to prepare and difficult to detect, hence its popularity with terrorists. The explosive has been used in suicide bomb attacks on buses, shops and nightclubs in Israel.

‘Before the development of the pen there was no way to detect this compound,’ said PET’s inventor, Prof Ehud Keinan, dean of the Faculty of Chemistry at Technion, the Israel Institute of Technology. ‘Conventional explosive detectors cannot identify it.’

Unlike standard explosives, TATP does not release heat during the explosion. It explodes through rapid decomposition of its solid state molecules to four gas phase molecules, rather like the reaction that produces gas to deploy vehicle airbags.

The PET can produce a result in around 20 seconds, and researchers are currently working to reduce its size further. The device has three push-down levers, each of which releases 100 microlitres of a solution into a central, transparent chamber.

The pen’s silicon rubber tip is designed to be detached from the device then placed against, for example, an item of clothing worn by a suspected terrorist, then reattached to the pen. Each of the three levers is then pressed in turn.

The first solution decomposes any explosive present to release hydrogen peroxide, while the others add a substrate then an enzyme that uses any hydrogen peroxide in the sample to catalyse oxidation of a pigment. If any explosive is present then the pigment is activated and the solution in the testing chamber turns blue-green. Though grains of the explosive resemble sugar, the PET can detect quantities that are invisible to the eye.

Keinan and his team are now working to develop similar devices that can identify traces of other explosives and illegal drugs.