Speedy Homemade-Explosive Detector

A new portable device detects homemade explosives of a kind frequently used for terrorist attacks about twenty times faster than previously possible (Anal. Chem., DOI: 10.1021/ac2020195). Researchers hope the test could expand the range of explosives detected by airport screening, without taking more of passengers’ time.

Today’s screening technologies, including those used at the airport to analyze swabs from suitcases, are good at detecting commercial explosives. These explosives are organic-based and contain volatile chemicals that are easy to separate out and identify by analytical methods.

“Homemade bombs are much harder to detect,” says Michael Breadmore, associate professor of chemistry at the University of Tasmania, in Australia. The problem is that these kinds of explosives contain inorganic molecules, such as nitrates and chlorates, that aren’t volatile. It takes some finesse, and time, to separate these ions out of a sample for detection, Breadmore says. Speed is key in explosives detection, he adds: Security officials don’t want to further irritate airline passengers during screening. Also investigators need to track down the source of an explosive, and its maker, as quickly as possible after a bomb detonates.

To speed up the process, Breadmore’s lab, with the support of Australian government agencies, developed instrumentation and chemistry to identify inorganic explosives before and after detonation in less than 60 seconds. The technique is based on capillary electrophoresis. After collecting a sample, either by swabbing a suitcase handle or gathering debris left after an explosion, the investigator dissolves it and then injects the solution into a capillary filled with a flowing electrolyte solution under the influence of a strong, applied electric field. The sample’s ions move through the capillary at different speeds depending on their electrical charge and size. As they move past a conductivity detector, the investigator can identify the ions based on their charge and the time it took them to travel through the capillary.

As proof of concept, the Tasmanian researchers showed that this setup could detect nitrate, perchlorate, chlorate, and azide molecules from detonated inorganic explosives in soil samples.

Bruce McCord, a forensic scientist at Florida International University, who was not involved with the project, says that what distinguishes the new system from older ones is its potential for portability, and “a definite advantage in terms of speed.”

Now the researchers are working with a contract engineering company to develop a user-friendly interface for security personnel. Breadmore says they’ll finish testing the completed system by mid-2012.

Chemical & Engineering News

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