Explosives detection research

Baggage Check
Technology strives to detect explosives faster

by DWAYNE STEWARD
Features Writer
Perspectives
Thursday May 31, 2007



Anyone who has traveled by air recently knows the frustration of passing through security checkpoints, where long lines and luggage searches have become commonplace. Airports have sought to improve security since September 11 and other terrorist attacks, and have looked at a variety of high-tech equipment that could eliminate vulnerabilities in the baggage screening process.

One innovative project in development at Ohio University is attempting to dramatically improve forensic chemistry techniques to detect explosives at a faster, more accurate rate.

“The technology used in airports takes about seven seconds but doesn’t contain a confirmatory technique to detect false positives,” says Glen Jackson, an assistant professor of chemistry and biochemistry. “Our system has cut down the number of false positives but it takes longer to complete the process.”

Jackson and his team must find a way to make the detection process quicker — the FBI, working on a similar technique, aims for 10 seconds. Jackson thinks the government might consider using the university’s technology someday, but the researchers must get it to work in less than a minute. What they’ve accomplished so far, however, is still much more precise than what’s currently used, Jackson says.

Airports employ a device called an ion mobility spectrometer. After a security agent swabs a suitcase, she places the cotton swab on a small heated platform, which is sucked into the machine. It breaks down the molecules and measures the time it takes the molecules to drift through the device. Each explosive takes a known amount of time to drift through the spectrometer, which is how they are identified. Once
the sample reaches the end, a red or green light flashes, showing whether or not it’s an explosive.

“The problem with the ion mobility spectrometer is that some molecules in hand lotions may have the same reading as RDX or TNT, which is why there are false positives,” says Jackson, who is working with the Ohio University Technology Transfer Office to secure a patent for the research.

The device Jackson and his students use is called a gas chromatography-mass spectrometer or GC-MS. It has been used for many years in courtrooms but has traditionally taken 25 minutes to process the data. The university’s researchers have cut that down to less than two and a half minutes.

The process mixes the material on the cotton swab with a liquid and sends it through a very thin tube in an oven, where it undergoes separation. When the compounds exit the gas chromatograph, the mass spectrometer then measures the molecular mass of each of the explosives present in the sample. That’s important, because the mass of an ion is unique and can help distinguish it from interferences, or false positives.

“It’s so selective that it’s essentially blind to interference and cuts out false positives,” says Jackson, who has published part of the findings in the Journal of Forensic Sciences and also presented the research at the Federation of Analytical Chemistry and Spectroscopy Societies in Orlando, Florida.

Eliminating inaccurate readings and cutting down the process, however, will not get the
university’s new device rushed into airports. At this point the GC-MS produces only a readout with charts and figures that must be interpreted by a specialist with an advanced degree in chemistry — someone not typically found on TSA or airport staff.

“The ultimate goal,” Jackson says, “is to create some sort of intelligence that interprets the data the GC-MS produces so that a green light or red light reading makes the presence of a chemist unnecessary.”