PNNL technology can 'sniff' explosives much like dogs

By Annette Cary, Tri-City HeraldFebruary 21, 2013 

Technology being developed at Pacific Northwest National Laboratory could put explosive-sniffing dogs out of business.

It shows promise to provide a quick, accurate and highly sensitive evaluation process to detect minute amounts of explosives. The technology could be used to screen passengers or luggage at airports or to assess large cargo containers at ports.

Just like dogs, the technology can "sniff" the air to detect vapors from explosives. That includes explosives such as RDX, a commonly used military explosive that is very dense and powerful, but does not easily vaporize.

But unlike dogs, it does not need to be fed, exercised regularly, rested and given breaks from searching for explosives.

"What we are attempting to develop is an instrument that replicates or surpasses the capabilities of a dog," said David Atkinson, senior research scientist at the Department of Energy's national lab in Richland.

Airports sometimes also look for explosives by running a clothlike wipe over luggage or items being carried onto a plane. Then the swipe samples are analyzed one at a time in a process that requires the sample to be heated to a temperature needed to create vapors for detection.

PNNL's technology "is much more sensitive than anything out there now," Atkinson said. It also eliminates the need for surfaces to be wiped to collect a sample and the sample to be heated or pre-concentrated.

The technology collects a sample of air and converts the sample to ions within a reaction tube. The ionized sample then moves to a mass spectrometer for ion detection and identification, which takes about one second.

"The key part is ionization," Atkinson said. "We tailored the chemistry to greatly enhance both ionization efficiency and selectivity, which results in the best possible detection."

The system works on samples of what are considered "low-volatility compounds" because they release very small amounts of the explosive vapor, typically at parts per trillion levels or lower, that are difficult to detect.

It can easily detect vapors from a contaminated fingerprint with RDX at levels below 25 parts per quadrillion, according to PNNL.

The technology was demonstrated on RDX for a recent issue of Analytical Chemistry, but it's also been shown to detect other explosive compounds, including PETN, another low-volatility compound used by the military, and nitroglycerine, along with plastic explosives that contain explosive materials at parts per quadrillion levels.

Atkinson envisions the detectors being integrated into current airport screening, automatically alerting if shoes or carry-on bags sent through an X-ray machine are contaminated, for instance.

It also has promise for screening large cargo containers.

A light cover might be placed over the containers and then a sample pulled from the air beneath it for analysis.

Now an X-ray might be used to check pallets of consolidated cargo, but the images are cluttered and difficult to read, Atkinson said. Or the cargo pallet might be pulled apart to allow explosive-sniffing dogs to crawl through it.

PNNL's next steps include research to detect other explosive threats by manipulating the ionization chemistry and lowering detection limits.

The detection technology uses commercially available mass spectrometers and researchers also want to test the technology with smaller mass spectrometers to increase its practicality.

The technology is in the prototype stage, but using it with commercially available mass spectrometer should speed its commercialization, according to PNNL. Several companies are interested in the technology, Atkinson said.

-- Annette Cary: 582-1533; acary@tricityherald.com; Twitter: @HanfordNews

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