Scientists from the U.S. Department of Energy's Pacific Northwest National Laboratory have developed an approach for detecting tiny amounts of hard-to-detect explosives from more than 8 feet away, thereby reducing the need to swipe clothing, luggage or other materials for traces of the material.

According to its developers, the approach detects trace amounts of explosives such as nitroglycerin and RDX — which is the explosive in C-4 — in the air at very low levels and within mere seconds using extremely sensitive detection equipment.

Source: Talanta. DOI: 10.1016/j.talanta.2023.125562Source: Talanta. DOI: 10.1016/j.talanta.2023.125562

While such explosive substances tend to emit just a few molecules, the researchers have developed equipment sensitive enough to recognize even the smallest hints of an explosive in an area full of common air molecules such as nitrogen and oxygen.

Building on more than a decade of work detecting vapors from explosives and other materials, the team’s latest explosive detection technology recognizes these substances it previously detected from half-an-inch away now from roughly 2 ft to 8 ft away — depending on the material.

Specifically, the researchers were focused on materials with low vapor pressure, which do not evaporate quickly. Unlike substances such as gasoline — with its higher vapor pressure and molecules that quickly become airborne, thereby making it easy to detect — materials with low vapor pressure tend to release so few molecules into the air that it's hard to capture and analyze them.

As such, the team developed a handheld air sampler to improve standoff detection distances, by drawing in roughly 300 liters of air per minute. This reportedly enables the scientists to capture all the air they need in just 5 to 10 seconds to detect those materials with lower vapor pressure.

The team described that the device draws in air through a filter that captures the vapors, which are subsequently delivered to a 2 ft long atmospheric flow tube, where molecules are ionized ahead of being sent to an accompanying mass spectrometer.

Increasing the device’s sensitivity of detection, the team suggests, is the distance of the atmospheric flow tube, which allows for more time (seconds versus milliseconds) for the target molecules to be ionized.

Using this device, the team can reportedly identify explosives at a level of less than 10 parts per quadrillion.

An article detailing this device, “Standoff trace explosives vapor detection at meter distances,” appears in the journal Talanta.

To contact the author of this article, email mdonlon@globalspec.com