For $10, common airport device will detect black powder

The same machine that analyzes those cloth swatches that TSA agents wipe against your carry-on could now be retrofitted to detect black powder explosives.
Written by Janet Fang, Contributor on

Invented in China over a millennium ago, black powder is a mixture of charcoal, sulfur, and potassium nitrate. It's widely available, yet very hard to detect (except by bomb-sniffing dogs).

Now, scientists have modified an existing bomb-sniffing machine to accurately spot very small amounts of black powder explosives. ScienceNOW reports.

You might already be familiar with the device -- it’s being used in thousands of airports around the world. After Transportation Security Administration (TSA) agents wipe across your carry-on or coat with that white cloth swatch, they use an ion mobility spectrometer (IMS) to analyze it.

Inside an IMS, a sample's volatile atoms and molecules receive an electrical charge, ionizing them in the process. An electric field carries these ions across a chamber several inches long against a headwind of purified air. Each ion's characteristic size and charge dictates how quickly it reaches a detector at the chamber's end, allowing experts to distinguish the components of a sample.

That is, it can analyze a sample in thousandths of a second. But until now, it couldn’t really detect black powder. That’s because sulfur and oxygen hit the detector at almost the same time, and a strong oxygen signal masks small sulfur amounts.

So a team led by Haiyang Li at the Dalian Institute of Chemical Physics in China modified an IMS to eliminate the oxygen signal and improve the device's sensitivity.

Using titration region IMS (TR-IMS), they found a way to ionize the sample and then pass it through a gas, which captures oxygen ions before the sample reaches the analysis chamber.

Since sulfur is a common ingredient in lots things, however, this would lead to a rise in false positives. The researchers reason that it would at least alert security to check the bag more carefully.

Li estimates that only about $10 in parts would be needed to retrofit a conventional IMS.

The work was published in Analytical Chemistry last month.

[Via ScienceNOW]

Image: Chinese rocket / NASA via Wikimedia

This post was originally published on Smartplanet.com

Editorial standards