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NMSU chemistry research finds applications in homeland security, space program

Twenty years ago there were only two university scientists known to be working on ion mobility spectrometry (IMS), an analytical science field that now is used widely for detecting dangerous substances.

Gary Eiceman, professor of chemistry at New Mexico State University, is a leading expert in the field of ion mobility spectrometry, which is widely used in homeland security, space and military applications. (NMSU photo by Darren Phillips)

them was Gary Eiceman, professor of chemistry at New Mexico State University.

Though neglected within academic circles at that time, IMS was being developed quietly within government agencies for military preparedness and commercial aviation security. Today, thanks in part to the contributions of Eiceman's laboratory, IMS-based technology is used extensively in homeland security, the space program and military applications.

U.S. soldiers use hand-held chemical agent monitors (CAMs) to detect the presence of chemical weapons, and more than 50,000 CAMs have been deployed with NATO armies. More than 12,000 IMS units are used in airports worldwide to screen hand-carried articles for traces of explosives. The air quality aboard the International Space Station is monitored by a device that Eiceman and his research team helped develop for NASA.

The current focus of Eiceman's laboratory, again with funding from NASA, is on developing IMS science and technology for detecting bacteria aboard manned spacecraft.

"When you live in a closed environment such as a spacecraft, it is like putting human beings in a container, and issues of chemical and bacterial contamination become a concern," he said. "IMS analyzers can detect trace levels of contaminants a long time before the contamination becomes a medical or operational problem."

The NASA project also involves development of micro-fabricated analyzers based on differential mobility spectrometry, a technical relative of IMS, Eiceman said.

To understand the principles behind IMS instruments, it helps to think of an ordinary household smoke detector. The smoke detector "contains a small radioactive source that produces gaseous ions and these are affected by changes in the composition of the air brought into the ionization chamber," Eiceman said.

Unlike a smoke alarm, which simply registers the presence of smoke particles, an IMS analyzer provides another dimension of chemical information that allows the detection and identification of ions formed from the sample. This is done by measuring the movement, or mobility, of ions within the analyzer.

Ions are molecules that have an electrical charge because they have either lost or gained electrons or protons. When air enters the ionization chamber of an IMS instrument, vapors are converted to ions through chemical reactions initiated by the radioactive source.

"We characterize those ions based on their movement in a comparatively weak electrical field," Eiceman said. Different chemical substances, when converted to ions, display different velocities in an electrical field, so IMS devices can be designed to detect and identify specific toxic chemicals, traces of explosives or other targets.

"In some instances, we need to be able to detect low levels of toxic vapors quickly, continuously and with sufficient specificity to make life-critical decisions," Eiceman said.

The beauty of IMS instruments is that the analysis is done at ambient pressure -- the gas pressure in the instrument is the same as in the surrounding atmosphere.

"This means our technology can be made small, inexpensive and portable," he said. "But it also makes the challenges in science more demanding. The events that happen at the molecular level are much more complex at ambient pressure than they are in a vacuum. We have spent the past 20-plus years studying the chemistry of gas phase ions in air in order to understand the analytical value of IMS analyzers."

His latest undertaking -- to lay the groundwork for a microbial analyzer for manned spacecraft -- has even more complications.

"Working with living organisms is fairly complex," Eiceman said. "Our strategy has been to view bacteria as chemically distinctive samples -- but also very complex samples."

Eiceman, who recently received NMSU's Westhafer Award for Excellence in Research and Creative Activity, is a founding member of the International Society for Ion Mobility Spectrometry and remains one of the world's leading experts in the field.