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Lessons from the lab

Jan. 4, 2006
By Kate DeRhodes

Kate DeRhodes won't wrap up her undergraduate studies until June, but her research endeavors already are getting attention. Her entry in this past spring's Student Research and Creative Activity Fair earned her first-place standing in the analytical chemistry category and provides focus for the hours she's spending in the lab this year.

The project, which details her proposed method for simultaneously detecting high and low explosives, was among 270 presented by undergraduate, graduate and medical students and post-doctoral fellows during the fourth annual fair. Other topics included innovative theater set design, hydrogen storage for the next generation of automobiles and President Bush's evolving speech patterns.

Here, DeRhodes, who has been guided in her research by Assistant Professor of Chemistry Glen Jackson, offers a tutorial on her project.

Kate DeRhodesTerrorist acts such as the Oklahoma City bombing of 1995 have made the fast and reliable detection of explosives more important than ever. Instrumental methods that can perform simultaneous detections make analyses quicker and more cost-efficient. The goal of my project is to detect both high and low explosives simultaneously in less than 10 minutes.

Low explosives burn; in order for an explosion to occur, they must be packaged so that pressure can build up inside a container that finally breaks to release the destructive shock. These explosives, such as ammonium nitrate fuel oil, often are used for improvised devices because ammonium nitrate (which is found in manure) and fuel oil are easy to obtain. High explosives, such as TNT and nitroglycerin, detonate; they do not require a container to generate a shock wave. The military and the mining industry are among those commonly using high explosives.

With this new method, a mixture of explosives is separated using a gas chromatograph, and each explosive is detected using an electron-capture detector. The ECD works by producing a stable flow of electrons or current. When a molecule with electron-capturing groups enters the detector, it captures electrons and causes the current to decrease. The timing of the reduction helps identify which explosive is present because each explosive takes a different amount of time to pass through the gas chromatograph.

High explosives already have electron-capturing groups. Low explosives do not have this characteristic, making them undetectable using the ECD. To address this, a chemical reaction known as a derivatization is performed. This procedure adds electron-capturing groups to the low-explosive molecule. The high explosives and derivatized low explosives are extracted from the sample using a fiber, which then is transferred to the gas chromatograph.

A mixture of nine high explosives was used to optimize the ECD and gas chromatographic method. All nine high explosives were separated in less than 2.5 minutes.

Based on this, we are confident the simultaneous detection of high and low explosives - the goal of my continuing research - can be performed in less than 10 minutes.

This story appears in the Fall 2005 issue of Ohio Today.

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Published: Jan 4, 2006 12:03:00 AM
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