Monday, October 10, 2005

"SECURITY: Detector senses tiny sample of explosives"

While the increased threat from terrorism today has airports X-raying all luggage for weapons, there has been no fast, practical way for security personnel to scan baggage for the presence of bombs. Now, a Purdue University research team claims to have developed a sensor that is fast enough to detect tiny amounts of residue from explosives, using standard mass spectrometers outfitted with a special puff-and-sniff, two-nostril "nose." Professor R. Graham Cooks developed the method with the assistance of the doctoral candidates in his research group (, Ismael Cotte-Rodriguez, Zoltan Takats, Nari Talaty and Huanwen Chen. In the lab, mass spectrometers can easily detect trace residues of explosives brushed from the hand of someone loading a suitcase, thus determining whether a hazardous substance is likely to be inside. But either the suitcase must be swabbed or other time-consuming methods must be used to prepare a sample taken from its surface. In contrast, the Purdue researchers puff a gas mixture of ions onto the suitcase as it passes by, thereby using the ionic charge to eject molecules from the surface of the suitcase and into the two-nostril nose of the mass spectrometer. The technique, called desorption electrospray ionization (Desi), detects picogram (trillionths of a gram) traces of the explosives TNT, RDX, HMX and PETN, which are found within the plastic compositions of C-4, Semtex-H and Detasheet. An ionized solvent that specifically pinpoints the suspected explosives is sprayed on the suitcase. Two mass spectrometers used in tandem-the nostrils of the device's nose-reduce false alarms to negligible levels, according to Cooks, who claims the technique worked directly on a wide variety of surfaces without swabbing or pretreating them, including metal, plastic, paper and polymers.