The chemical analysis tool sprays a fine mist of charged water droplets onto an object. The water droplets cling to particles on the surface of the object. The ionized particles are separated and dried out; the chemicals that remain thus provide a chemical map to the surface of the item tested or the object itself. If there are skin cells or other organic tissue on something, the device will detect it.
The system is really a combination of two existing devices, said R. Graham Cooks, the Henry Bohn Hass Distinguished Professor of Analytical Chemistry in Purdue University's College of Science. The first is a DESI, or desorption electrospray ionization, the component that creates the fine mist. The other is a handheld spectrometer.
Purdue University has helped develop a device that can detect bacteria, drugs or any other residue of interest.
Usually, spectrometers are used in more controlled environments, with the sample being tested sitting in a vacuum. Cooks, though, says that the accuracy of the device is not thrown off by using it in the field. Instead, the only issue has been with size. Most lab spectrometers weigh about 300 pounds, while the handheld devices weigh around 20 pounds.
"The accuracy is quite good," he said. "You suffer a little bit because every time you miniaturize, you lose something."
The research team has used the device to analyze clothes, foods and tablets, and to identify cocaine on $50 bills in less than a second. Commercially, the device may be used in the future to detect salmonella in food, biomarkers in urine or explosive residues on suitcases.
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