ionization step in the air or directly on surfaces outside of the mass spectrometer's vacuum chamber. When combined with portable mass spectrometers also under development at Purdue, DESI promises to provide a new class of compact detectors.
Purdue researchers are focusing on three potential applications for detecting and identifying pathogens: food safety, medical analysis and homeland security. Such a detector could quickly analyze foods, medical cultures and the air in hospitals, subway stations and airports, Cooks said.
The researchers are able to detect one nanogram, or a billionth of a gram, of a particular bacterium. More importantly, the method enables researchers to identify a particular bacterium down to its subspecies, a level of accuracy needed to detect and track infectious pathogens. The identifications are based on specific chemical compounds, called lipids and fatty acids, in the bacteria.
"We can determine the subspecies and glean other information by looking at the pattern of chemicals making up the pathogen, a sort of fingerprint revealed by mass spectrometry," Cooks said. "Conventional wisdom says quick methods such as ours will not be highly chemically or biologically specific, but we have proven that this technique is extremely accurate."
The procedure involves spraying water in the presence of an electric field, causing water molecules to become positively charged "hydronium ions," which contain an extra proton. When the positively charged droplets come into contact with the sample being tested, the hydronium ions transfer their extra proton to molecules in the sample, turning them into ions. The ionized molecules are then vacuumed from the surface into the mass spectrometer, where the masses of the ions are measured and the material analyzed.
Such a system could alert employees in the food and health-care industries to the presence of pathogens and could provide security personnel wiPage: 1 2 3 Related medicine news :1
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