Issue link: http://read.dmtmag.com/i/37334
can identify the presence of a com- pound, but not tell exactly how much it found. It could be used for screen- ing, but more careful analysis would be needed to quantify the finding. Two methods tested The team tested two ambient ion- ization methods, according to infor- mation in a news release from Purdue. Both involve ionizing mole- cules on a sample's surface. This ion- ization step gives charge to the molecules and allows them to be identified by the mass spectrometer. In one method, called paper spray “The method works without complicated sample collection and preparation. It can be used in situ, like when walking around in a ionization, a sample is wiped with a common lens wipe wet with alcohol. A small piece is cut from the wipe and placed on a special attachment of the miniature mass spectrometer where a high voltage is applied. The mixture of alcohol and residues from the sample's surface become fine droplets containing ionized molecules that pop off the wipe and are vacuumed into the mass spectrometer for analysis. In the other method, called low-temperature plasma supermarket.” —R. Graham Cooks medical diagnostics and airport security, Cooks said. The machine has been used to identify $50 bills containing traces of cocaine, to sniff luggage for bombs, and to analyze fingerprints for evidence of explosives. It can scan blood samples from patients to determine whether drugs adminis- tered for illness are circu- lating at therapeutic levels and detect molecular disease markers in urine samples. Mass spectrometry produces a graph showing peaks that are unique to every chemical compound, Cooks said. For the machine to identify a chemical, it must compare this to a known pattern. Over the years, a library of chem- ical fingerprints has been developed, and computers scan and match them automatically. A number of patents have been applied for or granted, ionization, a special probe sprays a collection of charged particles onto the sample's surface using a slow stream of helium gas. The charged particles ionize molecules on the sample's surface, which then bounce off the surface and are vacuumed into a mass spectrometer for analysis. While this new device has application in food safety, it is much more widely applicable. It has applications in and work is under way with companies interesting in commercializing the technology, Cooks said. In food safety applications, it could be used in testing all along the food chain, from producers to shoppers. It could be used by producers, in packing houses, or by regulators, but the price tag will probably be high initially. • www.goodfruit.com GOOD FRUIT GROWER AUGUST 2011 19