In a lab in Indianapolis, a student takes a tablet of a common antihistamine. About 40 minutes later, researchers detect the drug in his system simply by directing a spray of alcohol and water onto his finger and instantly analyzing the mixture with a common lab instrument. This is not a scene from CSI or ER but rather a real-life demonstration of a new technique developed by Purdue University analytical chemist R. Graham Cooks and his colleagues.

The advance expands the utility of a common laboratory method called mass spectrometry, and it could soon enable doctors and forensic specialists to immediately reveal what substances are present on surfaces such as wood, cloth, and even skin, eliminating the need to send samples off the lab and wait for the results.

“This method that they have worked out is a means of providing a new kind of nose on an old dog,” says John Fenn, an analytical chemist at Virginia Commonwealth University who won a share of the 2002 Nobel Prize for chemistry for developing the technique on which the new method is based. “It’s very exciting.”

Mass spectrometry is used to identify unknown samples by precisely determining their molecular weight. But analyzing substances this way requires that the molecules be given an electric charge. This ionization process has entailed the use of cumbersome vacuum chambers or extensive sample preparation, limiting mass spectrometry’s use to the lab. Cooks’s new technique, described in the October 15 issue of the journal Science, demands neither special preparation nor a vacuum. Instead, an electrically charged stream of pressurized liquid such as water or alcohol (or an alcohol-water mixture) is sprayed onto any surface to be analyzed. The droplets act as microscopic projectiles, knocking off invisible bits of the sample and transferring charge to those molecules as well. The droplets, along with whatever sample molecules they are now carrying, are then sucked into a standard mass spectrometer.

Forensics and public safety applications top Cooks’s list of possible uses for the new technique. “You could use it to examine a crime scene; you could use it to examine a suspect,” he says. Another use Cooks suggests is airport security, where agents could identify explosive residues on baggage or passengers more quickly and specifically than is possible with current techniques. Fenn expands the list: “You can look at the surface of soils or automobiles, or anything else, and look for toxic substances, chemical warfare agents, or even biological warfare agents.”

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