Conventional mass spectrometers also are cumbersome instruments that weigh more than 300 pounds. The miniature mass spectrometer Cooks' team developed, called the mini 10.5, is a handheld device roughly the size of shoebox that weighs 22 pounds.

"Accuracy is the price we pay for a much faster, cheaper and easier technology that can be taken out into the field almost anywhere," Cooks said. "The minis are not as precise as a standard mass spectrometer, but it would be a good first line defense to indicate when additional testing is necessary."

Fred Whitford, coordinator of the Purdue Pesticide Programs, said the ability to sample food quickly would be a great benefit to the regulation industry.

"Sometimes a test result comes too late and the food is already out, which can be a serious problem," Whitford said. "Currently only about 2 percent of the food is pulled and tested, and perhaps a faster and cheaper test would allow more samples to be taken."

The U.S. Department of Agriculture's most recent report stated that chemical residues exceeded the legal limits on 0.3 percent of the samples tested and 2.7 percent of the samples tested were found to have pesticides not approved for that crop, Whitford said.

"Chemicals can be misused in a variety of ways," he said. "Sometimes they are applied in the wrong amounts, sometimes the crop is harvested too soon after chemical application and sometimes a chemical is used that is not approved."

Graduate student Santosh Soparawalla and postdoctoral researcher Fatkhulla Tadjimukhamedov performed the grocery store field tests, which were limited to detecting the fungicide benzimidazole on oranges and the scald inhibitor diphenylamine on apples. Scald is a brown discoloration that appears on apples during storage.

"We could easily distinguish between treated produce, which had a strong signature for the chemicals, and organic produce, which showed no chemical residue on its surface," Soparawalla said. "This could be the first step toward a day when everyone will have the ability to make an informed decision of what they want to purchase and eat based on an analysis of the specific items."

In addition to the pilot test to validate the technology in the field, the team evaluated the quantities of diphenylamine, or DPA, present in a treated apple. The U.S. Environmental Protection Agency's limit for the concentration of DPA on an apple is 10 parts per million.