New dipstick tests for caffeine

If you ever have wondered whether your favorite coffee, tea, or soda contains caffeine--despite its decaf label or the absence of caffeine on the ingredients list--then you soon may be able to test the beverage yourself. Chemists at Washington University School of Medicine in St. Louis are developing a quick, convenient "dipstick" that they say could represent the first home testing kit to detect the stimulant.

Many consumers increasingly are trying to avoid caffeine due to unwanted health effects, including insomnia and irritability. Several studies have linked an increase in caffeine consumption with a higher risk of miscarriage. For years, the Food and Drug Administration specifically has advised pregnant women to avoid or limit their intake of caffeine.

However, the caffeine content of foods and beverages can be difficult for consumers to determine. Products do not always indicate whether they contain caffeine, and the caffeine content of similar food products can vary widely depending on the manufacturer. Even drinks that are labeled "decaf" can contain detectable amounts of caffeine.

Current tests to detect caffeine use sophisticated laboratory methods, including spectroscopy and chromatography, none of which are applicable to home use. While caffeine-specific antibodies are commercially available, they are destroyed at high temperatures, like those of hot beverages, and consequently are not practical for use in home tests.

"We envisioned that a simple method to measure caffeine, even in hot beverages, such as coffee, would be of value to individuals and institutions wanting to verify the absence of caffeine," says Jack H. Ladenson, professor of chemistry. Test strips that are treated with a specific antibody will react by changing color in the presence of caffeine.

To develop the new immunoassay test, Ladenson and his associates acquired an unusual antibody--derived from the blood of llamas--that is resistant to high temperatures due to its unusually stable structure. They obtained the antibodies by repeatedly injecting the animals with caffeine to illicit an immune response to the drug. The researchers then cloned the caffeine-specific antibody and combined it with other chemicals to facilitate caffeine detection.

The new test will be designed to be qualitative only: It allows a person to determine quickly whether caffeine is present, but does not indicate the exact amount or concentration of caffeine. In preliminary tests using coffee and cola, an experimental version effectively distinguished caffeinated versions of these products from their decaf counterparts, Ladenson explains.

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