Somewhere between 20 and 30 percent of supposedly decaffeinated coffee and tea is actually fairly high in caffeine, but a new test kit can help people tell the difference. A strip of paper soaks up fluid from a sample, and antibodies in the strip produce colored lines if the sample contains caffeine. The antibodies were designed by the test's manufacturer, Silver Lake Research, which also has antibody tests for contaminants in food sources and water.

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