SEATTLE -- For more than 15 years, scientists have fine-tuned a technique that determines the presence and concentration of chemicals by analyzing reflected light. Known as surface plasmon resonance, the technique is useful for detecting pollution and food poisoning and in an array of medical tests. However, cumbersome systems restricted surface plasmon resonance to the laboratory. This required doctors to wait for test samples to be returned from a lab. To remedy this problem, a group of scientists at the University of Washington's College of Engineering developed a handheld probe to perform the technique in the field. The new device is the size of a laptop computer. The price dropped from $200,000 to $2000. The group has patented the technology to Biacore, an international instrument manufacturer, and to Ikonos Corp., based in Portland, Ore.