A chemist at the National Institute of Standards and Technology (NIST) has demonstrated a relatively simple, inexpensive method for detecting and measuring elusive hazards such as concealed explosives and toxins, invisible spoilage in food or pesticides distributed in soil by wind and rain. The prototype method is more sensitive than conventional techniques for detecting traces of these materials, which are polarlike water molecules, having distinct electrically positive and negative endsand do not readily evaporate.
As described in a new paper,* NIST researcher Tom Bruno enhanced a technique called "headspace analysis," which is the detection and analysis of trace levels of chemical compounds from a solid or liquid that are released into the surrounding atmosphere. Bruno's enhancements greatly improve the efficiency of sample collection, for the first time making the technique suitable for detecting low concentrations of polar, low-volatility, compounds such as explosives. Preliminary results indicate the method is sensitive enough to measure amounts of target materials that constitute as little as 0.0000002 percent of a sample.
The sample collection device consists of several coils of fine tubing just 0.32 millimeters in inner diameter. Bruno modified the inner coating, which efficiently attracts and retains chemicals across its large surface area. The device can be used with a sample-heating oven as part of a laboratory analysis system or taken into the field for sample collection. To extract target molecules from a sample, the coil is placed inside an insulated cylinder and chilled with a cold air stream to minus 40 degrees Celsius. A gas, such as helium, is swept across the sample held in the oven or the coil device, gathering up target molecules along the way, and through the fine tubing. Chilling the coilspart of Bruno's innovationmakes collection of target molecules more efficient. The tubing is washed with a solvent, or heated, to rel
|Contact: Laura Ost|
National Institute of Standards and Technology (NIST)