Ion mobility spectrometry (IMS) is a technique used to detect and characterize organic vapors in air. IMS involves the ionization of molecules and their subsequent temporal drift through an electric field. Analysis and characterization are based on analyte separations resulting from ionic mobilities rather than ionic masses; this difference distinguishes IMS from mass spectrometry. IMS operates at atmospheric pressure, a characteristic that has practical advantages over mass spectrometry, allowing a smaller analytical unit, lower power requirements, lighter weight, and easier use. These factors may facilitate use of IMS for mobile, field applications.
The IMS units, which are intended to be used in a preprogrammed fashion, can monitor chloroform, ethylbenzene, and other volatile organic compounds in a defined situation. IMS units can analyze air, vapor, soil, and water samples. However, for analysis of liquid and solid materials, the contaminants must be introduced to the instrument in the gas phase, requiring some sample preparation.
Graseby Ionics, Ltd. (Graseby), and PCP, Inc. (PCP), participated in a laboratory
demonstration in 1990. Graseby used a commercially available, self-contained
instrument that weighs about 2 kilograms (kg) (see figure on previous page).
PCP used a larger (12 kg) transportable IMS. This laboratory demonstration
was the first opportunity to test the instruments on environmental samples.
The demonstration results highlighted that the following needs must be satisfied
before IMS is ready for field applications:
EPA PROJECT MANAGER:
Eric Koglin
U.S. EPA
National Exposure Research Laboratory
Characterization Research Division
P.O. Box 93478
Las Vegas, NV 89193-3478
702-798-2432
Fax: 702-798-2261
TECHNOLOGY DEVELOPER CONTACTS:
John Brokenshire
Graseby Ionics, Ltd.
Analytical Division
Park Avenue, Bushey
Watford, Hertfordshire
WD2 2BW
England
011-44-1923-816166
Martin J. Cohen
PCP, Inc.
2155 Indian Road
West Palm Beach, FL 33409-3287
561-683-0507
Fax: 561-683-0507 (call first)