| Use: | Ion mobility spectrometry (IMS) is a technique used to detect and characterize organic
vapors in air. Recent development of portable IMS detectors might make the technique an
alternative to FID and GC. See 9.1.4 for use with explosives. |
Description:
Ion mobility spectrometry analysis is based on analyte separations resulting from ionic mobilities rather than ionic masses. A sampling pump draws air through a semipermeable membrane, which is selected to exclude or attenuate possible interferents. The sample is ionized in a reaction region through interaction with a weak plasma of positive and negative ions produced by a radioactive source. A shutter grid allows periodic introduction of the ions into a drift tube, where they separate based on charge, mass, and shape with the arrival time recorded by a detector. The identity of the molecules is determined using a computer to match the signals to IMS signatures held in memory. If the IMS signature is known, it is also possible to program the instrument to detect specific compounds of interest. IMS operates at atmospheric pressure, a characteristic that has practical advantages over mass spectrometry, including smaller size, lower power requirements, less weight, and ease of use.
Analytes:
| 1. Non-Halogenated VOCs | 2. Non-Halogenated SVOCs | 3. Halogenated VOCs |
| 4. Halogenated SVOCs | 6. Pesticides/Herbicides |
Media:
| Soil/Sediment | Water | Gas/Air |
| Requires extraction to liquid or gas phase | Requires extraction to liquid or gas phase | BETTER |
| Selectivity: | Technique measures the specific contaminant directly. |
| Susceptibility to Interference: | Medium. |
| Detection Limits : | 100-100 ppb (soil); 1-50 ppb (water). |
| Turnaround Time per Sample: | Minutes. |
Applicable To:
|
Limitations:
ASTM Standards/EPA Methods:
No applicable ASTM standards or EPA methods are cited for this technology.
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