Content deleted Content added
Tags: Reverted Mobile edit Mobile web edit |
Tags: Manual revert Mobile edit Mobile web edit |
||
Line 27:
Several types of machines have been developed to detect trace signatures for various explosive materials. The most common technology for this application, as seen in US airports, is [[ion mobility spectrometry]] (IMS). This method is similar to [[mass spectrometry]] (MS), where molecules are ionized and then moved in an electric field in a vacuum, except that IMS operates at atmospheric pressure. The time that it takes for an ion, in IMS, to move a specified distance in an electric field is indicative of that ion's size-to-charge ratio: ions with a larger cross section will collide with more gas at atmospheric pressure and will, therefore, be slower.
[[Gas chromatography]] (GC) is often coupled to the detection methods discussed above in order to separate molecules before detection. This not only improves the performance of the detector but also adds another dimension of data, as the time it takes for a molecule to pass through the GC may be used as an indicator of its identity. Unfortunately, GC normally requires a bottled gas, which creates a consumable and ease of use issue for the system. GC columns operated in the field are prone to degradation from atmospheric gases and oxidation, as well as bleeding of the stationary phase. Columns must be very fast, as well, since many of the applications demand that the complete analysis be completed in less than a minute.{{Citation needed |date=January 2020}}
===Spectrometry===
| |||