Introduction:

Ions of a sample produced by ion-molecule reactions move at different rates       through a gas under the influence of an electric field. The time to traverse the field and the current registered at the detector are used to identify the sample.
 

IMS separates ionized molecular compounds on the basis of their transition times when subjected to an electric field in a tube.



This time is then compared to stored transition times of known compounds. Therefore it is possible to distinguish TNT from other molecules.
This technique is fast and makes a compact device possible.
Unfortunately the sensitivity is not very high, in particular for compact designs.
 

• Barringer Technologies, New Providence, N.J., is exploring the                 technology for land mines.