Comparison of electric fields within drift tubes for ion mobility spectrometry

The drift tube is the most crucial part of an ion mobility spectrometer (LM S), as it is here that the desired separation process of different ionic sp ecies takes place. A homogeneous electric field is assumed inside the drift tube, enabling an exact calculation of the mobilities of ionic species for med. For verification of this assumption, the electric field inside a drift tube was examined by means of a field simulation program, using an IMS develope d at the Institute of Spectrochemistry and Applied Spectroscopy as an examp le. A refined design of the drift tube was developed, yielding a dramatic i mprovement in the resolution achieved. The influences of geometric variations in the drift tube, as well as metall ic encapsulation neighbouring the drift tube, on the field homogeneity are estimated.