Electrical Parameters in Drift Tubes for Ion Mobility Spectrometry

Electrical parameters in a drift tube for ion mobility spectrometry (IMS) were evaluated and optimized in resolution and signal intensity for a mixture of three aromatic hydrocarbons. Electric fields which influenced ion currents and peak shapes most were those between the aperture grid and detector plate and between neighboring wires in the ion shutter where optimum electric fields were 3000 and 300 V/cm, respectively. Electric fields on other drift tube components exhibited minor influences on IMS performance suggesting that electrical parameters do not need to be rigidly established throughout most regions of an IMS drift tube. Ion behavior in the IMS drift tube was consistent with models of potential contours for a conducting plane with circular hole.