Temperature Corrections for Ion Mobility Spectrometry

Abstract

The displacements of 30 peaks of eight chemicals over a wide range of temperatures, from 30 to 250 °C, with 20 °C increments, were studied. Experimental results show that the separations remain fairly constant and ion mobility spectra can be corrected by shifting all drift times by Δ td (Δ T/T)[ a + b(Δ T/T)] where T is the absolute temperature and a and b are constants which depend on pressure and the instrumental parameters. Also, by using the reactant ion peak as an internal standard, a factor of k = ( t – tR)/ tR, has been defined, where t is the drift time, tR is the reactant ion drift time, and k is called the adjusted drift time. This factor is independent of instrumental parameters and increases linearly with temperature as: k = α( T1/2 − 11.88). It can be normalized to a standard temperature of 298 K to give k298 = 5.3827 kT/( T1/2 − 11.88). The k298 values were determined for the 30 peaks over a temperature range of 30–250 °C. These values show less sensitivity to temperature than their corresponding reduced mobilities. By transforming the entire drift time to the reduced adjusted drift time, k298, the peak shifts were corrected for all spectra recorded at temperatures (30–250 °C) such that the spectra superimposed.