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 t_d (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 – t_R)/ t_R, has been defined, where t is the drift time, t_R 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( T^1/2 − 11.88). It can be normalized to a standard temperature of 298 K to give k₂₉₈ = 5.3827 k_T/( T^1/2 − 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.