APODIZATION FUNCTIONS IN FOURIER-TRANSFORM ION MOBILITY SPECTROMETRY

Ion mobility spectrometry is a sensitive and selective detection method following capillary chromatography. Fourier transform ion mobility spectrometry (FT-IMS) is capable of collecting a complete mobility spectrum of a high-resolution chromatographic peak during its few seconds of residence in the spectrometer. An apodization function is a mathematical transformation carried out on data received from an interferometer to alter the instrument's response function before the Fourier transformation is calculated to obtain the spectrum. Peak broadening and base-line instabilities reported in earlier Fourier transform ion mobility studies can be eliminated using apodization functions. In this work, the resolution and sensitivity effects of various apodization functions applied to IMS interferograms are demonstrated. The studied functions include Hann, Hamm, super-Gausslan, and rectangular. Also, in this paper, spectral response, resolution, and noise were monitored as the FT-IMS frequency scan range was varied from 2.0 to 20.0 kHz. Comparisons are made between the frequency scan range in Fourier transform IMS and the pulse width in signal-averaged IMS. FT-IMS was shown to have signal/noise improvements of > 3 X over signal-averaged IMS under conditions of high resolution.