High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS) at 40 mbar

Abstract

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at an absolute pressure of 20 mbar reaching high reduced electric field strengths of up to 125 Td for controlled reaction kinetics. This significantly increases the linear range and limits chemical cross sensitivities. Furthermore, HiKE-IMS enables the ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to new reaction pathways and the inhibition of clustering reactions. In addition, HiKE-IMS allows the observation of additional orthogonal parameters related to an increased ion temperature such as fragmentation and field-dependent ion mobility, which may help to separate compounds that have similar ion mobility under low field conditions. Aiming for a hand-held HiKE-IMS to carry its benefits into field applications, reducing size and power consumption of the vacuum system is necessary. In this work, we present a novel HiKE-IMS design entirely manufactured from standard printed circuit boards (PCB) and experimentally investigate the analytical performance in dependence of the operating pressure between 20 mbar and 40 mbar. Hereby, the limit of detection (LoD) for benzene in purified, dry air (1.4 ppmV water) improved from 7 ppbV at 20 mbar down to 1.8 ppbV at 40 mbar. Furthermore, adding 0.9 ppmV toluene the signal of the benzene B+ peak decreases by only 2 % at 40 mbar. Even in the presence of high relative humidity in the sample gas above 90 % or toluene concentrations of up to 20 ppmV, the LoD for benzene just increases to 9 ppbV at 40 mbar.