High kinetic energy ion mobility spectrometer: quantitative analysis of gas mixtures with ion mobility spectrometry.

Abstract

We present a high kinetic energy ion mobility spectrometer (HiKE-IMS) for quantitative gas analysis. Drift tube and reaction tube can be operated at reduced fields up to 110 Td. At such conditions the distribution of reactant ion water clusters is shifted toward smaller clusters. Due to the resulting presence of bare reactant ions (e.g., H3O(+)) and the kinetic control of the ionization process with decreasing reaction time, unlike conventional IMS, a quantitative detection with ppbv detection limits of low proton affine analytes even in humid gas mixtures containing high proton affine compounds is possible using a direct sample gas inlet. A significantly improved dynamic range compared to conventional IMS is achieved. An incremental change in reduced fields enables the observation of parameters like field dependent ion mobilites or analyte fragmentation. Also, the characteristic of the analyte signal with respect to the reduced reaction field gives insight into the ionization process of the analyte. Thus, HiKE-IMS enables substance identification by ion mobility and additional analytical information that are not observed with conventional IMS. The instrumental effort is similar to conventional desktop IMS with overall dimensions of the drift and reaction tube of 4 cm × 4 cm × 28.5 cm. However, the mobility resolution is limited and between 30 and 40. Because of the moisture independent ionization and the decrease in competing ion-molecule reactions, no preseparation or membrane inlet is necessary when the compounds of interest are distinguishable either by a significant difference in ion mobility or the additional analytical information.