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.

One major drawback of ion mobility spectrometry (IMS) is the dependence of the response to a certain analyte on the concentration of water or the presence of other compounds in the sample gas. Especially for low proton affine analytes, e.g., benzene, which often exists in mixtures with other volatile organic compounds, such as toluene and xylene (BTX), a time-consuming preseparation is necessary. In this work, we investigate BTX mixtures using a compact IMS operated at decreased pressure (20 mbar) and high kinetic ion energies (HiKE-IMS). The reduced electric field in both the reaction tube and the drift tube can be independently increased up to 120 Td. Under these conditions, the water cluster distribution of reactant ions is shifted toward smaller clusters independent of the water content in the sample gas. Thus, benzene can be ionized via proton transfer from H3O(+) reactant ions. Also, a formation of benzene ions via charge transfer from NO(+) is possible. Furthermore, the time for interaction between ions and neutrals of different analytes is limited to such an extent that a simultaneous quantification of benzene, toluene, and xylene is possible from low ppbv up to several ppmv concentrations. The mobility resolution of the presented HiKE-IMS varies from R = 65 at high field (90 Td) to R = 73 at lower field (40 Td) in the drift tube, which is sufficient to separate the analyzed compounds. The detection limit for benzene is 29 ppbv (2 s of averaging) with 3700 ppmv water, 12.4 ppmv toluene, and 9 ppmv xylene present in the sample gas. Furthermore, a less-moisture-dependent benzene measurement with a detection limit of 32 ppbv with ca. 21 000 ppmv (90% relative humidity (RH) at 20 °C) water present in the sample gas is possible evaluating the signal from benzene ions formed via charge transfer.

Gas chromatographs equipped with electron capture detectors (ECD) are widely used for the analysis of electron affine substances. Achieving limits of detection in the low pptv-range, electron capture detectors are the most sensitive detectors available for such compounds. Based on their operating principle, they require free electrons at atmospheric pressure, which are usually generated by using a β --decay. However, the use of radioactive materials leads to regulatory restrictions regarding purchase, operation and disposal. Here, we present a new electron capture detector using a non-radioactive electron source, which is not subject to these limitations and offers further advantages such as adjustable and higher electron densities and energies.

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Abstract. Gas chromatographs with electron capture detectors are widely used for the analysis of electron affine substances such as pesticides or chlorofluorocarbons. With detection limits in the low ppt v range, electron capture detectors are the most sensitive detectors available for such compounds. Based on their operating principle, they require free electrons at atmospheric pressure, which are usually generated by a β − decay. However, the use of radioactive materials leads to regulatory restrictions regarding purchase, operation, and disposal. Here, we present a novel electron capture detector based on a non-radioactive electron source that shows similar detection limits compared to radioactive detectors but that is not subject to these limitations and offers further advantages such as adjustable electron densities and energies. In this work we show first experimental results using 1,1,2-trichloroethane and sevoflurane, and investigate the effect of several operating parameters on the analytical performance of this new non-radioactive electron capture detector (ECD).