Improving the analytical performance of ion mobility spectrometer using a non-radioactive electron source

Heptner, Andre; Angerstein, Nico; Reinecke, Tobias; Bunert, Erik; Kirk, Ansgar T.; Niedzwiecki, Igor; Zimmermann, Stefan

doi:10.1007/s12127-016-0205-4

Cited by 10 publications

(12 citation statements)

References 31 publications

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“…As our currently used software requires data acquisition to be completed before the next injection, reaction times shorter than 15 ms are not possible. However, as shown before, the protonated monomer and proton-bound dimer formation becomes also visible at shorter reaction times . This also illustrates that arbitrarily high repetition rates are not necessarily improving limits of detection with a field switching shutter, as shorter reaction times will lead to a higher loss of signal than the expected gain from more averaging.…”

Section: Resultssupporting

confidence: 64%

“…This way, the FS shutter achieves both extremely short injection widths and high ion currents. Furthermore, the long reaction times possible in the field-free region are beneficial to the detection of proton-bound dimer and trimer ion species, as was shown before for the proton-bound DMMP dimer . As the mobility of proton-bound dimer species is less affected by, for example, temperature and humidity changes, , proton-bound dimers are especially helpful for reliable substance identification.…”

mentioning

confidence: 84%

“…Having achieved an improved field-free region as shown by Figure D, even when compared to the single less transparent injection grid in Figure C, prevents analyte ions from being pulled from the ionization region. Thus, they may build up until an equilibrium between the ionization and ion losses, e.g., by ion–ion recombination, further reactions, or wall losses due to diffusion. , Therefore, especially for slow forming ions such as proton-bound dimer and trimers, a significant increase in sensitivity can be expected. Figure E shows that a FS shutter with the injection grid at the position of the extension grid of the eFS shutter still exhibits a strong residual field in the ionization region.…”

Section: Ion Shutter Simulationsmentioning

confidence: 99%

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Improving Ion Mobility Spectrometer Sensitivity through the Extended Field Switching Ion Shutter

et al. 2020

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Field switching ion shutters allow generating short ion packets with high ion densities by first ionizing for several milliseconds in a field-free ionization region and then quickly pushing the entire ion population out into the drift region. Thus, they are an excellent choice for compact ion mobility spectrometers with both high resolving power and low limits of detection. Here, we present an improved setup, named the extended field switching ion shutter. By generating a second field-free region between the ionization region and the drift region, shielding of the ionization region is significantly improved, even when using grids with higher optical transparency to improve ion transmission into the drift region. Furthermore, it is shown that under certain conditions, ion transmission through multiple grids in series can even surpass transmission through a single grid of the same transparency. For the studied ions, the signal intensity at low concentrations increases by approximately a factor of 7 to 9 for protonated monomers, 10 to 14 for proton-bound dimers, and 25 for the proton-bound 1-octanol trimer compared to the classical field switching shutter. However, due to the nonlinear response for ions containing multiple analyte molecules, the limits of detection improve only by a factor of 3 to 4 for proton-bound dimers and 3 for the proton-bound 1-octanol trimer. Nevertheless, this still leads to single-digit pptv limits of detection for protonated monomers and hundred pptv limits of detection for proton-bound dimers measured for a series of ketones. However, for the most intense peaks such as the reactant ion peak, a significant loss of resolving power by a factor of up to 1.4 was observed due to Coulomb repulsion.

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Section: Resultssupporting

confidence: 64%

mentioning

confidence: 84%

Section: Ion Shutter Simulationsmentioning

confidence: 99%

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Improving Ion Mobility Spectrometer Sensitivity through the Extended Field Switching Ion Shutter

et al. 2020

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“…By optimizing the geometric parameters and the control electronics, we can achieve electron pulses with a definable pulse width down to 23 ns. This allows to control the ion generation and ion-ion recombination kinetics, which can enhance the analytical performance of the IMS [10].…”

Section: Principle Of Ims With Non-radioactive Electron Sourcementioning

confidence: 99%

Pulsed electron source for atmospheric pressure chemical ionization in ion mobility spectrometry

Bunert

Heptner

Kirk

et al. 2017

2017 30th International Vacuum Nanoelectronics Conference (IVNC)

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Ion mobility spectrometers (IMS) are measurement devices for fast and ultra-sensitive trace gas analysis. Most IMS employ radioactive electron sources, such as 3 H or 63 Ni, to provide free electrons with high kinetic energy at atmospheric pressure for initiating a chemical gas phase ionization of the analytes. The disadvantage of these radioactive materials are legal restrictions and the electron emission cannot be adjusted or turned off. Therefore, we developed a non-radioactive electron source and replaced the 3 H-source of our existing IMS, leading to comparable spectra. An advantage of our non-radioactive electron source is that it can operate in a fast pulsed mode. By optimizing the geometric parameters and developing fast control electronics, we can achieve short electron emission pulses with high intensities and adjustable pulse width down to a few nanoseconds. This allows to control the ionization process, which can enhance the analytical performance of the IMS. Furthermore, a miniaturized non-radioactive electron source is desirable, e.g. for hand-held IMS devices. Therefore, we developed an emission current control for field emitter cathodes and investigated their suitability for this application.

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“…In these cases, separation time and instrumental effort are not significantly increased. Typically, the recombination rate of ions in DT-IMS is measured by introducing a delay between pulsed ionization and ion injection and has been extensively studied. , However, every additional component in the sample affects the recombination, making signal interpretation complex. The second is recently introduced in a field asymmetric time of flight ion mobility spectrometer (FAT-IMS), where peaks are shifted directly after injection based on their alpha function .…”

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Ion Fragmentation and Filtering by Alpha Function in Ion Mobility Spectrometry for Improved Compound Differentiation

et al. 2019

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Collision induced dissociation (CID) is a widely used technique in mass spectrometry to better understand the structural composition of ions and to improve the identification of compounds beyond the analysis of m/z. By increasing the kinetic energy of ions in an electric field, the collisions with neutral molecules may result in bond breakage, dissociation, or fragmentation of the molecular ion into smaller fragments if the necessary onset energy is exceeded. In this work and for the first time, we demonstrate CID in a field asymmetric time of flight ion mobility spectrometer (FAT-IMS). In contrast to the commonly used devices in mass spectrometry, the FAT-IMS operates at ambient pressure and temperature. Furthermore, the FAT-IMS allows separation of ions prior to dissociation, employing the shift occurring in the FAT region and, thus, an improved assignment of fragment ions to selected precursor ions. In this work, the effect of the operation parameters on the fragmentation efficiency of the FAT separator is analyzed. As proof of concept, eight saturated alcohols were investigated. The results show the expected substance-specific fragmentation behavior, which can be used to generate additional orthogonal information about certain analytes via their fragmentation pattern. Furthermore, a method for prefiltering analytes in FAT-IMS by the alpha function is introduced to remove spectral interferences.

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Improving the analytical performance of ion mobility spectrometer using a non-radioactive electron source

Cited by 10 publications

References 31 publications

Improving Ion Mobility Spectrometer Sensitivity through the Extended Field Switching Ion Shutter

Improving Ion Mobility Spectrometer Sensitivity through the Extended Field Switching Ion Shutter

Pulsed electron source for atmospheric pressure chemical ionization in ion mobility spectrometry

Ion Fragmentation and Filtering by Alpha Function in Ion Mobility Spectrometry for Improved Compound Differentiation

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