An official website of the United States government
The latest iteration of modular, open-source rolled ion mobility spectrometers was characterized and tailored for heated ion chemistry experiments. Because the nature of ion-neutral interactions is innately linked to the temperature of the drift cell, heated IMS experiments explicitly probe the fundamental characteristics of these collisions. While classic mobility experiments examine ions through inert buffer gasses, doping the drift cell with reactive vapor enables desolvated chemical reactions to be studied. By using materials with minimal outgassing and ensuring the isolation of the drift tube from the surrounding ambient conditions, an open-source drift cell outfitted with heating components enables investigations of chemical reactions as a function of temperature. We show here that elevated temperatures facilitate an increase in deuterium incorporation and allow for hydrogen/deuterium exchanges otherwise unattainable under ambient conditions. While the initial fast exchanges get faster as temperature is increased, the slow rate which rises from the kinetic nonlinearity though to be attributed to ion-neutral clustering, remains constant with no change in mobility shifts. Additionally, we show the analytical merit of multiplexing mobility data by comparing the performance of traditional signal-averaging and FT-IMS modes.
more »
« less
An open source ion gate pulser for ion mobility spectrometry
Excluding the ion source, an ion mobility spectrometer is fundamentally comprised of drift chamber, ion gate, pulsing electronics, and a mechanism for amplifying and recording ion signals. Historically, the solutions to each of these challenges have been custom and rarely replicated exactly. For the IMS research community few detailed resources exist that explicitly detail the construction and operation of ion mobility systems. In an effort to address this knowledge gap we outline a solution to one of the key aspects of a drift tube ion mobility system, the ion gate pulser. Bradbury-Nielsen or Tyndall ion gates are found in nearly every research-grade and commercial IMS system. While conceptually simple, these gate structures often require custom, high-voltage, floating electronics. In this report we detail the operation and performance characteristics of a wifi-enabled, MOSFET-based pulser design that uses a lithium-polymer battery and does not require high voltage isolation transformers. Currently, each output of this circuit follows a TTL signal with ~20 ns rise and fall times, pulses up to +/− 200 V, and is entirely isolated using fiber optics. Detailed schematics and source code are provided to enable continued use of robust pulsing electronics that ease experimental efforts for future comparison.
more »
« less
- Award ID(s):
- 1506672
- PAR ID:
- 10045946
- Date Published:
- Journal Name:
- International Journal for Ion Mobility Spectrometry
- ISSN:
- 1435-6163
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Low molecular weight metabolites are essential for defining the molecular phenotypes of cells. However, spatial metabolomics tools often lack the sensitivity, specify, and spatial resolution to provide comprehensive descriptions of these species in tissue. MALDI imaging mass spectrometry (IMS) of low molecular weight ions is particularly challenging as MALDI matrix clusters are often nominally isobaric with multiple metabolite ions, requiring high resolving power instrumentation or derivatization to circumvent this issue. An alternative to this is to perform ion mobility separation before ion detection, enabling the visualization of metabolites without the interference of matrix ions. Additional difficulties surrounding low weight metabolite visualization include high resolution imaging, while maintaining sufficient ion numbers for broad and representative analysis of the tissue chemical complement. Here, we use MALDI timsTOF IMS to image low molecular weight metabolites at higher spatial resolution than most metabolite MALDI IMS experiments (20 µm) while maintaining broad coverage within the human kidney. We demonstrate that trapped ion mobility spectrometry (TIMS) can resolve matrix peaks from metabolite signal and separate both isobaric and isomeric metabolites with different distributions within the kidney. The added ion mobility data dimension dramatically increased the peak capacity for spatial metabolomics experiments. Through this improved sensitivity, we have found >40 low molecular weight metabolites in human kidney tissue such as arginic acid, acetylcarnitine, and choline that localize to the cortex, medulla, and renal pelvis, respectively. Future work will involve further exploring metabolomic profiles of human kidneys as a function of age, gender, and ethnicity.more » « less
-
Ion mobility spectrometry (IMS) can delineate gas-phase ions and probe their geometries. Coupling with electrospray ionization and MS has brought IMS to structural biology, revealing the macromolecular folding and subunit connectivity. However, the orientational averaging of ion–molecule collision cross sections (Ω) in the linear and field asymmetric waveform IMS (FAIMS) diminishes the resolution and structural specificity. In the novel low-field differential (LOD) IMS, a field too weak for ion heating (and thus FAIMS) aligns strong macrodipoles, capturing their magnitudes and directional Ω across the dipole (Ω⊥). However, the bisinusoidal waveforms (from FAIMS) have compromised the resolution, measurement accuracy, and correlation to the ion properties. Large ions amenable to LODIMS have low mobility and diffuse slowly, allowing the waveform frequencies down to ∼10 kHz. The low field and frequency permit generating the ideal rectangular waveforms with a flexible frequency and duty cycle by direct switching (impractical for FAIMS) in a miniature low-power format. This new IMS stage is evaluated for the exemplary large protein albumin (66 kDa) previously studied using the bisinusoidal waveform. The flat voltages and greater form factor initiate the differential IMS effect at lower fields, expand the separation space, and enable the quantification of Ω⊥ values by varying the duty cycle.more » « less
-
Imaging mass spectrometry (IMS) technologies are capable of mapping a wide array of biomolecules in diverse cellular and tissue environments. IMS has emerged as an essential tool for providing spatially targeted molecular information due to its high sensitivity, wide molecular coverage and chemical specificity. One of the major challenges for mapping the complex cellular milieu is the presence of many isomers and isobars present in these samples. This challenge is traditionally addressed using orthogonal LC-based analysis, though, common approaches such as chromatography and electrophoresis are not able to be performed at timescales that are compatible with most imaging applications. Ion mobility offers rapid, gas-phase separations that are readily integrated with IMS workflows in order to provide additional data dimensionality that can improve signal-to-noise, dynamic range, and specificity. Here, we highlight recent examples of ion mobility coupled to imaging mass spectrometry and highlight their importance to the field.more » « less
-
The wide-gap semiconducting perovskite BaSnO3 has attracted attention since the discovery of outstanding mobility at high electron densities, spurred on by potential applications in oxide, transparent, and power electronics. Despite progress, much remains to be understood in terms of mobility-limiting scattering in BaSnO3 thin films and thus mobility optimization. Here, we apply solid-state ion-gel-based electrolyte gating to electrostatically control electron density over a wide range (1018 cm−3 to >1020 cm−3) in BaSnO3 films. Temperature- and gate-voltage-dependent transport data then probe scattering mechanisms and mobility vs electron density alone, independently of sample-to-sample defect density variations. This is done on molecular-beam-epitaxy- and sputter-deposited films as a function of thickness, initial chemical doping, and initial mobility. Remarkably universal behavior occurs, the mobility first increasing with electron density to ∼1020 cm−3 before decreasing slightly. This trend is quantitatively analyzed at cryogenic and room temperatures using analytical models for phonon, ionized impurity, charged dislocation, surface/interface roughness, and electrolyte-induced scattering. The mobility maximum is thus understood to arise from competition between charged impurity/dislocation scattering and electrolyte scattering. The gate-voltage-induced mobility enhancement is found as large as 2000%, realizing 300 K mobility up to 140 cm2 V−1 s−1. This work thus significantly advances the understanding of mobility-limiting scattering processes in BaSnO3, resulting in outstanding room temperature mobilities.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s12127-017-0223-x
