Characterization of Traveling Wave Ion Mobility Separations in Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Ibrahim, Yehia M.; Garimella, Venkata BS

We report on the development and characterization of a new traveling wave-based Structure for Lossless Ion Manipulations (TW-SLIM) for ion mobility separations (IMS). The TW-SLIM module uses parallel arrays of rf electrodes on two closely spaced surfaces for ion confinement, where the rf electrodes are separated by arrays of short electrodes, and using these TWs can be created to drive ion motion. In this initial work, TWs are created by the dynamic application of dc potentials. The capabilities of the TW-SLIM module for efficient ion confinement, lossless ion transport, and ion mobility separations at different rf and TW parameters aremore » reported. The TW-SLIM module is shown to transmit a wide mass range of ions (m/z 200–2500) utilizing a confining rf waveform (~1 MHz and ~300 V p-p) and low TW amplitudes (<20 V). Additionally, the short TW-SLIM module achieved resolutions comparable to existing commercially available low pressure IMS platforms and an ion mobility peak capacity of ~32 for TW speeds of <210 m/s. TW-SLIM performance was characterized over a wide range of rf and TW parameters and demonstrated robust performance. In conclusion, the combined attributes of the flexible design and low voltage requirements for the TW-SLIM module provide a basis for devices capable of much higher resolution and more complex ion manipulations.« less

High-Field Asymmetric-Waveform Ion Mobility Spectrometry and Electron Detachment Dissociation of Isobaric Mixtures of Glycosaminoglycans

NASA Astrophysics Data System (ADS)

Kailemia, Muchena J.; Park, Melvin; Kaplan, Desmond A.; Venot, Andre; Boons, Geert-Jan; Li, Lingyun; Linhardt, Robert J.; Amster, I. Jonathan

2014-02-01

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is shown to be capable of resolving isomeric and isobaric glycosaminoglycan negative ions and to have great utility for the analysis of this class of molecules when combined with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and tandem mass spectrometry. Electron detachment dissociation (EDD) and other ion activation methods for tandem mass spectrometry can be used to determine the sites of labile sulfate modifications and for assigning the stereochemistry of hexuronic acid residues of glycosaminoglycans (GAGs). However, mixtures with overlapping mass-to-charge values present a challenge, as their precursor species cannot be resolved by a mass analyzer prior to ion activation. FAIMS is shown to resolve two types of mass-to-charge overlaps. A mixture of chondroitin sulfate A (CSA) oligomers with 4-10 saccharides units produces ions of a single mass-to-charge by electrospray ionization, as the charge state increases in direct proportion to the degree of polymerization for these sulfated carbohydrates. FAIMS is shown to resolve the overlapping charge. A more challenging type of mass-to-charge overlap occurs for mixtures of diastereomers. FAIMS is shown to separate two sets of epimeric GAG tetramers. For the epimer pairs, the complexity of the separation is reduced when the reducing end is alkylated, suggesting that anomers are also resolved by FAIMS. The resolved components were activated by EDD and the fragment ions were analyzed by FTICR-MS. The resulting tandem mass spectra were able to distinguish the two epimers from each other.

Characterization Of Commonly Encountered Explosives Using Highfield Asymmetric Waveform Ion Mobility Spectrometry Coupled With Mass Spectrometry

DTIC Science & Technology

2007-05-01

symptoms depending on the relative concentration, even leading to death.32 2.4. Instrument Settings Both positive and negative ions can be formed...Detection Technology, pp. 619-633, 1992. 7. Osorio, Celia ; Gomez, Lewis M.; Hernandez, Samuel P.; Castro, Miguel E., Time-of- flight Mass Spectroscopy...vol. 15, pp. 1950-1952. 34. Federal Facilities Assessment Branch, Public Health Assessment, US Army Umatilla Depot Activity, Centers for Disease

Simulation of Ion Motion in FAIMS through Combined Use of SIMION and Modified SDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prasad, Satendra; Tang, Keqi; Manura, David

2009-11-01

Over the years, the use of Field Asymmetric Ion Mobility Spectrometry (FAIMS) has grown with applications spanning from explosives detection to separation of complex biological mixtures. Although, the principles of ion separation in FAIMS is understood and comprehensively characterized, little effort has been made in developing commercially available computational tools that can simulate ion motion in FAIMS. Such a tool could be of great value for refining theory, optimizing the performance of the instrument for specific applications, and in modeling the fringe-fields caused by rf decay at the entrance and exit of FAIMS which can significantly affect ion transmission. Anmore » algorithm using SIMIONTM as its core structure was developed in this study to realistically compute ion trajectory at different ratios of electric field to buffer gas number density (E/N). The E/N can vary from a few Td to ~80 Td in FAIMS as created by an asymmetric square waveform. The Statistical Diffusion Simulation (SDS) model was further incorporated in the algorithm to simulate the ion diffusion in the FAIMS gap. The algorithm was validated using a FAIMS analyzer model similar to the Sionex Corporation model SVAC in terms of its dimensions and geometry. Hydroxyproline and Leucine ions with similar reduced mobility Ko (2.17 and 2.18 cm2.V-1.s-1, respectively) were used as model ions to test the new algorithm and demonstrate the effects of gas flow and waveform (voltage pulse amplitude and frequency) on peak shape and ion current transmission. Simulation results from three ion types: O2-(H2O)3, (A type), (C3H6O)2H+ (B type), and (C12H24O)2H+ (C type) were then compared with the experimental data (available in the literature). The SIMION-SDS-Field Dependent Mobility Calculation (FDMC) algorithm provided good agreement with experimental measurements of the ion peak position in FAIMS compensation voltage (CV) spectrum, peak width, and the ion transmission over a broad range of E/N.« less

Improvement of Quantitative Measurements in Multiplex Proteomics Using High-Field Asymmetric Waveform Spectrometry.

PubMed

Pfammatter, Sibylle; Bonneil, Eric; Thibault, Pierre

2016-12-02

Quantitative proteomics using isobaric reagent tandem mass tags (TMT) or isobaric tags for relative and absolute quantitation (iTRAQ) provides a convenient approach to compare changes in protein abundance across multiple samples. However, the analysis of complex protein digests by isobaric labeling can be undermined by the relative large proportion of co-selected peptide ions that lead to distorted reporter ion ratios and affect the accuracy and precision of quantitative measurements. Here, we investigated the use of high-field asymmetric waveform ion mobility spectrometry (FAIMS) in proteomic experiments to reduce sample complexity and improve protein quantification using TMT isobaric labeling. LC-FAIMS-MS/MS analyses of human and yeast protein digests led to significant reductions in interfering ions, which increased the number of quantifiable peptides by up to 68% while significantly improving the accuracy of abundance measurements compared to that with conventional LC-MS/MS. The improvement in quantitative measurements using FAIMS is further demonstrated for the temporal profiling of protein abundance of HEK293 cells following heat shock treatment.

Ion Mobility Spectrometry (IMS) and Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shvartsburg, Alexandre A.

2010-04-20

In a media of finite viscosity, the Coulomb force of external electric field moves ions with some terminal speed. This dynamics is controlled by “mobility” - a property of the interaction potential between ions and media molecules. This fact has been used to separate and characterize gas-phase ions in various modes of ion mobility spectrometry (IMS) developed since 1970. Commercial IMS devices were introduced in 1980-s for field detection of volatile traces such as explosives and chemical warfare agents. Coupling to soft-ionization sources, mass spectrometry (MS), and chromatographic methods in 1990-s had allowed IMS to handle complex samples, enabling newmore » applications in biological and environmental analyses, nanoscience, and other areas. Since 2003, the introduction of commercial systems by major instrument vendors started bringing the IMS/MS capability to broad user community. The other major development of last decade has been the differential IMS or “field asymmetric waveform IMS” (FAIMS) that employs asymmetric time-dependent electric field to sort ions not by mobility itself, but by the difference between its values in strong and weak electric fields. Coupling of FAIMS to conventional IMS and stacking of conventional IMS stages have enabled two-dimensional separations that dramatically expand the power of ion mobility methods.« less

Implementation of Dipolar Resonant Excitation for Collision Induced Dissociation with Ion Mobility/Time-of-Flight MS

PubMed Central

Webb, Ian K.; Chen, Tsung-Chi; Danielson, William F.; Ibrahim, Yehia M.; Tang, Keqi; Anderson, Gordon A.; Smith, Richard D.

2014-01-01

An ion mobility/time-of-flight mass spectrometer (IMS/TOF MS) platform that allows for resonant excitation collision induced dissociation (CID) is presented. Highly efficient, mass-resolved fragmentation without additional excitation of product ions was accomplished and over-fragmentation common in beam-type CID experiments was alleviated. A quadrupole ion guide was modified to apply a dipolar AC signal across a pair of rods for resonant excitation. The method was characterized with singly protonated methionine enkephalin and triply protonated peptide angiotensin I, yielding maximum CID efficiencies of 44% and 84%, respectively. The Mathieu qx,y parameter was set at 0.707 for these experiments to maximize pseudopotential well depths and CID efficiencies. Resonant excitation CID was compared to beam-type CID for the peptide mixture. The ability to apply resonant waveforms in mobility-resolved windows is demonstrated with a peptide mixture yielding fragmentation over a range of mass-to-charge (m/z) ratios within a single IMS-MS analysis. PMID:24470195

Interface and process for enhanced transmission of non-circular ion beams between stages at unequal pressure

DOEpatents

Tang, Keqi [Richland, WA; Shvartsburg, Alexandre A [Richland, WA; Smith, Richard D [Richland, WA

2008-03-04

The invention discloses a new interface with non-circular conductance limit aperture(s) useful for effective transmission of non-circular ion beams between stages with different gas pressure. In particular, the invention provides an improved coupling of field asymmetric waveform ion mobility spectrometry (FAIMS) analyzers of planar or side-to-side geometry to downstream stages such as mass spectrometry or ion mobility spectrometry. In this case, the non-circular aperture is rectangular; other geometries may be optimum in other applications. In the preferred embodiment, the non-circular aperture interface is followed by an electrodynamic ion funnel that may focus wide ion beams of any shape into tight circular beams with virtually no losses. The jet disrupter element of the funnel may also have a non-circular geometry, matching the shape of arriving ion beam. The improved sensitivity of planar FAIMS/MS has been demonstrated in experiments using a non-contiguous elongated aperture but other embodiments (e.g., with a contiguous slit aperture) may be preferable, especially in conjunction with an ion funnel operated at high pressures.

Pulsed discharge ionization source for miniature ion mobility spectrometers

DOEpatents

Xu, Jun; Ramsey, J. Michael; Whitten, William B.

2004-11-23

A method and apparatus is disclosed for flowing a sample gas and a reactant gas (38, 43) past a corona discharge electrode (26) situated at a first location in an ion drift chamber (24), applying a pulsed voltage waveform comprising a varying pulse component and a dc bias component to the corona discharge electrode (26) to cause a corona which in turn produces ions from the sample gas and the reactant gas, applying a dc bias to the ion drift chamber (24) to cause the ions to drift to a second location (25) in the ion drift chamber (24), detecting the ions at the second location (25) in the drift chamber (24), and timing the period for the ions to drift from the corona discharge electrode to the selected location in the drift chamber.

High sensitivity field asymmetric ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni

2017-03-01

A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

Separation and Identification of Isomeric Glycopeptides by High Field Asymmetric Waveform Ion Mobility Spectrometry

PubMed Central

2012-01-01

The analysis of intact glycopeptides by mass spectrometry is challenging due to the numerous possibilities for isomerization, both within the attached glycan and the location of the modification on the peptide backbone. Here, we demonstrate that high field asymmetric wave ion mobility spectrometry (FAIMS), also known as differential ion mobility, is able to separate isomeric O-linked glycopeptides that have identical sequences but differing sites of glycosylation. Two glycopeptides from the glycoprotein mucin 5AC, GT(GalNAc)TPSPVPTTSTTSAP and GTTPSPVPTTST(GalNAc)TSAP (where GalNAc is O-linked N-acetylgalactosamine), were shown to coelute following reversed-phase liquid chromatography. However, FAIMS analysis of the glycopeptides revealed that the compensation voltage ranges in which the peptides were transmitted differed. Thus, it is possible at certain compensation voltages to completely separate the glycopeptides. Separation of the glycopeptides was confirmed by unique reporter ions produced by supplemental activation electron transfer dissociation mass spectrometry. These fragments also enable localization of the site of glycosylation. The results suggest that glycan position plays a key role in determining gas-phase glycopeptide structure and have implications for the application of FAIMS in glycoproteomics. PMID:22280549

Analysis of chemical warfare agents in food products by atmospheric pressure ionization-high field asymmetric waveform ion mobility spectrometry-mass spectrometry.

PubMed

Kolakowski, Beata M; D'Agostino, Paul A; Chenier, Claude; Mester, Zoltán

2007-11-01

Flow injection high field asymmetric waveform ion mobility spectrometry (FAIMS)-mass spectrometry (MS) methodology was developed for the detection and identification of chemical warfare (CW) agents in spiked food products. The CW agents, soman (GD), sarin (GB), tabun (GA), cyclohexyl sarin (GF), and four hydrolysis products, ethylphosphonic acid (EPA), methylphosphonic acid (MPA), pinacolyl methylphosphonic acid (Pin MPA), and isopropyl methylphosphonic acid (IMPA) were separated and detected by positive ion and negative ion atmospheric pressure ionization-FAIMS-MS. Under optimized conditions, the compensation voltages were 7.2 V for GD, 8.0 V for GA, 7.2 V for GF, 7.6 V for GB, 18.2 V for EPA, 25.9 V for MPA, -1.9 V for PinMPA, and +6.8 V for IMPA. Sample preparation was kept to a minimum, resulting in analysis times of 3 min or less per sample. The developed methodology was evaluated by spiking bottled water, canola oil, cornmeal, and honey samples at low microgram per gram (or microg/mL) levels with the CW agents or CW agent hydrolysis products. The detection limits observed for the CW agents in the spiked food samples ranged from 3 to 15 ng/mL in bottled water, 1-33 ng/mL in canola oil, 1-34 ng/g in cornmeal, and 13-18 ng/g in honey. Detection limits were much higher for the CW agent hydrolysis products, with only MPA being detected in spiked honey samples.

Ambient ionisation mass spectrometry for in situ analysis of intact proteins

PubMed Central

Kocurek, Klaudia I.; Griffiths, Rian L.

2018-01-01

Abstract Ambient surface mass spectrometry is an emerging field which shows great promise for the analysis of biomolecules directly from their biological substrate. In this article, we describe ambient ionisation mass spectrometry techniques for the in situ analysis of intact proteins. As a broad approach, the analysis of intact proteins offers unique advantages for the determination of primary sequence variations and posttranslational modifications, as well as interrogation of tertiary and quaternary structure and protein‐protein/ligand interactions. In situ analysis of intact proteins offers the potential to couple these advantages with information relating to their biological environment, for example, their spatial distributions within healthy and diseased tissues. Here, we describe the techniques most commonly applied to in situ protein analysis (liquid extraction surface analysis, continuous flow liquid microjunction surface sampling, nano desorption electrospray ionisation, and desorption electrospray ionisation), their advantages, and limitations and describe their applications to date. We also discuss the incorporation of ion mobility spectrometry techniques (high field asymmetric waveform ion mobility spectrometry and travelling wave ion mobility spectrometry) into ambient workflows. Finally, future directions for the field are discussed. PMID:29607564

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

PubMed

Pervukhin, Viktor V; Sheven, Dmitriy G

2010-01-01

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

Gas-Phase Enrichment of Multiply Charged Peptide Ions by Differential Ion Mobility Extend the Comprehensiveness of SUMO Proteome Analyses

NASA Astrophysics Data System (ADS)

Pfammatter, Sibylle; Bonneil, Eric; McManus, Francis P.; Thibault, Pierre

2018-04-01

The small ubiquitin-like modifier (SUMO) is a member of the family of ubiquitin-like modifiers (UBLs) and is involved in important cellular processes, including DNA damage response, meiosis and cellular trafficking. The large-scale identification of SUMO peptides in a site-specific manner is challenging not only because of the low abundance and dynamic nature of this modification, but also due to the branched structure of the corresponding peptides that further complicate their identification using conventional search engines. Here, we exploited the unusual structure of SUMO peptides to facilitate their separation by high-field asymmetric waveform ion mobility spectrometry (FAIMS) and increase the coverage of SUMO proteome analysis. Upon trypsin digestion, branched peptides contain a SUMO remnant side chain and predominantly form triply protonated ions that facilitate their gas-phase separation using FAIMS. We evaluated the mobility characteristics of synthetic SUMO peptides and further demonstrated the application of FAIMS to profile the changes in protein SUMOylation of HEK293 cells following heat shock, a condition known to affect this modification. FAIMS typically provided a 10-fold improvement of detection limit of SUMO peptides, and enabled a 36% increase in SUMO proteome coverage compared to the same LC-MS/MS analyses performed without FAIMS. [Figure not available: see fulltext.

Broad Separation of Isomeric Lipids by High-Resolution Differential Ion Mobility Spectrometry with Tandem Mass Spectrometry

NASA Astrophysics Data System (ADS)

Bowman, Andrew P.; Abzalimov, Rinat R.; Shvartsburg, Alexandre A.

2017-08-01

Maturation of metabolomics has brought a deeper appreciation for the importance of isomeric identity of lipids to their biological role, mirroring that for proteoforms in proteomics. However, full characterization of the lipid isomerism has been thwarted by paucity of rapid and effective analytical tools. A novel approach is ion mobility spectrometry (IMS) and particularly differential or field asymmetric waveform IMS (FAIMS) at high electric fields, which is more orthogonal to mass spectrometry. Here we broadly explore the power of FAIMS to separate lipid isomers, and find a 75% success rate across the four major types of glycero- and phospho- lipids ( sn, chain length, double bond position, and cis/ trans). The resolved isomers were identified using standards, and (for the first two types) tandem mass spectrometry. These results demonstrate the general merit of incorporating high-resolution FAIMS into lipidomic analyses.

Note: An inexpensive square waveform ion funnel driver

NASA Astrophysics Data System (ADS)

Hoffman, Nathan M.; Opačić, Bojana; Reilly, Peter T. A.

2017-01-01

An inexpensive frequency variable square waveform generator (WFG) was developed to use with existing sinusoidal waveform driven ion funnels. The developed WFG was constructed using readily available low voltage DC power supplies and discrete components placed in printed circuit boards. As applied to ion funnels, this WFG represents considerable cost savings over commercially available products without sacrificing performance. Operation of the constructed pulse generator has been demonstrated for a 1 nF ion funnel at an operating frequency of 1 MHz while switching 48 Vp-p.

Note: An inexpensive square waveform ion funnel driver.

PubMed

Hoffman, Nathan M; Opačić, Bojana; Reilly, Peter T A

2017-01-01

An inexpensive frequency variable square waveform generator (WFG) was developed to use with existing sinusoidal waveform driven ion funnels. The developed WFG was constructed using readily available low voltage DC power supplies and discrete components placed in printed circuit boards. As applied to ion funnels, this WFG represents considerable cost savings over commercially available products without sacrificing performance. Operation of the constructed pulse generator has been demonstrated for a 1 nF ion funnel at an operating frequency of 1 MHz while switching 48 V p-p .

Tailored-waveform Collisional Activation of Peptide Ion Electron Transfer Survivor Ions in Cation Transmission Mode Ion/Ion Reaction Experiments

PubMed Central

Han, Hongling; Londry, Frank A.; Erickson, David E.; McLuckey, Scott A.

2010-01-01

SUMMARY Broad-band resonance excitation via a tailored waveform in a high pressure collision cell (Q2) on a hybrid quadrupole/time-of-flight (QqTOF) tandem mass spectrometer has been implemented for cation transmission mode electron transfer ion/ion reactions of tryptic polypeptides. The frequency components in the broadband waveform were defined to excite the first generation intact electron transfer products for relatively large tryptic peptides. The optimum amplitude of the arbitrary waveform applied has been determined empirically to be 3.0 Vp-p, which is effective for relatively high mass-to-charge (m/z) ratio precursor ions with little elimination of sequence information for low m/z ions. The application of broadband activation during the transmission mode ion/ion reaction obviates frequency and amplitude tuning normally associated with ion trap collision induced dissociation (CID). This approach has been demonstrated with triply and doubly charged tryptic peptides with and without post-translational modifications. Enhanced structural information was achieved by production of a larger number of informative c- and z-type fragments using the tailored waveform on unmodified and modified (phosphorylated and glycosylated) peptides when the first generation intact electron transfer products fell into the defined frequency range. This approach can be applied to a wide range of tryptic peptide ions, making it attractive as a rapid and general approach for ETD LC-MS/MS of tryptic peptides in a QqTOF instrument. PMID:19305916

Application of stored waveform ion modulation 2D-FTICR MS/MS to the analysis of complex mixtures.

PubMed

Ross, Charles W; Simonsick, William J; Aaserud, David J

2002-09-15

Component identification of complex mixtures, whether they are from polymeric formulations or combinatorial synthesis, by conventional MS/MS techniques generally requires component separation by chromatography or mass spectrometry. An automated means of acquiring simultaneous MS/MS data from a complex mixture without prior separation is obtained from stored waveform ion modulation (SWIM) two-dimensional FTICR MS/MS. The technique applies a series of SWIFT excitation waveforms whose frequency domain magnitude spectrum is a sinusoid increasing in frequency from one waveform to the next. The controlled dissociation of the precursor ions produces an associated modulation of the product ion abundances. Fourier transformation of these abundances reveals the encoded modulation frequency from which connectivities of precursor and product ions are observed. The final result is total assignment of product ions for each precursor ion in a mixture from one automated experiment. We demonstrated the applicability of SWIM 2D-FTICR MS/MS to two diverse samples of industrial importance. We characterized structured polyester oligomers and products derived from combinatorial synthesis. Fragmentation pathways identified in standard serial ion isolation MS/MS experiments were observed for trimethylolpropane/methyl hexahydrophthalic anhydride. A 20-component sample derived from combinatorial synthesis was fragmented, and the template ion along with another key fragment ion was identified for each of the 20 components.

High-Voltage, Asymmetric-Waveform Generator

NASA Technical Reports Server (NTRS)

Beegle, Luther W.; Duong, Tuan A.; Duong, Vu A.; Kanik, Isik

2008-01-01

The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise leave the fundamental timing signal unchanged. The buffered timing signal would be fed as input to the level shifter. The output of the level shifter would serve as a timing and control signal for the high-voltage switch, causing the switch to alternately be (1) opened, allowing the capacitive load to be charged from a high-voltage DC power supply; then (2) closed to discharge the capacitive load to ground. Hence, the output waveform would closely approximate a series of exponential charging and discharging curves (see Figure 2).

Planar differential mobility spectrometer as a pre-filter for atmospheric pressure ionization mass spectrometry

PubMed Central

Schneider, Bradley B.; Covey, Thomas R.; Coy, Stephen L.; Krylov, Evgeny V.

2010-01-01

Ion filters based on planar DMS can be integrated with the inlet configuration of most mass spectrometers, and are able to enhance the quality of mass analysis and quantitative accuracy by reducing chemical noise, and by pre-separating ions of similar mass. This paper is the first in a series of three papers describing the optimization of DMS / MS instrumentation. In this paper the important physical parameters of a planar DMS-MS interface including analyzer geometry, analyzer coupling to a mass spectrometer, and transport gas flow control are considered. The goal is to optimize ion transmission and transport efficiency, provide optimal and adjustable resolution, and produce stable operation under conditions of high sample contamination. We discuss the principles of DMS separations and highlight the theoretical underpinnings. The main differences between planar and cylindrical geometries are presented, including a discussion of the advantages and disadvantages of RF ion focusing. In addition, we present a description of optimization of the frequency and amplitude of the DMS fields for resolution and ion transmission, and a discussion of the influence and importance of ion residence time in DMS. We have constructed a mass spectrometer interface for planar geometries that takes advantage of atmospheric pressure gas dynamic principles, rather than ion focusing, to minimize ion losses from diffusion in the analyzer and to maximize total ion transport into the mass spectrometer. A variety of experimental results has been obtained that illustrate the performance of this type of interface, including tests of resistance to high contamination levels, and the separation of stereoisomers. In a subsequent publication the control of the chemical interactions that drive the separation process of a DMS / MS system will be considered. In a third publication we describe novel electronics designed to provide the high voltages asymmetric waveform fields (SV) required for these devices as well as the effects of different waveforms. PMID:21278836

Identification of N-nitrosamines in treated drinking water using nanoelectrospray ionization high-field asymmetric waveform ion mobility spectrometry with quadrupole time-of-flight mass spectrometry.

PubMed

Zhao, Yuan Yuan; Liu, Xin; Boyd, Jessica M; Qin, Feng; Li, Jianjun; Li, Xing-Fang

2009-01-01

We report a nanoelectrospray ionization (nESI) with high-field asymmetric waveform ion mobility spectrometry (FAIMS) and tandem mass spectrometry (MS-MS) method for determination of small molecules of m/z 50 to 200 and its potential application in environmental analysis. Integration of nESI with FAIMS and MS-MS combines the advantages of these three techniques into one method. The nESI provides efficient sample introduction and ionization and allows for collection of multiple data from only microliters of samples. The FAIMS provides rapid separation, reduces or eliminates background interference, and improves the signal-to-noise ratio as much as 10-fold over nESI-MS-MS. The tandem quadrupole time-of-flight MS detection provides accurate mass and mass spectral measurements for structural identification. Characteristics of FAIMS compensation voltage (CV) spectra of seven nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), N-nitrosodi-n-butylamine (NDBA), N-nitrosopiperidine (NPip), and N-nitrosopyrrolidine (NPyr), were analyzed. The optimal CV of the nitrosamines (at DV -4000 V) were: -1.6 V, NDBA; 2.6 V, NDPA; 6.6 V, NPip; 8.8 V, NDEA; 13.2 V, NPyr; 14.4 V, NMEA; and 19.4 V, NDMA. Fragmentation patterns of the seven nitrosamines in the nESI-FAIMS-MS-MS were also obtained. The specific CV and MS-MS spectra resulted in positive identification of NPyr and NPip in a treated water sample, demonstrating the potential application of this technique in environmental analysis.

Analysis of a series of chlorogenic acid isomers using differential ion mobility and tandem mass spectrometry.

PubMed

Willems, Jamie L; Khamis, Mona M; Mohammed Saeid, Waleed; Purves, Randy W; Katselis, George; Low, Nicholas H; El-Aneed, Anas

2016-08-24

Chlorogenic acids are among the most abundant phenolics found in the human diet. Of these, the mono-caffeoylquinic acids are the predominant phenolics found in fruits, such as apples and pears, and products derived from them. In this research, a comprehensive study of the electrospray ionization (ESI) tandem mass spectrometric (MS/MS) dissociation behavior of the three most common mono-caffeoylquinic acids, namely 5-O-caffeoylquinic acid (5-CQA), 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were determined using both positive and negative ionization. All proposed structures of the observed product ions were confirmed with second-generation MS(3) experiments. Similarities and differences between the dissociation pathways in the positive and negative ion modes are discussed, confirming the proposed structures and the established MS/MS fingerprints. MS/MS dissociation was primarily driven via the cleavage of the ester bond linking the quinic acid moiety to the caffeic acid moiety within tested molecules. Despite being structural isomers with the same m/z values and dissociation behaviors, the MS/MS data in the negative ion mode was able to differentiate the three isomers based on ion intensity for the major product ions, observed at m/z 191, 179 and 173. This differentiation was consistent among various MS instruments. In addition, ESI coupled with high-field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) was employed for the separation of these compounds for the first time. By combining MS/MS data and differential ion mobility, a method for the separation and identification of mono-caffeoylquinic in apple/pear juice samples was developed with a run time of less than 1 min. It is envisaged that this methodology could be used to identify pure juices based on their chlorogenic acid profile (i.e., metabolomics), and could also be used to detect juice-to-juice adulteration (e.g., apple juice addition to pear juice). Copyright © 2016 Elsevier B.V. All rights reserved.

Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruneau, B., E-mail: bastien.bruneau@polytechnique.edu; Johnson, E.; Korolov, I.

2016-04-28

We report investigations of capacitively coupled carbon tetrafluoride (CF{sub 4}) plasmas excited with tailored voltage waveforms containing up to five harmonics of a base frequency of 5.5 MHz. The impact of both the slope asymmetry, and the amplitude asymmetry, of these waveforms on the discharge is examined by combining experiments with particle-in-cell simulations. For all conditions studied herein, the discharge is shown to operate in the drift-ambipolar mode, where a comparatively large electric field in the plasma bulk (outside the sheaths) is the main mechanism for electron power absorption leading to ionization. We show that both types of waveform asymmetries stronglymore » influence the ion energy at the electrodes, with the particularity of having the highest ion flux on the electrode where the lowest ion energy is observed. Even at the comparatively high pressure (600 mTorr) and low fundamental frequency of 5.5 MHz used here, tailoring the voltage waveforms is shown to efficiently create an asymmetry of both the ion energy and the ion flux in geometrically symmetric reactors.« less

Ponderomotive lower hybrid wave growth in electric fields associated with electron beam injection and transverse ion acceleration

NASA Astrophysics Data System (ADS)

Bale, S. D.; Kellogg, P. J.; Erickson, K. N.; Monson, S. J.; Arnoldy, R. L.

During electron beam injection, the Echo 7 rocket experiment observed large bursts of transversely accelerated ions. These ions seem to have been energized in the region of the beam or the payload return current. Electric field waveforms (<= 30 kHz) during gun operation show both low frequency fluctuations and broad band power. An analysis of the waveforms shows nonlinear mode coupling between waves near the ion cyclotron frequency and waves above the lower hybrid frequency.

Effects of Different Waveforms on the Performance of Active Capillary Dielectric Barrier Discharge Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Dumlao, Morphy C.; Xiao, Dan; Zhang, Daming; Fletcher, John; Donald, William A.

2017-04-01

Active capillary dielectric barrier discharge ionization (DBDI) is emerging as a compact, low-cost, and robust method to form intact ions of small molecules for detection in near real time by portable mass spectrometers. Here, we demonstrate that by using a 10 kHz, 2.5 kVp-p high-voltage square-wave alternating current plasma, active capillary DBDI can consume less than 1 μW of power. In contrast, the power consumed using a sine and triangle alternating current waveform is more than two orders of magnitude higher than that for the square waveform to obtain a similar voltage for plasma generation. Moreover, the plasma obtained using a square waveform can be significantly more homogenous than that obtained using sine and triangle waveforms. Protonated dimethyl methylphosphonate (DMMP) and deprotonated perfluorooctanoic acid (PFOA) can be detected at about the same or higher abundances using square-wave DBDI mass spectrometry compared with the use of sine and triangle waveforms. By use of benzylammonium thermometer ions, the extent of internal energy deposition using square, sine, or triangle waveform excited plasmas are essentially the same at the optimum voltages for ion detection. Using an H-bridge circuit driving a transformer optimized to reduce losses, square-wave active capillary DBDI can be continuously powered for 50 h by common 9 V-battery (PP3).

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

NASA Astrophysics Data System (ADS)

Gibson, Andrew R.; Gans, Timo

2017-11-01

The charged particle dynamics in low-pressure oxygen plasmas excited by odd harmonic dual frequency waveforms (low frequency of 13.56 MHz and high frequency of 40.68 MHz) are investigated using a one-dimensional numerical simulation in regimes of both low and high electronegativity. In the low electronegativity regime, the time and space averaged electron and negative ion densities are approximately equal and plasma sustainment is dominated by ionisation at the sheath expansion for all combinations of low and high frequency and the phase shift between them. In the high electronegativity regime, the negative ion density is a factor of 15-20 greater than the low electronegativity cases. In these cases, plasma sustainment is dominated by ionisation inside the bulk plasma and at the collapsing sheath edge when the contribution of the high frequency to the overall voltage waveform is low. As the high frequency component contribution to the waveform increases, sheath expansion ionisation begins to dominate. It is found that the control of the average voltage drop across the plasma sheath and the average ion flux to the powered electrode are similar in both regimes of electronegativity, despite the differing electron dynamics using the considered dual frequency approach. This offers potential for similar control of ion dynamics under a range of process conditions, independent of the electronegativity. This is in contrast to ion control offered by electrically asymmetric waveforms where the relationship between the ion flux and ion bombardment energy is dependent upon the electronegativity.

Integration of paper spray ionization high-field asymmetric waveform ion mobility spectrometry for forensic applications.

PubMed

Tsai, Chia-Wei; Tipple, Christopher A; Yost, Richard A

2018-04-15

Paper spray ionization (PSI) is an attractive ambient ionization source for mass spectrometry (MS) since it allows the combination of surface sampling and ionization. The minimal sample preparation inherent in this approach greatly reduces the time needed for analysis. However, the ions generated from interfering compounds in the sample and the paper substrate may interfere with the analyte ions. Therefore, the integration of PSI with high-field asymmetric ion mobility spectrometry (FAIMS) is of significant interest since it should reduce the background ions entering the mass analyzer without complicating the analysis or increasing analysis time. Here we demonstrate the integration of PSI with FAIMS/MS and its potential for analysis of samples of forensic interest. In this work, the parameters that can influence the integration, including sampling and ionization by paper spray, the FAIMS separation of analytes from each other and background interferences, and the length of time that a usable signal can be observed for explosives on paper, were evaluated with the integrated system. In the negative ion analysis of 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), amounts as low as 1 ng on paper were readily observed. The successful positive ion separation of a set of illicit drugs including heroin, methamphetamine, and cocaine was also achieved. In addition, the positive ion analysis of the chemical warfare agent simulants dimethyl methylphosphonate (DMMP) and diisopropyl methylphosphonate (DIMP) was evaluated. The integration of PSI-FAIMS/MS was demonstrated for the analyses of explosives in negative ion mode and for illicit drugs and CW simulants in positive mode. Paper background ions that could interfere with these analyses were separated by FAIMS. The compensation voltage of an ion obtained by FAIMS provided an additional identification parameter to be combined with the mass spectrum for each analyte. Copyright © 2018 John Wiley & Sons, Ltd.

UGV Interoperability Profile (IOP) Communications Profile, Version 0

DTIC Science & Technology

2011-12-21

some UGV systems employ Orthogonal Frequency Division Multiplexing ( OFDM ) or Coded Orthogonal Frequency Division Multiplexing (COFDM) waveforms which...other portions of the IOP. Attribute Paragraph Title Values Waveform 3.3 Air Interface/ Waveform OFDM , COFDM, DDL, CDL, None OCU to Platform...Sight MANET Mobile Ad-hoc Network Mbps Megabits per second MC/PM Master Controller/ Payload Manager MHz Megahertz MIMO Multiple Input Multiple

Nanospray FAIMS Fractionation Provides Significant Increases in Proteome Coverage of Unfractionated Complex Protein Digests*

PubMed Central

Swearingen, Kristian E.; Hoopmann, Michael R.; Johnson, Richard S.; Saleem, Ramsey A.; Aitchison, John D.; Moritz, Robert L.

2012-01-01

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is an atmospheric pressure ion mobility technique that can be used to reduce sample complexity and increase dynamic range in tandem mass spectrometry experiments. FAIMS fractionates ions in the gas-phase according to characteristic differences in mobilities in electric fields of different strengths. Undesired ion species such as solvated clusters and singly charged chemical background ions can be prevented from reaching the mass analyzer, thus decreasing chemical noise. To date, there has been limited success using the commercially available Thermo Fisher FAIMS device with both standard ESI and nanoLC-MS. We have modified a Thermo Fisher electrospray source to accommodate a fused silica pulled tip capillary column for nanospray ionization, which will enable standard laboratories access to FAIMS technology. Our modified source allows easily obtainable stable spray at flow rates of 300 nL/min when coupled with FAIMS. The modified electrospray source allows the use of sheath gas, which provides a fivefold increase in signal obtained when nanoLC is coupled to FAIMS. In this work, nanoLC-FAIMS-MS and nanoLC-MS were compared by analyzing a tryptic digest of a 1:1 mixture of SILAC-labeled haploid and diploid yeast to demonstrate the performance of nanoLC-FAIMS-MS, at different compensation voltages, for post-column fractionation of complex protein digests. The effective dynamic range more than doubled when FAIMS was used. In total, 10,377 unique stripped peptides and 1649 unique proteins with SILAC ratios were identified from the combined nanoLC-FAIMS-MS experiments, compared with 6908 unique stripped peptides and 1003 unique proteins with SILAC ratios identified from the combined nanoLC-MS experiments. This work demonstrates how a commercially available FAIMS device can be combined with nanoLC to improve proteome coverage in shotgun and targeted type proteomics experiments. PMID:22186714

Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms.

PubMed

Franek, James; Brandt, Steven; Berger, Birk; Liese, Martin; Barthel, Matthias; Schüngel, Edmund; Schulze, Julian

2015-05-01

We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

Generalization of the Child-Langmuir law to the alternate extraction of positive and negative ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lafleur, T., E-mail: trevor.lafleur@lpp.polytechnique.fr; ONERA-The French Aerospace Lab, 91120 Palaiseau; Aanesland, A.

Using a combined analytical and simulation approach, we investigate positive and negative ion extraction between two electrodes from an ion-ion plasma source. With a square voltage waveform applied to the electrodes, we obtain approximate analytical solutions for the time-averaged extracted current densities, which are given simply by: J{sub p}{sup ac}=[α−fL√((M{sub p})/(q{sub p}V{sub 0}) )]J{sub p}{sup dc}, and J{sub n}{sup ac}=[(1−α)−fL√((M{sub n})/(q{sub n}V{sub 0}) )]J{sub n}{sup dc}, where J{sup ac} is the time-averaged current density, α is the square waveform duty cycle, f is the frequency, L is the electrode gap length, M is the ion mass, q is the ionmore » charge, V{sub 0} is the applied voltage amplitude, J{sup dc} is the dc extracted current density, and the subscripts p and n refer to positive and negative ions, respectively. In particular, if J{sup dc} is the dc space-charge limited current density, then these equations describe the square waveform generalization of the Child-Langmuir law.« less

Microwave-induced resistance oscillations on a high-mobility two-dimensional electron gas: Exact waveform, absorption/reflection and temperature damping

NASA Astrophysics Data System (ADS)

Studenikin, S. A.; Potemski, M.; Sachrajda, A.; Hilke, M.; Pfeiffer, L. N.; West, K. W.

2005-06-01

In this work we address experimentally a number of unresolved issues related to microwave induced resistance oscillations (MIROs) leading to the zero-resistance states observed recently on 2D electron gases in GaAs/AlGaAs heterostructures. We stress the importance of the electrodynamic effects detected in both reflection and absorption experiments, although they are not revealed in transport experiments on very high mobility samples. We also study the exact waveform of MIROs and their damping due to temperature. A simple equation is given, which can be considered as phenomenological, which describes precisely the experimental MIROs waveform. The waveform depends only on a single parameter—the width of the Landau levels, which is related to the quantum lifetime. A very good correlation was found between the temperature dependencies of the quantum lifetime from MIROs and the transport scattering time from the electron mobility with a ratio τtr/τq≃20 . It is found that the prefactor in the equation for MIROs decays as 1/T2 with the temperature which can be explained within the distribution function model suggested by Dmitriev . The results are compared with measurements of the Shubnikov-de Haas oscillations down to 30mK on the same sample.

Nonlinear waves in electron-positron-ion plasmas including charge separation

NASA Astrophysics Data System (ADS)

Mugemana, A.; Moolla, S.; Lazarus, I. J.

2017-02-01

Nonlinear low-frequency electrostatic waves in a magnetized, three-component plasma consisting of hot electrons, hot positrons and warm ions have been investigated. The electrons and positrons are assumed to have Boltzmann density distributions while the motion of the ions are governed by fluid equations. The system is closed with the Poisson equation. This set of equations is numerically solved for the electric field. The effects of the driving electric field, ion temperature, positron density, ion drift, Mach number and propagation angle are investigated. It is shown that depending on the driving electric field, ion temperature, positron density, ion drift, Mach number and propagation angle, the numerical solutions exhibit waveforms that are sinusoidal, sawtooth and spiky. The introduction of the Poisson equation increased the Mach number required to generate the waveforms but the driving electric field E 0 was reduced. The results are compared with satellite observations.

Capacitively coupled hydrogen plasmas sustained by tailored voltage waveforms: excitation dynamics and ion flux asymmetry

DOE PAGES

Bruneau, B.; Diomede, P.; Economou, D. J.; ...

2016-06-08

Parallel plate capacitively coupled plasmas in hydrogen at relatively high pressure (~1 Torr) are excited with tailored voltage waveforms containing up to five frequencies. Predictions of a hybrid model combining a particle-in-cell simulation with Monte Carlo collisions and a fluid model are compared to phase resolved optical emission spectroscopy measurements, yielding information on the dynamics of the excitation rate in these discharges. When the discharge is excited with amplitude asymmetric waveforms, the discharge becomes electrically asymmetric, with different ion energies at each of the two electrodes. Unexpectedly, large differences in themore » $$\\text{H}_{2}^{+}$$ fluxes to each of the two electrodes are caused by the different $$\\text{H}_{3}^{+}$$ energies. When the discharge is excited with slope asymmetric waveforms, only weak electrical asymmetry of the discharge is observed. In this case, electron power absorption due to fast sheath expansion at one electrode is balanced by electron power absorption at the opposite electrode due to a strong electric field reversal.« less

Particle-in-cell simulation of ion energy distributions on an electrode by applying tailored bias waveforms in the afterglow of a pulsed plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diomede, Paola; Economou, Demetre J.; Donnelly, Vincent M.

2011-04-15

A Particle-in-Cell simulation with Monte Carlo Collisions (PIC-MCC) was conducted of the application of tailored DC voltage steps on an electrode, during the afterglow of a capacitively-coupled pulsed-plasma argon discharge, to control the energy of ions incident on the counter-electrode. Staircase voltage waveforms with selected amplitudes and durations resulted in ion energy distributions (IED) with distinct narrow peaks, with controlled energies and fraction of ions under each peak. Temporary electron heating at the moment of application of a DC voltage step did not influence the electron density decay in the afterglow. The IED peaks were 'smeared' by collisions, especially atmore » the higher pressures of the range (10-40 mTorr) investigated.« less

On an Aerodynamic Mechanism to Enhance Ion Transmission and Sensitivity of FAIMS for Nano-Electrospray Ionization-Mass Spectrometry

NASA Astrophysics Data System (ADS)

Prasad, Satendra; Belford, Michael W.; Dunyach, Jean-Jacques; Purves, Randy W.

2014-12-01

Simulations show that significant ion losses occur within the commercial electrospray ionization-field asymmetric waveform ion mobility spectrometer (ESI-FAIMS) interface owing to an angular desolvation gas flow and because of the impact of the FAIMS carrier gas onto the inner rf (radio frequency) electrode. The angular desolvation gas flow diverts ions away from the entrance plate orifice while the carrier gas annihilates ions onto the inner rf electrode. A novel ESI-FAIMS interface is described that optimizes FAIMS gas flows resulting in large improvements in transmission. Simulations with the bromochloroacetate anion showed an improvement of ~9-fold to give ~70% overall transmission). Comparable transmission improvements were attained experimentally for six peptides (2+) in the range of m/z 404.2 to 653.4 at a chromatographic flow rate of 300 nL/min. Selected ion chromatograms (SIC) from nano-LC-FAIMS-MS analyses showed 71% (HLVDEPQNLIK, m/z 653.4, 2+) to 95% (LVNELTEFAK, m/z 582.3, 2+) of ion signal compared with ion signal in the SIC from LC-MS analysis. IGSEVYHNLK (580.3, 2+) showed 24% more ion signal compared with LC-MS and is explained by enhanced desolvation in FAIMS. A 3-10 times lower limits of quantitation (LOQ) (<15% RSD) was achieved for chemical noise limited peaks with FAIMS. Peaks limited by ion statistics showed subtle improvement in RSD and yielded comparable LOQ to that attained with nano-LC-MS (without FAIMS). These improvements were obtained using a reduced FAIMS separation gap (from 2.5 to 1.5 mm) that results in a shorter residence time (13.2 ms ± 3.9 ms) and enables the use of a helium free transport gas (100% nitrogen).

FAST TRACK COMMUNICATION: Nanocrystalline silicon film growth morphology control through RF waveform tailoring

NASA Astrophysics Data System (ADS)

Johnson, Erik V.; Verbeke, Thomas; Vanel, Jean-Charles; Booth, Jean-Paul

2010-10-01

We demonstrate the application of RF waveform tailoring to generate an electrical asymmetry in a capacitively coupled plasma-enhanced chemical vapour deposition system, and its use to control the growth mode of hydrogenated amorphous and nanocrystalline silicon thin films deposited at low temperature (150 °C). A dramatic shift in the dc bias potential at the powered electrode is observed when simply inverting the voltage waveform from 'peaks' to 'troughs', indicating an asymmetric distribution of the sheath voltage. By enhancing or suppressing the ion bombardment energy at the substrate (situated on the grounded electrode), the growth of thin silicon films can be switched between amorphous and nanocrystalline modes, as observed using in situ spectroscopic ellipsometry. The effect is observed at pressures sufficiently low that the collisional reduction in average ion bombardment energy is not sufficient to allow nanocrystalline growth (<100 mTorr).

Ion mobility sensor

DOEpatents

Koo, Jackson C.; Yu, Conrad M.

2005-08-23

An ion mobility sensor which can detect both ion and molecules simultaneously. Thus, one can measure the relative arrival times between various ions and molecules. Different ions have different mobility in air, and the ion sensor enables measurement of ion mobility, from which one can identify the various ions and molecules. The ion mobility sensor which utilizes a pair of glow discharge devices may be designed for coupling with an existing gas chromatograph, where various gas molecules are already separated, but numbers of each kind of molecules are relatively small, and in such cases a conventional ion mobility sensor cannot be utilized.

Resolving Structural Isomers of Monosaccharide Methyl Glycosides Using Drift Tube and Traveling Wave Ion Mobility Mass Spectrometry

PubMed Central

Li, Hongli; Giles, Kevin; Bendiak, Brad; Kaplan, Kimberly; Siems, William F.; Hill, Herbert H.

2013-01-01

Monosaccharide structural isomers including sixteen methyl-D-glycopyranosides and four methyl-N-acetylhexosamines were subjected to ion mobility measurements by electrospray ion mobility mass spectrometry. Two ion mobility-MS systems were employed: atmospheric pressure drift tube ion mobility time-of-flight mass spectrometry and a Synapt G2 HDMS system which incorporates a low pressure traveling wave ion mobility separator. All the compounds were investigated as [M+Na]+ ions in the positive mode. A majority of the monosaccharide structural isomers exhibited different mobility drift times in either system, depending on differences in their anomeric and stereochemical configurations. In general, drift time patterns (relative drift times of isomers) matched between the two instruments. Higher resolving power was observed using the atmospheric pressure drift tube. Collision cross section values of monosaccharide structural isomers were directly calculated from the atmospheric pressure ion mobility experiments and a collision cross section calibration curve was made for the traveling wave ion mobility instrument. Overall, it was demonstrated that ion mobility-mass spectrometry using either drift tube or traveling wave ion mobility is a valuable technique for resolving subtle variations in stereochemistry among the sodium adducts of monosaccharide methyl glycosides. PMID:22339760

DoD and Commercial Advanced Waveform Developments and Programs with Multiple Nunn-McCurdy Breaches. Volume 5

DTIC Science & Technology

2014-01-01

and insightful reviews of our report. It is a stron- ger document because of their efforts. xxi Abbreviations 2G second generation 3G third...in the commercial world. LTE includes a set of standards developed by 3GPP for mobile 3G and 4G mobile communications. The currently fielded...generation ( 2G ) digital mobile phone system, Global System for Mobile Communications (GSM). The GSM standard was developed by the European

Mobility-Resolved Ion Selection in Uniform Drift Field Ion Mobility Spectrometry/Mass Spectrometry: Dynamic Switching in Structures for Lossless Ion Manipulations

DOE PAGES

Webb, Ian K.; Garimella, Sandilya V. B.; Tolmachev, Aleksey V.; ...

2014-09-15

A Structures for Lossless Ion Manipulations (SLIM) module that allows ion mobility separations and the switching of ions between alternative drift paths is described. The SLIM switch component has a “Tee” configuration and allows switching of ions between a linear path and a 90-degree bend. By controlling switching times, ions can be deflected to an alternative channel as a function of their mobilities. In the initial evaluation the switch is used in a static mode and shown compatible with high performance ion mobility separations at 4 torr. In the “dynamic mode” we show that mobility-selected ions can be switched intomore » the alternative channel, and that various ion species can be independently selected based on their mobilities for time-of-flight mass spectrometer (TOF MS) IMS detection and mass analysis. Ultimately, this development also provides the basis for e.g. the selection of specific mobilities for storage and accumulation, and key modules for the assembly of SLIM devices enabling much more complex sequences of ion manipulations.« less

Analysis of Soldier Radio Waveform Performance in Operational Test

DTIC Science & Technology

2015-05-01

different frequencies based on carrier, uplink/downlink, and generation. In general, 2G and 3G cellular phones operate at 850 MHz uplink, and 1,900 MHz...spectrum management that may not be operationally feasible. These issues are not unique to SRW, but rather have plagued the mobile ad-hoc network... mobile ad-hoc network (MANET), enabling communication through a self-configuring, infrastructure-less network of mobile nodes. In the SS domain, these

Mobilities of uranium and mercury ions in helium

NASA Technical Reports Server (NTRS)

Johnsen, R.; Biondi, M. A.

1972-01-01

The mobilities of mass-identified U(+) and Hg (+) ions in helium were determined in a drift tube-mass spectrometer. For uranium ions, a reduced mobility value is obtained at 305 K and a standard gas density of 2.69 x 10 to the 19th power/cu cm. The mobility of mercury ions is in agreement with two previous determinations. The effect of fast ion injection in drift mobility measurements is discussed, and a technique to circumvent these problems is described. The results are compared with existing theories of ion mobilities.

A mobile phone-based ECG monitoring system.

PubMed

Iwamoto, Junichi; Yonezawa, Yoshiharu; Maki, Hiromichi; Ogawa, Hidekuni; Ninomiya, Ishio; Sada, Kouji; Hamada, Shingo; Hahn, Allen W; Caldwell, W Morton

2006-01-01

We have developed a telemedicine system for monitoring a patient's electrocardiogram during daily activities. The recording system consists of three ECG chest electrodes, a variable gain instrumentation amplifier, a low power 8-bit single-chip microcomputer, a 256 KB EEPROM and a 2.4 GHz low transmitting power mobile phone (PHS). The complete system is mounted on a single, lightweight, chest electrode array. When a heart discomfort is felt, the patient pushes the data transmission switch on the recording system. The system sends the recorded ECG waveforms of the two prior minutes and ECG waveforms of the two minutes after the switch is pressed, directly in the hospital server computer via the PHS. The server computer sends the data to the physician on call. The data is displayed on the doctor's Java mobile phone LCD (Liquid Crystal Display), so he or she can monitor the ECG regardless of their location. The developed ECG monitoring system is not only applicable to at-home patients, but should also be useful for monitoring hospital patients.

Development of a Fourier-transform ion cyclotron resonance mass spectrometer-ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Bluhm, Brian K.; Gillig, Kent J.; Russell, David H.

2000-11-01

In an effort to incorporate ion-molecule reaction chemistry with ion mobility measurements we designed and constructed a novel instrument that combines a Fourier-transform ion cyclotron resonance (ICR) mass spectrometer with an ion mobility drift cell and a time-of-flight mass spectrometer. Measured mobilities for Ar+ and CO+ in helium are in excellent agreement with accepted literature values demonstrating that there are no adverse effects from the magnetic field on ion mobility measurements. Drift cell pressure, extracted from the measured mobility of Ar+ in helium, indicate that a pressure of ˜0.25 Torr is achieved in the present configuration. There are significant technological challenges associated with combining ICR and ion mobility that occurred during construction of this instrument, such as differential pumping and aperture alignment are presented.

AC Electroosmotic Pumping in Nanofluidic Funnels.

PubMed

Kneller, Andrew R; Haywood, Daniel G; Jacobson, Stephen C

2016-06-21

We report efficient pumping of fluids through nanofluidic funnels when a symmetric AC waveform is applied. The asymmetric geometry of the nanofluidic funnel induces not only ion current rectification but also electroosmotic flow rectification. In the base-to-tip direction, the funnel exhibits a lower ion conductance and a higher electroosmotic flow velocity, whereas, in the tip-to-base direction, the funnel has a higher ion conductance and a lower electroosmotic flow velocity. Consequently, symmetric AC waveforms easily pump fluid through the nanofunnels over a range of frequencies, e.g., 5 Hz to 5 kHz. In our experiments, the nanofunnels were milled into glass substrates with a focused ion beam (FIB) instrument, and the funnel design had a constant 5° taper with aspect ratios (funnel tip width to funnel depth) of 0.1 to 1.0. We tracked ion current rectification by current-voltage (I-V) response and electroosmotic flow rectification by transport of a zwitterionic fluorescent probe. Rectification of ion current and electroosmotic flow increased with increasing electric field applied to the nanofunnel. Our results support three-dimensional simulations of ion transport and electroosmotic transport through nanofunnels, which suggest the asymmetric electroosmotic transport stems from an induced pressure at the junction of the nanochannel and nanofunnel tip.

Buffer Gas Modifiers Effect Resolution in Ion Mobility Spectrometry through Selective Ion-Molecule Clustering Reactions

PubMed Central

Fernández-Maestre, Roberto; Wu, Ching; Hill, Herbert H.

2013-01-01

RATIONALE When polar molecules (modifiers) are introduced into the buffer gas of an ion mobility spectrometer, most ion mobilities decrease due to the formation of ion-modifier clusters. METHODS We used ethyl lactate, nitrobenzene, 2-butanol, and tetrahydrofuran-2-carbonitrile as buffer gas modifiers and electrospray ionization ion mobility spectrometry (IMS) coupled to quadrupole mass spectrometry. Ethyl lactate, nitrobenzene, and tetrahydrofuran-2-carbonitrile had not been tested as buffer gas modifiers and 2-butanol had not been used with basic amino acids. RESULTS The ion mobilities of several diamines (arginine, histidine, lysine, and atenolol) were not affected or only slightly reduced when these modifiers were introduced into the buffer gas (3.4% average reduction in an analyte's mobility for the three modifiers). Intramolecular bridges caused limited change in the ion mobilities of diamines when modifiers were added to the buffer gas; these bridges hindered the attachment of modifier molecules to the positive charge of ions and delocalized the charge, which deterred clustering. There was also a tendency towards large changes in ion mobility when the mass of the analyte decreased; ethanolamine, the smallest compound tested, had the largest reduction in ion mobility with the introduction of modifiers into the buffer gas (61%). These differences in mobilities, together with the lack of shift in bridge-forming ions, were used to separate ions that overlapped in IMS, such as isoleucine and lysine, and arginine and phenylalanine, and made possible the prediction of separation or not of overlapping ions. CONCLUSIONS The introduction of modifiers into the buffer gas in IMS can selectively alter the mobilities of analytes to aid in compound identification and/or enable the separation of overlapping analyte peaks. PMID:22956312

An ionization region model of the reactive Ar/O2 high power impulse magnetron sputtering discharge

NASA Astrophysics Data System (ADS)

Gudmundsson, J. T.; Lundin, D.; Brenning, N.; Raadu, M. A.; Huo, Chunqing; Minea, T. M.

2016-12-01

A new reactive ionization region model (R-IRM) is developed to describe the reactive Ar/O2 high power impulse magnetron sputtering (HiPIMS) discharge with a titanium target. It is then applied to study the temporal behavior of the discharge plasma parameters such as electron density, the neutral and ion composition, the ionization fraction of the sputtered vapor, the oxygen dissociation fraction, and the composition of the discharge current. We study and compare the discharge properties when the discharge is operated in the two well established operating modes, the metal mode and the poisoned mode. Experimentally, it is found that in the metal mode the discharge current waveform displays a typical non-reactive evolution, while in the poisoned mode the discharge current waveform becomes distinctly triangular and the current increases significantly. Using the R-IRM we explore the current increase and find that when the discharge is operated in the metal mode Ar+ and Ti+ -ions contribute most significantly (roughly equal amounts) to the discharge current while in the poisoned mode the Ar+ -ions contribute most significantly to the discharge current and the contribution of O+ -ions, Ti+ -ions, and secondary electron emission is much smaller. Furthermore, we find that recycling of atoms coming from the target, that are subsequently ionized, is required for the current generation in both modes of operation. From the R-IRM results it is found that in the metal mode self-sputter recycling dominates and in the poisoned mode working gas recycling dominates. We also show that working gas recycling can lead to very high discharge currents but never to a runaway. It is concluded that the dominating type of recycling determines the discharge current waveform.

Ion mobility sensor system

DOEpatents

Xu, Jun; Watson, David B.; Whitten, William B.

2013-01-22

An ion mobility sensor system including an ion mobility spectrometer and a differential mobility spectrometer coupled to the ion mobility spectrometer. The ion mobility spectrometer has a first chamber having first end and a second end extending along a first direction, and a first electrode system that generates a constant electric field parallel to the first direction. The differential mobility spectrometer includes a second chamber having a third end and a fourth end configured such that a fluid may flow in a second direction from the third end to the fourth end, and a second electrode system that generates an asymmetric electric field within an interior of the second chamber. Additionally, the ion mobility spectrometer and the differential mobility spectrometer form an interface region. Also, the first end and the third end are positioned facing one another so that the constant electric field enters the third end and overlaps the fluid flowing in the second direction.

Ion dynamics in a trapped ion mobility spectrometer†

PubMed Central

Hernandez, Diana Rosa; DeBord, John Daniel; Ridgeway, Mark E.; Kaplan, Desmond A.; Park, Melvin A.; Fernandez-Lima, Francisco

2014-01-01

In the present paper, theoretical simulations and experimental observations are used to describe the ion dynamics in a trapped ion mobility spectrometer. In particular, the ion motion, ion transmission and mobility separation are discussed as a function of the bath gas velocity, radial confinement, analysis time and speed. Mobility analysis and calibration procedure are reported for the case of sphere-like molecules for positive and negative ion modes. Results showed that a maximal mobility resolution can be achieved by optimizing the gas velocity, radial confinement (RF amplitude) and ramp speed (voltage range and ramp time). The mobility resolution scales with the electric field and gas velocity and R = 100–250 can be routinely obtained at room temperature. PMID:24571000

Ion Mobility Mass Spectrometry Analysis of Isomeric Disaccharide Precursor, Product and Cluster Ions

PubMed Central

Li, Hongli; Bendiak, Brad; Siems, William F.; Gang, David R.; Hill, Herbert H.

2015-01-01

RATIONALE Carbohydrates are highly variable in structure owing to differences in their anomeric configurations, monomer stereochemistry, inter-residue linkage positions and general branching features. The separation of carbohydrate isomers poses a great challenge for current analytical techniques. METHODS The isomeric heterogeneity of disaccharide ions and monosaccharideglycolaldehyde product ions evaluated using electrospray traveling wave ion mobility mass spectrometry (Synapt G2 high definition mass spectrometer) in both positive and negative ion modes investigation. RESULTS The separation of isomeric disaccharide ions was observed but not fully achieved based on their mobility profiles. The mobilities of isomeric product ions, the monosaccharide-glycolaldehydes, derived from different disaccharide isomers were measured. Multiple mobility peaks were observed for both monosaccharide-glycolaldehyde cations and anions, indicating that there was more than one structural configuration in the gas phase as verified by NMR in solution. More importantly, the mobility patterns for isomeric monosaccharide-glycolaldehyde product ions were different, which enabled partial characterization of their respective disaccharide ions. Abundant disaccharide cluster ions were also observed. The Results showed that a majority of isomeric cluster ions had different drift times and, moreover, more than one mobility peak was detected for a number of specific cluster ions. CONCLUSIONS It is demonstrated that ion mobility mass spectrometry is an advantageous method to assess the isomeric heterogeneity of carbohydrate compounds. It is capable of differentiating different types of carbohydrate ions having identical m/z values as well as multiple structural configurations of single compounds. PMID:24591031

Interfacing an aspiration ion mobility spectrometer to a triple quadrupole mass spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamov, Alexey; Viidanoja, Jyrki; Kaerpaenoja, Esko

2007-04-15

This article presents the combination of an aspiration-type ion mobility spectrometer with a mass spectrometer. The interface between the aspiration ion mobility spectrometer and the mass spectrometer was designed to allow for quick mounting of the aspiration ion mobility spectrometer onto a Sciex API-300 triple quadrupole mass spectrometer. The developed instrumentation is used for gathering fundamental information on aspiration ion mobility spectrometry. Performance of the instrument is demonstrated using 2,6-di-tert-butyl pyridine and dimethyl methylphosphonate.

Method for enhancing the resolving power of ion mobility separations over a limited mobility range

DOEpatents

Shvartsburg, Alexandre A; Tang, Keqi; Smith, Richard D

2014-09-23

A method for raising the resolving power, specificity, and peak capacity of conventional ion mobility spectrometry is disclosed. Ions are separated in a dynamic electric field comprising an oscillatory field wave and opposing static field, or at least two counter propagating waves with different parameters (amplitude, profile, frequency, or speed). As the functional dependencies of mean drift velocity on the ion mobility in a wave and static field or in unequal waves differ, only single species is equilibrated while others drift in either direction and are mobility-separated. An ion mobility spectrum over a limited range is then acquired by measuring ion drift times through a fixed distance inside the gas-filled enclosure. The resolving power in the vicinity of equilibrium mobility substantially exceeds that for known traveling-wave or drift-tube IMS separations, with spectra over wider ranges obtainable by stitching multiple segments. The approach also enables low-cutoff, high-cutoff, and bandpass ion mobility filters.

Correlation between cation conduction and ionic morphology in a PEO-based single ion conductor

NASA Astrophysics Data System (ADS)

Lin, Kan-Ju; Maranas, Janna

2011-03-01

We use molecular dynamics simulation to study ion transport and backbone mobility of a PEO-based single ion conductor. Ion mobility depends on the chemical structure and the local environment of the ions, which consequently impact ionic conductivity. We characterize the aggregation state of the ions, and assess the role of ion complexes in ionomer dynamics. In addition to solvated cations and pairs, higher order ion clusters are found. Most of the ion clusters are in string-like structure and cross-link two or more different ionomer chains through ionic binding. Ionic crosslinks decrease mobility at the ionic co-monomer; hence the mobility of the adjacent PEO segment is influenced. Na ions show slow mobility when they are inside large clusters. The hopping timescale for Na varies from 20 ns to 200. A correlation is found between Na mobility and the number of hops from one coordination site to another. Besides ether oxygens, Na ions in the ionomer also use the anion and the edge of the cluster as hopping sites. The string-like structure of clusters provide less stable sites at the two ends thus ions are more mobile in those regions. We observed Grotthus like mechanism in our ionomer, in which the positive charge migrates within the string-like cluster without the cations actually moving.

A radio-frequency sheath model for complex waveforms

NASA Astrophysics Data System (ADS)

Turner, M. M.; Chabert, P.

2014-04-01

Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, Ian K.; Garimella, Sandilya V. B.; Tolmachev, Aleksey V.

A Structures for Lossless Ion Manipulations (SLIM) module that allows ion mobility separations and the switching of ions between alternative drift paths is described. The SLIM switch component has a “Tee” configuration and allows switching of ions between a linear path and a 90-degree bend. By controlling switching times, ions can be deflected to an alternative channel as a function of their mobilities. In the initial evaluation the switch is used in a static mode and shown compatible with high performance ion mobility separations at 4 torr. In the “dynamic mode” we show that mobility-selected ions can be switched intomore » the alternative channel, and that various ion species can be independently selected based on their mobilities for time-of-flight mass spectrometer (TOF MS) IMS detection and mass analysis. Ultimately, this development also provides the basis for e.g. the selection of specific mobilities for storage and accumulation, and key modules for the assembly of SLIM devices enabling much more complex sequences of ion manipulations.« less

Dynamic Stabilization of the Ablative Rayleigh-Taylor Instability for Heavy Ion Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Hong; Davidson, Ronald C.; Logan, B. Grant

2012-10-04

Dynamic stabilization of the ablative Rayleigh-Taylor instability of a heavy ion fusion target induced by a beam wobbling system is studied. Using a sharp-boundary model and Courant-Synder theory, it is shown, with an appropriately chosen modulation waveform, that the instability can be sta- bilized in certain parameter regimes. It is found that the stabilization e ect has a strong dependence on the modulation frequency and the waveform. Modulation with frequency comparable to the instability growth rate is the most e ective in terms of stabilizing the instability. A modulation with two frequency components can result in a reduction of themore » growth rate larger than the sum of that due to the two components when applied separately.« less

Studying Townsend and glow modes in an atmospheric-pressure DBD using mass spectrometry

NASA Astrophysics Data System (ADS)

McKay, Kirsty; Donaghy, David; He, Feng; Bradley, James W.

2018-01-01

Ambient molecular beam mass spectrometry has been employed to examine the effects of the mode of operation and the excitation waveform on the ionic content of a helium-based atmospheric-pressure parallel plate dielectric barrier discharge. By applying 10 kHz microsecond voltage pulses with a nanosecond rise times and 10 kHz sinusoidal voltage waveforms, distinctly different glow and Townsend modes were produced, respectively. Results showed a significant difference in the dominant ion species between the two modes. In the Townsend mode, molecular oxygen ions, atomic oxygen anions and nitric oxide anions are the most abundant species, however, in the glow mode water clusters ions and hydrated nitric oxygen anions dominate. Several hypotheses are put forward to explain these differences, including low electron densities and energies in the Townsend mode, more efficient ionization of water molecules through penning ionization and charge exchange with other species in glow mode, and large temperature gradients due to the pulsed nature of the glow mode, leading to more favorable conditions for cluster formation.

Fast Orthogonal Separation by Superposition of Time of Flight and Field Asymmetric Ion Mobility Spectrometry.

PubMed

Bohnhorst, Alexander; Kirk, Ansgar T; Berger, Marc; Zimmermann, Stefan

2018-01-16

Ion mobility spectrometry is a powerful and low-cost technique for the identification of chemical warfare agents, toxic chemicals, or explosives in air. Drift tube ion mobility spectrometers (DT-IMS) separate ions by the absolute value of their low field ion mobility, while field asymmetric ion mobility spectrometers (FAIMS) separate them by the change of their ion mobility at high fields. However, using one of these devices alone, some common and harmless substances show the same response as the hazardous target substances. In order to increase the selectivity, orthogonal data are required. Thus, in this work, we present for the first time an ambient pressure ion mobility spectrometer which is able to separate ions both by their differential and low field mobility, providing additional information for selectivity enhancement. This novel field asymmetric time of flight ion mobility spectrometer (FAT-IMS) allows high repetition rates and reaches limits of detection in the low ppb range common for DT-IMS. The device consists of a compact 44 mm drift tube with a tritium ionization source and a resolving power of 70. An increased separation of four substances with similar low field ion mobility is shown: phosgene (K 0 = 2.33 cm 2 /(V s)), 1,1,2-trichlorethane (K 0 = 2.31 cm 2 /(V s)), chlorine (K 0 = 2.24 cm 2 /(V s)), and nitrogen dioxide (K 0 = 2.25 cm 2 /(V s)). Furthermore, the behavior and limits of detection for acetonitrile, dimethyl methylphosphonate, diisopropyl methyl phosphonate in positive polarity and carbon dioxide, sulfur dioxide, hydrochloric acid, cyanogen chloride, and hydrogen cyanide in negative polarity are investigated.

Mobilities of ground-state and metastable O/+/, O2/+/, O/2+/, and O2/2+/ ions in helium and neon

NASA Astrophysics Data System (ADS)

Johnsen, R.; Biondi, M. A.; Hayashi, M.

1982-09-01

The ionic mobilities of O(+), O2(+), O(2+), and O2(2+) in helium and neon have been measured using a selected-ion drift apparatus (SIDA). It is found that the mobilities of both O(+) and O2(+) ions in the metastable states (2D or 4Pi u) are measurably smaller than those of the same ions carried out by using known, state-selective ion-molecule reactions. A similar mobility differentiation of ground-state and metastable ions was not observed for the O(2+) and O2(2+) ions.

Normal-inverse bimodule operation Hadamard transform ion mobility spectrometry.

PubMed

Hong, Yan; Huang, Chaoqun; Liu, Sheng; Xia, Lei; Shen, Chengyin; Chu, Yannan

2018-10-31

In order to suppress or eliminate the spurious peaks and improve signal-to-noise ratio (SNR) of Hadamard transform ion mobility spectrometry (HT-IMS), a normal-inverse bimodule operation Hadamard transform - ion mobility spectrometry (NIBOHT-IMS) technique was developed. In this novel technique, a normal and inverse pseudo random binary sequence (PRBS) was produced in sequential order by an ion gate controller and utilized to control the ion gate of IMS, and then the normal HT-IMS mobility spectrum and the inverse HT-IMS mobility spectrum were obtained. A NIBOHT-IMS mobility spectrum was gained by subtracting the inverse HT-IMS mobility spectrum from normal HT-IMS mobility spectrum. Experimental results demonstrate that the NIBOHT-IMS technique can significantly suppress or eliminate the spurious peaks, and enhance the SNR by measuring the reactant ions. Furthermore, the gas CHCl 3 and CH 2 Br 2 were measured for evaluating the capability of detecting real sample. The results show that the NIBOHT-IMS technique is able to eliminate the spurious peaks and improve the SNR notably not only for the detection of larger ion signals but also for the detection of small ion signals. Copyright © 2018 Elsevier B.V. All rights reserved.

Tandem Mass Spectrometry and Ion Mobility Reveals Structural Insight into Eicosanoid Product Ion Formation

NASA Astrophysics Data System (ADS)

Di Giovanni, James P.; Barkley, Robert M.; Jones, David N. M.; Hankin, Joseph A.; Murphy, Robert C.

2018-04-01

Ion mobility measurements of product ions were used to characterize the collisional cross section (CCS) of various complex lipid [M-H]- ions using traveling wave ion mobility mass spectrometry (TWIMS). TWIMS analysis of various product ions derived after collisional activation of mono- and dihydroxy arachidonate metabolites was found to be more complex than the analysis of intact molecular ions and provided some insight into molecular mechanisms involved in product ion formation. The CCS observed for the molecular ion [M-H]- and certain product ions were consistent with a folded ion structure, the latter predicted by the proposed mechanisms of product ion formation. Unexpectedly, product ions from [M-H-H2O-CO2]- and [M-H-H2O]- displayed complex ion mobility profiles suggesting multiple mechanisms of ion formation. The [M-H-H2O]- ion from LTB4 was studied in more detail using both nitrogen and helium as the drift gas in the ion mobility cell. One population of [M-H-H2O]- product ions from LTB4 was consistent with formation of covalent ring structures, while the ions displaying a higher CCS were consistent with a more open-chain structure. Using molecular dynamics and theoretical CCS calculations, energy minimized structures of those product ions with the open-chain structures were found to have a higher CCS than a folded molecular ion structure. The measurement of product ion mobility can be an additional and unique signature of eicosanoids measured by LC-MS/MS techniques. [Figure not available: see fulltext.

Tandem Mass Spectrometry and Ion Mobility Reveals Structural Insight into Eicosanoid Product Ion Formation.

PubMed

Di Giovanni, James P; Barkley, Robert M; Jones, David N M; Hankin, Joseph A; Murphy, Robert C

2018-04-23

Ion mobility measurements of product ions were used to characterize the collisional cross section (CCS) of various complex lipid [M-H] - ions using traveling wave ion mobility mass spectrometry (TWIMS). TWIMS analysis of various product ions derived after collisional activation of mono- and dihydroxy arachidonate metabolites was found to be more complex than the analysis of intact molecular ions and provided some insight into molecular mechanisms involved in product ion formation. The CCS observed for the molecular ion [M-H] - and certain product ions were consistent with a folded ion structure, the latter predicted by the proposed mechanisms of product ion formation. Unexpectedly, product ions from [M-H-H 2 O-CO 2 ] - and [M-H-H 2 O] - displayed complex ion mobility profiles suggesting multiple mechanisms of ion formation. The [M-H-H 2 O] - ion from LTB 4 was studied in more detail using both nitrogen and helium as the drift gas in the ion mobility cell. One population of [M-H-H 2 O] - product ions from LTB 4 was consistent with formation of covalent ring structures, while the ions displaying a higher CCS were consistent with a more open-chain structure. Using molecular dynamics and theoretical CCS calculations, energy minimized structures of those product ions with the open-chain structures were found to have a higher CCS than a folded molecular ion structure. The measurement of product ion mobility can be an additional and unique signature of eicosanoids measured by LC-MS/MS techniques. Graphical Abstract ᅟ.

Effect of gas properties on the dynamics of the electrical slope asymmetry effect in capacitive plasmas: comparison of Ar, H 2 and CF 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruneau, Bastien; Lafleur, T.; Gans, T.

2015-12-01

Tailored voltage excitation waveforms provide an efficient control of the ion energy (through the electrical asymmetry effect) in capacitive plasmas by varying the 'amplitude' asymmetry of the waveform. In this work, the effect of a 'slope' asymmetry of the waveform is investigated by using sawtooth-like waveforms, through which the sheath dynamic can be manipulated. A remarkably different discharge dynamic is found for Ar, H 2, and CF 4 gases, which is explained by the different dominant electron heating mechanisms and plasma chemistries. In comparison to Argon we find that the electrical asymmetry can even be reversed by using an electronegativemore » gas such as CF 4. Phase resolved optical emission spectroscopy measurements, probing the spatiotemporal distribution of the excitation rate show excellent agreement with the results of particle-in-cell simulations, confirming the high degree of correlation between the excitation rates with the dominant heating mechanisms in the various gases. It is shown that, depending on the gas used, sawtooth-like voltage waveforms may cause a strong asymmetry.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamson, B. D.; Coughlan, N. J. A.; Markworth, P. B.

An ion mobility mass spectrometry apparatus for investigating the photoisomerization and photodissociation of electrosprayed molecular ions in the gas phase is described. The device consists of a drift tube mobility spectrometer, with access for a laser beam that intercepts the drifting ion packet either coaxially or transversely, followed by a quadrupole mass filter. An ion gate halfway along the drift region allows the instrument to be used as a tandem ion mobility spectrometer, enabling mobility selection of ions prior to irradiation, with the photoisomer ions being separated over the second half of the drift tube. The utility of the devicemore » is illustrated with photoisomerization and photodissociation action spectra of carbocyanine molecular cations. The mobility resolution of the device for singly charged ions is typically 80 and it has a mass range of 100-440 Da, with the lower limit determined by the drive frequency for the ion funnels, and the upper limit by the quadrupole mass filter.« less

Waveform control of orientation-dependent ionization of DCl in few-cycle laser fields.

PubMed

Znakovskaya, I; von den Hoff, P; Schirmel, N; Urbasch, G; Zherebtsov, S; Bergues, B; de Vivie-Riedle, R; Weitzel, K-M; Kling, M F

2011-05-21

Strong few-cycle light fields with stable electric field waveforms allow controlling electrons on time scales down to the attosecond domain. We have studied the dissociative ionization of randomly oriented DCl in 5 fs light fields at 720 nm in the tunneling regime. Momentum distributions of D(+) and Cl(+) fragments were recorded via velocity-map imaging. A waveform-dependent anti-correlated directional emission of D(+) and Cl(+) fragments is observed. Comparison of our results with calculations indicates that tailoring of the light field via the carrier envelope phase permits the control over the orientation of DCl(+) and in turn the directional emission of charged fragments upon the breakup of the molecular ion. © The Owner Societies 2011

Tandem mass spectrometry in combination with product ion mobility for the identification of phospholipids

DOE PAGES

Berry, Karin A. Zemski; Barkley, Robert M.; Berry, Joseph J.; ...

2016-11-29

Concerted tandem and traveling wave ion mobility mass spectrometry (CTS analysis) is a unique method that results in a four-dimensional data set including nominal precursor ion mass, product ion mobility, accurate mass of product ion, and ion abundance. This nontargeted lipidomics CTS approach was applied in both positive- and negative-ion mode to phospholipids present in human serum, and the data set was used to evaluate the value of product ion mobility in identifying lipids in a complex mixture. As a result, it was determined that the combination of diagnostic product ions and unique collisional cross-section values of product ions ismore » a powerful tool in the structural identification of lipids in a complex biological sample.« less

Tandem mass spectrometry in combination with product ion mobility for the identification of phospholipids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berry, Karin A. Zemski; Barkley, Robert M.; Berry, Joseph J.

Concerted tandem and traveling wave ion mobility mass spectrometry (CTS analysis) is a unique method that results in a four-dimensional data set including nominal precursor ion mass, product ion mobility, accurate mass of product ion, and ion abundance. This nontargeted lipidomics CTS approach was applied in both positive- and negative-ion mode to phospholipids present in human serum, and the data set was used to evaluate the value of product ion mobility in identifying lipids in a complex mixture. As a result, it was determined that the combination of diagnostic product ions and unique collisional cross-section values of product ions ismore » a powerful tool in the structural identification of lipids in a complex biological sample.« less

Experimental Characterization of Secular Frequency Scanning in Ion Trap Mass Spectrometers

NASA Astrophysics Data System (ADS)

Snyder, Dalton T.; Pulliam, Christopher J.; Wiley, Joshua S.; Duncan, Jason; Cooks, R. Graham

2016-07-01

Secular frequency scanning is implemented and characterized using both a benchtop linear ion trap and a miniature rectilinear ion trap mass spectrometer. Separation of tetraalkylammonium ions and those from a mass calibration mixture and from a pesticide mixture is demonstrated with peak widths approaching unit resolution for optimized conditions using the benchtop ion trap. The effects on the spectra of ion trap operating parameters, including waveform amplitude, scan direction, scan rate, and pressure are explored, and peaks at black holes corresponding to nonlinear (higher-order field) resonance points are investigated. Reverse frequency sweeps (increasing mass) on the Mini 12 are shown to result in significantly higher ion ejection efficiency and superior resolution than forward frequency sweeps that decrement mass. This result is accounted for by the asymmetry in ion energy absorption profiles as a function of AC frequency and the shift in ion secular frequency at higher amplitudes in the trap due to higher order fields. We also found that use of higher AC amplitudes in forward frequency sweeps biases ions toward ejection at points of higher order parametric resonance, despite using only dipolar excitation. Higher AC amplitudes also increase peak width and decrease sensitivity in both forward and reverse frequency sweeps. Higher sensitivity and resolution were obtained at higher trap pressures in the secular frequency scan, in contrast to conventional resonance ejection scans, which showed the opposite trend in resolution on the Mini 12. Mass range is shown to be naturally extended in secular frequency scanning when ejecting ions by sweeping the AC waveform through low frequencies, a method which is similar, but arguably superior, to the more usual method of mass range extension using low q resonance ejection.

Experimental Characterization of Secular Frequency Scanning in Ion Trap Mass Spectrometers.

PubMed

Snyder, Dalton T; Pulliam, Christopher J; Wiley, Joshua S; Duncan, Jason; Cooks, R Graham

2016-07-01

Secular frequency scanning is implemented and characterized using both a benchtop linear ion trap and a miniature rectilinear ion trap mass spectrometer. Separation of tetraalkylammonium ions and those from a mass calibration mixture and from a pesticide mixture is demonstrated with peak widths approaching unit resolution for optimized conditions using the benchtop ion trap. The effects on the spectra of ion trap operating parameters, including waveform amplitude, scan direction, scan rate, and pressure are explored, and peaks at black holes corresponding to nonlinear (higher-order field) resonance points are investigated. Reverse frequency sweeps (increasing mass) on the Mini 12 are shown to result in significantly higher ion ejection efficiency and superior resolution than forward frequency sweeps that decrement mass. This result is accounted for by the asymmetry in ion energy absorption profiles as a function of AC frequency and the shift in ion secular frequency at higher amplitudes in the trap due to higher order fields. We also found that use of higher AC amplitudes in forward frequency sweeps biases ions toward ejection at points of higher order parametric resonance, despite using only dipolar excitation. Higher AC amplitudes also increase peak width and decrease sensitivity in both forward and reverse frequency sweeps. Higher sensitivity and resolution were obtained at higher trap pressures in the secular frequency scan, in contrast to conventional resonance ejection scans, which showed the opposite trend in resolution on the Mini 12. Mass range is shown to be naturally extended in secular frequency scanning when ejecting ions by sweeping the AC waveform through low frequencies, a method which is similar, but arguably superior, to the more usual method of mass range extension using low q resonance ejection. Graphical Abstract ᅟ.

Dual mode ion mobility spectrometer and method for ion mobility spectrometry

DOEpatents

Scott, Jill R [Idaho Falls, ID; Dahl, David A [Idaho Falls, ID; Miller, Carla J [Idaho Falls, ID; Tremblay, Paul L [Idaho Falls, ID; McJunkin, Timothy R [Idaho Falls, ID

2007-08-21

Ion mobility spectrometer apparatus may include an ion interface that is operable to hold positive and negative ions and to simultaneously release positive and negative ions through respective positive and negative ion ports. A first drift chamber is operatively associated with the positive ion port of the ion interface and encloses an electric field therein. A first ion detector operatively associated with the first drift chamber detects positive ions from the first drift chamber. A second drift chamber is operatively associated with the negative ion port of the ion interface and encloses an electric field therein. A second ion detector operatively associated with the second drift chamber detects negative ions from said second drift chamber.

Initial Thrust Measurements of Marshall's Ion-ioN Thruster

NASA Technical Reports Server (NTRS)

Caruso, Natalie R. S.; Scogin, Tyler; Liu, Thomas M.; Walker, Mitchell L. R.; Polzin, Kurt A.; Dankanich, John W.

2015-01-01

Electronegative ion thrusters are a variation of traditional gridded ion thruster technology differentiated by the production and acceleration of both positive and negative ions. Benefits of electronegative ion thrusters include the elimination of lifetime-limiting cathodes from the thruster architecture and the ability to generate appreciable thrust from both charge species. While much progress has been made in the development of electronegative ion thruster technology, direct thrust measurements are required to unambiguously demonstrate the efficacy of the concept and support continued development. In the present work, direct thrust measurements of the thrust produced by the MINT (Marshall's Ion-ioN Thruster) are performed using an inverted-pendulum thrust stand in the High-Power Electric Propulsion Laboratory's Vacuum Test Facility-1 at the Georgia Institute of Technology with operating pressures ranging from 4.8 x 10(exp -5) and 5.7 x 10(exp -5) torr. Thrust is recorded while operating with a propellant volumetric mixture ratio of 5:1 argon to nitrogen with total volumetric flow rates of 6, 12, and 24 sccm (0.17, 0.34, and 0.68 mg/s). Plasma is generated using a helical antenna at 13.56 MHz and radio frequency (RF) power levels of 150 and 350 W. The acceleration grid assembly is operated using both sinusoidal and square waveform biases of +/-350 V at frequencies of 4, 10, 25, 125, and 225 kHz. Thrust is recorded for two separate thruster configurations: with and without the magnetic filter. No thrust is discernable during thruster operation without the magnetic filter for any volumetric flow rate, RF forward Power level, or acceleration grid biasing scheme. For the full thruster configuration, with the magnetic filter installed, a brief burst of thrust of approximately 3.75 mN +/- 3 mN of error is observed at the start of grid operation for a volumetric flow rate of 24 sccm at 350 W RF power using a sinusoidal waveform grid bias at 125 kHz and +/- 350 V. Similar bursts in thrust are observed using a square waveform grid bias at 10 kHz and +/- 350 V for volumetric flow rates of 6, 10, and 12 sccm at 150, 350, and 350 W respectively. The only operating condition that exhibits repeated thrust spikes throughout thruster operation is the 24 sccm condition with a 5:1 mixture ratio at 150 W RF power using the 10 kHz square waveform acceleration grid bias. Thrust spikes for this condition measure 3 mN with an error of +/- 2.5 mN. There are no operating conditions tested that show continuous thrust production.

Redefinition of the self-bias voltage in a dielectrically shielded thin sheath RF discharge

NASA Astrophysics Data System (ADS)

Ho, Teck Seng; Charles, Christine; Boswell, Rod

2018-05-01

In a geometrically asymmetric capacitively coupled discharge where the powered electrode is shielded from the plasma by a layer of dielectric material, the self-bias manifests as a nonuniform negative charging in the dielectric rather than on the blocking capacitor. In the thin sheath regime where the ion transit time across the powered sheath is on the order of or less than the Radiofrequency (RF) period, the plasma potential is observed to respond asymmetrically to extraneous impedances in the RF circuit. Consequently, the RF waveform on the plasma-facing surface of the dielectric is unknown, and the behaviour of the powered sheath is not easily predictable. Sheath circuit models become inadequate for describing this class of discharges, and a comprehensive fluid, electrical, and plasma numerical model is employed to accurately quantify this behaviour. The traditional definition of the self-bias voltage as the mean of the RF waveform is shown to be erroneous in this regime. Instead, using the maxima of the RF waveform provides a more rigorous definition given its correlation with the ion dynamics in the powered sheath. This is supported by a RF circuit model derived from the computational fluid dynamics and plasma simulations.

Multidimensional Separation of Natural Products Using Liquid Chromatography Coupled to Hadamard Transform Ion Mobility Mass Spectrometry

NASA Astrophysics Data System (ADS)

Liu, Wenjie; Zhang, Xing; Knochenmuss, Richard; Siems, William F.; Hill, Herbert H.

2016-05-01

A high performance liquid chromatograph (HPLC)was interfaced to an atmospheric drift tube ion mobility time of flight mass spectrometry. The power of multidimensional separation was demonstrated using chili pepper extracts. The ambient pressure drift tube ion mobility provided high resolving powers up to 166 for the HPLC eluent. With implementation of Hadamard transform (HT), the duty cycle for the ion mobility drift tube was increased from less than 1% to 50%, and the ion transmission efficiency was improved by over 200 times compared with pulsed mode, improving signal to noise ratio 10 times. HT ion mobility and TOF mass spectrometry provide an additional dimension of separation for complex samples without increasing the analysis time compared with conventional HPLC.

Effect of nonsinusoidal bias waveforms on ion energy distributions and fluorocarbon plasma etch selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarwal, Ankur; Kushner, Mark J.; Iowa State University, Department of Electrical and Computer Engineering, 104 Marston Hall, Ames, Iowa 50011-2151

2005-09-15

The distributions of ion energies incident on the wafer significantly influence feature profiles and selectivity during plasma etching. Control of ion energies is typically obtained by varying the amplitude or frequency of a radio frequency sinusoidal bias voltage applied to the substrate. The resulting ion energy distribution (IED), though, is generally broad. Controlling the width and shape of the IED can potentially improve etch selectivity by distinguishing between threshold energies of surface processes. In this article, control of the IED was computationally investigated by applying a tailored, nonsinusoidal bias waveform to the substrate of an inductively coupled plasma. The waveformmore » we investigated, a quasi-dc negative bias having a short positive pulse each cycle, produced a narrow IED whose width was controllable based on the length of the positive spike and frequency. We found that the selectivity between etching Si and SiO{sub 2} in fluorocarbon plasmas could be controlled by adjusting the width and energy of the IED. Control of the energy of a narrow IED enables etching recipes that transition between speed and selectivity without change of gas mixture.« less

The interplay of ion crosslinking, free ion content, and polymer mobility in PEO-based single-ion conductors

NASA Astrophysics Data System (ADS)

Lin, Kan-Ju; Maranas, Janna

2010-03-01

We use molecular dynamics simulation to study ion clustering and dynamics in ion containing polymers. This PEO based single-ion conducting ionomer serves as a model system for understanding cation transport in solid state polymer electrolytes (SPEs). Although small-angle x-ray scattering does not show an ionomer peak, we observer various cation-anion complexes in the simulation, suggesting ionomer backbones are crosslinked through ion complexes. These crosslinks reduce the adjacent PEO mobility resulting in a symmetric mobility gradient along the PEO chain. We vary the cation-anion interaction in the simulation to observe the interplay of cation-anion association, polymer mobility and cation motion. Cation-anion association controls the number of free ions, which is important in ionic conductivity when these materials are used as SPEs. Polymer mobility controls how fast the free ions are able to move through the SPE. High conductivity requires both a high free ion content and fast polymer motion. To understand the connection between the two, we ``tune'' the force field in order to manipulate the free ion content and observe the influence on PEO dynamics.

Exploitation of Full-Waveform LiDAR to Characterize / Exploit Under Canopy Targets - Foliage Penetration (FOPEN)

DTIC Science & Technology

2015-09-28

Figure 3 USACE ERDC mobile measurement system with Riegl VZ‐400  laser  scanner (a) and OSU GPSVan  with targets (b...five target  materials (red: retro reflective, blue: wood, cyan: fluffy plastic, yellow: cardboard, and black:  painted   wood...and black:  painted  wood) ........................ 28  Figure 21 Waveforms shapes of in the three classes

Severe storm electricity

NASA Technical Reports Server (NTRS)

Rust, W. D.; Macgorman, D. R.; Taylor, W.; Arnold, R. T.

1984-01-01

Severe storms and lightning were measured with a NASA U2 and ground based facilities, both fixed base and mobile. Aspects of this program are reported. The following results are presented: (1) ground truth measurements of lightning for comparison with those obtained by the U2. These measurements include flash type identification, electric field changes, optical waveforms, and ground strike location; (2) simultaneous extremely low frequency (ELF) waveforms for cloud to ground (CG) flashes; (3) the CG strike location system (LLP) using a combination of mobile laboratory and television video data are assessed; (4) continued development of analog-to-digital conversion techniques for processing lightning data from the U2, mobile laboratory, and NSSL sensors; (5) completion of an all azimuth TV system for CG ground truth; (6) a preliminary analysis of both IC and CG lightning in a mesocyclone; and (7) the finding of a bimodal peak in altitude lightning activity in some storms in the Great Plains and on the east coast. In the forms on the Great Plains, there was a distinct class of flash what forms the upper mode of the distribution. These flashes are smaller horizontal extent, but occur more frequently than flashes in the lower mode of the distribution.

Electrochemical measurements on a droplet using gold microelectrodes

NASA Astrophysics Data System (ADS)

Jenabi, Amin; Souri, Asma; Rastkhadiv, Ali

2016-03-01

Facile methods of ion recognition are important for the fabrication of electronic tongue systems. In this work, we demonstrate performing pulsed conductometry on microliter electrolyte droplets dropped on gold microelectrodes vapor deposited on soda lime glass slides. A droplet is dropped between two microelectrodes when a voltage waveform from a preprogramed power supply is applied on them. The temporal variation of the electric current passing through the droplet is recorded, digitized and stored. The obtained data are compared with the database formed out of the previous experiences for the classification of the sample electrolytes. It is shown that the shape of the voltage waveform is the important parameter of the process. We devised a method for the optimization of the voltage waveform profile for obtaining the maximum of discriminating information from the recorded current variations.

The mobility and diffusion of ions in gases

NASA Technical Reports Server (NTRS)

Mcdaniel, E. W.; Mason, E. A.

1973-01-01

Experimental and theoretical aspects of the mobility and diffusion of ions in gases are studied in detail. Some of the subjects discussed include ion-ion interaction, boundary condition and ion and electron behavior. Also discussed in separate chapters are the problems of the diffusion coefficients and the afterglow techniques. Finally, a special chapter studies the kinetic theory of diffusion and mobility, stressing the low-, medium- and high-field theory.

Optimal Pulse Configuration Design for Heart Stimulation. A Theoretical, Numerical and Experimental Study.

NASA Astrophysics Data System (ADS)

Hardy, Neil; Dvir, Hila; Fenton, Flavio

Existing pacemakers consider the rectangular pulse to be the optimal form of stimulation current. However, other waveforms for the use of pacemakers could save energy while still stimulating the heart. We aim to find the optimal waveform for pacemaker use, and to offer a theoretical explanation for its advantage. Since the pacemaker battery is a charge source, here we probe the stimulation current waveforms with respect to the total charge delivery. In this talk we present theoretical analysis and numerical simulations of myocyte ion-channel currents acting as an additional source of charge that adds to the external stimulating charge for stimulation purposes. Therefore, we find that as the action potential emerges, the external stimulating current can be reduced accordingly exponentially. We then performed experimental studies in rabbit and cat hearts and showed that indeed exponential truncated pulses with less total charge can still induce activation in the heart. From the experiments, we present curves showing the savings in charge as a function of exponential waveform and we calculated that the longevity of the pacemaker battery would be ten times higher for the exponential current compared to the rectangular waveforms. Thanks to Petit Undergraduate Research Scholars Program and NSF# 1413037.

A Hybrid Constant and Oscillatory Field Ion Mobility Analyzer in Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran Nair Syamala Amma, Aneesh; Hamid, Ahme

2018-02-28

Ion mobility (IM) spectrometry is becoming an important approach for analyzing molecular ions in the gas phase with applications that span a multitude of scientific areas. There are a variety of IM-based approaches that utilize either constant or oscillatory electric fields. Here, we explore the combination of constant and oscillatory fields applied in a single device to affect the separation and filtering of ions based on their mobilities. The mobility analyzer allows confining and manipulating ions utilizing a combination of radio frequency (RF), direct current (DC) fields, and traveling waves (TW) in a structures for lossless ion manipulations (SLIM) module.more » In this work, we have investigated theoretically and experimentally the concept for continuous filtering of ions based on their mobilities where ions are mobility separated and selected by a combination of TW and constant fields providing opposing forces on the ions. The SLIM module was composed of two surfaces with mirror-image arrays of electrodes and had two regions where the different TW and opposing DC fields could be applied. By appropriately choosing the DC gradient and TW parameters for the two sections, it is possible to transmit ions of a selected mobility while filtering out others. The filtering capabilities are determined by the applied DC gradient and the TW parameters, such as frequency, amplitude and the TW sequence (i.e., the duty cycle of the traveling wave). The effect of different parameters on the sensitivity and the IM resolution of the device have been investigated.« less

A Hybrid Constant and Oscillatory Field Ion Mobility Analyzer Using Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran, Aneesh; Hamid, Ahmed M.; Garimella, Sandilya V. B.

Ion mobility (IM) spectrometry is becoming an important approach for analyzing molecular ions in the gas phase with applications that span a multitude of scientific areas. There are a variety of IM-based approaches that utilize either constant or oscillatory electric fields. Here, we explore the combination of constant and oscillatory fields applied in a single device to affect the separation and filtering of ions based on their mobilities. The mobility analyzer allows confining and manipulating ions utilizing a combination of radio frequency (RF), direct current (DC) fields, and traveling waves (TW) in a structures for lossless ion manipulations (SLIM) module.more » In this work, we have investigated theoretically and experimentally the concept for continuous filtering of ions based on their mobilities where ions are mobility separated and selected by a combination of TW and constant fields providing opposing forces on the ions. The SLIM module was composed of two surfaces with mirror-image arrays of electrodes and had two regions where the different TW and opposing DC fields could be applied. By appropriately choosing the DC gradient and TW parameters for the two sections, it is possible to transmit ions of a selected mobility while filtering out others. The filtering capabilities are determined by the applied DC gradient and the TW parameters, such as frequency, amplitude and the TW sequence (i.e., the duty cycle of the traveling wave). The effect of different parameters on the sensitivity and the IM resolution of the device have been investigated.« less

Discriminant analysis of fused positive and negative ion mobility spectra using multivariate self-modeling mixture analysis and neural networks.

PubMed

Chen, Ping; Harrington, Peter B

2008-02-01

A new method coupling multivariate self-modeling mixture analysis and pattern recognition has been developed to identify toxic industrial chemicals using fused positive and negative ion mobility spectra (dual scan spectra). A Smiths lightweight chemical detector (LCD), which can measure positive and negative ion mobility spectra simultaneously, was used to acquire the data. Simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) was used to separate the analytical peaks in the ion mobility spectra from the background reactant ion peaks (RIP). The SIMPLSIMA analytical components of the positive and negative ion peaks were combined together in a butterfly representation (i.e., negative spectra are reported with negative drift times and reflected with respect to the ordinate and juxtaposed with the positive ion mobility spectra). Temperature constrained cascade-correlation neural network (TCCCN) models were built to classify the toxic industrial chemicals. Seven common toxic industrial chemicals were used in this project to evaluate the performance of the algorithm. Ten bootstrapped Latin partitions demonstrated that the classification of neural networks using the SIMPLISMA components was statistically better than neural network models trained with fused ion mobility spectra (IMS).

A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources

NASA Astrophysics Data System (ADS)

Kirk, Ansgar Thomas; Kobelt, Tim; Spehlbrink, Hauke; Zimmermann, Stefan

2018-05-01

Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with high ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region. [Figure not available: see fulltext.

A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources.

PubMed

Kirk, Ansgar Thomas; Kobelt, Tim; Spehlbrink, Hauke; Zimmermann, Stefan

2018-05-08

Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with high ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region. Graphical Abstract ᅟ.

Mobility-Selected Ion Trapping and Enrichment Using Structures for Lossless Ion Manipulations

DOE PAGES

Chen, Tsung-Chi; Ibrahim, Yehia M.; Webb, Ian K.; ...

2016-01-11

The integration of ion mobility spectrometry (IMS) with mass spectrometry (MS) and the ability to trap ions in IMS-MS measurements is of great importance for performing reactions, accumulating ions, and increasing analytical measurement sensitivity. The development of Structures for Lossless Ion Manipulations (SLIM) offers the potential for ion manipulations in a more reliable and cost-effective manner, while opening opportunities for much more complex sequences of manipulations. Here, we demonstrate an ion separation and trapping module and a method based upon SLIM that consists of a linear mobility ion drift region, a switch/tee and a trapping region that allows the isolationmore » and accumulation of mobility-separated species. The operation and optimization of the SLIM switch/tee and trap are described and demonstrated for the enrichment of the low abundance ions. Lastly, we observed a linear increase in ion intensity with the number of trapping/accumulation events using the SLIM trap, illustrating its potential for enhancing the sensitivity of low abundance or targeted species.« less

Effect of solenoidal magnetic field on drifting laser plasma

NASA Astrophysics Data System (ADS)

Takahashi, Kazumasa; Okamura, Masahiro; Sekine, Megumi; Cushing, Eric; Jandovitz, Peter

2013-04-01

An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

Langmuir waveforms at interplanetary shocks: STEREO statistical analysis

NASA Astrophysics Data System (ADS)

Briand, C.

2016-12-01

Wave-particle interactions and particle acceleration are the two main processes allowing energy dissipation at non collisional shocks. Ion acceleration has been deeply studied for many years, also for their central role in the shock front reformation. Electron dynamics is also important in the shock dynamics through the instabilities they can generate which may impact the ion dynamics.Particle measurements can be efficiently completed by wave measurements to determine the characteristics of the electron beams and study the turbulence of the medium. Electric waveforms obtained from the S/WAVES instrument of the STEREO mission between 2007 to 2014 are analyzed. Thus, clear signature of Langmuir waves are observed on 41 interplanetary shocks. These data enable a statistical analysis and to deduce some characteristics of the electron dynamics on different shocks sources (SIR or ICME) and types (quasi-perpendicular or quasi-parallel). The conversion process between electrostatic to electromagnetic waves has also been tested in several cases.

Power coupling mode transitions induced by tailored voltage waveforms in capacitive oxygen discharges

NASA Astrophysics Data System (ADS)

Derzsi, Aranka; Bruneau, Bastien; Gibson, Andrew Robert; Johnson, Erik; O'Connell, Deborah; Gans, Timo; Booth, Jean-Paul; Donkó, Zoltán

2017-03-01

Low-pressure capacitively coupled radio frequency discharges operated in O2 and driven by tailored voltage waveforms are investigated experimentally and by means of kinetic simulations. Pulse-type (peaks/valleys) and sawtooth-type voltage waveforms that consist of up to four consecutive harmonics of the fundamental frequency are used to study the amplitude asymmetry effect as well as the slope asymmetry effect at different fundamental frequencies (5, 10, and 15 MHz) and at different pressures (50-700 mTorr). Values of the DC self-bias determined experimentally and spatio-temporal excitation rates derived from phase resolved optical emission spectroscopy measurements are compared with particle-in-cell/Monte Carlo collisions simulations. The spatio-temporal distributions of the excitation rate obtained from experiments are well reproduced by the simulations. Transitions of the discharge electron heating mode from the drift-ambipolar mode to the α-mode are induced by changing the number of consecutive harmonics included in the driving voltage waveform or by changing the gas pressure. Changing the number of harmonics in the waveform has a strong effect on the electronegativity of the discharge, on the generation of the DC self-bias and on the control of ion properties at the electrodes, both for pulse-type, as well as sawtooth-type driving voltage waveforms The effect of the surface quenching rate of oxygen singlet delta metastable molecules on the spatio-temporal excitation patterns is also investigated.

Combined corona discharge and UV photoionization source for ion mobility spectrometry.

PubMed

Bahrami, Hamed; Tabrizchi, Mahmoud

2012-08-15

An ion mobility spectrometer is described which is equipped with two non-radioactive ion sources, namely an atmospheric pressure photoionization and a corona discharge ionization source. The two sources cannot only run individually but are additionally capable of operating simultaneously. For photoionization, a UV lamp was mounted parallel to the axis of the ion mobility cell. The corona discharge electrode was mounted perpendicular to the UV radiation. The total ion current from the photoionization source was verified as a function of lamp current, sample flow rate, and drift field. Simultaneous operation of the two ionization sources was investigated by recording ion mobility spectra of selected samples. The design allows one to observe peaks from either the corona discharge or photoionization individually or simultaneously. This makes it possible to accurately compare peaks in the ion mobility spectra from each individual source. Finally, the instrument's capability for discriminating two peaks appearing in approximately identical drift times using each individual ionization source is demonstrated. Copyright © 2012 Elsevier B.V. All rights reserved.

Ion mobility spectrometer using frequency-domain separation

DOEpatents

Martin, Stephen J.; Butler, Michael A.; Frye, Gregory C.; Schubert, W. Kent

1998-01-01

An apparatus and method is provided for separating and analyzing chemical species in an ion mobility spectrometer using a frequency-domain technique wherein the ions generated from the chemical species are selectively transported through an ion flow channel having a moving electrical potential therein. The moving electrical potential allows the ions to be selected according to ion mobility, with certain of the ions being transported to an ion detector and other of the ions being effectively discriminated against. The apparatus and method have applications for sensitive chemical detection and analysis for monitoring of exhaust gases, hazardous waste sites, industrial processes, aerospace systems, non-proliferation, and treaty verification. The apparatus can be formed as a microelectromechanical device (i.e. a micromachine).

Cerium Ion Mobility and Diffusivity Rates in Perfluorosulfonic Acid Membranes Measured via Hydrogen Pump Operation

DOE PAGES

Baker, Andrew M.; Babu, Siddharth Komini; Mukundan, Rangachary; ...

2017-09-21

Ion mobility and diffusivity coefficients were determined for cerium ions in Nafion XL perfluorosulfonic acid ionomer membranes at 100% and 50% relative humidity in a conductivity cell using a hydrogen pump. We quantified Ce ion migration profiles as a function of charge transfer through the cell using X-ray fluorescence (XRF). To decouple simultaneous effects of Ce ion mobility and back-diffusion which occur due to potential and concentration gradients, respectively, a one-dimensional model was developed and fit to these intermittent XRF profiles. The resulting mobility and diffusivity coefficients demonstrate the dramatic effects of potential and concentration gradients on Ce ion migrationmore » during PEM fuel cell operation.« less

Cerium Ion Mobility and Diffusivity Rates in Perfluorosulfonic Acid Membranes Measured via Hydrogen Pump Operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Andrew M.; Babu, Siddharth Komini; Mukundan, Rangachary

Ion mobility and diffusivity coefficients were determined for cerium ions in Nafion XL perfluorosulfonic acid ionomer membranes at 100% and 50% relative humidity in a conductivity cell using a hydrogen pump. We quantified Ce ion migration profiles as a function of charge transfer through the cell using X-ray fluorescence (XRF). To decouple simultaneous effects of Ce ion mobility and back-diffusion which occur due to potential and concentration gradients, respectively, a one-dimensional model was developed and fit to these intermittent XRF profiles. The resulting mobility and diffusivity coefficients demonstrate the dramatic effects of potential and concentration gradients on Ce ion migrationmore » during PEM fuel cell operation.« less

Achieving High Resolution Ion Mobility Separations Using Traveling Waves in Compact Multiturn Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Garimella, Sandilya V. B.; Ibrahim, Yehia M.

We report on ion mobility separations (IMS) achievable using traveling waves in a Structures for Lossless Ion Manipulations (TW-SLIM) module having a 44-cm path length and sixteen 90º turns. The performance of the TW-SLIM module was evaluated for ion transmission, and ion mobility separations with different RF, TW parameters and SLIM surface gaps in conjunction with mass spectrometry. In this work TWs were created by the transient and dynamic application of DC potentials. The TW-SLIM module demonstrated highly robust performance and the ion mobility resolution achieved even with sixteen close spaced turns was comparable to a similar straight path TW-SLIMmore » module. We found an ion mobility peak capacity of ~ 31 and peak generation rate of 780 s-1 for TW speeds of <210 m/s using the current multi-turn TW-SLIM module. The separations achieved for isomers of peptides and tetrasaccharides were found to be comparable to those from a ~ 0.9-m drift tube-based IMS-MS platform operated at the same pressure (4 torr). The combined attributes of flexible design, low voltage requirements and lossless ion transmission through multiple turns for the present TW-SLIM module provides a basis for SLIM devices capable of achieving much greater ion mobility resolutions via greatly extended ion path lengths and compact serpentine designs that do not significantly impact the instrumentation profile, a direction described in a companion manuscript.« less

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

DOE PAGES

Pace, D. C.; Collins, C. S.; Crowley, B.; ...

2016-09-28

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak. Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significantmore » changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. As a result, developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.« less

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pace, D. C.; Collins, C. S.; Crowley, B.

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak. Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significantmore » changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. As a result, developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.« less

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

NASA Astrophysics Data System (ADS)

Pace, D. C.; Collins, C. S.; Crowley, B.; Grierson, B. A.; Heidbrink, W. W.; Pawley, C.; Rauch, J.; Scoville, J. T.; Van Zeeland, M. A.; Zhu, Y. B.; The DIII-D Team

2017-01-01

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak (Luxon 2002 Nucl. Fusion 42 614). Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significant changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. Developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.

Air ion mobility spectra and concentrations upwind and downwind of overhead AC high voltage power lines

NASA Astrophysics Data System (ADS)

Wright, Matthew D.; Buckley, Alison J.; Matthews, James C.; Shallcross, Dudley E.; Henshaw, Denis L.

2014-10-01

Corona ions produced by high-voltage power lines (HVPLs) can alter the nearby electrical environment, potentially increasing aerosol charge levels downwind. However, there is a lack of knowledge concerning the concentration and mobility of ions from AC HVPLs and their dispersion away from the line. We present ion concentration and mobility measurements made near AC HVPLs in South-West England. Examples of typical mobility spectra are shown highlighting features commonly observed. Corona was observed during 33 of 46 measurements, at 9 of 11 sites, with positive or ‘bipolar' (both polarities) ion production commonly seen. Ion production usually increases atmospheric concentrations by only a modest amount, but extreme cases can enhance concentration by an order of magnitude or more. A polarity imbalance is required to increase aerosol charge via ion attachment; this was observed on 15 of 24 days when positive corona was observed, but was not seen for negative ions. Ion mobility was higher downwind compared with upwind for both ion polarities, but the increase was not statistically significant. Future work should focus on identifying and characterising ‘heavy-producing' HVPLs, and obtaining results in conditions which may favour negative ion production e.g. high humidity, inclement weather or during nighttime.

Correlation ion mobility spectroscopy

DOEpatents

Pfeifer, Kent B [Los Lunas, NM; Rohde, Steven B [Corrales, NM

2008-08-26

Correlation ion mobility spectrometry (CIMS) uses gating modulation and correlation signal processing to improve IMS instrument performance. Closely spaced ion peaks can be resolved by adding discriminating codes to the gate and matched filtering for the received ion current signal, thereby improving sensitivity and resolution of an ion mobility spectrometer. CIMS can be used to improve the signal-to-noise ratio even for transient chemical samples. CIMS is especially advantageous for small geometry IMS drift tubes that can otherwise have poor resolution due to their small size.

Infrared Spectroscopy of Mobility-Selected H+-Gly-Pro-Gly-Gly (GPGG)

NASA Astrophysics Data System (ADS)

Masson, Antoine; Kamrath, Michael Z.; Perez, Marta A. S.; Glover, Matthew S.; Rothlisberger, U.; Clemmer, David E.; Rizzo, Thomas R.

2015-09-01

We report the first results from a new instrument capable of acquiring infrared spectra of mobility-selected ions. This demonstration involves using ion mobility to first separate the protonated peptide Gly-Pro-Gly-Gly (GPGG) into two conformational families with collisional cross-sections of 93.8 and 96.8 Å2. After separation, each family is independently analyzed by acquiring the infrared predissociation spectrum of the H2-tagged molecules. The ion mobility and spectroscopic data combined with density functional theory (DFT) based molecular dynamics simulations confirm the presence of one major conformer per family, which arises from cis/ trans isomerization about the proline residue. We induce isomerization between the two conformers by using collisional activation in the drift tube and monitor the evolution of the ion distribution with ion mobility and infrared spectroscopy. While the cis-proline species is the preferred gas-phase structure, its relative population is smaller than that of the trans-proline species in the initial ion mobility drift distribution. This suggests that a portion of the trans-proline ion population is kinetically trapped as a higher energy conformer and may retain structural elements from solution.

Electrostatic effects on clustering and ion dynamics in ionomer melts

NASA Astrophysics Data System (ADS)

Ma, Boran; Nguyen, Trung; Pryamitsyn, Victor; Olvera de La Cruz, Monica

An understanding of the relationships between ionomer chain morphology, dynamics and counter-ion mobility is a key factor in the design of ion conducting membranes for battery applications. In this study, we investigate the influence of electrostatic coupling between randomly charged copolymers (ionomers) and counter ions on the structural and dynamic features of a model system of ionomer melts. Using coarse-grained molecular dynamics (CGMD) simulations, we found that variations in electrostatic coupling strength (Γ) remarkably affect the formation of ion-counter ion clusters, ion mobility, and polymer dynamics for a range of charged monomer fractions. Specifically, an increase in Γ leads to larger ionic cluster sizes and reduced polymer and ion mobility. Analysis of the distribution of the radius of gyration of the clusters further reveals that the fractal dimension of the ion clusters is nearly independent from Γ for all the cases studied. Finally, at sufficiently high values of Γ, we observed arrested heterogeneous ions mobility, which is correlated with an increase in ion cluster size. These findings provide insight into the role of electrostatics in governing the nanostructures formed by ionomers.

Ion mobility spectrometer using frequency-domain separation

DOEpatents

Martin, S.J.; Butler, M.A.; Frye, G.C.; Schubert, W.K.

1998-08-04

An apparatus and method are provided for separating and analyzing chemical species in an ion mobility spectrometer using a frequency-domain technique wherein the ions generated from the chemical species are selectively transported through an ion flow channel having a moving electrical potential therein. The moving electrical potential allows the ions to be selected according to ion mobility, with certain of the ions being transported to an ion detector and other of the ions being effectively discriminated against. The apparatus and method have applications for sensitive chemical detection and analysis for monitoring of exhaust gases, hazardous waste sites, industrial processes, aerospace systems, non-proliferation, and treaty verification. The apparatus can be formed as a microelectromechanical device (i.e. a micromachine). 6 figs.

Chemometric studies for the characterization and differentiation of microorganisms using in situ derivatization and thermal desorption ion mobility spectrometry.

PubMed

Ochoa, Mariela L; Harrington, Peter B

2005-02-01

Whole-cell bacteria were characterized and differentiated by thermal desorption ion mobility spectrometry and chemometric modeling. Principal component analysis was used to evaluate the differences in the ion mobility spectra of whole-cell bacteria and the fatty acid methyl esters (FAMEs) generated in situ after derivatization of the bacterial lipids. Alternating least squares served to extract bacterial peaks from the complex ion mobility spectra of intact microorganisms and, therefore, facilitated the characterization of bacterial strains, species, and Gram type. In situ thermal hydrolysis/methylation with tetramethylammonium hydroxide was necessary for the differentiation of Escherichia coli strains, which otherwise could not be distinguished by spectra acquired with the ITEMISER ion mobility spectrometer. The addition of the methylating agent had no effect on Gram-positive bacteria, and therefore, they could not be differentiated by genera. The classification of E. coli strains was possible by analysis of the IMS spectra from the FAMEs generated in situ. By using the fuzzy multivariate rule-building expert system and cross-validation, a correct classification rate of 96% (22 out of 23 spectra) was obtained. Chemometric modeling on bacterial ion mobility spectra coupled to thermal hydrolysis/methylation proved a simple, rapid (2 min/sample), inexpensive, and sensitive technique to characterize and differentiate intact microorganisms. The ITEMISER ion mobility spectrometer could detect as few as 4 x 10(6) cells/sample.

New Insights into the Compositional Dependence of Li-Ion Transport in Polymer-Ceramic Composite Electrolytes.

PubMed

Zheng, Jin; Hu, Yan-Yan

2018-01-31

Composite electrolytes are widely studied for their potential in realizing improved ionic conductivity and electrochemical stability. Understanding the complex mechanisms of ion transport within composites is critical for effectively designing high-performance solid electrolytes. This study examines the compositional dependence of the three determining factors for ionic conductivity, including ion mobility, ion transport pathways, and active ion concentration. The results show that with increase in the fraction of ceramic Li 7 La 3 Zr 2 O 12 (LLZO) phase in the LLZO-poly(ethylene oxide) composites, ion mobility decreases, ion transport pathways transit from polymer to ceramic routes, and the active ion concentration increases. These changes in ion mobility, transport pathways, and concentration collectively explain the observed trend of ionic conductivity in composite electrolytes. Liquid additives alter ion transport pathways and increase ion mobility, thus enhancing ionic conductivity significantly. It is also found that a higher content of LLZO leads to improved electrochemical stability of composite electrolytes. This study provides insight into the recurring observations of compositional dependence of ionic conductivity in current composite electrolytes and pinpoints the intrinsic limitations of composite electrolytes in achieving fast ion conduction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garimella, Sandilya V. B.; Ibrahim, Yehia M.; Tang, Keqi

A novel concept for ion spatial peak compression is described, and discussed primarily in the context of ion mobility spectrometry (IMS). Using theoretical and numerical methods, the effects of using non-constant (e.g., linearly varying) electric fields on ion distributions (e.g., an ion mobility peak) is evaluated both in the physical and temporal domains. The application of linearly decreasing electric field in conjunction with conventional drift field arrangements is shown to lead to a reduction in IMS physical peak width. When multiple ion packets in a selected mobility window are simultaneously subjected to such fields, there is ion packet compression, i.e.,more » a reduction in peak widths of all species. This peak compression occurs with a modest reduction of resolution, but which can be quickly recovered as ions drift in a constant field after the compression event. Compression also yields a significant increase in peak intensities. In addition, approaches for peak compression in traveling wave IMS are also discussed. Ion mobility peak compression can be particularly useful for mitigating diffusion driven peak spreading over very long path length separations (e.g., in cyclic multi-pass arrangements), and for achieving higher S/N and IMS resolution over a selected mobility range.« less

Ion-mobility study of two functionalized pentacene structural isomers using a modified electrospray/triple quadrupole mass spectrometer

NASA Astrophysics Data System (ADS)

Prada, Svitlana V.; Bohme, Diethard K.; Baranov, Vladimir I.

2007-03-01

We report ion-mobility measurements with a modified triple quadrupole mass spectrometer fitted with an ion molecule reactor (IMR) designed to investigate ion molecule reactivity in organic mass spectrometry. Functionalized pentacene ions, which are generally unreactive were chosen for study to decouple drift/diffusion effects from reactivity (including clustering). The IMR is equipped with a variable axial electrostatic drift field (ADF) and is able to trap ions. These capabilities were successfully employed in the measurement of ion mobilities in different modes of IMR operation. Theoretical modeling of the drift dynamics and the special localization of the large ion packet was successfully implemented. The contribution of the quadrupole RF field to the drift dynamics also was taken into consideration.

Experimental studies on ion mobility in xenon-trimethylamine mixtures

NASA Astrophysics Data System (ADS)

Trindade, A. M. F.; Encarnação, P. M. C. C.; Escada, J.; Cortez, A. F. V.; Neves, P. N. B.; Conde, C. A. N.; Borges, F. I. G. M.; Santos, F. P.

2017-07-01

In this paper we present experimental results for ion reduced mobilities (K0) in gaseous trimethylamine, TMA—(CH3)3N, and xenon-TMA mixtures for reduced electric fields E/N between 7.5 and 60 Td and in the pressure range from 0.5 to 10 Torr, at room temperature. Both in the mixtures and in pure TMA only one peak was observed in the time of arrival spectra, which is believed to be due to two TMA ions with similar mass, (CH3)3N+ (59 u) and (CH3)2CH2N+ (58 u), whose mobility is indistinguishable in our experimental system. The possibility of ion cluster formation is also discussed. In pure TMA, for the E/N range investigated, an average value of 0.56 cm2V-1s-1 was obtained for the reduced mobility of TMA ions. For the studied mixtures, it was observed that even a very small amount of gaseous TMA (~0.2%) in xenon leads to the production of the above referred TMA ions or clusters. The reduced mobility value of this ion or ions in Xe-TMA mixtures is higher than the value in pure TMA: around 0.8 cm2V-1s-1 for TMA concentrations from 0.2% to about 10%, decreasing for higher TMA percentages, eventually converging to the reduced mobility value in pure TMA.

Predictive lethal proarrhythmic risk evaluation using a closed-loop-circuit cell network with human induced pluripotent stem cells derived cardiomyocytes

NASA Astrophysics Data System (ADS)

Nomura, Fumimasa; Hattori, Akihiro; Terazono, Hideyuki; Kim, Hyonchol; Odaka, Masao; Sugio, Yoshihiro; Yasuda, Kenji

2016-06-01

For the prediction of lethal arrhythmia occurrence caused by abnormality of cell-to-cell conduction, we have developed a next-generation in vitro cell-to-cell conduction assay, i.e., a quasi in vivo assay, in which the change in spatial cell-to-cell conduction is quantitatively evaluated from the change in waveforms of the convoluted electrophysiological signals from lined-up cardiomyocytes on a single closed loop of a microelectrode of 1 mm diameter and 20 µm width in a cultivation chip. To evaluate the importance of the closed-loop arrangement of cardiomyocytes for prediction, we compared the change in waveforms of convoluted signals of the responses in the closed-loop circuit arrangement with that of the response of cardiomyocyte clusters using a typical human ether a go-go related gene (hERG) ion channel blocker, E-4031. The results showed that (1) waveform prolongation and fluctuation both in the closed loops and clusters increased depending on the E-4031 concentration increase. However, (2) only the waveform signals in closed loops showed an apparent temporal change in waveforms from ventricular tachycardia (VT) to ventricular fibrillation (VF), which is similar to the most typical cell-to-cell conductance abnormality. The results indicated the usefulness of convoluted waveform signals of a closed-loop cell network for acquiring reproducible results acquisition and more detailed temporal information on cell-to-cell conduction.

Effective Ion Mobility Peak Width as a New Isomeric Descriptor for the Untargeted Analysis of Complex Mixtures Using Ion Mobility-Mass Spectrometry

NASA Astrophysics Data System (ADS)

Farenc, Mathilde; Paupy, Benoit; Marceau, Sabrina; Riches, Eleanor; Afonso, Carlos; Giusti, Pierre

2017-07-01

Ion mobility coupled with mass spectrometry was proven to be an efficient way to characterize complex mixtures such as petroleum samples. However, the identification of isomeric species is difficult owing to the molecular complexity of petroleum and no availability of standard molecules. This paper proposes a new simple indicator to estimate the isomeric content of highly complex mixtures. This indicator is based on the full width at half maximum (FWHM) of the extracted ion mobility peak measured in millisecond or square angstrom that is corrected for instrumental factors such as ion diffusion. This value can be easily obtained without precisely identifying the number of isomeric species under the ion mobility peaks. Considering the Boduszynski model, the ion mobility profile for a particular elemental composition is expected to be a continuum of various isomeric species. The drift time-dependent fragmentation profile was studied and confirmed this hypothesis, a continuous evolution of the fragmentation profile showing that the larger alkyl chain species were detected at higher drift time values. This new indicator was proven to be a fast and efficient method to compare vacuum gas oils for which no difference was found using other analytical techniques.

Ion Mobility-Mass Spectrometry Analysis of Serum N-linked Glycans from Esophageal Adenocarcinoma Phenotypes

PubMed Central

Gaye, M. M.; Valentine, S. J.; Hu, Y.; Mirjankar, N.; Hammoud, Z. T.; Mechref, Y.; Lavine, B. K.; Clemmer, D. E.

2012-01-01

Three disease phenotypes, Barrett’s esophagus (BE), high-grade dysplasia (HGD), esophageal adenocarcinoma (EAC), and a set of normal control (NC) serum samples are examined using a combination of ion mobility spectrometry (IMS), mass spectrometry (MS) and principal component analysis (PCA) techniques. Samples from a total of 136 individuals were examined, including: 7 characterized as BE, 12 as HGD, 56 as EAC and 61 as NC. In typical datasets it was possible to assign ~20 to 30 glycan ions based on MS measurements. Ion mobility distributions for these ions show multiple features. In some cases, such as the [S1H5N4+3Na]3+ and [S1F1H5N4+3Na]3+ glycan ions, the ratio of intensities of high-mobility features to low-mobility features vary significantly for different groups. The degree to which such variations in mobility profiles can be used to distinguish phenotypes is evaluated for eleven N-linked glycan ions. An outlier analysis on each sample class followed by an unsupervised PCA using a genetic algorithm for pattern recognition reveals that EAC samples are separated from NC samples based on 46 features originating from the 11-glycan composite IMS distribution. PMID:23126309

THE DEPENDENCE OF ION AND ELECTRON MOBILITY UPON MOLECULAR STRUCTURE IN DIELECTRIC LIQUIDS (in German)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamczewski, I.

1961-09-01

The viscosity coefficient of dielectric liquids was found to be dependent upon molecular structure and temperature. From this a general formula for ion and electron mobility was derived. This formula includes the dependence of mobility upon molecular structure and temperature, thus making it possible to give a theoretical explanation of other published experimental results. In addition, the formula can be used to calculate ion mobility for a number of other liquids at various temperatures. (auth)

Using a portable ion mobility spectrometer to screen dietary supplements for sibutramine.

PubMed

Dunn, Jamie D; Gryniewicz-Ruzicka, Connie M; Kauffman, John F; Westenberger, Benjamin J; Buhse, Lucinda F

2011-02-20

In response to recent incidents of undeclared sibutramine, an appetite suppressant found in dietary supplements, we developed a method to detect sibutramine using hand-held ion mobility spectrometers with an analysis time of 15 s. Ion mobility spectrometry is a high-throughput and sensitive technique that has been used for illicit drug, explosive, volatile organic compound and chemical warfare detection. We evaluated a hand-held ion mobility spectrometer as a tool for the analysis of supplement extracts containing sibutramine. The overall instrumental limit of detection of five portable ion mobility spectrometers was 2 ng of sibutramine HCl. When sample extractions containing 30 ng/μl or greater of sibutramine were analyzed, saturation of the ionization chamber of the spectrometer occurred and the instrument required more than three cleaning cycles to remove the drug. Hence, supplement samples suspected of containing sibutramine should be prepared at concentrations of 2-20 ng/μl. To obtain this target concentration range for products containing unknown amounts of sibutramine, we provided a simple sample preparation procedure, allowing the U.S. Food and Drug Administration or other agencies to screen products using the portable ion mobility spectrometer. Published by Elsevier B.V.

Structural Studies of Fucosylated N-Glycans by Ion Mobility Mass Spectrometry and Collision-Induced Fragmentation of Negative Ions

NASA Astrophysics Data System (ADS)

Harvey, David J.; Struwe, Weston B.

2018-05-01

There is considerable potential for the use of ion mobility mass spectrometry in structural glycobiology due in large part to the gas-phase separation attributes not typically observed by orthogonal methods. Here, we evaluate the capability of traveling wave ion mobility combined with negative ion collision-induced dissociation to provide structural information on N-linked glycans containing multiple fucose residues forming the Lewisx and Lewisy epitopes. These epitopes are involved in processes such as cell-cell recognition and are important as cancer biomarkers. Specific information that could be obtained from the intact N-glycans by negative ion CID included the general topology of the glycan such as the presence or absence of a bisecting GlcNAc residue and the branching pattern of the triantennary glycans. Information on the location of the fucose residues was also readily obtainable from ions specific to each antenna. Some isobaric fragment ions produced prior to ion mobility could subsequently be separated and, in some cases, provided additional valuable structural information that was missing from the CID spectra alone.

Structure of Hybrid Polyhedral Oligomeric Silsesquioxane Polymethacrylate Oligomers Using Ion Mobility Mass Spectrometry and Molecular Mechanics

DTIC Science & Technology

2004-12-01

Jones interaction potential is included45 better results are obtained but this method at times overestimates cross-sections in the intermediate 1500 to...utilized to generate sodiated [(PMA)Cp7T8]xNa+ ions, and their collision cross-sections were measured in helium using ion mobility based methods...were measured in helium using ion mobility based methods. Results for x = 1, 2, and 3 were consistent with only one conformer occurring for the Na+1

Ion mobility mass spectrometry for ion recovery and clean-up of MS and MS/MS spectra obtained from low abundance viral samples

PubMed Central

Harvey, David J.; Crispin, Max; Bonomelli, Camille; Scrivens, Jim H.

2016-01-01

Graphical abstract Many samples of complex mixtures of N-glycans released from small amounts of material, such as glycoproteins from viruses, present problems for mass spectrometric analysis because of the presence of contaminating material that is difficult to remove by conventional methods without involving sample loss. This paper describes the use of ion mobility for extraction of glycan profiles from such samples and for obtaining clean CID spectra when targeted m/z values capture additional ions from those of the target compound. N-Glycans were released enzymatically from within SDS-PAGE gels, from the representative glycoprotein, gp120 of the human immunodeficiency virus, and examined by direct infusion electrospray in negative mode followed by ion mobility with a Waters Synapt G2 mass spectrometer. Clean profiles of singly, doubly and triply charged N-glycans were obtained from samples in cases where the raw electrospray spectra displayed only a few glycan ions as the result of low sample concentration or the presence of contamination. Ion mobility also enabled uncontaminated CID spectra to be obtained from glycans when their molecular ions displayed coincidence with ions from fragments or multiply charged ions with similar m/z values. This technique proved to be invaluable for removing extraneous ions from many CID spectra. The presence of such ions often produces spectra that are difficult to interpret. Most CID spectra, even those from abundant glycan constituents, benefited from such clean-up showing that the extra dimension provided by ion mobility was invaluable for studies of this type. PMID:26204966

Comparison of reactant and analyte ions for ⁶³Nickel, corona discharge, and secondary electrospray ionization sources with ion mobility-mass spectrometry.

PubMed

Crawford, C L; Hill, H H

2013-03-30

(63)Nickel radioactive ionization ((63)Ni) is the most common and widely used ion source for ion mobility spectrometry (IMS). Regulatory, financial, and operational concerns with this source have promoted recent development of non-radioactive sources, such as corona discharge ionization (CD), for stand-alone IMS systems. However, there has been no comparison of the negative ion species produced by all three sources in the literature. This study compares the negative reactant and analyte ions produced by three sources on an ion mobility-mass spectrometer: conventional (63)Ni, CD, and secondary electrospray ionization (SESI). Results showed that (63)Ni and SESI produced the same reactant ion species while CD produced only the nitrate monomer and dimer ions. The analyte ions produced by each ion source were the same except for the CD source which produced a different ion species for the explosive RDX than either the (63)Ni or SESI source. Accurate and reproducible reduced mobility (K0) values, including several values reported here for the first time, were found for each explosive with each ion source. Overall, the SESI source most closely reproduced the reactant ion species and analyte ion species profiles for (63)Ni. This source may serve as a non-radioactive, robust, and flexible alternative for (63)Ni. Copyright © 2013 Elsevier B.V. All rights reserved.

Measurement of acetates in air using differential ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Szczurek, Andrzej; Maciejewska, Monika; Zajiczek, Żaneta; Maziejuk, Mirosław

2017-11-01

Volatile organic compounds are one of the most important group of air pollutants. Potential health and environmental problems resulting from their emission prompted the requirement for monitoring these species. It motivates development of new measurement techniques which are fast, cost effective, reliable and field deployable. One of novel approaches is ion mobility spectrometry. It dwells on ion separation in electric field, based on differences in ion mobility. Many variants of this method are developed. In this wok, differential ion mobility spectrometry (DMS) was considered in respect of acetate measurements in air. It was demonstrated that DMS offers linear response to methyl, ethyl, propyl and butyl acetate in concentration range from 0.3 ppm to 7 ppm. Positive ions spectrum has to be utilised for this purpose. We showed that fragments of DMS spectrum which secure linearity are compound-specific. The obtained results are promising from the application point of view.

Measurement of Electron Density and Ion Collision Frequency with Dual Assisted Grounded Electrode DBD in Atmospheric Pressure Helium Plasma Jet

NASA Astrophysics Data System (ADS)

Zhou, Qiujiao; Qi, Bing; Huang, Jianjun; Pan, Lizhu; Liu, Ying

2016-04-01

The properties of a helium atmospheric-pressure plasma jet (APPJ) are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device. In the glow discharge, we captured the current waveforms at the positions of the three grounded rings. From the current waveforms, the time delay between the adjacent positions of the rings is employed to calculate the plasma bullet velocity of the helium APPJ. Moreover, the electron density is deduced from a model combining with the time delay and current intensity, which is about 1011 cm-3. In addition, The ion-neutral particles collision frequency in the radial direction is calculated from the current phase difference between two rings, which is on the order of 107 Hz. The results are helpful for understanding the basic properties of APPJs. supported by National Natural Science Foundation of China (No. 11105093), the Technological Project of Shenzhen, China (No. JC201005280485A), and the Planned S&T Program of Shenzhen, China (No. JC201105170703A)

Tandem ion mobility spectrometry coupled to laser excitation

NASA Astrophysics Data System (ADS)

Simon, Anne-Laure; Chirot, Fabien; Choi, Chang Min; Clavier, Christian; Barbaire, Marc; Maurelli, Jacques; Dagany, Xavier; MacAleese, Luke; Dugourd, Philippe

2015-09-01

This manuscript describes a new experimental setup that allows to perform tandem ion mobility spectrometry (IMS) measurements and which is coupled to a high resolution time-of-flight mass spectrometer. It consists of two 79 cm long drift tubes connected by a dual ion funnel assembly. The setup was built to permit laser irradiation of the ions in the transfer region between the two drift tubes. This geometry allows selecting ions according to their ion mobility in the first drift tube, to irradiate selected ions, and examine the ion mobility of the product ions in the second drift tube. Activation by collision is possible in the same region (between the two tubes) and between the second tube and the time-of-flight. IMS-IMS experiments on Ubiquitin are reported. We selected a given isomer of charge state +7 and explored its structural rearrangement following collisional activation between the two drift tubes. An example of IMS-laser-IMS experiment is reported on eosin Y, where laser irradiation was used to produce radical ions by electron photodetachment starting from doubly deprotonated species. This allowed measuring the collision cross section of the radical photo-product, which cannot be directly produced with an electrospray source.

Study and optimization of key parameters of a laser ablation ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Ni, Kai; Li, Jianan; Tang, Binchao; Shi, Yuan; Yu, Quan; Qian, Xiang; Wang, Xiaohao

2016-11-01

Ion Mobility Spectrometry (IMS), having an advantage in real-time and on-line detection, is an atmospheric pressure detecting technique. LA-IMS (Laser Ablation Ion Mobility Spectrometry) uses Nd-YAG laser as ionization source, whose energy is high enough to ionize metal. In this work, we tested the signal in different electric field intensity by a home-made ion mobility spectrometer, using silicon wafers the sample. The transportation of metal ions was match with the formula: Td = d/K • 1/E, when the electric field intensity is greater than 350v/cm. The relationship between signal intensity and collection angle (the angle between drift tube and the surface of the sample) was studied. With the increasing of the collection angle, signal intensity had a significant increase; while the variation of incident angle of the laser had no significant influence. The signal intensity had a 140% increase when the collection angle varied from 0 to 45 degree, while the angle between the drift tube and incident laser beam keeping the same as 90 degree. The position of ion gate in LA-IMS(Laser Ablation Ion Mobility Spectrometry) is different from the traditional ones for the kinetic energy of the ions is too big, if the distance between ion gate and sampling points less than 2.5cm the ion gate will not work, the ions could go through ion gate when it closed. The SNR had been improved by define the signal when the ion gate is closed as background signal, the signal noise including shock wave and electrical field perturbation produced during the interaction between laser beam and samples is eliminated when the signal that the ion gate opened minus the background signal.

Simple area determination of strongly overlapping ion mobility peaks.

PubMed

Borovcová, Lucie; Hermannová, Martina; Pauk, Volodymyr; Šimek, Matěj; Havlíček, Vladimír; Lemr, Karel

2017-08-15

Coupling of ion mobility with mass spectrometry has brought new frontiers in separation and quantitation of a wide range of isobaric/isomeric compounds. Ion mobility spectrometry may separate ions possessing the identical molecular formula but having different molecular shapes. The separation space in most commercially available instruments is limited and rarely the mobility resolving power exceeds one hundred. From this perspective, new approaches allowing for extracting individual compound signals out of a more complex mixture are needed. In this work we present a new simple analytical approach based on fitting of arrival time distribution (ATD) profiles by Gaussian functions and generating of ATD functions. These ATD functions well describe even distorted ion mobility peaks of individual compounds and allow for extracting their peaks from mobilograms of mixtures. Contrary to classical integration, our approach works well with irregular overlapping peaks. Using mobilograms of standards to generate ATD functions, poorly separated compounds, e.g. isomers, with identical mass spectra representing a hard to solve task for various chemometric methods can be easily distinguished by our procedure. Alternatively ATD functions can be obtained from ATD profiles of ions unique to individual mixture components (if such ions exist) and mobilograms of standards are not required. On a set of hyaluronan-derived oligosaccharides we demonstrated excellent ATD repeatability enabling the resolution of binary mixtures, including mixtures with minor component level about 5%. Ion mobility quantitative data of isomers were confirmed by high performance liquid chromatography. Copyright © 2017 Elsevier B.V. All rights reserved.

The Influence of Drift Gas Composition on the Separation Mechanism in Traveling Wave Ion Mobility Spectrometry: Insight from Electrodynamic Simulations

PubMed Central

May, Jody C.; McLean, John A.

2013-01-01

The influence of three different drift gases (helium, nitrogen, and argon) on the separation mechanism in traveling wave ion mobility spectrometry is explored through ion trajectory simulations which include considerations for ion diffusion based on kinetic theory and the electrodynamic traveling wave potential. The model developed for this work is an accurate depiction of a second-generation commercial traveling wave instrument. Three ion systems (cocaine, MDMA, and amphetamine) whose reduced mobility values have previously been measured in different drift gases are represented in the simulation model. The simulation results presented here provide a fundamental understanding of the separation mechanism in traveling wave, which is characterized by three regions of ion motion: (1) ions surfing on a single wave, (2) ions exhibiting intermittent roll-over onto subsequent waves, and (3) ions experiencing a steady state roll-over which repeats every few wave cycles. These regions of ion motion are accessed through changes in the gas pressure, wave amplitude, and wave velocity. Resolving power values extracted from simulated arrival times suggest that momentum transfer in helium gas is generally insufficient to access regions (2) and (3) where ion mobility separations occur. Ion mobility separations by traveling wave are predicted to be effectual for both nitrogen and argon, with slightly lower resolving power values observed for argon as a result of band-broadening due to collisional scattering. For the simulation conditions studied here, the resolving power in traveling wave plateaus between regions (2) and (3), with further increases in wave velocity contributing only minor improvements in separations. PMID:23888124

The Influence of Drift Gas Composition on the Separation Mechanism in Traveling Wave Ion Mobility Spectrometry: Insight from Electrodynamic Simulations.

PubMed

May, Jody C; McLean, John A

2003-06-01

The influence of three different drift gases (helium, nitrogen, and argon) on the separation mechanism in traveling wave ion mobility spectrometry is explored through ion trajectory simulations which include considerations for ion diffusion based on kinetic theory and the electrodynamic traveling wave potential. The model developed for this work is an accurate depiction of a second-generation commercial traveling wave instrument. Three ion systems (cocaine, MDMA, and amphetamine) whose reduced mobility values have previously been measured in different drift gases are represented in the simulation model. The simulation results presented here provide a fundamental understanding of the separation mechanism in traveling wave, which is characterized by three regions of ion motion: (1) ions surfing on a single wave, (2) ions exhibiting intermittent roll-over onto subsequent waves, and (3) ions experiencing a steady state roll-over which repeats every few wave cycles. These regions of ion motion are accessed through changes in the gas pressure, wave amplitude, and wave velocity. Resolving power values extracted from simulated arrival times suggest that momentum transfer in helium gas is generally insufficient to access regions (2) and (3) where ion mobility separations occur. Ion mobility separations by traveling wave are predicted to be effectual for both nitrogen and argon, with slightly lower resolving power values observed for argon as a result of band-broadening due to collisional scattering. For the simulation conditions studied here, the resolving power in traveling wave plateaus between regions (2) and (3), with further increases in wave velocity contributing only minor improvements in separations.

Ion Mobility Mass Spectrometry for Extracting Spectra of N-Glycans Directly from Incubation Mixtures Following Glycan Release: Application to Glycans from Engineered Glycoforms of Intact, Folded HIV gp120

NASA Astrophysics Data System (ADS)

Harvey, David J.; Sobott, Frank; Crispin, Max; Wrobel, Antoni; Bonomelli, Camille; Vasiljevic, Snezana; Scanlan, Christopher N.; Scarff, Charlotte A.; Thalassinos, Konstantinos; Scrivens, James H.

2011-03-01

The analysis of glycosylation from native biological sources is often frustrated by the low abundances of available material. Here, ion mobility combined with electrospray ionization mass spectrometry have been used to extract the spectra of N-glycans released with PNGase F from a serial titration of recombinantly expressed envelope glycoprotein, gp120, from the human immunodeficiency virus (HIV). Analysis was also performed on gp120 expressed in the α-mannosidase inhibitor, and in a matched mammalian cell line deficient in GlcNAc transferase I. Without ion mobility separation, ESI spectra frequently contained no observable ions from the glycans whereas ions from other compounds such as detergents and residual buffer salts were abundant. After ion mobility separation on a Waters T-wave ion mobility mass spectrometer, the N-glycans fell into a unique region of the ion mobility/ m/z plot allowing their profiles to be extracted with good signal:noise ratios. This method allowed N-glycan profiles to be extracted from crude incubation mixtures with no clean-up even in the presence of surfactants such as NP40. Furthermore, this technique allowed clear profiles to be obtained from sub-microgram amounts of glycoprotein. Glycan profiles were similar to those generated by MALDI-TOF MS although they were more susceptible to double charging and fragmentation. Structural analysis could be accomplished by MS/MS experiments in either positive or negative ion mode but negative ion mode gave the most informative spectra and provided a reliable approach to the analysis of glycans from small amounts of glycoprotein.

Space charge effect in spectrometers of ion mobility increment with planar drift chamber.

PubMed

Elistratov, A A; Sherbakov, L A

2007-01-01

The effect of space charge on the ion beam in a spectrometer of ion mobility increment with the planar drift chamber has been investigated. A model for the drift of ions under a non-uniform high-frequency electric field(1-3) has been developed recently. We have amplified this model by taking space charge effect into account. The ion peak shape taking into consideration the space charge effect is obtained. The output current saturation effect limiting the rise of the ion peak with increasing ion density at the input of the drift chamber of a spectrometer is observed. We show that the saturation effect is caused by the following phenomenon. The maximum possible output ion density exists, depending on the ion type (constant ion mobility, k(0)) and the time of the motion of ions through the drift chamber. At the same time, the ion density does not depend on the parameters of the drift chamber.

Ion profiling in an ambient drift tube-ion mobility spectrometer using a high pixel density linear array detector IonCCD.

PubMed

Davila, Stephen J; Hadjar, Omar; Eiceman, Gary A

2013-07-16

A linear pixel-based detector array, the IonCCD, is characterized for use under ambient conditions with thermal (<1 eV) positive ions derived from purified air and a 10 mCi (63)Ni foil. The IonCCD combined with a drift tube-ion mobility spectrometer permitted the direct detection of gas phase ions at atmospheric pressure and confirmed a limit of detection of 3000 ions/pixel/frame established previously in both the keV (1-2 keV) and the hyper-thermal (10-40 eV) regimes. Results demonstrate the "broad-band" application of the IonCCD over 10(5) orders in ion energy and over 10(10) in operating pressure. The Faraday detector of a drift tube for an ion mobility spectrometer was replaced with the IonCCD providing images of ion profiles over the cross-section of the drift tube. Patterns in the ion profiles were developed in the drift tube cross-section by control of electric fields between wires of Bradbury Nielson and Tyndall Powell shutter designs at distances of 1-8 cm from the detector. Results showed that ion beams formed in wire sets, retained their shape with limited mixing by diffusion and Coulombic repulsion. Beam broadening determined as 95 μm/cm for hydrated protons in air with moisture of ~10 ppmv. These findings suggest a value of the IonCCD in further studies of ion motion and diffusion of thermalized ions, enhancing computational results from simulation programs, and in the design or operation of ion mobility spectrometers.

High Mobility SiGe/Si Transistor Structures on Sapphire Substrates Using Ion Implantation

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Mueller, C. H.; Croke, E. T.

2003-01-01

High mobility n-type SiGe/Si transistor structures have been fabricated on sapphire substrates by ion implanting phosphorus ions into strained 100 Angstrom thick silicon channels for the first time. The strained Si channels were sandwiched between Si(sub 0.7)Ge(sub 0.3) layers, which, in turn, were deposited on Si(sub 0.7)Ge(sub 0.3) virtual substrates and graded SiGe buffer layers. After the molecular beam epitaxy (MBE) film growth process was completed, ion thick silicon channels implantation and post-annealing were used to introduce donors. The phosphorous ions were preferentially located in the Si channel at a peak concentration of approximately 1x10(exp 18)/cu cm. Room temperature electron mobilities exceeding 750 sq cm/V-sec at carrier densities of 1x10(exp 12)/sq cm were measured. Electron concentration appears to be the key factor that determines mobility, with the highest mobility observed for electron densities in the 1 - 2x10(exp 12)/sq cm range.

LC-IMS-MS Feature Finder. Detecting Multidimensional Liquid Chromatography, Ion Mobility, and Mass Spectrometry Features in Complex Datasets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowell, Kevin L.; Slysz, Gordon W.; Baker, Erin Shammel

2013-09-05

We introduce a command line software application LC-IMS-MS Feature Finder that searches for molecular ion signatures in multidimensional liquid chromatography-ion mobility spectrometry-mass spectrometry (LC-IMS-MS) data by clustering deisotoped peaks with similar monoisotopic mass, charge state, LC elution time, and ion mobility drift time values. The software application includes an algorithm for detecting and quantifying co-eluting chemical species, including species that exist in multiple conformations that may have been separated in the IMS dimension.

Experimental ion mobility measurements in Xe-CH4

NASA Astrophysics Data System (ADS)

Perdigoto, J. M. C.; Cortez, A. F. V.; Veenhof, R.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.

2017-09-01

Data on ion mobility is important to improve the performance of large volume gaseous detectors. In the present work, the method, experimental setup and results for the ion mobility measurements in Xe-CH4 mixtures are presented. The results for this mixture show the presence of two distinct groups of ions. The nature of the ions depend on the mixture ratio since they are originated by both Xe and CH4. The results here presented were obtained for low reduced electric fields, E/N, 10-25 Td (2.4-6.1 kV ṡ cm-1 ṡ bar-1), at low pressure (8 Torr) (10.6 mbar), and at room temperature.

Plasma characteristics in non-sinusoidally excited CCP discharges

NASA Astrophysics Data System (ADS)

Lafleur, Trevor; Booth, Jean-Paul

2012-10-01

Using particle-in-cell (PIC) simulations we perform a characterization of the plasma response to positive pulse-type voltage excitations (with a repetition frequency of 13.56 MHz) in a geometrically symmetric CCP reactor (with a gap length of 2 cm) operated with argon (for pressures between 20-500 mTorr). Use of these non-sinusoidal waveforms generates an electrical asymmetry effect in the system, which necessitates the formation of a DC bias. This DC bias, together with the shape of the voltage waveforms used, produces a number of new phenomena that are not present in typical sinusoidal discharges: (1) the plasma density and ion flux can be increased as the pulse width is reduced, (2) a significant asymmetry in the ion fluxes to the powered and grounded electrodes develops as the pressure increases, (3) the average ion energy striking the grounded electrode remains low and approximately constant as the pulse width decreases, and (4) the sheath at the grounded electrode never fully collapses; electrons are no longer lost in sharp pulses, but escape essentially throughout the rf cycle. Effects (1) and (3) above offer the possibility for a new form of control in these types of discharges, where the ion flux can be increased while the ion energy on the grounded electrode can be kept small and essentially constant. This effect has recently been exploited to control the crystallinity of silicon thin films [1], where the low ion bombarding energy was found to improve the quality of films grown. [4pt] [1] Johnson E V, Pouliquen S, Delattre P A, and Booth J P, J. Non-Cryst. Solids 2012, in press.

Using different drift gases to change separation factors (alpha) in ion mobility spectrometry

PubMed

Asbury; Hill

2000-02-01

The use of different drift gases to alter separation factors (alpha) in ion mobility spectrometry has been demonstrated. The mobility of a series of low molecular weight compounds and three small peptides was determined in four different drift gases. The drift gases chosen were helium, argon, nitrogen, and carbon dioxide. These drift gases provide a range of polarizabilities and molecular weights. In all instances, the compounds showed the greatest mobility in helium and the lowest mobility in carbon dioxide; however the percentage change of mobility for each compound was different, effectively changing the alpha value. The alpha value changes were primarily due to differences in drift gas polarizability but were also influenced by the mass of the drift gas. In addition, gas-phase ion radii were calculated in each of the different drift gases. These radii were then plotted against drift gas polarizability producing linear plots with r2 values greater than 0.99. The intercept of these plots provides the gas-phase radius of an ion in a nonpolarizing environment, whereas the slope is indicative of the magnitude of the ion's mobility change related to polarizability. It therefore, should be possible to separate any two compounds that have different slopes with the appropriate drift gas.

Ion mobility spectrometric analysis of vaporous chemical warfare agents by the instrument with corona discharge ionization ammonia dopant ambient temperature operation.

PubMed

Satoh, Takafumi; Kishi, Shintaro; Nagashima, Hisayuki; Tachikawa, Masumi; Kanamori-Kataoka, Mieko; Nakagawa, Takao; Kitagawa, Nobuyoshi; Tokita, Kenichi; Yamamoto, Soichiro; Seto, Yasuo

2015-03-20

The ion mobility behavior of nineteen chemical warfare agents (7 nerve gases, 5 blister agents, 2 lachrymators, 2 blood agents, 3 choking agents) and related compounds including simulants (8 agents) and organic solvents (39) was comparably investigated by the ion mobility spectrometry instrument utilizing weak electric field linear drift tube with corona discharge ionization, ammonia doping, purified inner air drift flow circulation operated at ambient temperature and pressure. Three alkyl methylphosphonofluoridates, tabun, and four organophosphorus simulants gave the intense characteristic positive monomer-derived ion peaks and small dimer-derived ion peaks, and the later ion peaks were increased with the vapor concentrations. VX, RVX and tabun gave both characteristic positive monomer-derived ions and degradation product ions. Nitrogen mustards gave the intense characteristic positive ion peaks, and in addition distinctive negative ion peak appeared from HN3. Mustard gas, lewisite 1, o-chlorobenzylidenemalononitrile and 2-mercaptoethanol gave the characteristic negative ion peaks. Methylphosphonyl difluoride, 2-chloroacetophenone and 1,4-thioxane gave the characteristic ion peaks both in the positive and negative ion mode. 2-Chloroethylethylsulfide and allylisothiocyanate gave weak ion peaks. The marker ion peaks derived from two blood agents and three choking agents were very close to the reactant ion peak in negative ion mode and the respective reduced ion mobility was fluctuated. The reduced ion mobility of the CWA monomer-derived peaks were positively correlated with molecular masses among structurally similar agents such as G-type nerve gases and organophosphorus simulants; V-type nerve gases and nitrogen mustards. The slope values of the calibration plots of the peak heights of the characteristic marker ions versus the vapor concentrations are related to the detection sensitivity, and within chemical warfare agents examined the slope values for sarin, soman, tabun and nitrogen mustards were higher. Some CWA simulants and organic solvents gave the ion peaks eluting at the similar positions of the CWAs, resulting in false positive alarms. Copyright © 2015 Elsevier B.V. All rights reserved.

Detection of explosives using negative ion mobility spectrometry in air based on dopant-assisted thermal ionization.

PubMed

Shahraki, Hassan; Tabrizchi, Mahmoud; Farrokhpor, Hossein

2018-05-26

The ionization source is an essential component of most explosive detectors based on negative ion mobility spectrometry. Conventional ion sources suffer from such inherent limitations as special safety regulations on radioactive sources or generating interfering ions (for non-radioactive sources) such as corona discharge operating in the air. In this study, a new negative ion source is introduced for ion mobility spectrometry that is based on thermal ionization and operates in the air, applicable to explosives detection. Our system consists of a heating filament powered by an isolated power supply connected to negative high voltage. The ionization is assisted by doping chlorinated compounds in the gas phase using chlorinated hydrocarbons in contact with the heating element to yield Cl - reactant ions. Several chlorinated hydrocarbons are evaluated as the reagent chemicals for providing Cl- reactant ions, of which CCl 4 is identified as the best ionizing reagent. The ion source is evaluated by recording the ion mobility spectra of common explosives, including TNT, RDX, and PETN in the air. A detection limit of 150 pg is obtained for TNT. Compared to other ionization sources, the new source is found to be low-cost, simple, and long-lived, making it suited to portable explosives detection devices. Copyright © 2018 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Economou, Demetre J.

As microelectronic device features continue to shrink approaching atomic dimensions, control of the ion energy distribution on the substrate during plasma etching and deposition becomes increasingly critical. The ion energy should be high enough to drive ion-assisted etching, but not too high to cause substrate damage or loss of selectivity. In many cases, a nearly monoenergetic ion energy distribution (IED) is desired to achieve highly selective etching. In this work, the author briefly reviews: (1) the fundamentals of development of the ion energy distribution in the sheath and (2) methods to control the IED on plasma electrodes. Such methods includemore » the application of “tailored” voltage waveforms on an electrode in continuous wave plasmas, or the application of synchronous bias on a “boundary electrode” during a specified time window in the afterglow of pulsed plasmas.« less

Ion mobilities in diatomic gases: measurement versus prediction with non-specular scattering models.

PubMed

Larriba, Carlos; Hogan, Christopher J

2013-05-16

Ion/electrical mobility measurements of nanoparticles and polyatomic ions are typically linked to particle/ion physical properties through either application of the Stokes-Millikan relationship or comparison to mobilities predicted from polyatomic models, which assume that gas molecules scatter specularly and elastically from rigid structural models. However, there is a discrepancy between these approaches; when specular, elastic scattering models (i.e., elastic-hard-sphere scattering, EHSS) are applied to polyatomic models of nanometer-scale ions with finite-sized impinging gas molecules, predictions are in substantial disagreement with the Stokes-Millikan equation. To rectify this discrepancy, we developed and tested a new approach for mobility calculations using polyatomic models in which non-specular (diffuse) and inelastic gas-molecule scattering is considered. Two distinct semiempirical models of gas-molecule scattering from particle surfaces were considered. In the first, which has been traditionally invoked in the study of aerosol nanoparticles, 91% of collisions are diffuse and thermally accommodating, and 9% are specular and elastic. In the second, all collisions are considered to be diffuse and accommodating, but the average speed of the gas molecules reemitted from a particle surface is 8% lower than the mean thermal speed at the particle temperature. Both scattering models attempt to mimic exchange between translational, vibrational, and rotational modes of energy during collision, as would be expected during collision between a nonmonoatomic gas molecule and a nonfrozen particle surface. The mobility calculation procedure was applied considering both hard-sphere potentials between gas molecules and the atoms within a particle and the long-range ion-induced dipole (polarization) potential. Predictions were compared to previous measurements in air near room temperature of multiply charged poly(ethylene glycol) (PEG) ions, which range in morphology from compact to highly linear, and singly charged tetraalkylammonium cations. It was found that both non-specular, inelastic scattering rules lead to excellent agreement between predictions and experimental mobility measurements (within 5% of each other) and that polarization potentials must be considered to make correct predictions for high-mobility particles/ions. Conversely, traditional specular, elastic scattering models were found to substantially overestimate the mobilities of both types of ions.

Dependence of ion beam current on position of mobile plate tuner in multi-frequencies microwaves electron cyclotron resonance ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurisu, Yosuke; Kiriyama, Ryutaro; Takenaka, Tomoya

2012-02-15

We are constructing a tandem-type electron cyclotron resonance ion source (ECRIS). The first stage of this can supply 2.45 GHz and 11-13 GHz microwaves to plasma chamber individually and simultaneously. We optimize the beam current I{sub FC} by the mobile plate tuner. The I{sub FC} is affected by the position of the mobile plate tuner in the chamber as like a circular cavity resonator. We aim to clarify the relation between the I{sub FC} and the ion saturation current in the ECRIS against the position of the mobile plate tuner. We obtained the result that the variation of the plasmamore » density contributes largely to the variation of the I{sub FC} when we change the position of the mobile plate tuner.« less

Separating intrinsic and scattering attenuation in full waveform sonic logging with radiative transfer theory

NASA Astrophysics Data System (ADS)

Durán, Evert L.; van Wijk, Kasper; Adam, Ludmila; Wallis, Irene C.

2018-05-01

Fitting the intensity of ensembles of sonic log waveforms with a radiative transfer model allows us to separate scattering from intrinsic attenuation in two wells of the Ngatamariki geothermal field, New Zealand. Independent estimates of scattering and intrinsic attenuation add to the geologic interpretation based on other well log data. Particularly, our estimates of the intrinsic attenuation confirm or refine inferences on fluid mobility in the subsurface. Zones of strong intrinsic attenuation in Well 1 correlate with identified feed zones in three of the six cases, and hint at permeability just above two of the other three zones. In Well 2, intrinsic attenuation estimates help identify all three identified permeable intervals, including a washout.

Engineering of electronic properties of single layer graphene by swift heavy ion irradiation

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Kumar, Ashish; Tripathi, Ambuj; Tyagi, Chetna; Avasthi, D. K.

2018-04-01

In this work, swift heavy ion irradiation induced effects on the electrical properties of single layer graphene are reported. The modulation in minimum conductivity point in graphene with in-situ electrical measurement during ion irradiation was studied. It is found that the resistance of graphene layer decreases at lower fluences up to 3 × 1011 ions/cm2, which is accompanied by the five-fold increase in electron and hole mobilities. The ion irradiation induced increase in electron and hole mobilities at lower fluence up to 1 × 1011 ions/cm2 is verified by separate Hall measurements on another irradiated graphene sample at the selected fluence. In contrast to the adverse effects of irradiation on the electrical properties of materials, we have found improvement in electrical mobility after irradiation. The increment in mobility is explained by considering the defect annealing in graphene after irradiation at a lower fluence regime. The modification in carrier density after irradiation is also observed. Based on findings of the present work, we suggest ion beam irradiation as a useful tool for tuning of the electrical properties of graphene.

Hydronium ion motion in nanometer 3-methyl-pentane films

NASA Astrophysics Data System (ADS)

Bell, Richard C.; Wu, Kai; Iedema, Martin J.; Cowin, James P.

2007-07-01

An ion soft-landing approach was applied to study the motion of hydronium (D3O+) and cesium (Cs+) ions from 84to104K in glassy 3-methyl-pentane (3MP) films vapor deposited on Pt(111). Both ions were found to have very similar mobilities in 3MP. The span of ion mobilities probed is from ˜10-18to˜10-13m2V-1s-1. Ion transport in these films was studied as a function of film thickness and electric field strength. The drift velocity was found to be linear with applied field below about 2×108V/m and deviated from linearity above this. To a large extent, D3O+ and Cs+ motion in 3MP was well predicted by a simple continuum-based ion mobility model in films from 25 to 20 000 ML thick (including pronounced perturbations 7 ML from both the vacuum and Pt interfaces). The mobility varied with temperature more slowly than predicted by Stokes' law, which may be due to extended inhomogeneous structures in the 3MP near its glass transition at 77K.

Effect of mobile ions on the electric field needed to orient charged diblock copolymer thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dehghan, Ashkan; Shi, An-Chang; Schick, M.

We examine the behavior of lamellar phases of charged/neutral diblock copolymer thin films containing mobile ions in the presence of an external electric field. We employ self-consistent field theory and focus on the aligning effect of the electric field on the lamellae. Of particular interest are the effects of the mobile ions on the critical field, the value required to reorient the lamellae from the parallel configuration favored by the surface interaction to the perpendicular orientation favored by the field. We find that the critical field depends strongly on whether the neutral or charged species is favored by the substrates.more » In the case in which the neutral species is favored, the addition of charges decreases the critical electric field significantly. The effect is greater when the mobile ions are confined to the charged lamellae. In contrast, when the charged species is favored by the substrate, the addition of mobile ions stabilizes the parallel configuration and thus results in an increase in the critical electric field. The presence of ions in the system introduces a new mixed phase in addition to those reported previously.« less

D-region positive and negative ion concentration and mobilities during the February 1979 eclipse

NASA Astrophysics Data System (ADS)

Conley, T. D.; Narcisi, R. S.; Hegblom, E. R.

1983-07-01

Positive and negative ion concentrations and mobilities have been obtained from an analysis of Gerdien condenser measurements on rocket flights, A10.802-1 and A10.802-2, during and after eclipse totality. The aerodynamic instrument calibration and the data analysis techniques are discussed. The measured concentrations on both flights were about 10,000/cu cm in the altitudes range, 45-80 km. These high concentrations at very low altitudes suggest that a relativistic electron precipitation event was occurring during the measurements. The ion concentration measurements along with electron density measurements made by other groups during the eclipse were used to calculate the negative ion/ electron ratio, and the lumped parameter detachment rate. These results are compared with prior measurements during eclipse and solar proton events and code results. The analysis shows that the present negative ion model is incomplete. The reduced mobilities were also determined. The mobility distributions show that the heavy ions of both the positive and negative species dominate from 45 to 70 km. The data reveal more massive ions at higher altitudes than at low altitudes (1000 vs 300 a.m.u.) as well as possible evidence for multiply charged ions below about 60 km.

A Comprehensive Ubiquitous Healthcare Solution on an Android™ Mobile Device

PubMed Central

Hii, Pei-Cheng; Chung, Wan-Young

2011-01-01

Provision of ubiquitous healthcare solutions which provide healthcare services at anytime anywhere has become more favorable nowadays due to the emphasis on healthcare awareness and also the growth of mobile wireless technologies. Following this approach, an Android™ smart phone device is proposed as a mobile monitoring terminal to observe and analyze ECG (electrocardiography) waveforms from wearable ECG devices in real time under the coverage of a wireless sensor network (WSN). The exploitation of WSN in healthcare is able to substitute the complicated wired technology, moving healthcare away from a fixed location setting. As an extension to the monitoring scheme, medicine care is taken into consideration by utilizing the mobile phone as a barcode decoder, to verify and assist out-patients in the medication administration process, providing a better and more comprehensive healthcare service. PMID:22163986

Method of multiplexed analysis using ion mobility spectrometer

DOEpatents

Belov, Mikhail E [Richland, WA; Smith, Richard D [Richland, WA

2009-06-02

A method for analyzing analytes from a sample introduced into a Spectrometer by generating a pseudo random sequence of a modulation bins, organizing each modulation bin as a series of submodulation bins, thereby forming an extended pseudo random sequence of submodulation bins, releasing the analytes in a series of analyte packets into a Spectrometer, thereby generating an unknown original ion signal vector, detecting the analytes at a detector, and characterizing the sample using the plurality of analyte signal subvectors. The method is advantageously applied to an Ion Mobility Spectrometer, and an Ion Mobility Spectrometer interfaced with a Time of Flight Mass Spectrometer.

Pseudo-Random Sequence Modifications for Ion Mobility Orthogonal Time of Flight Mass Spectrometry

PubMed Central

Clowers, Brian H.; Belov, Mikhail E.; Prior, David C.; Danielson, William F.; Ibrahim, Yehia; Smith, Richard D.

2008-01-01

Due to the inherently low duty cycle of ion mobility spectrometry (IMS) experiments that sample from continuous ion sources, a range of experimental advances have been developed to maximize ion utilization efficiency. The use of ion trapping mechanisms prior to the ion mobility drift tube has demonstrated significant gains over discrete sampling from continuous sources; however, these technologies have traditionally relied upon a signal averaging to attain analytically relevant signal-to-noise ratios (SNR). Multiplexed (MP) techniques based upon the Hadamard transform offer an alternative experimental approach by which ion utilization efficiency can be elevated to ∼ 50 %. Recently, our research group demonstrated a unique multiplexed ion mobility time-of-flight (MP-IMS-TOF) approach that incorporates ion trapping and can extend ion utilization efficiency beyond 50 %. However, the spectral reconstruction of the multiplexed signal using this experiment approach requires the use of sample-specific weighing designs. Though general weighing designs have been shown to significantly enhance ion utilization efficiency using this MP technique, such weighing designs cannot be applied to all samples. By modifying both the ion funnel trap and the pseudo random sequence (PRS) used for the MP experiment we have eliminated the need for complex weighing matrices. For both simple and complex mixtures SNR enhancements of up to 13 were routinely observed as compared to the SA-IMS-TOF experiment. In addition, this new class of PRS provides a two fold enhancement in ion throughput compared to the traditional HT-IMS experiment. PMID:18311942

Squeezing of Ion Populations and Peaks in Traveling Wave Ion Mobility Separations and Structures for Lossless Ion Manipulations using Compression Ratio Ion Mobility Programming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garimella, Venkata BS; Hamid, Ahmed M.; Deng, Liulin

In this work, we report an approach for spatial and temporal gas phase ion population manipulation, and demonstrate its application for the collapse of the ion distributions in ion mobility (IM) separations into tighter packets providing higher sensitivity measurements in conjunction with mass spectrometry (MS). We do this for ions moving from a conventionally traveling wave (TW)-driven region to a region where the TW is intermittently halted or ‘stuttered’. This approach causes the ion packets spanning a number of TW-created traveling traps (TT) to be redistributed into fewer TT, resulting in spatial compression. The degree of spatial compression is controllablemore » and determined by the ratio of stationary time of the TW in the second region to its moving time. This compression ratio ion mobility programming (CRIMP) approach has been implemented using Structures for Lossless Ion Manipulations (SLIM) in conjunction with MS. CRIMP with the SLIM-MS platform is shown to provide increased peak intensities, reduced peak widths, and improved S/N ratios with MS detection. CRIMP also provides a foundation for extremely long path length and multi-pass IM separations in SLIM providing greatly enhanced IM resolution by reducing the detrimental effects of diffusional peak broadening due to increasing peak widths.« less

Electrospun-sodiumtetrafluoroborate-polyethylene oxide membranes for solvent-free sodium ion transport in solid state sodium ion batteries

NASA Astrophysics Data System (ADS)

Freitag, K. M.; Walke, P.; Nilges, T.; Kirchhain, H.; Spranger, R. J.; van Wüllen, L.

2018-02-01

Electrospinning is used to fabricate sodium ion conducting fiber membranes composed of polyethylene oxide (PEO), sodium tetrafluoroborate (NaBF4), and succinonitrile (SN) as plasticizer. As compared to conventionally prepared lithium electrolyte membranes with identical composition (PEO:SN:LiBF4), those membranes exhibit conductivities up to 10-4 S cm-1 at 328 K (activation energy ∼36 kJ mol-1, 36:8:1 membrane), which favors such systems as a solid-state electrolyte alternative for batteries. The conduction mechanism is evaluated and the ion mobility are examined. We identified the segment mobility of the polyethylene oxide as the main driving force for the enhanced ion mobility in the membranes. The introduction of SN has only a minor influence on the conductivity and segment mobility at room temperature, but extents the anion and cation mobility to temperatures below ambient. For the 36:8:1 (PEO:SN:NaBF4) membrane we found the highest ion mobility of all membranes under investigation. A comparison of the present sodium membranes with lithium systems of the same composition shows that the overall performance of the sodium systems is comparable. Taking plasticizer-free sodium membranes into account they perform even better than the lithium containing counterparts, and plasticizer-modified membranes show only half an order of magnitude lower conductivities than comparable lithium ones.

Evaluation of Ion Mobility-Mass Spectrometry for Comparative Analysis of Monoclonal Antibodies

NASA Astrophysics Data System (ADS)

Ferguson, Carly N.; Gucinski-Ruth, Ashley C.

2016-05-01

Analytical techniques capable of detecting changes in structure are necessary to monitor the quality of monoclonal antibody drug products. Ion mobility mass spectrometry offers an advanced mode of characterization of protein higher order structure. In this work, we evaluated the reproducibility of ion mobility mass spectrometry measurements and mobiligrams, as well as the suitability of this approach to differentiate between and/or characterize different monoclonal antibody drug products. Four mobiligram-derived metrics were identified to be reproducible across a multi-day window of analysis. These metrics were further applied to comparative studies of monoclonal antibody drug products representing different IgG subclasses, manufacturers, and lots. These comparisons resulted in some differences, based on the four metrics derived from ion mobility mass spectrometry mobiligrams. The use of collision-induced unfolding resulted in more observed differences. Use of summed charge state datasets and the analysis of metrics beyond drift time allowed for a more comprehensive comparative study between different monoclonal antibody drug products. Ion mobility mass spectrometry enabled detection of differences between monoclonal antibodies with the same target protein but different production techniques, as well as products with different targets. These differences were not always detectable by traditional collision cross section studies. Ion mobility mass spectrometry, and the added separation capability of collision-induced unfolding, was highly reproducible and remains a promising technique for advanced analytical characterization of protein therapeutics.

Comparison of pulse glow discharge-ion mobility spectrometry and liquid chromatography with tandem mass spectrometry based on multiplug filtration cleanup for the analysis of tricaine mesylate residues in fish and water.

PubMed

Zou, Nan; Chen, Ronghua; Qin, Yuhong; Song, Shuangyu; Tang, Xinglin; Pan, Canping

2016-09-01

Analytical methods based on multiplug filtration cleanup coupled with pulse glow discharge-ion mobility spectrometry and liquid chromatography tandem mass spectrometry were developed for the analysis of tricaine mesylate residue in fish and fish-raising water samples. A silica fiber holder and an appropriate new interface were designed to make the direct introduction of the fiber into the pulse glow discharge-ion mobility spectrometry introduction mechanism. The multiplug filtration cleanup method with adsorption mixtures was optimized for the determination of tricaine mesylate in fish samples. Good linear relationships were obtained by the two methods. For fish samples, limits of detection were 6 and 0.6 μg/kg by ion mobility spectrometry and liquid chromatography with tandem mass spectrometry, respectively. The matrix effect of the established liquid chromatography tandem mass spectrometry method was negligible for fish samples but that of the ion mobility spectrometry method was not. The two methods were compared. The ion mobility spectrometry system could be used a rapid screening tool on site with the advantage of rapidity, simplicity, and portability, and the liquid chromatography tandem mass spectrometry system could be used for validation in laboratory conditions with the advantage of lower limit of detection, stability, and precision. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new mobile phone-based ECG monitoring system.

PubMed

Iwamoto, Junichi; Yonezawa, Yoshiharu; Ogawa, Hiromichi Maki Hidekuni; Ninomiya, Ishio; Sada, Kouji; Hamada, Shingo; Hahn, Allen W; Caldwell, W Morton

2007-01-01

We have developed a system for monitoring a patient's electrocardiogram (ECG) and movement during daily activities. The complete system is mounted on chest electrodes and continuously samples the ECG and three axis accelerations. When the patient feels a heart discomfort, he or she pushes the data transmission switch on the recording system and the system sends the recorded ECG waveforms and three axis accelerations of the two prior minutes, and for two minutes after the switch is pressed. The data goes directly to a hospital server computer via a 2.4 GHz low power mobile phone. These data are stored on a server computer and downloaded to the physician's Java mobile phone. The physician can display the data on the phone's liquid crystal display.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Tsung-Chi; Ibrahim, Yehia M.; Webb, Ian K.

The integration of ion mobility spectrometry (IMS) with mass spectrometry (MS) and the ability to trap ions in IMS-MS measurements is of great importance for performing reactions, accumulating ions, and increasing analytical measurement sensitivity. The development of Structures for Lossless Ion Manipulations (SLIM) offers the potential for ion manipulations in a more reliable and cost-effective manner, while opening opportunities for much more complex sequences of manipulations. Here, we demonstrate an ion separation and trapping module and a method based upon SLIM that consists of a linear mobility ion drift region, a switch/tee and a trapping region that allows the isolationmore » and accumulation of mobility-separated species. The operation and optimization of the SLIM switch/tee and trap are described and demonstrated for the enrichment of the low abundance ions. Lastly, we observed a linear increase in ion intensity with the number of trapping/accumulation events using the SLIM trap, illustrating its potential for enhancing the sensitivity of low abundance or targeted species.« less

Size, weight and position: ion mobility spectrometry and imaging MS combined.

PubMed

Kiss, András; Heeren, Ron M A

2011-03-01

Size, weight and position are three of the most important parameters that describe a molecule in a biological system. Ion mobility spectrometry is capable of separating molecules on the basis of their size or shape, whereas imaging mass spectrometry is an effective tool to measure the molecular weight and spatial distribution of molecules. Recent developments in both fields enabled the combination of the two technologies. As a result, ion-mobility-based imaging mass spectrometry is gaining more and more popularity as a (bio-)analytical tool enabling the determination of the size, weight and position of several molecules simultaneously on biological surfaces. This paper reviews the evolution of ion-mobility-based imaging mass spectrometry and provides examples of its application in analytical studies of biological surfaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Yingying; Triscari, Joseph M.; Tseng, George C.

Data mining was performed on 28 330 unique peptide tandem mass spectra for which sequences were assigned with high confidence. By dividing the spectra into different sets based on structural features and charge states of the corresponding peptides, chemical interactions involved in promoting specific cleavage patterns in gas-phase peptides were characterized. Pairwise fragmentation maps describing cleavages at all Xxx-Zzz residue combinations for b and y ions reveal that the difference in basicity between Arg and Lys results in different dissociation patterns for singly charged Arg- and Lys-ending tryptic peptides. While one dominant protonation form (proton localized) exists for Arg-ending peptides,more » a heterogeneous population of different protonated forms or more facile interconversion of protonated forms (proton partially mobile) exists for Lys-ending peptides. Cleavage C-terminal to acidic residues dominates spectra from peptides that have a localized proton and cleavage N-terminal to Pro dominates those that have a mobile or partially mobile proton. When Pro is absent from peptides that have a mobile or partially mobile proton, cleavage at each peptide bond becomes much more prominent. Whether the above patterns can be found in b ions, y ions, or both depends on the location of the proton holder(s). Enhanced cleavages C-terminal to branched aliphatic residues (Ile, Val, Leu) are observed in both b and y ions from peptides that have a mobile proton, as well as in y ions from peptides that have a partially mobile proton; enhanced cleavages N-terminal to these residues are observed in b ions from peptides that have a partially mobile proton. Statistical tools have been designed to visualize the fragmentation maps and measure the similarity between them. The pairwise cleavage patterns observed expand our knowledge of peptide gas-phase fragmentation behaviors and should be useful in algorithm development that employs improved models to predict fragment ion intensities.« less

MALDI-MS/MS with Traveling Wave Ion Mobility for the Structural Analysis of N-Linked Glycans

NASA Astrophysics Data System (ADS)

Harvey, David J.; Scarff, Charlotte A.; Crispin, Max; Scanlan, Christopher N.; Bonomelli, Camille; Scrivens, James H.

2012-11-01

The preference for singly charged ion formation by MALDI makes it a better choice than electrospray ionization for profiling mixtures of N-glycans. For structural analysis, fragmentation of negative ions often yields more informative spectra than fragmentation of positive ones but such ions are more difficult to produce from neutral glycans under MALDI conditions. This work investigates conditions for the formation of both positive and negative ions by MALDI from N-linked glycans released from glycoproteins and their subsequent MS/MS and ion mobility behaviour. 2,4,6-Trihydroxyacetophenone (THAP) doped with ammonium nitrate was found to give optimal ion yields in negative ion mode. Ammonium chloride or phosphate also yielded prominent adducts but anionic carbohydrates such as sulfated N-glycans tended to ionize preferentially. Carbohydrates adducted with all three adducts (phosphate, chloride, and nitrate) produced good negative ion CID spectra but those adducted with iodide and sulfate did not yield fragment ions although they gave stronger signals. Fragmentation paralleled that seen following electrospray ionization providing superior spectra than could be obtained by PSD on MALDI-TOF instruments or with ion traps. In addition, ion mobility drift times of the adducted glycans and the ability of this technique to separate isomers also mirrored those obtained following ESI sample introduction. Ion mobility also allowed profiles to be obtained from samples whose MALDI spectra showed no evidence of such ions allowing the technique to be used in conditions where sample amounts were limiting. The method was applied to N-glycans released from the recombinant human immunodeficiency virus glycoprotein, gp120.

The influence of ion content on mobility and ion aggregation in PEO-based single-ion conductors

NASA Astrophysics Data System (ADS)

Caldwell, David; Maranas, Janna

2013-03-01

PEO-based ionomers reduce concentration polarization in solid polymer electrolytes by binding the anion to the polymer backbone. Ionomers have significant ion aggregation compared to PEO/salt systems, and the influence of these aggregates is unclear. When ion transport is coupled to the segmental dynamics of the polymer, aggregation will always reduce ion motion and conductivity. However, the conductivity of PEO ionomers is not sensitive to the degree of aggregation. We present results of molecular dynamics simulations where ion content is systematically varied. We consider the influence of ion content on ion aggregation, polymer mobility and cation motion.

Determination of N-linked glycosylation in viral glycoproteins by negative ion mass spectrometry and ion mobility

PubMed Central

Bitto, David; Harvey, David J.; Halldorsson, Steinar; Doores, Katie J.; Pritchard, Laura K.; Huiskonen, Juha T.; Bowden, Thomas A.; Crispin, Max

2016-01-01

Summary Glycan analysis of virion-derived glycoproteins is challenging due to the difficulties in glycoprotein isolation and low sample abundance. Here, we describe how ion mobility mass spectrometry can be used to obtain spectra from virion samples. We also describe how negative ion fragmentation of glycans can be used to probe structural features of virion glycans. PMID:26169737

Application of Ni-63 photo and corona discharge ionization for the analysis of chemical warfare agents and toxic wastes

NASA Technical Reports Server (NTRS)

Stach, J.; Adler, J.; Brodacki, M.; Doring, H.-R.

1995-01-01

Over the past decade, advances in instrumental design and refinements in the understanding of ion molecule reactions at atmospheric pressure enabled the application of Ion Mobility Spectrometry (IMS) as a simple inexpensive and sensitive analytical method for the detection of organic trace compounds. Positive and negative gas-phase ions for ion mobility spectrometry have been produced by a variety of methods, including photo-ionization, laser multi photon ionization, surface ionization, corona discharge ionization. The most common ion source used in ion mobility spectrometry is a radioactive Ni-63 foil which is favored due to simplicity, stability, convenience, and high selectivity. If reactant ions like (H2O(n)H)(+) or (H2O(n)O2)(-) dominate in the reaction region, nearly all kinds of compounds with a given proton or electron affinity; are ionized. However, the radioactivity of the Ni-63 foil is one disadvantage of this ion source that stimulates the development and application of other ionization techniques. In this paper, we report analyses of old chemical warfare agents and toxic wastes using Bruker RAID ion mobility spectrometers. Due to the modular construction of the measuring cell, the spectrometers can be equipped with different ion sources. The combined use of Ni-63, photo- and corona discharge ionization allows the identification of different classes of chemical compounds and yields in most cases comparable results.

Effect of Mobile Phone Usage on Nickel Ions Release and pH of Saliva in Patients Undergoing Fixed Orthodontic Treatment.

PubMed

Nanjannawar, Lalita Girish; Girme, Tejashree Suresh; Agrawal, Jiwanasha Manish; Agrawal, Manish Suresh; Fulari, Sangamesh Gurunath; Shetti, Shraddha Subhash; Kagi, Vishwal Ajith

2017-09-01

Hand held mobile phones are presently the most popular means of communication worldwide and have transformed our lives in many aspects. The widespread use of such devices have resulted in growing concerns regarding harmful effects of radiations emitted by them. This study was designed to evaluate the effects of mobile phone usage on nickel ion release as well as pH of saliva in patients with fixed orthodontic appliances. To assess the level of nickel ions in saliva and pH of saliva in mobile phone users undergoing fixed orthodontic treatment using inductively coupled plasma atomic emission spectrometry. A total of 42 healthy patients with fixed orthodontic appliance in mouth for a duration of six to nine months were selected for the study. They were divided into experimental group (n=21) consisting of mobile phone users and control group (n=21) of non mobile phone users. Saliva samples were collected from both the groups and nickel ion levels were measured using inductively coupled plasma-mass spectroscopy. The pH values were also assessed for both groups using pH meter. Unpaired t-test was used for the data analysis. Statistical analysis revealed that though the pH levels were reduced and the nickel ion levels were higher in the experimental group compared to the control group, the results were non significant. Mobile phone usage may affect the pH of saliva and result in increased release of nickel ions in saliva of patients with fixed orthodontic appliances in the oral cavity.

Stability of proton-bound clusters of alkyl alcohols, aldehydes and ketones in Ion Mobility Spectrometry.

PubMed

Jurado-Campos, Natividad; Garrido-Delgado, Rocío; Martínez-Haya, Bruno; Eiceman, Gary A; Arce, Lourdes

2018-08-01

Significant substances in emerging applications of ion mobility spectrometry such as breath analysis for clinical diagnostics and headspace analysis for food purity include low molar mass alcohols, ketones, aldehydes and esters which produce mobility spectra containing protonated monomers and proton-bound dimers. Spectra for all n- alcohols, aldehydes and ketones from carbon number three to eight exhibited protonated monomers and proton-bound dimers with ion drift times of 6.5-13.3 ms at ambient pressure and from 35° to 80 °C in nitrogen. Only n-alcohols from 1-pentanol to 1-octanol produced proton-bound trimers which were sufficiently stable to be observed at these temperatures and drift times of 12.8-16.3 ms. Polar functional groups were protected in compact structures in ab initio models for proton-bound dimers of alcohols, ketones and aldehydes. Only alcohols formed a V-shaped arrangement for proton-bound trimers strengthening ion stability and lifetime. In contrast, models for proton-bound trimers of aldehydes and ketones showed association of the third neutral through weak, non-specific, long-range interactions consistent with ion dissociation in the ion mobility drift tube before arriving at the detector. Collision cross sections derived from reduced mobility coefficients in nitrogen gas atmosphere support the predicted ion structures and approximate degrees of hydration. Copyright © 2018 Elsevier B.V. All rights reserved.

Complex fluids with mobile charge-regulating macro-ions

NASA Astrophysics Data System (ADS)

Markovich, Tomer; Andelman, David; Podgornik, Rudi

2017-10-01

We generalize the concept of charge regulation of ionic solutions, and apply it to complex fluids with mobile macro-ions having internal non-electrostatic degrees of freedom. The suggested framework provides a convenient tool for investigating systems where mobile macro-ions can self-regulate their charge (e.g., proteins). We show that even within a simplified charge-regulation model, the charge dissociation equilibrium results in different and notable properties. Consequences of the charge regulation include a positional dependence of the effective charge of the macro-ions, a non-monotonic dependence of the effective Debye screening length on the concentration of the monovalent salt, a modification of the electric double-layer structure, and buffering by the macro-ions of the background electrolyte.

Balloon-borne Langmuir probe measurement of stratospheric ions in low latitudes

NASA Astrophysics Data System (ADS)

Banerjee, A.; Somayajulu, Y. V.; Subrahmanyam, P.

1984-12-01

A balloon carrying a Langmuir probe payload for measuring the positive and negative ion densities in the stratosphere was flown around midnight IST on Mar. 23, 1982 from the National Balloon Facility at Hyderabad, a low latitude station. The Langmuir probe with a guard ring arrangement is given a symmetrical probe voltage of triangular waveform with amplitude + or - 4.2 V and with a repetition frequency of 0.28 Hz. The balloon reached a ceiling altitude of 33 km and data were taken from 15 km up to the ceiling altitude. The altitude profiles of the ion density show a peak around 18 km with densities decreasing with altitude. The results are discussed in terms of cosmic ray production and ion chemistry. The structures in the positive ion density profile are interpreted in terms of the presence of aerosol layers.

49 CFR 175.10 - Exceptions for passengers, crewmembers, and air operators.

Code of Federal Regulations, 2012 CFR

2012-10-01

... words “Battery, wet, with wheelchair.” (17) A lithium ion battery-powered wheelchair or other mobility aid as follows: (i) A wheelchair or other mobility aid equipped with a lithium ion battery, when carried as checked baggage, provided— (A) The lithium ion battery must be of a type that successfully...

49 CFR 175.10 - Exceptions for passengers, crewmembers, and air operators.

Code of Federal Regulations, 2011 CFR

2011-10-01

... words “Battery, wet, with wheelchair.” (17) A lithium ion battery-powered wheelchair or other mobility aid as follows: (i) A wheelchair or other mobility aid equipped with a lithium ion battery, when carried as checked baggage, provided— (A) The lithium ion battery must be of a type that successfully...

Desorption electrospray ionization (DESI) with atmospheric pressure ion mobility spectrometry for drug detection.

PubMed

Roscioli, Kristyn M; Tufariello, Jessica A; Zhang, Xing; Li, Shelly X; Goetz, Gilles H; Cheng, Guilong; Siems, William F; Hill, Herbert H

2014-04-07

Desorption electrospray ionization (DESI) was coupled to an ambient pressure drift tube ion mobility time-of-flight mass spectrometer (IM-TOFMS) for the direct analysis of active ingredients in pharmaceutical samples. The DESI source was also coupled with a standalone IMS demonstrating potential of portable and inexpensive drug-quality testing platforms. The DESI-IMS required no sample pretreatment as ions were generated directly from tablets and cream formulations. The analysis of a range of over-the-counter and prescription tablet formations was demonstrated for amphetamine (methylphenidate), antidepressant (venlafaxine), barbiturate (Barbituric acid), depressant (alprazolam), narcotic (3-methylmorphine) and sympatholytic (propranolol) drugs. Active ingredients from soft and liquid formulations, such as Icy Hot cream (methyl salicylate) and Nyquil cold medicine (acetaminophen, dextromethorphan, doxylamine) were also detected. Increased sensitivity for selective drug responses was demonstrated through the formation of sodiated adduct ions by introducing small quantities of NaCl into the DESI solvent. Of the drugs and pharmaceuticals tested in this study, 68% (22 total samples) provided a clear ion mobility response at characteristic mobilities either as (M + H)(+), (M - H)(-), or (M + Na)(+) ions.

Trying to detect gas-phase ions? Understanding Ion Mobility Spectrometry

PubMed Central

Cumeras, R.; Figueras, E.; Davis, C.E.; Baumbach, J.I.; Gràcia, I.

2014-01-01

Ion Mobility Spectrometry (IMS) is a widely used and ‘well-known’ technique of ion separation in gaseous phase based on the differences of ion mobilities under an electric field. This technique has received increased interest over the last several decades as evidenced by the pace and advances of new IMS devices available. In this review we explore the hyphenated techniques that are used with IMS, especially mass spectrometry as identification approach and multi-capillary column as pre-separation approach. Also, we will pay special attention to the key figures of merit of the ion mobility spectrum and how data is treated, and the influences of the experimental parameters in both a conventional drift time IMS (DTIMS) and a miniaturized IMS also known as high Field Asymmetric IMS (FAIMS) in the planar configuration. The current review article is preceded by a companion review article which details the current instrumentation and to the sections that configures both a conventional DTIMS and FAIMS devices. Those reviews will give the reader an insightful view of the main characteristics and aspects of the IMS technique. PMID:25465248

Pb2+ ions mobility perturbation by iron particles during electrokinetic remediation of contaminated soil.

PubMed

Zulfiqar, Waqas; Iqbal, Muhammad Asad; Butt, Mehwish Khalid

2017-02-01

Electrokinetic (EK) remediation is one of the most useful approaches for de-contamination of soils. However, it is unclear that how and when the electrokinetic remediation gives advantages over other remediation techniques in soil. This study was designed to find the influence of Fe 2+ particles on the mobility of Pb 2+ ions, during electrokinetic remediation, in soil contaminated purposely by lead nitrate Pb(NO 3 ) 2 . Two types of electrokinetic experiments were performed, by using iron and graphite electrodes. The Fe 2+ ions from the iron electrodes, produced due to acidic environment in anode compartment, affected the mobility of lead particles by precipitating as Fe(OH) 2 . Fe 2+ ions enhance the adsorption of lead ions in soil. The results show Fe 2+ ions of lower ionic conductivity decreased mobility of other particles in soil. Electrokinetic remediation for up to 120 h with iron electrodes is shown to be less effective for removal of lead. In contrast, graphite electrodes were 15 times more effective in lead removal from soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Initial Thrust Measurements of Marshall's Ion-ioN Thruster

NASA Technical Reports Server (NTRS)

Schloeder, Natalie R.; Scogin, Tyler; Liu, Thomas M.; Walker, Mitchell L. R.; Polzin, Kurt A.; Dankanich, John W.; Aanesland, Ane

2015-01-01

Electronegative ion thrusters are a variation of tradition gridded ion thruster technology differentiated by the production and acceleration of both positive and negative ions. Benefits of electronegative ion thrusters include the elimination of lifetime-limiting cathodes from the thruster architecture and the ability to generate appreciable thrust from both charge species. Following the continued development of electronegative ion thruster technology as exhibited by the PEGASES (Plasma Propulsion with Electronegative GASES) thruster, direct thrust measurements are required to push interest in electronegative ion thruster technology forward. For this work, direct thrust measurements of the MINT (Marshall's Ion-ioN Thruster) will be taken on a hanging pendulum thrust stand for propellant mixtures of Sulfur Hexafluoride and Argon at volumetric flow rates of 5-25 sccm at radio frequency power levels of 100-600 watts at a radio frequency of 13.56 MHz. Acceleration grid operation is operated using a square waveform bias of +/-300 volts at a frequency of 25 kHz.

A new Ion Mobility Spectrometer

NASA Astrophysics Data System (ADS)

Butler, M. A.

1998-03-01

A new ion mobility spectrometer (IMS) concept has been demonstrated that traps ions in a potential well and then moves the well down a tube to a detector. The charge remaining in the well is measured as a function of well velocity or electric field that the ion experiences; thus separating the ions by mobility. The potential wave is generated and propagated down the tube by a series of ring electrodes along the tube under real-time computer control via an array of DACs. The operating characteristics of this device have been explored including the effects of ion "lifetime," well shape, and well velocity. The ion "lifetime" results from a radial field at the bottom of the potential well that pushes the ions toward the tube wall. This work was supported by the United States Department of Energy under Contract DE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy.

Collision Cross Sections and Ion Mobility Separation of Fragment Ions from Complex N-Glycans.

PubMed

Harvey, David J; Watanabe, Yasunori; Allen, Joel D; Rudd, Pauline; Pagel, Kevin; Crispin, Max; Struwe, Weston B

2018-06-01

Ion mobility mass spectrometry (IM-MS) holds great potential for structural glycobiology, in particular in its ability to resolve glycan isomers. Generally, IM-MS has largely been applied to intact glycoconjugate ions with reports focusing on the separation of different adduct types. Here, we explore IM separation and report the collision cross section (CCS) of complex type N-glycans and their fragments in negative ion mode following collision-induced dissociation (CID). CCSs of isomeric fragment ions were found, in some cases, to reveal structural details that were not present in CID spectra themselves. Many fragment ions were confirmed as possessing multiple structure, details of which could be obtained by comparing their drift time profiles to different glycans. By using fragmentation both before and after mobility separation, information was gathered on the fragmentation pathways producing some of the ions. These results help demonstrate the utility of IM and will contribute to the growing use of IM-MS for glycomics. Graphical Abstract ᅟ.

Collision Cross Sections and Ion Mobility Separation of Fragment Ions from Complex N-Glycans

NASA Astrophysics Data System (ADS)

Harvey, David J.; Watanabe, Yasunori; Allen, Joel D.; Rudd, Pauline; Pagel, Kevin; Crispin, Max; Struwe, Weston B.

2018-04-01

Ion mobility mass spectrometry (IM-MS) holds great potential for structural glycobiology, in particular in its ability to resolve glycan isomers. Generally, IM-MS has largely been applied to intact glycoconjugate ions with reports focusing on the separation of different adduct types. Here, we explore IM separation and report the collision cross section (CCS) of complex type N-glycans and their fragments in negative ion mode following collision-induced dissociation (CID). CCSs of isomeric fragment ions were found, in some cases, to reveal structural details that were not present in CID spectra themselves. Many fragment ions were confirmed as possessing multiple structure, details of which could be obtained by comparing their drift time profiles to different glycans. By using fragmentation both before and after mobility separation, information was gathered on the fragmentation pathways producing some of the ions. These results help demonstrate the utility of IM and will contribute to the growing use of IM-MS for glycomics. [Figure not available: see fulltext.

Continuous scanning of the mobility and size distribution of charged clusters and nanometer particles in atmospheric air and the Balanced Scanning Mobility Analyzer BSMA

NASA Astrophysics Data System (ADS)

Tammet, H.

2006-12-01

Measuring of charged nanometer particles in atmospheric air is a routine task in research on atmospheric electricity, where these particles are called the atmospheric ions. An aspiration condenser is the most popular instrument for measuring atmospheric ions. Continuous scanning of a mobility distribution is possible when the aspiration condenser is connected as an arm of a balanced bridge. Transfer function of an aspiration condenser is calculated according to the measurements of geometric dimensions, air flow rate, driving voltage, and electric current. The most complicated phase of the calibration is the estimation of the inlet loss of ions due to the Brownian deposition. The available models of ion deposition on the protective inlet screen and the inlet control electrofilter have the uncertainty of about 20%. To keep the uncertainty of measurements low the adsorption should not exceed a few tens of percent. The online conversion of the mobility distribution to the size distribution and a correct reduction of inlet losses are possible when air temperature and pressure are measured simultaneously with the mobility distribution. Two instruments called the Balanced Scanning Mobility Analyzers (BSMA) were manufactured and tested in routine atmospheric measurements. The concentration of atmospheric ions of the size of about a few nanometers is very low and a high air flow rate is required to collect enough of ion current. The air flow of 52 l/s exceeds the air flow in usual aerosol instruments by 2-3 orders of magnitude. The high flow rate reduces the time of ion passage to 60 ms and the heating of air in an analyzer to 0.2 K, which suppresses a possible transformation of ions inside the instrument. The mobility range of the BSMA of 0.032-3.2 cm 2 V - 1 s - 1 is logarithmically uniformly divided into 16 fractions. The size distribution is presented by 12 fractions in the diameter range of 0.4-7.5 nm. The measurement noise of a fraction concentration is typically about 5 cm - 3 and the time resolution is about 10 min when measuring simultaneously both positive and negative ions in atmospheric air.

Determination and identification of malathion, ethion and dichlorovos using ion mobility spectrometry.

PubMed

Jafari, Mohammad T

2006-07-15

Positive ion mobility spectra of different organophosphorus pesticides such as malathion (s-(1,2-dicarb-ethoxyethyl) o,o-dimethyl dithiophosphate), ethion (o,o,o',o'-tetraethyl s,s'-methylene bis(phosphorodithioate)) and dichlorovos (2,2-dichlorovinyl dimethyl phosphate) have been studied in air at ambient pressure using ion mobility spectrometry method with (63)Ni ionization source. The limits of quantification (LOQs) were 1.0 x 10(-9), 1.0 x 10(-9) and 5.0 x 10(-9)g for malathion, ethion and dichlorovos, respectively. The working range of these compounds was about three orders of magnitude and the relative standard deviation (R.S.D.) of repeatability at the 5 microg ml(-1) level were all below 15%. Furthermore, in this study, the influences of IMS cell temperature on the ion mobility spectra of these compounds were investigated.

Solvent-mediated nonelectrostatic ion-ion interactions predicting anomalies in electrophoresis.

PubMed

Goswami, Prakash; Dhar, Jayabrata; Ghosh, Uddipta; Chakraborty, Suman

2017-03-01

We study the effects of solvent-mediated nonelectrostatic ion-ion interactions on electrophoretic mobility of a charged spherical particle. To this end, we consider the case of low surface electrostatic potential resulting in the linearization of the governing equations, which enables us to deduce a closed-form analytical solution to the electrophoretic mobility. We subsequently compare our results to the standard model using Henry's approach and report the changes brought about by the nonelectrostatic potential. The classical approach to determine the electrophoretic mobility underpredicts the particle velocity when compared with experiments. We show that this issue can be resolved by taking into account nonelectrostatic interactions. Our analysis further reveals the phenomenon of electrophoretic mobility reversal that has been experimentally observed in numerous previous studies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High voltage series resonant inverter ion engine screen supply. [SCR series resonant inverter for space applications

NASA Technical Reports Server (NTRS)

Biess, J. J.; Inouye, L. Y.; Shank, J. H.

1974-01-01

A high-voltage, high-power LC series resonant inverter using SCRs has been developed for an Ion Engine Power Processor. The inverter operates within 200-400Vdc with a maximum output power of 2.5kW. The inverter control logic, the screen supply electrical and mechanical characteristics, the efficiency and losses in power components, regulation on the dual feedback principle, the SCR waveforms and the component weight are analyzed. Efficiency of 90.5% and weight density of 4.1kg/kW are obtained.

Wireless Content Repurposing Architecture for DC Command and Control

DTIC Science & Technology

2003-09-01

was a natural choice as our primary mobile device for the DC investigators. 28 The Clie uses a Lithium Ion battery , which is the longest...projects the screen of the PDA on a head-mounted display maybe used. Battery life of PDAs is relatively short. This means many Lithium Ion...Mobile Devices Mobile devices such as PDAs, mobile phones, and Smartphones have become tightly interwoven as an important part of everyday lives

Identity confirmation of drugs and explosives in ion mobility spectrometry using a secondary drift gas.

PubMed

Kanu, Abu B; Hill, Herbert H

2007-10-15

This work demonstrated the potential of using a secondary drift gas of differing polarizability from the primary drift gas for confirmation of a positive response for drugs or explosives by ion mobility spectrometry (IMS). The gas phase mobilities of response ions for selected drugs and explosives were measured in four drift gases. The drift gases chosen for this study were air, nitrogen, carbon dioxide and nitrous oxide providing a range of polarizability and molecular weights. Four other drift gases (helium, neon, argon and sulfur hexafluoride) were also investigated but design limitations of the commercial instrument prevented their use for this application. When ion mobility was plotted against drift gas polarizability, the resulting slopes were often unique for individual ions, indicating that selectivity factors between any two analytes varied with the choice of drift gas. In some cases, drugs like THC and heroin, which are unresolved in air or nitrogen, were well resolved in carbon dioxide or nitrous oxide.

Mechanisms Underlying Ionic Mobilities in Nanocomposite Polymer Electrolytes

NASA Astrophysics Data System (ADS)

Ganesan, Venkat; Hanson, Benjamin; Pryamitsyn, Victor

2014-03-01

Recently, a number of experiments have demonstrated that addition of ceramics with nanoscale dimensions can lead to substantial improvements in the low temperature conductivity of the polymeric materials. However, the origin of such behaviors, and more generally, the manner by which nanoscale fillers impact the ion mobilities remain unresolved. In this communication, we report the results of atomistic molecular dynamics simulations which used multibody polarizable force-fields to study lithium ion diffusivities in an amorphous poly(ethylene-oxide) (PEO) melt containing well-dispersed TiO2 nanoparticles. We observed that the lithium ion diffusivities decrease with increased particle loading. Our analysis suggests that the ion mobilities are correlated to the nanoparticle-induced changes in the polymer segmental dynamics. Interestingly, the changes in polymer segmental dynamics were seen to be related to the nanoparticle's influence on the polymer conformational features. Overall, our results indicate that addition of nanoparticle fillers modify polymer conformations and the polymer segmental dynamics, and thereby influence the ion mobilities of polymer electrolytes.

Ion mobility spectrometry-mass spectrometry examination of the structures, stabilities, and extents of hydration of dimethylamine-sulfuric acid clusters.

PubMed

Thomas, Jikku M; He, Siqin; Larriba-Andaluz, Carlos; DePalma, Joseph W; Johnston, Murray V; Hogan, Christopher J

2016-08-17

We applied an atmospheric pressure differential mobility analyzer (DMA) coupled to a time-of-flight mass spectrometer to examine the stability, mass-mobility relationship, and extent of hydration of dimethylamine-sulfuric acid cluster ions, which are of relevance to nucleation in ambient air. Cluster ions were generated by electrospray ionization and were of the form: [H((CH3)2NH)x(H2SO4)y](+) and [(HSO4)((CH3)2NH)x(H2SO4)y](-), where 4 ≤ x ≤ 8, and 5 ≤ y ≤ 12. Under dry conditions, we find that positively charged cluster ions dissociated via loss of both multiple dimethylamine and sulfuric acid molecules after mobility analysis but prior to mass analysis, and few parent ions were detected in the mass spectrometer. Dissociation also occurred for negative ions, but to a lesser extent than for positive ions for the same mass spectrometer inlet conditions. Under humidified conditions (relative humidities up to 30% in the DMA), positively charged cluster ion dissociation in the mass spectrometer inlet was mitigated and occurred primarily by H2SO4 loss from ions containing excess acid molecules. DMA measurements were used to infer collision cross sections (CCSs) for all identifiable cluster ions. Stokes-Millikan equation and diffuse/inelastic gas molecule scattering predicted CCSs overestimate measured CCSs by more than 15%, while elastic-specular collision model predictions are in good agreement with measurements. Finally, cluster ion hydration was examined by monitoring changes in CCSs with increasing relative humidity. All examined cluster ions showed a modest amount of water molecule adsorption, with percentage increases in CCS smaller than 10%. The extent of hydration correlates directly with cluster ion acidity for positive ions.

Contribution of Li-ion batteries to the environmental impact of electric vehicles.

PubMed

Notter, Dominic A; Gauch, Marcel; Widmer, Rolf; Wäger, Patrick; Stamp, Anna; Zah, Rainer; Althaus, Hans-Jörg

2010-09-01

Battery-powered electric cars (BEVs) play a key role in future mobility scenarios. However, little is known about the environmental impacts of the production, use and disposal of the lithium ion (Li-ion) battery. This makes it difficult to compare the environmental impacts of BEVs with those of internal combustion engine cars (ICEVs). Consequently, a detailed lifecycle inventory of a Li-ion battery and a rough LCA of BEV based mobility were compiled. The study shows that the environmental burdens of mobility are dominated by the operation phase regardless of whether a gasoline-fueled ICEV or a European electricity fueled BEV is used. The share of the total environmental impact of E-mobility caused by the battery (measured in Ecoindicator 99 points) is 15%. The impact caused by the extraction of lithium for the components of the Li-ion battery is less than 2.3% (Ecoindicator 99 points). The major contributor to the environmental burden caused by the battery is the supply of copper and aluminum for the production of the anode and the cathode, plus the required cables or the battery management system. This study provides a sound basis for more detailed environmental assessments of battery based E-mobility.

Correlating Resolving Power, Resolution, and Collision Cross Section: Unifying Cross-Platform Assessment of Separation Efficiency in Ion Mobility Spectrometry.

PubMed

Dodds, James N; May, Jody C; McLean, John A

2017-11-21

Here we examine the relationship among resolving power (R p ), resolution (R pp ), and collision cross section (CCS) for compounds analyzed in previous ion mobility (IM) experiments representing a wide variety of instrument platforms and IM techniques. Our previous work indicated these three variables effectively describe and predict separation efficiency for drift tube ion mobility spectrometry experiments. In this work, we seek to determine if our previous findings are a general reflection of IM behavior that can be applied to various instrument platforms and mobility techniques. Results suggest IM distributions are well characterized by a Gaussian model and separation efficiency can be predicted on the basis of the empirical difference in the gas-phase CCS and a CCS-based resolving power definition (CCS/ΔCCS). Notably traveling wave (TWIMS) was found to operate at resolutions substantially higher than a single-peak resolving power suggested. When a CCS-based R p definition was utilized, TWIMS was found to operate at a resolving power between 40 and 50, confirming the previous observations by Giles and co-workers. After the separation axis (and corresponding resolving power) is converted to cross section space, it is possible to effectively predict separation behavior for all mobility techniques evaluated (i.e., uniform field, trapped ion mobility, traveling wave, cyclic, and overtone instruments) using the equations described in this work. Finally, we are able to establish for the first time that the current state-of-the-art ion mobility separations benchmark at a CCS-based resolving power of >300 that is sufficient to differentiate analyte ions with CCS differences as small as 0.5%.

Effect of Mobile Phone Usage on Nickel Ions Release and pH of Saliva in Patients Undergoing Fixed Orthodontic Treatment

PubMed Central

Girme, Tejashree Suresh; Agrawal, Jiwanasha Manish; Agrawal, Manish Suresh; Fulari, Sangamesh Gurunath; Shetti, Shraddha Subhash; Kagi, Vishwal Ajith

2017-01-01

Introduction Hand held mobile phones are presently the most popular means of communication worldwide and have transformed our lives in many aspects. The widespread use of such devices have resulted in growing concerns regarding harmful effects of radiations emitted by them. This study was designed to evaluate the effects of mobile phone usage on nickel ion release as well as pH of saliva in patients with fixed orthodontic appliances. Aim To assess the level of nickel ions in saliva and pH of saliva in mobile phone users undergoing fixed orthodontic treatment using inductively coupled plasma atomic emission spectrometry. Materials and Methods A total of 42 healthy patients with fixed orthodontic appliance in mouth for a duration of six to nine months were selected for the study. They were divided into experimental group (n=21) consisting of mobile phone users and control group (n=21) of non mobile phone users. Saliva samples were collected from both the groups and nickel ion levels were measured using inductively coupled plasma-mass spectroscopy. The pH values were also assessed for both groups using pH meter. Unpaired t-test was used for the data analysis. Results Statistical analysis revealed that though the pH levels were reduced and the nickel ion levels were higher in the experimental group compared to the control group, the results were non significant. Conclusion Mobile phone usage may affect the pH of saliva and result in increased release of nickel ions in saliva of patients with fixed orthodontic appliances in the oral cavity. PMID:29207841

Temperature dependent mobility measurements of alkali earth ions in superfluid helium

NASA Astrophysics Data System (ADS)

Putlitz, Gisbert Zu; Baumann, I.; Foerste, M.; Jungmann, K.; Riediger, O.; Tabbert, B.; Wiebe, J.; Zühlke, C.

1998-05-01

Mobility measurements of impurity ions in superfluid helium are reported. Alkali earth ions were produced with a laser sputtering technique and were drawn inside the liquid by an electric field. The experiments were carried out in the temperature region from 1.27 up to 1.66 K. The temperature dependence of the mobility of Be^+-ions (measured here for the first time) differs from that of the other alkali earth ions Mg^+, Ca^+, Sr^+ and Ba^+, but behaves similar to that of He^+ (M. Foerste, H. Günther, O. Riediger, J. Wiebe, G. zu Putlitz, Z. Phys. B) 104, 317 (1997). Theories of Atkins (A. Atkins, Phys. Rev.) 116, 1339 (1959) and Cole (M.W. Cole, R.A. Bachmann Phys. Rev. B) 15, 1388 (1977) predict a different defect structure for He^+ and the alkali earth ions: the helium ion is assumed to form a snowball like structure whereas for the alkali earth ions a bubble structure is assumed. If the temperature dependence is a characteristic feature for the different structures, then it seems likely that the Be^+ ion builds a snowball like structure.

Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques

NASA Technical Reports Server (NTRS)

Borsdorf, H.; Nazarov, E. G.; Eiceman, G. A.

2002-01-01

The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization. c. 2002 American Society for Mass Spectrometry.

Plasma wave interactions with energetic ions near the magnetic equator

NASA Technical Reports Server (NTRS)

Gurnett, D. A.

1975-01-01

An intense band of electromagnetic noise is frequently observed near the magnetic equatorial plane at radial distance from about 2 to 5 Re. Recent wideband wave-form measurements with the IMP-6 and Hawkeye-1 satellites have shown that the equatorial noise consists of a complex superposition of many harmonically spaced lines. Several distinctly different frequency spacings are often evident in the same spectrum. The frequency spacing typically ranges from a few Hz to a few tens of Hz. It is suggested that these waves are interacting with energetic protons, alpha particles, and other heavy ions trapped near the magnetic equator. The possible role these waves play in controlling the distribution of the energetic ions is considered.

IMS - MS Data Extractor

DOE Office of Scientific and Technical Information (OSTI.GOV)

2015-10-20

An automated drift time extraction and computed associated collision cross section software tool for small molecule analysis with ion mobility spectrometry-mass spectrometry (IMS-MS). The software automatically extracts drift times and computes associated collision cross sections for small molecules analyzed using ion mobility spectrometry-mass spectrometry (IMS-MS) based on a target list of expected ions provided by the user.

Experimental ion mobility measurements in Xe-CO2

NASA Astrophysics Data System (ADS)

Cortez, A. F. V.; Santos, M. A. G.; Veenhof, R.; Patra, R. N.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.

2017-06-01

Data on ion mobility is important to improve the performance of large volume gaseous detectors. In the present work the method, experimental setup and results for the ion mobility measurements in Xe-CO2 mixtures are presented. The results for this mixture show the presence of only one peak for all gas ratios of Xe-CO2, low reduced electric fields, E/N, 10-25 Td (2.4-6.1 kV·cm-1·bar-1), low pressures 6-8 Torr (8-10.6 mbar), at room temperature.

Assessment of Dimeric Metal-Glycan Adducts via Isotopic Labeling and Ion Mobility-Mass Spectrometry.

PubMed

Morrison, Kelsey A; Bendiak, Brad K; Clowers, Brian H

2018-05-25

Adduction of multivalent metal ions to glycans has been shown in recent years to produce altered tandem mass spectra with collision-induced dissociation, electron transfer techniques, and photon-based fragmentation approaches. However, these approaches assume the presence of a well-characterized precursor ion population and do not fully account for the possibility of multimeric species for select glycan-metal complexes. With the use of ion mobility separations prior to mass analysis, doubly charged dimers are not necessarily problematic for tandem MS experiments given that monomer and dimer drift times are sufficiently different. However, multistage mass spectrometric experiments performed on glycans adducted to multivalent metals without mobility separation can yield chimeric fragmentation spectra that are essentially a superposition of the fragments from both the monomeric and dimeric adducts. For homodimeric adducts, where the dimer contains two of the same glycan species, this is less of a concern but if heterodimers can form, there exists the potential for erroneous and misleading fragment ions to appear if a heterodimer containing two different isomers is fragmented along with a targeted monomer. We present an assessment of heterodimer formation between a series of six tetrasaccharides, of which three are isomers, adducted with cobalt(II) and a monodeuterated tetrasaccharide. Using ion mobility separations prior to single-stage and tandem mass analysis, the data shown demonstrate that heterodimeric species can indeed form, and that ion mobility separations are highly necessary prior to using tandem techniques on metal-glycan adducts. Graphical Abstract ᅟ.

Determination of ion mobility in EHD flow zone of plasma generator

NASA Astrophysics Data System (ADS)

Sumariyah, Kusminarto, Hermanto, Arief; Nuswantoro, Pekik

2015-12-01

Determination has been carried out for ion mobility in EHD flow zone generated using a pin-concentric multiple ring electrodes and a pin-single ring electrode used as a comparator. The pin needle was made from stainless steel with a tip diameter of 0.18 mm. The concentris multiple ring electrode in form three/two concentric ring electrodes which made of metal material connected to each other. Each ring of three concentric ring electrode has a diameter of 24 mm, 16 mm and 8 mm. And each ring of two concentric ring electrode has a diameter of 24 mm and 16 mm. Single ring electrode has a diameter24 mm. The all ring has same of width and thickness were 2 mm and 3 mm. EHD was generated by using a DC high voltage of 10 kV. Pin functional as an active electrode of corona discharge while the all ring electrodes acted as ions collector and passive electrodes. The experimental results show that the ion current is proportional to V2 according to calculations by Chouelo for hyperbolic-field approach. Ion mobility obtained from the quadratic polynomial fitting of experimental data were current and voltage as well as Choelo formulation. The results showed that the mobility of ions in the EHD flow zones utilizing pin-consentric multiple ring electrode larger than utilizing pin-single ring electrode. Pin-three Consentic ring electrode has the largest of ion mobility

Assessment of Dimeric Metal-Glycan Adducts via Isotopic Labeling and Ion Mobility-Mass Spectrometry

NASA Astrophysics Data System (ADS)

Morrison, Kelsey A.; Bendiak, Brad K.; Clowers, Brian H.

2018-05-01

Adduction of multivalent metal ions to glycans has been shown in recent years to produce altered tandem mass spectra with collision-induced dissociation, electron transfer techniques, and photon-based fragmentation approaches. However, these approaches assume the presence of a well-characterized precursor ion population and do not fully account for the possibility of multimeric species for select glycan-metal complexes. With the use of ion mobility separations prior to mass analysis, doubly charged dimers are not necessarily problematic for tandem MS experiments given that monomer and dimer drift times are sufficiently different. However, multistage mass spectrometric experiments performed on glycans adducted to multivalent metals without mobility separation can yield chimeric fragmentation spectra that are essentially a superposition of the fragments from both the monomeric and dimeric adducts. For homodimeric adducts, where the dimer contains two of the same glycan species, this is less of a concern but if heterodimers can form, there exists the potential for erroneous and misleading fragment ions to appear if a heterodimer containing two different isomers is fragmented along with a targeted monomer. We present an assessment of heterodimer formation between a series of six tetrasaccharides, of which three are isomers, adducted with cobalt(II) and a monodeuterated tetrasaccharide. Using ion mobility separations prior to single-stage and tandem mass analysis, the data shown demonstrate that heterodimeric species can indeed form, and that ion mobility separations are highly necessary prior to using tandem techniques on metal-glycan adducts.

Tone calibration technique: A digital signaling scheme for mobile applications

NASA Technical Reports Server (NTRS)

Davarian, F.

1986-01-01

Residual carrier modulation is conventionally used in a communication link to assist the receiver with signal demodulation and detection. Although suppressed carrier modulation has a slight power advantage over the residual carrier approach in systems enjoying a high level of stability, it lacks sufficient robustness to be used in channels severely contaminated by noise, interference and propagation effects. In mobile links, in particular, the vehicle motion and multipath waveform propagation affect the received carrier in an adverse fashion. A residual carrier scheme that uses a pilot carrier to calibrate a mobile channel against multipath fading anomalies is described. The benefits of this scheme, known as tone calibration technique, are described. A brief study of the system performance in the presence of implementation anomalies is also given.

[Design and Implementation of a Mobile Operating Room Information Management System Based on Electronic Medical Record].

PubMed

Liu, Baozhen; Liu, Zhiguo; Wang, Xianwen

2015-06-01

A mobile operating room information management system with electronic medical record (EMR) is designed to improve work efficiency and to enhance the patient information sharing. In the operating room, this system acquires the information from various medical devices through the Client/Server (C/S) pattern, and automatically generates XML-based EMR. Outside the operating room, this system provides information access service by using the Browser/Server (B/S) pattern. Software test shows that this system can correctly collect medical information from equipment and clearly display the real-time waveform. By achieving surgery records with higher quality and sharing the information among mobile medical units, this system can effectively reduce doctors' workload and promote the information construction of the field hospital.

Extending the Dynamic Range of the Ion Trap by Differential Mobility Filtration

PubMed Central

Hall, Adam B.; Coy, Stephen L.; Kafle, Amol; Glick, James; Nazarov, Erkinjon

2013-01-01

A miniature, planar, differential ion mobility spectrometer (DMS) was interfaced to an LCQ classic ion trap to conduct selective ion filtration prior to mass analysis in order to extend the dynamic range of the trap. Space charge effects are known to limit the functional ion storage capacity of ion trap mass analyzers and this, in turn, can affect the quality of the mass spectral data generated. This problem is further exacerbated in the analysis of mixtures where the indiscriminate introduction of matrix ions results in premature trap saturation with non-targeted species, thereby reducing the number of parent ions that may be used to conduct MS/MS experiments for quantitation or other diagnostic studies. We show that conducting differential mobility-based separations prior to mass analysis allows the isolation of targeted analytes from electrosprayed mixtures preventing the indiscriminate introduction of matrix ions and premature trap saturation with analytically unrelated species. Coupling these two analytical techniques is shown to enhance the detection of a targeted drug metabolite from a biological matrix. In its capacity as a selective ion filter, the DMS can improve the analytical performance of analyzers such as quadrupole (3-D or linear) and ion cyclotron resonance (FT-ICR) ion traps that depend on ion accumulation. PMID:23797861

Ion mobility spectrometer with virtual aperture grid

DOEpatents

Pfeifer, Kent B.; Rumpf, Arthur N.

2010-11-23

An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

Real space mapping of ionic diffusion and electrochemical activity in energy storage and conversion materials

DOEpatents

Kalinin, Sergei V; Balke, Nina; Kumar, Amit; Dudney, Nancy J; Jesse, Stephen

2014-05-06

A method and system for probing mobile ion diffusivity and electrochemical reactivity on a nanometer length scale of a free electrochemically active surface includes a control module that biases the surface of the material. An electrical excitation signal is applied to the material and induces the movement of mobile ions. An SPM probe in contact with the surface of the material detects the displacement of mobile ions at the surface of the material. A detector measures an electromechanical strain response at the surface of the material based on the movement and reactions of the mobile ions. The use of an SPM tip to detect local deformations allows highly reproducible measurements in an ambient environment without visible changes in surface structure. The measurements illustrate effective spatial resolution comparable with defect spacing and well below characteristic grain sizes of the material.

Determination of gas phase protein ion densities via ion mobility analysis with charge reduction.

PubMed

Maisser, Anne; Premnath, Vinay; Ghosh, Abhimanyu; Nguyen, Tuan Anh; Attoui, Michel; Hogan, Christopher J

2011-12-28

We use a charge reduction electrospray (ESI) source and subsequent ion mobility analysis with a differential mobility analyzer (DMA, with detection via both a Faraday cage electrometer and a condensation particle counter) to infer the densities of single and multiprotein ions of cytochrome C, lysozyme, myoglobin, ovalbumin, and bovine serum albumin produced from non-denaturing (20 mM aqueous ammonium acetate) and denaturing (1 : 49.5 : 49.5, formic acid : methanol : water) ESI. Charge reduction is achieved through use of a Po-210 radioactive source, which generates roughly equal concentrations of positive and negative ions. Ions produced by the source collide with and reduce the charge on ESI generated drops, preventing Coulombic fissions, and unlike typical protein ESI, leading to gas-phase protein ions with +1 to +3 excess charges. Therefore, charge reduction serves to effectively mitigate any role that Coulombic stretching may play on the structure of the gas phase ions. Density inference is made via determination of the mobility diameter, and correspondingly the spherical equivalent protein volume. Through this approach it is found that for both non-denaturing and denaturing ESI-generated ions, gas-phase protein ions are relatively compact, with average densities of 0.97 g cm(-3) and 0.86 g cm(-3), respectively. Ions from non-denaturing ESI are found to be slightly more compact than predicted from the protein crystal structures, suggesting that low charge state protein ions in the gas phase are slightly denser than their solution conformations. While a slight difference is detected between the ions produced with non-denaturing and denaturing ESI, the denatured ions are found to be much more dense than those examined previously by drift tube mobility analysis, in which charge reduction was not employed. This indicates that Coulombic stretching is typically what leads to non-compact ions in the gas-phase, and suggests that for gas phase measurements to be correlated to biomolecular structures in solution, low charge state ions should be analyzed. Further, to determine if different solution conditions give rise to ions of different structure, ions of similar charge state should be compared. Non-denatured protein ion densities are found to be in excellent agreement with non-denatured protein ion densities inferred from prior DMA and drift tube measurements made without charge reduction (all ions with densities in the 0.85-1.10 g cm(-3) range), showing that these ions are not strongly influenced by Coulombic stretching nor by analysis method.

Boundary layer charge dynamics in ionic liquid-ionic polymer transducers

NASA Astrophysics Data System (ADS)

Davidson, Jacob D.; Goulbourne, N. C.

2011-01-01

Ionic polymer transducers (IPTs), also known as ionic polymer-metal composites, are soft sensors and actuators which operate through a coupling of microscale chemical, electrical, and mechanical interactions. The use of an ionic liquid as solvent for an IPT has been shown to dramatically increase transducer lifetime in free-air use, while also allowing for higher applied voltages without electrolysis. In this work, we apply Nernst-Planck/Poisson theory to model charge transport in an ionic liquid IPT by considering a certain fraction of the ionic liquid ions as mobile charge carriers, a phenomenon which is unique to ionic liquid IPTs compared to their water-based counterparts. Numerical simulations are performed using the finite element method to examine how the introduction of another pair of mobile ions affects boundary layer charge dynamics, concentration, and charge density distributions in the electric double layer, and the overall charge transferred and current response of the IPT. Due to interactions with the Nafion ionomer, not all of the ionic liquid ions will function as mobile charge carriers; only a certain fraction will exist as "free" ions. The presence of mobile ionic liquid ions in the transducer will increase the overall charge transferred when a voltage is applied, and cause the current in the transducer to decay more slowly. The additional mobile ions also cause the ionic concentration profiles to exhibit a nonlinear dynamic response, characterized by nonmonotonic ionic concentration profiles in space and time. Although the presence of mobile ionic liquid ions increases the overall amount of charge transferred, this additional charge transfer occurs in a somewhat symmetric manner. Therefore, the additional charge transferred due to the ionic liquid ions does not greatly increase the net bending moment of the transducer; in fact, it is possible that ionic liquid ion movement actually decreases the observed bending response. This suggests that an optimal electromechanical conversion efficiency for bending actuation is achieved by using an ionic liquid where only a relatively small fraction of the ionic liquid ions exist as free ions. Conversely, if it is desired to increase the overall amount of charge transferred, an ionic liquid with a large fraction of free ions should be used. These theoretical considerations are found to be in good qualitative agreement with recent experimental results.

Compression Ratio Ion Mobility Programming (CRIMP) Accumulation and Compression of Billions of Ions for Ion Mobility-Mass Spectrometry Using Traveling Waves in Structures for Lossless Ion Manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Liulin; Garimella, Sandilya V. B.; Hamid, Ahmed M.

We report on the implementation of a traveling wave (TW) based compression ratio ion mobility programming (CRIMP) approach within Structures for Lossless Ion Manipulations (SLIM) that enables both greatly enlarged trapped ion charge capacities and also their subsequent efficient compression for use in ion mobility (IM) separations. Ion accumulation is conducted in a long serpentine path TW SLIM region after which CRIMP allows the large ion populations to be ‘squeezed’. The compression process occurs at an interface between two SLIM regions, one operating conventionally and the second having an intermittently pausing or ‘stuttering’ TW, allowing the contents of multiple binsmore » of ions from the first region to be merged into a single bin in the second region. In this initial work stationary voltages in the second region were used to block ions from exiting the first (trapping) region, and the resumption of TWs in the second region allows ions to exit, and the population to also be compressed if CRIMP is applied. In our initial evaluation we show that the number of charges trapped for a 40 s accumulation period was ~5×109, more than two orders of magnitude greater than the previously reported charge capacity using an ion funnel trap. We also show that over 1×109 ions can be accumulated with high efficiency in the present device, and that the extent of subsequent compression is only limited by the space charge capacity of the trapping region. Lower compression ratios allow increased IM peak heights without significant loss of signal, while excessively large compression ratios can lead to ion losses and other artifacts. Importantly, we show that extended ion accumulation in conjunction with CRIMP and multiple passes provides the basis for a highly desirable combination of ultra-high sensitivity and ultra-high resolution IM separations using SLIM.« less

Comprehensive Peptide Ion Structure Studies Using Ion Mobility Techniques: Part 3. Relating Solution-Phase to Gas-Phase Structures.

PubMed

Kondalaji, Samaneh Ghassabi; Khakinejad, Mahdiar; Valentine, Stephen J

2018-06-01

Molecular dynamics (MD) simulations have been utilized to study peptide ion conformer establishment during the electrospray process. An explicit water model is used for nanodroplets containing a model peptide and hydronium ions. Simulations are conducted at 300 K for two different peptide ion charge configurations and for droplets containing varying numbers of hydronium ions. For all conditions, modeling has been performed until production of the gas-phase ions and the resultant conformers have been compared to proposed gas-phase structures. The latter species were obtained from previous studies in which in silico candidate structures were filtered according to ion mobility and hydrogen-deuterium exchange (HDX) reactivity matches. Results from the present study present three key findings namely (1) the evidence from ion production modeling supports previous structure refinement studies based on mobility and HDX reactivity matching, (2) the modeling of the electrospray process is significantly improved by utilizing initial droplets existing below but close to the calculated Rayleigh limit, and (3) peptide ions in the nanodroplets sample significantly different conformers than those in the bulk solution due to altered physicochemical properties of the solvent. Graphical Abstract ᅟ.

A Novel Microwave-Induced Plasma Ionization Source for Ion Mobility Spectrometry

NASA Astrophysics Data System (ADS)

Dai, Jianxiong; Zhao, Zhongjun; Liang, Gaoling; Duan, Yixiang

2017-03-01

This work demonstrates the application of a novel microwave induced plasma ionization (MIPI) source to ion mobility spectrometry (IMS). The MIPI source, called Surfatron, is composed of a copper cavity and a hollow quartz discharge tube. The ion mobility spectrum of synthetics air has a main peak with reduced mobility of 2.14 cm2V-1s-1 for positive ion mode and 2.29 cm2V-1s-1 for negative ion mode. The relative standard deviations (RSD) are 0.7% and 1.2% for positive and negative ion mode, respectively. The total ion current measured was more than 3.5 nA, which is much higher than that of the conventional 63Ni source. This indicates that a better signal-to-noise ratio (SNR) can be acquired from the MIPI source. The SNR was 110 in the analysis of 500 pptv methyl tert-butyl ether (MTBE), resulting in the limit of detection (SNR = 3) of 14 pptv. The linear range covers close to 2.5 orders of magnitude in the detection of triethylamine with a concentration range from 500 pptv to 80 ppbv. Finally, this new MIPI-IMS was used to detect some volatile organic compounds, which demonstrated that the MIPI-IMS has great potential in monitoring pollutants in air.

Usefulness of cardiotoxicity assessment using calcium transient in human induced pluripotent stem cell-derived cardiomyocytes.

PubMed

Watanabe, Hitoshi; Honda, Yayoi; Deguchi, Jiro; Yamada, Toru; Bando, Kiyoko

2017-01-01

Monitoring dramatic changes in intracellular calcium ion levels during cardiac contraction and relaxation, known as calcium transient, in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) would be an attractive strategy for assessing compounds on cardiac contractility. In addition, as arrhythmogenic compounds are known to induce characteristic waveform changes in hiPSC-CMs, it is expected that calcium transient would allow evaluation of not only compound-induced effects on cardiac contractility, but also compound arrhythmogenic potential. Using a combination of calcium transient in hiPSC-CMs and a fast kinetic fluorescence imaging detection system, we examined in this study changes in calcium transient waveforms induced by a series of 17 compounds that include positive/negative inotropic agents as well as cardiac ion channel activators/inhibitors. We found that all positive inotropic compounds induced an increase in peak frequency and/or peak amplitude. The effects of a negative inotropic compound could clearly be detected in the presence of a β-adrenergic receptor agonist. Furthermore, most arrhythmogenic compounds raised the ratio of peak decay time to peak rise time (D/R ratio) in calcium transient waveforms. Compound concentrations at which these parameters exceeded cutoff values correlated well with systemic exposure levels at which arrhythmias were reported to be evoked. In conclusion, we believe that peak analysis of calcium transient and determination of D/R ratio are reliable methods for assessing compounds' cardiac contractility and arrhythmogenic potential, respectively. Using these approaches would allow selection of compounds with low cardiotoxic potential at the early stage of drug discovery.

STEREO and Wind Observations of Intense Cyclotron Harmonic Waves at the Earth's Bow Shock and Inside the Magnetosheath

NASA Technical Reports Server (NTRS)

Breneman, A. W.; Cattell, C.

2013-01-01

We present the first observations of electron cyclotron harmonic waves at the Earth's bow shock from STEREO and Wind burst waveform captures. These waves are observed at magnetic field gradients at a variety of shock geometries ranging from quasi-parallel to nearly perpendicular along with whistler mode waves, ion acoustic waves, and electrostatic solitary waves. Large amplitude cyclotron harmonic waveforms are also observed in the magnetosheath in association with magnetic field gradients convected past the bow shock. Amplitudes of the cyclotron harmonic waves range from a few tens to more than 500 millivolts/meter peak-peak. A comparison between the short (15 meters) and long (100 meters) Wind spin plane antennas shows a similar response at low harmonics and a stronger response on the short antenna at higher harmonics. This indicates that wavelengths are not significantly larger than 100 meters, consistent with the electron cyclotron radius. Waveforms are broadband and polarizations are distinctively comma-shaped with significant power both perpendicular and parallel to the magnetic field. Harmonics tend to be more prominent in the perpendicular directions. These observations indicate that the waves consist of a combination of perpendicular Bernstein waves and field-aligned waves without harmonics. A likely source is the electron cyclotron drift instability which is a coupling between Bernstein and ion acoustic waves. These waves are the most common type of high-frequency wave seen by STEREO during bow shock crossings and magnetosheath traversals and our observations suggest that they are an important component of the high-frequency turbulent spectrum in these regions.

Digitally Controlled Four Harmonic Buncher for FSU LINAC

NASA Astrophysics Data System (ADS)

Moerland, Daniel S.; Wiedenhoever, Ingo; Baby, Lagy T.; Caussyn, David; Spingler, David

2012-03-01

Florida State University's John D. Fox Superconducting Accelerator Laboratory is operating a Tandem-Linac system for heavy ion beams at energies of 5-10 MeV/u. Recently, the accelerator has been used as the driver for the radioactive beam facility RESOLUT, which poses new demands on its high-intensity performance and time-resolution. These demands motivated us to optimize the RF bunching system and to switch the bunch frequency from 48.5 to 12.125 MHz. We installed a four-harmonic resonant transformer to create 3-4 kV potential oscillations across a pair of wire-mesh grids. This setup is modulating the energy of the beam injected into the tandem accelerator, with the aim to create short bunches of beam particles. Asawtooth-like wave-form is created using the Fourier series method, by combining the basis sinusoidal wave of 12.125MHz and its 3 higher order harmonics, in a manner similar to the systems used at ATLAS [1] and other RF-accelerators. A new aspect of our setup is the use of a digital 1GHz function generator, which allows us to optimize and stabilize the synthesized waveform. The control system was realized using labview and integrated into the recently updated controls of the accelerator. We characterize the bunching quality achievedand discuss the optimization of the bunching wave-form. The bunching system has been successfully used in a number of Linac-experiments performed during 2011.[4pt][1] S. Sharamentov, J. Bogaty, B.E. Clifft, R. Pardo, UPGRADE OF THE ATLAS POSITIVE ION INJECTOR BUNCHING SYSTEM, Proceedings of 2005 Particle Accelerator Conference, Knoxville, Tennessee

Detection of Radiation-Exposure Biomarkers by Differential Mobility Prefiltered Mass Spectrometry (DMS-MS)

PubMed Central

Coy, Stephen L.; Krylov, Evgeny V.; Schneider, Bradley B.; Covey, Thomas R.; Brenner, David J.; Tyburski, John B.; Patterson, Andrew D.; Krausz, Kris W.; Fornace, Albert J.; Nazarov, Erkinjon G.

2010-01-01

Technology to enable rapid screening for radiation exposure has been identified as an important need, and, as a part of a NIH / NIAD effort in this direction, metabolomic biomarkers for radiation exposure have been identified in a recent series of papers. To reduce the time necessary to detect and measure these biomarkers, differential mobility spectrometry – mass spectrometry (DMS-MS) systems have been developed and tested. Differential mobility ion filters preselect specific ions and also suppress chemical noise created in typical atmospheric-pressure ionization sources (ESI, MALDI, and others). Differential-mobility-based ion selection is based on the field dependence of ion mobility, which, in turn, depends on ion characteristics that include conformation, charge distribution, molecular polarizability, and other properties, and on the transport gas composition which can be modified to enhance resolution. DMS-MS is able to resolve small-molecule biomarkers from nearly-isobaric interferences, and suppresses chemical noise generated in the ion source and in the mass spectrometer, improving selectivity and quantitative accuracy. Our planar DMS design is rapid, operating in a few milliseconds, and analyzes ions before fragmentation. Depending on MS inlet conditions, DMS-selected ions can be dissociated in the MS inlet expansion, before mass analysis, providing a capability similar to MS/MS with simpler instrumentation. This report presents selected DMS-MS experimental results, including resolution of complex test mixtures of isobaric compounds, separation of charge states, separation of isobaric biomarkers (citrate and isocitrate), and separation of nearly-isobaric biomarker anions in direct analysis of a bio-fluid sample from the radiation-treated group of a mouse-model study. These uses of DMS combined with moderate resolution MS instrumentation indicate the feasibility of field-deployable instrumentation for biomarker evaluation. PMID:20305793

Evolution of the optimum bidirectional (+/- biphasic) wave for defibrillation.

PubMed

Geddes, L A; Havel, W

2000-01-01

Introduction of the asymmetric bidirectional (+/- biphasic) current waveform has made it possible to achieve ventricular defibrillation with less energy and current than are needed with a unidirectional (monophasic) waveform. The symmetrical bidirectional (sinusoidal) waveform was used for the first human-heart defibrillation. Subsequent studies employed the underdamped and overdamped sine waves, then the trapezoidal (monophasic) wave. Studies were then undertaken to investigate the benefit of adding a second identical and inverted wave; little success rewarded these efforts until it was discovered that the second inverted wave needed to be much less in amplitude to lower the threshold for defibrillation. However, there is no physiologic theory that explains the mechanism of action of the bidirectional wave, nor does any theory predict the optimum amplitude and time dimensions for the second inverted wave. The authors analyze the research that shows that the threshold defibrillation energy is lowest when the charge in the second, inverted phase is slightly more than a third of that in the first phase. An ion-flux, spatial-K+ summation hypothesis is presented that shows the effect on myocardial cells of adding the second inverted current pulse.

LC-IMS-MS Feature Finder: detecting multidimensional liquid chromatography, ion mobility and mass spectrometry features in complex datasets.

PubMed

Crowell, Kevin L; Slysz, Gordon W; Baker, Erin S; LaMarche, Brian L; Monroe, Matthew E; Ibrahim, Yehia M; Payne, Samuel H; Anderson, Gordon A; Smith, Richard D

2013-11-01

The addition of ion mobility spectrometry to liquid chromatography-mass spectrometry experiments requires new, or updated, software tools to facilitate data processing. We introduce a command line software application LC-IMS-MS Feature Finder that searches for molecular ion signatures in multidimensional liquid chromatography-ion mobility spectrometry-mass spectrometry (LC-IMS-MS) data by clustering deisotoped peaks with similar monoisotopic mass, charge state, LC elution time and ion mobility drift time values. The software application includes an algorithm for detecting and quantifying co-eluting chemical species, including species that exist in multiple conformations that may have been separated in the IMS dimension. LC-IMS-MS Feature Finder is available as a command-line tool for download at http://omics.pnl.gov/software/LC-IMS-MS_Feature_Finder.php. The Microsoft.NET Framework 4.0 is required to run the software. All other dependencies are included with the software package. Usage of this software is limited to non-profit research to use (see README). rds@pnnl.gov. Supplementary data are available at Bioinformatics online.

Analysis of biogenic amines using corona discharge ion mobility spectrometry.

PubMed

Hashemian, Z; Mardihallaj, A; Khayamian, T

2010-05-15

A new method based on corona discharge ion mobility spectrometry (CD-IMS) was developed for the analysis of biogenic amines including spermidine, spermine, putrescine, and cadaverine. The ion mobility spectra of the compounds were obtained with and without n-Nonylamine used as the reagent gas. The high proton affinity of n-Nonylamine prevented ion formation from compounds with a proton affinity lower than that of n-Nonylamine and, therefore, enhanced its selectivity. It was also realized that the ion mobility spectrum of n-Nonylamine varied with its concentration. A sample injection port of a gas chromatograph was modified and used as the sample introduction system into the CD-IMS. The detection limits, dynamic ranges, and analytical parameters of the compounds with and without using the reagent gas were obtained. The detection limits and dynamic ranges of the compounds were about 2ng and 2 orders of magnitude, respectively. The wide dynamic range of CD-IMS originates from the high current of the corona discharge. The results revealed the high capability of the CD-IMS for the analysis of biogenic amines.

Development of an ion mobility spectrometer with UV ionization source to detect ketones and BTX

NASA Astrophysics Data System (ADS)

Ni, Kai; Guo, Jingran; Ou, Guangli; Lei, Yu; Wang, Xiaohao

2014-11-01

Ion mobility spectrometry (IMS) is an attractive material analysis technology for developing a miniaturized volatile organic compounds (VOCs) on-site monitoring sensor. Having simple instrumentation, IMS is especially suitable when portability and sensitivity are required. In this work, we designed an ion mobility spectrometer with UV ionization. The geometric parameters of the UV-IMS were optimized based on a numerical simulation. The simulation results demonstrated that the drift electric field in the drift region was approximately homogenous and in the reaction region had an ion focusing effect, which could improve the sensitivity and resolving power of the IMS. The UV-IMS has been constructed and used to detect VOCs, such as acetone, benzene, toluene and m-xylene (BTX). The resolution of these substance measured from the UV-IMS in the atmospheric conditions are about 30 and the limit of detection (LOD) is low to ppmv. The ion mobility module and electric circuit are integrated in a main PCB, which can facilitate mass production and miniaturization. The present UV-IMS is expected to become a tool of choice for the on-site monitoring for VOCs.

Ion mobility studies of carbohydrates as group I adducts: isomer specific collisional cross section dependence on metal ion radius.

PubMed

Huang, Yuting; Dodds, Eric D

2013-10-15

Carbohydrates play numerous critical roles in biological systems. Characterization of oligosaccharide structures is essential to a complete understanding of their functions in biological processes; nevertheless, their structural determination remains challenging in part due to isomerism. Ion mobility spectrometry provides the means to resolve gas phase ions on the basis of their shape-to-charge ratios, thus providing significant potential for separation and differentiation of carbohydrate isomers. Here, we report on the determination of collisional cross sections for four groups of isomeric carbohydrates (including five isomeric disaccharides, four isomeric trisaccharides, two isomeric pentasaccharides, and two isomeric hexasaccharides) as their group I metal ion adducts (i.e., [M + Li](+), [M + Na](+), [M + K](+), [M + Rb](+), and [M + Cs](+)). In all, 65 collisional cross sections were measured, the great majority of which have not been previously reported. As anticipated, the collisional cross sections of the carbohydrate metal ion adducts generally increase with increasing metal ion radius; however, the collisional cross sections were found to scale with the group I cation size in isomer specific manners. Such measurements are of substantial analytical value, as they illustrate how the selection of charge carrier influences carbohydrate ion mobility determinations. For example, certain pairs of isomeric carbohydrates assume unique collisional cross sections upon binding one metal ion, but not another. On the whole, these data suggest a role for the charge carrier as a probe of carbohydrate structure and thus have significant implications for the continued development and application of ion mobility spectrometry for the distinction and resolution of isomeric carbohydrates.

Atmospheric pressure chemical ionization of fluorinated phenols in atmospheric pressure chemical ionization mass spectrometry, tandem mass spectrometry, and ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Eiceman, G. A.; Bergloff, J. F.; Rodriguez, J. E.; Munro, W.; Karpas, Z.

1999-01-01

Atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) for fluorinated phenols (C6H5-xFxOH Where x = 0-5) in nitrogen with Cl- as the reagent ion yielded product ions of M Cl- through ion associations or (M-H)- through proton abstractions. Proton abstraction was controllable by potentials on the orifice and first lens, suggesting that some proton abstraction occurs through collision induced dissociation (CID) in the interface region. This was proven using CID of adduct ions (M Cl-) with Q2 studies where adduct ions were dissociated to Cl- or proton abstracted to (M-H)-. The extent of proton abstraction depended upon ion energy and structure in order of calculated acidities: pentafluorophenol > tetrafluorophenol > trifluorophenol > difluorophenol. Little or no proton abstraction occurred for fluorophenol, phenol, or benzyl alcohol analogs. Ion mobility spectrometry was used to determine if proton abstraction reactions passed through an adduct intermediate with thermalized ions and mobility spectra for all chemicals were obtained from 25 to 200 degrees C. Proton abstraction from M Cl- was not observed at any temperature for phenol, monofluorophenol, or difluorophenol. Mobility spectra for trifluorophenol revealed the kinetic transformations to (M-H)- either from M Cl- or from M2 Cl- directly. Proton abstraction was the predominant reaction for tetra- and penta-fluorophenols. Consequently, the evidence suggests that proton abstraction occurs from an adduct ion where the reaction barrier is reduced with increasing acidity of the O-H bond in C6H5-xFxOH.

High-mobility low-temperature ZnO transistors with low-voltage operation

NASA Astrophysics Data System (ADS)

Bong, Hyojin; Lee, Wi Hyoung; Lee, Dong Yun; Kim, Beom Joon; Cho, Jeong Ho; Cho, Kilwon

2010-05-01

Low voltage high mobility n-type thin film transistors (TFTs) based on sol-gel processed zinc oxide (ZnO) were fabricated using a high capacitance ion gel gate dielectric. The ion gel gated solution-processed ZnO TFTs were found to exhibit excellent electrical properties. TFT carrier mobilities were 13 cm2/V s, ON/OFF current ratios were 105, regardless of the sintering temperature used for the preparation of the ZnO thin films. Ion gel gated ZnO TFTs are successfully demonstrated on plastic substrates for the large area flexible electronics.

Third International Workshop on Ion Mobility Spectrometry

NASA Technical Reports Server (NTRS)

Cross, John H. (Editor)

1995-01-01

Basic research in ion mobility spectrometry has given rise to rapid advancement in hardware development and applications. The Third International Workshop on Ion Mobility Spectrometry (IMS) was held October 16-19, 1994, at Johnson Space Center to provide a forum for investigators to present the most recent results of both basic and applied IMS research. Presenters included manufacturers and various users, including military research organizations and drug enforcement agencies. Thirty papers were given in the following five sessions: Fundamental IMS Studies, Instrument Development, Hyphenated IMS Techniques, Applications, and Data Reduction and Signal Processing. Advances in hardware development, software development, and user applications are described.

Laser-stimulated desorption of organic molecules from surfaces, as a method of increasing the efficiency of ion mobility spectrometry analysis.

PubMed

Akmalov, Artem E; Chistyakov, Alexander A; Kotkovskii, Gennadii E

2017-08-01

Application of laser-induced desorption was investigated as a method of increasing the efficiency of gas phase analyzers on principles of field asymmetric ion mobility spectrometry. Mass spectrometric data of investigations of laser desorption of pentaerythritoltetranitrate molecules and cyclotetramethylenetetranitramine molecules from quartz substrate under vacuum were obtained. Laser sources a Nd 3+ :YAG with nanosecond pulse duration (λ = 532 nm) and a continuous wave diode laser (λ = 440 nm) were used. It was shown that both laser sources have different desorption abilities. This is expressed in various time of appearance of desorbed products that is caused by different heating mechanisms of surface layer. The desorbed quantity under action of both laser sources exceeds the detection threshold for all modern gas phase analyzers. It should be noted that despite the presence of surface dissociation of explosives under laser radiation, the quantity of nondissociated molecules is large enough for detection by ion mobility and field asymmetric ion mobility spectrometers. The optimal parameters of laser radiation for effective removal (evaporation) molecules of low-volatile compounds from surfaces are defined. The conclusion about preferable use of a Nd 3+ :YAG laser for increasing the detection ability of detectors based on ion mobility spectrometry was made.

Determination of Benzene, Toluene, and Xylene by means of an ion mobility spectrometer device using photoionization

NASA Technical Reports Server (NTRS)

Leonhardt, J. W.; Bensch, H.; Berger, D.; Nolting, M.; Baumbach, J. I.

1995-01-01

The continuous monitoring of changes on the quality of ambient air is a field of advantage of ion mobility spectrometry. Benzene, Toluene, and Xylene are substances of special interest because of their toxicity. We present an optimized drift tube for ion mobility spectrometers, which uses photo-ionization tubes to produce the ions to be analyzed. The actual version of this drift tube has a length of 45 mm, an electric field strength established within the drift tube of about 180 V/cm and a shutter-opening-time of 400 mus. With the hydrogen tube used for ionisation a mean flux of 10(exp 12) photons/sq cm s was established for the experiments described. We discuss the results of investigations on Benzene, Toluene, and Xylene in normal used gasoline SUPER. The detection limits obtained with the ion mobility spectrometer developed in co-operation are in the range of 10 ppbv in this case. Normally, charge transfer from Benzene ions to Toluene takes place. Nevertheless the simultaneous determination in mixtures is possible by a data evaluation procedure developed for this case. The interferences found between Xylene and others are rather weak. The ion mobility spectra of different concentrations of gasoline SUPER are attached as an example for the resolution and the detection limit of the instrument developed. Resolution and sensitivity of the system are well demonstrated. A hand-held portable device produced just now is to be tested for special environmental analytical problems in some industrial and scientific laboratories in Germany.

Multifactorial Understanding of Ion Abundance in Tandem Mass Spectrometry Experiments.

PubMed

Fazal, Zeeshan; Southey, Bruce R; Sweedler, Jonathan V; Rodriguez-Zas, Sandra L

2013-01-29

In a bottom-up shotgun approach, the proteins of a mixture are enzymatically digested, separated, and analyzed via tandem mass spectrometry. The mass spectra relating fragment ion intensities (abundance) to the mass-to-charge are used to deduce the amino acid sequence and identify the peptides and proteins. The variables that influence intensity were characterized using a multi-factorial mixed-effects model, a ten-fold cross-validation, and stepwise feature selection on 6,352,528 fragment ions from 61,543 peptide ions. Intensity was higher in fragment ions that did not have neutral mass loss relative to any mass loss or that had a +1 charge state. Peptide ions classified for proton mobility as non-mobile had lowest intensity of all mobility levels. Higher basic residue (arginine, lysine or histidine) counts in the peptide ion and low counts in the fragment ion were associated with lower fragment ion intensities. Higher counts of proline in peptide and fragment ions were associated with lower intensities. These results are consistent with the mobile proton theory. Opposite trends between peptide and fragment ion counts and intensity may be due to the different impact of factor under consideration at different stages of the MS/MS experiment or to the different distribution of observations across peptide and fragment ion levels. Presence of basic residues at all three positions next to the fragmentation site was associated with lower fragment ion intensity. The presence of proline proximal to the fragmentation site enhanced fragmentation and had the opposite trend when located distant from the site. A positive association between fragment ion intensity and presence of sulfur residues (cysteine and methionine) on the vicinity of the fragmentation site was identified. These results highlight the multi-factorial nature of fragment ion intensity and could improve the algorithms for peptide identification and the simulation in tandem mass spectrometry experiments.

Multifactorial Understanding of Ion Abundance in Tandem Mass Spectrometry Experiments

PubMed Central

Fazal, Zeeshan; Southey, Bruce R; Sweedler, Jonathan V.; Rodriguez-Zas, Sandra L.

2013-01-01

In a bottom-up shotgun approach, the proteins of a mixture are enzymatically digested, separated, and analyzed via tandem mass spectrometry. The mass spectra relating fragment ion intensities (abundance) to the mass-to-charge are used to deduce the amino acid sequence and identify the peptides and proteins. The variables that influence intensity were characterized using a multi-factorial mixed-effects model, a ten-fold cross-validation, and stepwise feature selection on 6,352,528 fragment ions from 61,543 peptide ions. Intensity was higher in fragment ions that did not have neutral mass loss relative to any mass loss or that had a +1 charge state. Peptide ions classified for proton mobility as non-mobile had lowest intensity of all mobility levels. Higher basic residue (arginine, lysine or histidine) counts in the peptide ion and low counts in the fragment ion were associated with lower fragment ion intensities. Higher counts of proline in peptide and fragment ions were associated with lower intensities. These results are consistent with the mobile proton theory. Opposite trends between peptide and fragment ion counts and intensity may be due to the different impact of factor under consideration at different stages of the MS/MS experiment or to the different distribution of observations across peptide and fragment ion levels. Presence of basic residues at all three positions next to the fragmentation site was associated with lower fragment ion intensity. The presence of proline proximal to the fragmentation site enhanced fragmentation and had the opposite trend when located distant from the site. A positive association between fragment ion intensity and presence of sulfur residues (cysteine and methionine) on the vicinity of the fragmentation site was identified. These results highlight the multi-factorial nature of fragment ion intensity and could improve the algorithms for peptide identification and the simulation in tandem mass spectrometry experiments. PMID:24031159

Transport coefficients of gaseous ions in an electric field

NASA Technical Reports Server (NTRS)

Whealton, J. H.; Mason, E. A.

1974-01-01

A general theory of ion mobility formulated by Kihara (1953) is extended to ion diffusion and to mixtures of neutral gases. The theory assumes that only binary collisions between ions and neutral particles need to be taken into account and that the velocity distribution function of the neutral particles is Maxwellian. These assumptions make it possible to use a linearized Boltzmann equation. Questions of mobility are considered along with aspects of diffusion and deviations from Fick's law of diffusion.

New, high-efficiency ion trap mobility detection system for narcotics and explosives

NASA Astrophysics Data System (ADS)

McGann, William J.; Bradley, V.; Borsody, A.; Lepine, S.

1994-10-01

A new patented Ion Trap Mobility Spectrometer (ITMS) design is presented. Conventional IMS designs typically operate below 0.1% efficiency. This is due primarily to electric field driven, sample ion discharge on a shutter grid. Since 99.9% of the sample ions generated in the reaction region are lost in this discharge process, the sensitivity of conventional systems is limited. The new design provides greater detection efficiency than conventional designs through the use of an `ion trap' concept. The paper describes the plasma and sample ion dynamics in the reaction region of the new detector and discusses the advantages of utilizing a `field-free' space to generate sample ions with high efficiency. Fast electronic switching is described which is used to perturb the field-free space and pulse the sample ions into the drift region for separation and subsequent detection using pseudo real-time software for analysis and display of the data. Many applications for this new detector are now being considered including the detection of narcotics and explosives. Preliminary ion spectra, reduced mobility data and sensitivity data are presented for fifteen narcotics, including cocaine, THC and LSD are reported.

New high-efficiency ion trap mobility detection system for narcotics and explosives

NASA Astrophysics Data System (ADS)

McGann, William J.; Jenkins, Anthony; Ribiero, K.; Napoli, J.

1994-03-01

A new patented ion trap mobility spectrometer design is presented. Conventional IMS designs typically operate below 0.1% efficiency. This is due primarily to electrical-field-driven, sample ion discharge on a shutter grid. Since 99.9% of the sample ions generated in the reaction region are lost in this discharge process, the sensitivity of conventional systems is limited. The new design provides greater detection efficiency than conventional designs through the use of an `ion trap' concept. The paper describes the plasma and sample ion dynamics in the reaction region of the new detector and discusses the advantages of utilizing a `field-free' space to generate sample ions with high efficiency. Fast electronic switching is described which is used to perturb the field-free space and pulse the sample ions into the drift region for separation and subsequent detection using pseudo real-time software for analysis and display of the data. Many applications for this new detector are now being considered including the detection of narcotics and explosives. Preliminary ion spectra, reduced mobility data and sensitivity data are presented for fifteen narcotics, including cocaine, THC, and LSD are reported.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, Anne-Laure; Choi, Chang Min; Clavier, Christian

This manuscript describes a new experimental setup that allows to perform tandem ion mobility spectrometry (IMS) measurements and which is coupled to a high resolution time-of-flight mass spectrometer. It consists of two 79 cm long drift tubes connected by a dual ion funnel assembly. The setup was built to permit laser irradiation of the ions in the transfer region between the two drift tubes. This geometry allows selecting ions according to their ion mobility in the first drift tube, to irradiate selected ions, and examine the ion mobility of the product ions in the second drift tube. Activation by collisionmore » is possible in the same region (between the two tubes) and between the second tube and the time-of-flight. IMS-IMS experiments on Ubiquitin are reported. We selected a given isomer of charge state +7 and explored its structural rearrangement following collisional activation between the two drift tubes. An example of IMS-laser-IMS experiment is reported on eosin Y, where laser irradiation was used to produce radical ions by electron photodetachment starting from doubly deprotonated species. This allowed measuring the collision cross section of the radical photo-product, which cannot be directly produced with an electrospray source.« less

Towards unsupervised polyaromatic hydrocarbons structural assignment from SA-TIMS-FTMS data.

PubMed

Benigni, Paolo; Marin, Rebecca; Fernandez-Lima, Francisco

2015-10-01

With the advent of high resolution ion mobility analyzers and their coupling to ultrahigh resolution mass spectrometers, there is a need to further develop a theoretical workflow capable of correlating experimental accurate mass and mobility measurements with tridimensional candidate structures. In the present work, a general workflow is described for unsupervised tridimensional structural assignment based on accurate mass measurements, mobility measurements, in silico 2D-3D structure generation, and theoretical mobility calculations. In particular, the potential of this workflow will be shown for the analysis of polyaromatic hydrocarbons from Coal Tar SRM 1597a using selected accumulation - trapped ion mobility spectrometry (SA-TIMS) coupled to Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The proposed workflow can be adapted to different IMS scenarios, can utilize different collisional cross-section calculators and has the potential to include MS n and IMS n measurements for faster and more accurate tridimensional structural assignment.

The Formation and Thermochemical Properties of Multiligand Complexes

DTIC Science & Technology

1987-08-25

SUBJECT TERMS (Continue on revers, if necessary and identify by block numoer) FIELD GROUP SUB-GROUP Ion-molecule reactions, clusters, multiligand...mercaptans, and phosphonates for which the results may be useful in the development of detection techniques that employ ion mobility analyzers or... field involve the use of ion mobility and mass spectrometers. Detection of a species by such instruments in an atmospheric environment requires that the

A remote patient monitoring system using a Java-enabled 3G mobile phone.

PubMed

Zhang, Pu; Kogure, Yuichi; Matsuoka, Hiroki; Akutagawa, Masatake; Kinouchi, Yohsuke; Zhang, Qinyu

2007-01-01

Telemedicine systems have become an important supporting for the medical staffs. As the development of the mobile phones, it is possible to apply the mobile phones to be a part of telemedicine systems. We developed an innovative Remote Patient Monitoring System using a Java-enabled 3G mobile phone. By using this system, doctors can monitor the vital biosignals of patients in ICU/CCU, such as ECG, RESP, SpO2, EtCO2 and so on by using the real-time waveform and data monitoring and list trend data monitoring functions of installed Java jiglet application on the mobile phone. Futhermore, doctors can check the patients' information by using the patient information checking function. The 3G mobile phone used has the ability to implement the application as the same time as being used to mak a voice call. Therefore, the doctor can get more and more information both from the browsing the screen of the mobile phone and the communicating with the medical staffs who are beside the patients and the monitors. The system can be conducted to evaluate the diagnostic accuracy, efficiency, and safety of telediagnosis.

Automatic control of a negative ion source

NASA Astrophysics Data System (ADS)

Saadatmand, K.; Sredniawski, J.; Solensten, L.

1989-04-01

A CAMAC based control architecture is devised for a Berkeley-type H - volume ion source [1]. The architecture employs three 80386 TM PCs. One PC is dedicated to control and monitoring of source operation. The other PC functions with digitizers to provide data acquisition of waveforms. The third PC is used for off-line analysis. Initially, operation of the source was put under remote computer control (supervisory). This was followed by development of an automated startup procedure. Finally, a study of the physics of operation is now underway to establish a data base from which automatic beam optimization can be derived.

Ion propagation in an aluminum hollow cylinder target laser ion source

NASA Astrophysics Data System (ADS)

Saquilayan, Glynnis Mae Q.; Wada, Motoi

2018-01-01

Experimental results for the laser produced plasma in an aluminum hollow cylinder target are presented. Observing the plasma formation inside the cylinder, a high-speed camera captured the images of the plasma expanding towards the adjacent walls of target. The optical emission spectrum is obtained for the plasma inside the hollow cylinder and positive singly charged aluminum ions and neutrals are identified from emission spectral lines. Time dependent current signals of the Faraday cup displayed an enlarged signal intensity as the laser power density is increased up to 6.5 GW/cm2. Signal arrival times corresponding to fast ions appeared at the onset of the current waveforms when the laser power density exceeded 4.7 GW/cm2. For the mass analysis of plasma, an accelerating electric field was applied to separate the ions and the time-of-flight measurements showed positive ion signals with an identified peak to have an estimated mass of 350 amu.

Ion Mobility Spectrometry-Mass Spectrometry Coupled with Gas-Phase Hydrogen/Deuterium Exchange for Metabolomics Analyses

NASA Astrophysics Data System (ADS)

Maleki, Hossein; Karanji, Ahmad K.; Majuta, Sandra; Maurer, Megan M.; Valentine, Stephen J.

2018-02-01

Ion mobility spectrometry-mass spectrometry (IMS-MS) in combination with gas-phase hydrogen/deuterium exchange (HDX) and collision-induced dissociation (CID) is evaluated as an analytical method for small-molecule standard and mixture characterization. Experiments show that compound ions exhibit unique HDX reactivities that can be used to distinguish different species. Additionally, it is shown that gas-phase HDX kinetics can be exploited to provide even further distinguishing capabilities by using different partial pressures of reagent gas. The relative HDX reactivity of a wide variety of molecules is discussed in light of the various molecular structures. Additionally, hydrogen accessibility scoring (HAS) and HDX kinetics modeling of candidate ( in silico) ion structures is utilized to estimate the relative ion conformer populations giving rise to specific HDX behavior. These data interpretation methods are discussed with a focus on developing predictive tools for HDX behavior. Finally, an example is provided in which ion mobility information is supplemented with HDX reactivity data to aid identification efforts of compounds in a metabolite extract.

Adaptation of a 3-D Quadrupole Ion Trap for Dipolar DC Collisional Activation

PubMed Central

Prentice, Boone M.; Santini, Robert E.; McLuckey, Scott A.

2011-01-01

Means to allow for the application of a dipolar DC pulse to the end-cap electrodes of a three-dimensional (3-D) quadrupole ion trap for as short as a millisecond to as long as hundreds of milliseconds are described. The implementation of dipolar DC does not compromise the ability to apply AC waveforms to the end-cap electrodes at other times in the experiment. Dipolar DC provides a nonresonant means for ion acceleration by displacing ions from the center of the ion trap where they experience stronger rf electric fields, which increases the extent of micro-motion. The evolution of the product ion spectrum to higher generation products with time, as shown using protonated leucine enkephalin as a model protonated peptide, illustrates the broad-band nature of the activation. Dipolar DC activation is also shown to be effective as an ion heating approach in mimicking high amplitude short time excitation (HASTE)/pulsed Q dissociation (PQD) resonance excitation experiments that are intended to enhance the likelihood for observing low m/z products in ion trap tandem mass spectrometry. PMID:21953251

Foreshock waves as observed in energetic ion flux

NASA Astrophysics Data System (ADS)

Petrukovich, A. A.; Chugunova, O. M.; Inamori, T.; Kudela, K.; Stetiarova, J.

2017-05-01

Oscillations of energetic ion fluxes with periods 10-100 s are often present in the Earth's foreshock. Detailed analysis of wave properties with Time History of Events and Macroscale Interactions during Substorms data and comparisons with other data sets confirm that these oscillations are the previously unnoticed part of well-known "30 s" waves but are observed mainly for higher-speed solar wind. Simultaneous magnetic oscillations have similar periods, large amplitudes, and nonharmonic unstable waveforms or shocklet-type appearance, suggesting their nonlinearity, also typical for high solar wind speed. Analysis of the general foreshock data set of Interball project shows that the average flux of the backstreaming energetic ions increases more than 1 order of magnitude, when solar wind speed increases from 400 to 500 km/s.

Highly Efficient Transmitter for High Peak to Average Power Ratio (PAPR) Waveforms

DTIC Science & Technology

2011-01-19

on the modulated signal topology. N00039-10-C-0071 Page 1 ACRONYM DESCRIPTION FREQUENCY Lower Upper MHz MHz ACAS Avionics Identification ...450 GSM Global Mobile Communications 380 921 HAVE QUICK Military Aircraft Radio 225 400 IFF Avionics Identification . Collision Avoidance and...Channel Ground Air Radio System 30 88 TCAS Avionics Identification , Collision Avoidance and Traffic Alert 1030 1090 VIII Air Traffic Control (Civilian

A flowing atmospheric pressure afterglow as an ion source coupled to a differential mobility analyzer for volatile organic compound detection.

PubMed

Bouza, Marcos; Orejas, Jaime; López-Vidal, Silvia; Pisonero, Jorge; Bordel, Nerea; Pereiro, Rosario; Sanz-Medel, Alfredo

2016-05-23

Atmospheric pressure glow discharges have been widely used in the last decade as ion sources in ambient mass spectrometry analyses. Here, an in-house flowing atmospheric pressure afterglow (FAPA) has been developed as an alternative ion source for differential mobility analysis (DMA). The discharge source parameters (inter-electrode distance, current and helium flow rate) determining the atmospheric plasma characteristics have been optimized in terms of DMA spectral simplicity with the highest achievable sensitivity while keeping an adequate plasma stability and so the FAPA working conditions finally selected were: 35 mA, 1 L min(-1) of He and an inter-electrode distance of 8 mm. Room temperature in the DMA proved to be adequate for the coupling and chemical analysis with the FAPA source. Positive and negative ions for different volatile organic compounds were tested and analysed by FAPA-DMA using a Faraday cup as a detector and proper operation in both modes was possible (without changes in FAPA operational parameters). The FAPA ionization source showed simpler ion mobility spectra with narrower peaks and a better, or similar, sensitivity than conventional UV-photoionization for DMA analysis in positive mode. Particularly, the negative mode proved to be a promising field of further research for the FAPA ion source coupled to ion mobility, clearly competitive with other more conventional plasmas such as corona discharge.

Improved momentum-transfer theory for ion mobility. 1. Derivation of the fundamental equation.

PubMed

Siems, William F; Viehland, Larry A; Hill, Herbert H

2012-11-20

For the first time the fundamental ion mobility equation is derived by a bottom-up procedure, with N real atomic ion-atomic neutral collisions replaced by N repetitions of an average collision. Ion drift velocity is identified as the average of all pre- and postcollision velocities in the field direction. To facilitate velocity averaging, collisions are sorted into classes that "cool" and "heat" the ion. Averaging over scattering angles establishes mass-dependent relationships between pre- and postcollision velocities for the cooling and heating classes, and a combined expression for drift velocity is obtained by weighted addition according to relative frequencies of the cooling and heating encounters. At zero field this expression becomes identical to the fundamental low-field ion mobility equation. The bottom-up derivation identifies the low-field drift velocity as 3/4 of the average precollision ion velocity in the field direction and associates the passage from low-field to high-field conditions with the increasing dominance of "cooling" collisions over "heating" collisions. Most significantly, the analysis provides a direct path for generalization to fields of arbitrary strength.

Aerosol Vacuum-Assisted Plasma Ionization (Aero-VaPI) Coupled to Ion Mobility-Mass Spectrometry

NASA Astrophysics Data System (ADS)

Blair, Sandra L.; Ng, Nga L.; Zambrzycki, Stephen C.; Li, Anyin; Fernández, Facundo M.

2018-02-01

In this communication, we report on the real-time analysis of organic aerosol particles by Vacuum-assisted Plasma Ionization-Mass Spectrometry (Aero-VaPI-MS) using a home-built VaPI ion source coupled to a Synapt G2-S HDMS ion mobility-mass spectrometry (IM-MS) system. Standards of organic molecules of interest in prebiotic chemistry were used to generate aerosols. Monocaprin and decanoic acid aerosol particles were successfully detected in both the positive and negative ion modes, respectively. A complex aerosol mixture of different sizes of polymers of L-malic acid was also examined through ion mobility (IM) separations, resulting in the detection of polymers of up to eight monomeric units. This noncommercial plasma ion source is proposed as a low cost alternative to other plasma ionization platforms used for aerosol analysis, and a higher-performance alternative to more traditional aerosol mass spectrometers. VaPI provides robust online ionization of organics in aerosols without extensive ion activation, with the coupling to IM-MS providing higher peak capacity and excellent mass accuracy. [Figure not available: see fulltext.

High magnesium mobility in ternary spinel chalcogenides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Canepa, Pieremanuele; Bo, Shou-Hang; Sai Gautam, Gopalakrishnan

Magnesium batteries appear a viable alternative to overcome the safety and energy density limitations faced by current lithium-ion technology. Furthermore, the development of a competitive magnesium battery is plagued by the existing notion of poor magnesium mobility in solids. We demonstrate by using ab initio calculations, nuclear magnetic resonance, and impedance spectroscopy measurements that substantial magnesium ion mobility can indeed be achieved in close-packed frameworks (~ 0.01-0.1 mS cm -1 at 298 K), specifically in the magnesium scandium selenide spinel. Our theoretical predictions also indicate that high magnesium ion mobility is possible in other chalcogenide spinels, opening the door formore » the realization of other magnesium solid ionic conductors and the eventual development of an all-solid-state magnesium battery.« less

High magnesium mobility in ternary spinel chalcogenides

DOE PAGES

Canepa, Pieremanuele; Bo, Shou-Hang; Sai Gautam, Gopalakrishnan; ...

2017-11-24

Magnesium batteries appear a viable alternative to overcome the safety and energy density limitations faced by current lithium-ion technology. Furthermore, the development of a competitive magnesium battery is plagued by the existing notion of poor magnesium mobility in solids. We demonstrate by using ab initio calculations, nuclear magnetic resonance, and impedance spectroscopy measurements that substantial magnesium ion mobility can indeed be achieved in close-packed frameworks (~ 0.01-0.1 mS cm -1 at 298 K), specifically in the magnesium scandium selenide spinel. Our theoretical predictions also indicate that high magnesium ion mobility is possible in other chalcogenide spinels, opening the door formore » the realization of other magnesium solid ionic conductors and the eventual development of an all-solid-state magnesium battery.« less

Graphene/Pentacene Barristor with Ion-Gel Gate Dielectric: Flexible Ambipolar Transistor with High Mobility and On/Off Ratio.

PubMed

Oh, Gwangtaek; Kim, Jin-Soo; Jeon, Ji Hoon; Won, EunA; Son, Jong Wan; Lee, Duk Hyun; Kim, Cheol Kyeom; Jang, Jingon; Lee, Takhee; Park, Bae Ho

2015-07-28

High-quality channel layer is required for next-generation flexible electronic devices. Graphene is a good candidate due to its high carrier mobility and unique ambipolar transport characteristics but typically shows a low on/off ratio caused by gapless band structure. Popularly investigated organic semiconductors, such as pentacene, suffer from poor carrier mobility. Here, we propose a graphene/pentacene channel layer with high-k ion-gel gate dielectric. The graphene/pentacene device shows both high on/off ratio and carrier mobility as well as excellent mechanical flexibility. Most importantly, it reveals ambipolar behaviors and related negative differential resistance, which are controlled by external bias. Therefore, our graphene/pentacene barristor with ion-gel gate dielectric can offer various flexible device applications with high performances.

Improved Differential Ion Mobility Separations Using Linked Scans of Carrier Gas Composition and Compensation Field

NASA Astrophysics Data System (ADS)

Santiago, Brandon G.; Harris, Rachel A.; Isenberg, Samantha L.; Ridgeway, Mark E.; Pilo, Alice L.; Kaplan, Desmond A.; Glish, Gary L.

2015-07-01

Differential ion mobility spectrometry (DIMS) separates ions based on differences in their mobilities in low and high electric fields. When coupled to mass spectrometric analyses, DIMS has the ability to improve signal-to-background by eliminating isobaric and isomeric compounds for analytes in complex mixtures. DIMS separation power, often measured by resolution and peak capacity, can be improved through increasing the fraction of helium in the nitrogen carrier gas. However, because the mobility of ions is higher in helium, a greater number of ions collide with the DIMS electrodes or housing, yielding losses in signal intensity. To take advantage of the benefits of helium addition on DIMS separations and reduce ion losses, linked scans were developed. In a linked scan the helium content of the carrier gas is reduced as the compensation field is increased. Linked scans were compared with conventional compensation field scans with constant helium content for the protein ubiquitin and a tryptic digest of bovine serum albumin (BSA). Linked scans yield better separation of ubiquitin charge states and enhanced peak capacities for the analysis of BSA compared with compensation field scans with constant helium carrier gas percentages. Linked scans also offer improved signal intensity retention in comparison to compensation field scans with constant helium percentages in the carrier gas.

Ion-neutral potential models in atmospheric pressure ion mobility time-of-flight mass spectrometry IM(tof)MS.

PubMed

Steiner, Wes E; English, William A; Hill, Herbert H

2006-02-09

The ion mobilities and their respective masses of several classes of amines (primary, secondary, and tertiary) were measured by electrospray ionization atmospheric pressure ion mobility time-of-flight mass spectrometry IM(tof)MS. The experimental data obtained were comparatively analyzed by the one-temperature kinetic theory of Chapman-Enskog. Several theoretical models were used to estimate the collision cross-sections; they include the rigid-sphere, polarization-limit, 12-6-4, and 12-4 potential models. These models were investigated to represent the interaction potentials contained within the collision integral that occurs between the polyatomic ions and the neutral drift gas molecules. The effectiveness of these collision cross-section models on predicting the mobility of these amine ions was explored. Moreover, the effects of drift gas selectivity on the reduced-mass term and in the collision cross-section term was examined. Use of a series of drift gases, namely, helium, neon, argon, nitrogen, and carbon dioxide, made it possible to distinguish between mass effects and polarizability effects. It was found that the modified 12-4 potential that compensates for the center of charge not being at the same location as the centers of mass showed improved agreement over the other collision cross-section models with respect to experimental data.

Internal friction and vulnerability of mixed alkali glasses.

PubMed

Peibst, Robby; Schott, Stephan; Maass, Philipp

2005-09-09

Based on a hopping model we show how the mixed alkali effect in glasses can be understood if only a small fraction c(V) of the available sites for the mobile ions is vacant. In particular, we reproduce the peculiar behavior of the internal friction and the steep fall ("vulnerability") of the mobility of the majority ion upon small replacements by the minority ion. The single and mixed alkali internal friction peaks are caused by ion-vacancy and ion-ion exchange processes. If c(V) is small, they can become comparable in height even at small mixing ratios. The large vulnerability is explained by a trapping of vacancies induced by the minority ions. Reasonable choices of model parameters yield typical behaviors found in experiments.

[Ion mobility spectrometer (IMS): a novel online monitor of trace volatile organic compounds].

PubMed

Li, Fang; Xie, Zhi-yong; Schmidt, H; Sielemann, S; Baumbach, J I

2002-12-01

The principle, character and developments of the instrument of ion mobility spectrometry are introduced, the applications of IMS to chemical warfare agents, explosives, drugs, environments monitoring and on-site industrial sensing are discussed, and some work on IMS in ISAS is represented.

An Investigation of Traveling-Wave Electrophoresis using a Trigonometric Potential

NASA Astrophysics Data System (ADS)

Vopal, James

Traveling-wave electrophoresis, a technique for microfluidic separations in lab-on-achip devices, is investigated using a trigonometric model that naturally incorporates the spatial periodicity of the device. Traveling-wave electrophoresis can be used to separate high-mobility ions from low-mobility ions in forensic and medical applications, with a separation threshold that can be tuned for specific applications by simply choosing the traveling wave frequency. Our simulations predict plateaus in the average ion velocity verses the mobility, plateaus that correspond to Farey fractions and yield Devil's staircases for non-zero discreteness values. The plateaus indicate that ions with different mobilities can travel with the same average velocity. To determine the conditions for chaos, Lyapunov exponents and contact maps are employed. Through the use of contact maps, the chaotic trajectories are determined to be either narrowband or broadband. Narrowband chaotic trajectories are exhibited in the plateaus of the average velocity, while broadband chaotic trajectories are exhibited where the average velocity varies nonmonotonically with the mobility. Narrowband chaos will be investigated in future work incorporating the role of diffusion. The results of this and future work can be used to develop new tools for electrophoretic separation.

Electrotransfer in Liquid Binary Aluminum Alloys

NASA Astrophysics Data System (ADS)

Tekuchev, V. V.; Kalinkin, D. P.; Ivanova, I. V.

2018-07-01

The mobility of ions in a liquid binary metal system based on aluminum is calculated for the first time in a wide range of concentrations, based on studies of its resistivity and self-diffusion coefficient. It is established that in an Al-Cu system, the ions of aluminum move to the anode, while Al-Mg, Al-Sn, and Al-Sb move to the cathode; i.e., there is inversion of the electrotransfer of aluminum ions. When the concentration of a component is reduced, the mobility of its ions is increased by the module.

Exchange, interpretation, and database-search of ion mobility spectra supported by data format JCAMP-DX

NASA Technical Reports Server (NTRS)

Baumback, J. I.; Davies, A. N.; Vonirmer, A.; Lampen, P. H.

1995-01-01

To assist peak assignment in ion mobility spectrometry it is important to have quality reference data. The reference collection should be stored in a database system which is capable of being searched using spectral or substance information. We propose to build such a database customized for ion mobility spectra. To start off with it is important to quickly reach a critical mass of data in the collection. We wish to obtain as many spectra combined with their IMS parameters as possible. Spectra suppliers will be rewarded for their participation with access to the database. To make the data exchange between users and system administration possible, it is important to define a file format specially made for the requirements of ion mobility spectra. The format should be computer readable and flexible enough for extensive comments to be included. In this document we propose a data exchange format, and we would like you to give comments on it. For the international data exchange it is important, to have a standard data exchange format. We propose to base the definition of this format on the JCAMP-DX protocol, which was developed for the exchange of infrared spectra. This standard made by the Joint Committee on Atomic and Molecular Physical Data is of a flexible design. The aim of this paper is to adopt JCAMP-DX to the special requirements of ion mobility spectra.

Travelling-wave ion mobility and negative ion fragmentation of high mannose N-glycans

PubMed Central

Harvey, David J.; Scarff, Charlotte A.; Edgeworth, Matthew; Struwe, Weston B.; Pagel, Kevin; Thalassinos, Konstantinos; Crispin, Max; Scrivens, Jim

2016-01-01

The isomeric structure of high-mannose N-glycans can significantly impact biological recognition events. Here, the utility of travelling-wave ion mobility-mass spectrometry (TW IM-MS)for isomer separation of high-mannose N-glycans is investigated. Negative ion fragmentation using collision-induced dissociation (CID) gave more informative spectra than positive ion spectra with mass-different fragment ions characterizing many of the isomers. Isomer separation by ion mobility in both ionization modes was generally limited, with the arrival time distributions (ATD) often showing little sign of isomers. However, isomers could be partially resolved by plotting extracted fragment ATDs of the diagnostic fragment ions from the negative ion spectra and the fragmentation spectra of the isomers could be extracted by using ions from limited areas of the ATD peak. In some cases, asymmetric ATDs were observed but no isomers could be detected by fragmentation. In these cases, it was assumed that conformers were being separated. Collision cross sections (CCSs) of the isomers in positive and negative fragmentation mode were estimated from TW IM-MS data using dextran glycans as calibrant. More complete CCS data were achieved in negative ion mode by utilizing the diagnostic fragment ions. Examples of isomer separations are shown for N-glycans released from the well-characterized glycoproteins chicken ovalbumin, porcine thyroglobulin and gp120 from the human immunodeficiency virus. In addition to the cross sectional data, details of the negative ion collision-induced dissociation (CID) spectra of all resolved isomers are discussed. PMID:26956389

A salient effect of density on the dynamics of nonaqueous electrolytes.

PubMed

Han, Sungho

2017-04-24

The mobility and solvation of lithium ions in electrolytes are crucial for the performance and safety of lithium ion batteries. It has been known that a single type of solvent cannot satisfy the requirements of both mobility and solvation simultaneously for electrolytes. Therefore, complex solvent mixtures have been used to optimize both properties. Here we present the effects of density on the dynamics and solvation of organic liquid electrolytes via extensive molecular dynamics simulations. Our study finds that a small variation in density can induce a significant effect on the mobility of electrolytes but does not influence the solvation structure of a lithium ion. It turns out that an adjustment of the density of electrolytes could provide a more effective way to enhance mobility than a control of the solvent mixture ratio of electrolytes. Our study reveals that the density change of electrolytes mainly affects the residence time of solvents in the first solvation shell of a lithium ion rather than the structural change of the solvation sheath. Finally, our results suggest an intriguing point for understanding and designing electrolytes of lithium ion batteries for better performance and safety.

A salient effect of density on the dynamics of nonaqueous electrolytes

NASA Astrophysics Data System (ADS)

Han, Sungho

2017-04-01

The mobility and solvation of lithium ions in electrolytes are crucial for the performance and safety of lithium ion batteries. It has been known that a single type of solvent cannot satisfy the requirements of both mobility and solvation simultaneously for electrolytes. Therefore, complex solvent mixtures have been used to optimize both properties. Here we present the effects of density on the dynamics and solvation of organic liquid electrolytes via extensive molecular dynamics simulations. Our study finds that a small variation in density can induce a significant effect on the mobility of electrolytes but does not influence the solvation structure of a lithium ion. It turns out that an adjustment of the density of electrolytes could provide a more effective way to enhance mobility than a control of the solvent mixture ratio of electrolytes. Our study reveals that the density change of electrolytes mainly affects the residence time of solvents in the first solvation shell of a lithium ion rather than the structural change of the solvation sheath. Finally, our results suggest an intriguing point for understanding and designing electrolytes of lithium ion batteries for better performance and safety.

Miniaturized Ion Mobility Spectrometer

NASA Technical Reports Server (NTRS)

Stimac, Robert M. (Inventor); Kaye, William J (Inventor)

2017-01-01

By utilizing the combination of a unique electronic ion injection control circuit in conjunction with a particularly designed drift cell construction, the instantly disclosed ion mobility spectrometer (IMS) achieves increased levels of sensitivity, while achieving significant reductions in size and weight. The instant IMS is of a much simpler and easy to manufacture design, rugged and hermetically sealed, capable of operation at high temperatures to at least 250 degrees Centigrade, and is uniquely sensitive, particularly to explosive chemicals.

Miniaturized Ion Mobility Spectrometer

NASA Technical Reports Server (NTRS)

Kaye, William J. (Inventor); Stimac, Robert M. (Inventor)

2015-01-01

By utilizing the combination of a unique electronic ion injection control circuit in conjunction with a particularly designed drift cell construction, the instantly disclosed ion mobility spectrometer achieves increased levels of sensitivity, while achieving significant reductions in size and weight. The instant IMS is of a much simpler and easy to manufacture design, rugged and hermetically sealed, capable of operation at high temperatures to at least 250.degree. C., and is uniquely sensitive, particularly to explosive chemicals.

Note: Buffer gas temperature inhomogeneities and design of drift-tube ion mobility spectrometers: Warnings for real-world applications by non-specialists

NASA Astrophysics Data System (ADS)

Fernandez-Maestre, R.

2017-09-01

Ion mobility spectrometry (IMS) separates gas phase ions moving under an electric field according to their size-to-charge ratio. IMS is the method of choice to detect illegal drugs and explosives in customs and airports making accurate determination of reduced ion mobilities (K0) important for national security. An ion mobility spectrometer with electrospray ionization coupled to a quadrupole mass spectrometer was used to study uncertainties in buffer gas temperatures during mobility experiments. Differences up to 16°C were found in the buffer gas temperatures in different regions of the drift tube and up to 42°C between the buffer gas and the drift tube temperatures. The drift tube temperature is used as an approximation to the buffer gas temperature for the calculation of K0 because the buffer gas temperature is hard to measure. This is leading to uncertainties in the determination of K0 values. Inaccurate determination of K0 values yields false positives that delay the cargo and passengers in customs and airports. Therefore, recommendations are issued for building mobility tubes to assure a homogeneous temperature of the buffer gas. Because the temperature and other instrumental parameters are difficult to measure in IMS, chemical standards should always be used when calculating K0. The difference of 42°C between the drift tube and buffer gas temperatures found in these experiments produces a 10.5% error in the calculation of K0. This large inaccuracy in K0 shows the importance of a correct temperature measurement in IMS.

Ultra High-Resolution Electrospray Ionization/Ion Mobility Spectrometer System for In-Situ Detection of Organic Compounds

NASA Technical Reports Server (NTRS)

Kanik, I.; Beegle, L. W.; Hill, H. H.

2001-01-01

The potential of the high-resolution Electrospray Ionization/Ion Mobility Spectrometry (ESI/IMS) technique as analytical separation tool in analyzing bio-molecular mixtures in the search for the chemical signatures of life is demonstrated. Additional information is contained in the original extended abstract.

Influence of variation in mobile phase pH and solute pK(a) with the change of organic modifier fraction on QSRRs of hydrophobicity and RP-HPLC retention of weakly acidic compounds.

PubMed

Han, Shu-ying; Liang, Chao; Zou, Kuan; Qiao, Jun-qin; Lian, Hong-zhen; Ge, Xin

2012-11-15

The variation in mobile phase pH and ionizable solute dissociation constant (pK(a)) with the change of organic modifier fraction in hydroorganic mobile phase has seemingly been a troublesome problem in studies and applications of reversed phase high performance liquid chromatography (RP-HPLC). Most of the early studies regarding the RP-HPLC of acid-base compounds have to measure the actual pH of the mixed mobile phase rigorously, sometimes bringing difficulties in the practices of liquid chromatographic separation. In this paper, the effect of this variation on the apparent n-octanol/water partition coefficient (K(ow)″) and the related quantitative structure-retention relationship (QSRR) of logK(ow)″ vs. logk(w), the logarithm of retention factor of analytes in neat aqueous mobile phases, was investigated for weakly acidic compounds. This QSRR is commonly used as a classical method for K(ow) measurement by RP-HPLC. The theoretical and experimental derivation revealed that the variation in mobile phase pH and solute pK(a) will not affect the QSRRs of acidic compounds. This conclusion is proved to be suitable for various types of ion-suppressors, i.e., strong acid (perchloric acid), weak acid (acetic acid) and buffer salt (potassium dihydrogen phosphate/phosphoric acid, PBS). The QSRRs of logK(ow)″ vs. logk(w) were modeled by 11 substituted benzoic acids using different types of ion-suppressors in a binary methanol-water mobile phase to confirm our deduction. Although different types of ion-suppressor all can be used as mobile phase pH modifiers, the QSRR model obtained by using perchloric acid as the ion-suppressor was found to have the best result, and the slightly inferior QSRRs were obtained by using acetic acid or PBS as the ion-suppressor. Copyright © 2012 Elsevier B.V. All rights reserved.

Terahertz transmission properties of silicon wafers using continuous-wave terahertz spectroscopy

NASA Astrophysics Data System (ADS)

Kim, Chihoon; Ahn, Jae Sung; Ji, Taeksoo; Eom, Joo Beom

2017-04-01

We present the spectral properties of Si wafers using continuous-wave terahertz (CW-THz) spectroscopy. By using a tunable laser source and a fixed distributed-feedback laser diode (DFB-LD), a stably tunable beat source for CW-THz spectroscopy system can be implemented. THz radiation is generated in the frequency range of 100 GHz-800 GHz by photomixing in a photoconductive antenna. We also measured CW-THz waveforms by changing the beat frequency and confirmed repeatability through repeated measurement. We calculated the peaks of the THz frequency by taking fast Fourier transforms (FFTs) of measured THz waveforms. The feasibility of CW-THz spectroscopy is demonstrated by the THz spectra of Si wafers with different resistivities, mobilities, and carrier concentrations. The results show that Si wafers with a lower resistivity absorb more THz waves. Thus, we expect our CW-THz system to have the advantage of being able to perform fast non-destructive analysis.

Application of ion mobility-mass spectrometry to microRNA analysis.

PubMed

Takebayashi, Kosuke; Hirose, Kenji; Izumi, Yoshihiro; Bamba, Takeshi; Fukusaki, Eiichiro

2013-03-01

Liquid chromatography/mass spectrometry is widely used for studying sequence determination and modification analysis of small RNAs. However, the efficiency of liquid chromatography-based separation of intact small RNA species is insufficient, since the physiochemical properties among small RNAs are very similar. In this study, we focused on ion mobility-mass spectrometry (IM-MS), which is a gas-phase separation technique coupled with mass spectrometry; we have evaluated the utility of IM-MS for microRNA (miRNA) analysis. A multiply charged deprotonated ion derived from an 18-24-nt-long miRNA was formed by electrospray ionization, and then the time, called the "drift time", taken by each ion to migrate through a buffer gas was measured. Each multivalent ion was temporally separated on the basis of the charge state and structural formation; 3 types of unique mass-mobility correlation patterns (i.e., chainlike-form, hairpin-form, and dimer-form) were present on the two-dimensional mobility-mass spectrum. Moreover, we found that the ion size (sequence length) and the secondary structures of the small RNAs strongly contributed to the IM-MS-based separation, although solvent conditions such as pH had no effect. Therefore, sequence isomers could also be discerned by the selection of each specific charged ion, i.e., the 6(-) charged ion reflected a majority among chainlike-, hairpin-, and other structures. We concluded that the IM-MS provides additional capability for separation; thus, this analytical method will be a powerful tool for comprehensive small RNA analysis. Copyright © 2012. Published by Elsevier B.V.

Utilizing Ion-Mobility Data to Estimate Molecular Masses

NASA Technical Reports Server (NTRS)

Duong, Tuan; Kanik, Isik

2008-01-01

A method is being developed for utilizing readings of an ion-mobility spectrometer (IMS) to estimate molecular masses of ions that have passed through the spectrometer. The method involves the use of (1) some feature-based descriptors of structures of molecules of interest and (2) reduced ion mobilities calculated from IMS readings as inputs to (3) a neural network. This development is part of a larger effort to enable the use of IMSs as relatively inexpensive, robust, lightweight instruments to identify, via molecular masses, individual compounds or groups of compounds (especially organic compounds) that may be present in specific environments or samples. Potential applications include detection of organic molecules as signs of life on remote planets, modeling and detection of biochemicals of interest in the pharmaceutical and agricultural industries, and detection of chemical and biological hazards in industrial, homeland-security, and industrial settings.

Structural Characterization of Unsaturated Phosphatidylcholines Using Traveling Wave Ion Mobility Spectrometry

PubMed Central

Kim, Hugh I.; Kim, Hyungjun; Pang, Eric S.; Ryu, Ernest K.; Beegle, Luther W.; Loo, Joseph A.; Goddard, William A.; Kanik, Isik

2009-01-01

A number of phosphatidylcholine (PC) cations spanning a mass range of 400 to 1000 Da are investigated using electrospray ionization mass spectrometry coupled with traveling wave ion mobility spectrometry (TWIMS). A high correlation between mass and mobility is demonstrated with saturated phosphatidylcholine cations in N2. A significant deviation from this mass-mobility correlation line is observed for the unsaturated PC cation. We found that the double bond in the acyl chain causes a 5% reduction in drift time. The drift time is reduced at a rate of ~1% for each additional double bond. Theoretical collision cross sections of PC cations exhibit good agreement with experimentally evaluated values. Collision cross sections are determined using the recently derived relationship between mobility and drift time in TWIMS stacked ring ion guide (SRIG) and compared to estimate collision cross-sections using empiric calibration method. Computational analysis was performed using the modified trajectory (TJ) method with nonspherical N2 molecules as the drift gas. The difference between estimated collision cross-sections and theoretical collision cross-sections of PC cations is related to the sensitivity of the PC cation collision cross-sections to the details of the ion-neutral interactions. The origin of the observed correlation and deviation between mass and mobility of PC cations is discussed in terms of the structural rigidity of these molecules using molecular dynamic simulations. PMID:19764704

Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Space Systems, Norfolk, Virginia, 22-25 February 1982. Volume 2

DTIC Science & Technology

1982-02-25

However, because the mobility of the ions is much smaller than the mobility of the electrons (for cesium i = 1/500 Me), and because of ion...space applications of this high temperature in- sulation. Use of glass-alumina insulation for motors in mobile applications would reduce cooling...present and/or mobile only during irradiation. VII-7-7 WS 710 01AS$ AesowRpIOr MEA8IJRtED MOt AN FTER L5 MvV ELECTRON NtADIATION Fig. 7 -- Growth of

Field ion spectrometry: a new technology for cocaine and heroin detection

NASA Astrophysics Data System (ADS)

Carnahan, Byron L.; Day, Stephen; Kouznetsov, Viktor; Tarassov, Alexandre

1997-02-01

Field ion spectrometry, also known as transverse field compensation ion mobility spectrometry, is a new technique for trace gas analysis that can be applied to the detection of cocaine and heroin. Its principle is based on filtering ion species according to the functional dependence of their mobilities with electric field strength. Field ion spectrometry eliminates the gating electrodes needed in conventional IMS to pulse ions into the spectrometer; instead, ions are injected in to the spectrometer and reach the detector continuously, resulting in improved sensitivity. The technique enables analyses that are difficult with conventional constant field strength ion mobility spectrometers. We have shown that a filed ion spectrometer can selectively detect the vapors from cocaine and heroin emitted from both their base and hydrochloride forms. The estimated volumetric limits of detection are in the low pptv range, based on testing with standardized drug vapor generation systems. The spectrometer can detect cocaine base in the vapor phase, at concentrations well below its estimated 100 pptv vapor pressure equivalent at 20 degrees C. This paper describes the underlying principles of field ion spectrometry in relation to narcotic drug detection, and recent results obtained for cocaine and heroin. The work has been sponsored in part by the United States Advanced Research Projects Agency under contract DAAB10-95C-0004, for the DOD Counterdrug Technology Development Program.

Ion manipulations in structures for lossless ion manipulations (SLIM): computational evaluation of a 90° turn and a switch

DOE PAGES

Garimella, Sandilya V. B.; Ibrahim, Yehia. M.; Webb, Ian K.; ...

2015-08-19

The process of redirecting ions through 90° turns and ‘tee’ switches utilizing Structures for Lossless Ion Manipulations (SLIM) was evaluated using theoretical and simulation methods at 4 Torr pressure. SIMION simulations were used to optimize and evaluate conditions for performing turns without loss of signal intensity or ion mobility resolving power. Fundamental considerations indicated that the “race track” effect during ion turns may incur only small losses to the ion mobility resolving power at 4 Torr pressure for the typical plume widths predicted in an optimized SLIM ‘tee’ switch design. The dynamic switching of ions into orthogonal channels was alsomore » evaluated using SIMION ion trajectory simulations, and achieved similar performance. Simulation results were in close agreement with experimental results and were used to refine SLIM designs and applied potentials for their use.« less

Construction and development of IGP DMC of China National Seismological Network

NASA Astrophysics Data System (ADS)

Zheng, X.; Zheng, J.; Lin, P.; Yao, Z.; Liang, J.

2011-12-01

In 2003, CEA (China Earthquake Administration) commenced the construction of China Digital Seismological Observation Network. By the end of 2007, a new-generation digital seismological observation system had been established, which consists of 1 National Seismic Network, 32 regional seismic networks, 2 small-aperture seismic arrays, 6 volcano monitoring networks and 19 mobile seismic networks, as well as CENC (China Earthquake Network Center) DMC (Data Management Centre) and IGP (Institute of Geophysics) DMC. Since then, the seismological observation system of China has completely entered a digital time. For operational, data backup and data security considerations, the DMC at the Institute of Geophysics (IGP), CEA was established at the end of 2007. IGP DMC now receives and archives waveform data from more than 1000 permanent seismic stations around China in real-time. After the great Wenchuan and Yushu earthquakes, the real-time waveform data from 56 and 8 portable seismic stations deployed in the aftershock area are added to IGP DMC. The technical system of IGP DMC is designed to conduct data management, processing and service through the network of CEA. We developed and integrated a hardware system with high-performance servers, large-capacity disc arrays, tape library and other facilities, as well as software packages for real-time waveform data receiving, storage, quality control, processing and service. Considering the demands from researchers for large quantities of seismic event waveform data, IGP DMC adopts an innovative "user order" method to extract event waveform data. Users can specify seismic stations, epicenter distance and record length. In a short period of 3 years, IGP DMC has supplied about 350 Terabytes waveform data to over 200 researches of more than 40 academic institutions. According to incomplete statistics, over 40 papers have been published in professional journals, in which 30 papers were indexed by SCI. Now, IGP DMC has become an important platform of promoting seismological researches in China. In the future, IGP DMC will continue to improve its technical system with powerful ability of waveform data processing, management and service, and to provide better and more data service to the research community. We expect IGP DMC to become an exchange and collaboration platform for geo-scientific researchers around the world.

The role of ion optics modeling in the design and development of ion mobility spectrometers

NASA Astrophysics Data System (ADS)

Griffin, Matthew T.

2005-05-01

Detection of trace gases by ion mobility spectroscopy (IMS) has become common in recent years. In fact, IMS devices are the most commonly deployed military devices for the detection of classical chemical warfare agents (CWA). IMS devices are protecting the homeland by aiding first responders in the identification of toxic industrial chemicals (TICs) and providing explosive and narcotic screening systems. Spurred by the asymmetric threat posed by new threat agents and the ever expanding list of toxic chemicals, research in the development, improvement, and optimization of IMS systems has increased. Much of the research is focused on increasing the sensitivity and selectivity of IMS systems. Ion optics is a large area of study in the field of mass spectrometry, but has been mostly overlooked in the design and development of IMS systems. Ion optics provides insight into particle trajectories, duty cycle, and efficiency of these systems. This paper will outline the role that ion optics can have in the development of IMS systems and introduce the trade space for traditional IMS as well as differential mobility spectroscopy.

Molecular Dynamics Simulations of Ion Transport and Mechanisms in Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Mogurampelly, Santosh; Ganesan, Venkat

2015-03-01

Using all atom molecular dynamics and trajectory-extending kinetic Monte Carlo simulations, we study the influence of Al2O3 nanoparticles on the transport properties of Li+ ions in polymer electrolytes consisting of polyethylene oxide (PEO) melt solvated with LiBF4 salt. We observe that the nanoparticles have a strong influence on polymer segmental dynamics which in turn correlates with the mobility of Li+ ions. Explicitly, polymer segmental relaxation times and Li+ ion residence times around polymer were found to increase with the addition of nanoparticles. We also observe that increasing short range repulsive interactions between nanoparticles and polymer membrane leads to increasing polymer dynamics and ion mobility. Overall, our simulation results suggest that nanoparticle induced changes in conformational and dynamic properties of the polymer influences the ion mobilities in polymer electrolytes and suggests possible directions for using such findings to improve the polymer matrix conductivity. The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing computing resources that have contributed to the research.

Assessment of the magnetic field exposure due to the battery current of digital mobile phones.

PubMed

Jokela, Kari; Puranen, Lauri; Sihvonen, Ari-Pekka

2004-01-01

Hand-held digital mobile phones generate pulsed magnetic fields associated with the battery current. The peak value and the waveform of the battery current were measured for seven different models of digital mobile phones, and the results were applied to compute approximately the magnetic flux density and induced currents in the phone-user's head. A simple circular loop model was used for the magnetic field source and a homogeneous sphere consisting of average brain tissue equivalent material simulated the head. The broadband magnetic flux density and the maximal induced current density were compared with the guidelines of ICNIRP using two various approaches. In the first approach the relative exposure was determined separately at each frequency and the exposure ratios were summed to obtain the total exposure (multiple-frequency rule). In the second approach the waveform was weighted in the time domain with a simple low-pass RC filter and the peak value was divided by a peak limit, both derived from the guidelines (weighted peak approach). With the maximum transmitting power (2 W) the measured peak current varied from 1 to 2.7 A. The ICNIRP exposure ratio based on the current density varied from 0.04 to 0.14 for the weighted peak approach and from 0.08 to 0.27 for the multiple-frequency rule. The latter values are considerably greater than the corresponding exposure ratios 0.005 (min) to 0.013 (max) obtained by applying the evaluation based on frequency components presented by the new IEEE standard. Hence, the exposure does not seem to exceed the guidelines. The computed peak magnetic flux density exceeded substantially the derived peak reference level of ICNIRP, but it should be noted that in a near-field exposure the external field strengths are not valid indicators of exposure. Currently, no biological data exist to give a reason for concern about the health effects of magnetic field pulses from mobile phones.

Profiling neuronal ion channelopathies with non-invasive brain imaging and dynamic causal models: Case studies of single gene mutations

PubMed Central

Gilbert, Jessica R.; Symmonds, Mkael; Hanna, Michael G.; Dolan, Raymond J.; Friston, Karl J.; Moran, Rosalyn J.

2016-01-01

Clinical assessments of brain function rely upon visual inspection of electroencephalographic waveform abnormalities in tandem with functional magnetic resonance imaging. However, no current technology proffers in vivo assessments of activity at synapses, receptors and ion-channels, the basis of neuronal communication. Using dynamic causal modeling we compared electrophysiological responses from two patients with distinct monogenic ion channelopathies and a large cohort of healthy controls to demonstrate the feasibility of assaying synaptic-level channel communication non-invasively. Synaptic channel abnormality was identified in both patients (100% sensitivity) with assay specificity above 89%, furnishing estimates of neurotransmitter and voltage-gated ion throughput of sodium, calcium, chloride and potassium. This performance indicates a potential novel application as an adjunct for clinical assessments in neurological and psychiatric settings. More broadly, these findings indicate that biophysical models of synaptic channels can be estimated non-invasively, having important implications for advancing human neuroimaging to the level of non-invasive ion channel assays. PMID:26342528

Comparison of Different Ion Mobility Setups Using Poly (Ethylene Oxide) PEO Polymers: Drift Tube, TIMS, and T-Wave

NASA Astrophysics Data System (ADS)

Haler, Jean R. N.; Massonnet, Philippe; Chirot, Fabien; Kune, Christopher; Comby-Zerbino, Clothilde; Jordens, Jan; Honing, Maarten; Mengerink, Ynze; Far, Johann; Dugourd, Philippe; De Pauw, Edwin

2018-01-01

Over the years, polymer analyses using ion mobility-mass spectrometry (IM-MS) measurements have been performed on different ion mobility spectrometry (IMS) setups. In order to be able to compare literature data taken on different IM(-MS) instruments, ion heating and ion temperature evaluations have already been explored. Nevertheless, extrapolations to other analytes are difficult and thus straightforward same-sample instrument comparisons seem to be the only reliable way to make sure that the different IM(-MS) setups do not greatly change the gas-phase behavior. We used a large range of degrees of polymerization (DP) of poly(ethylene oxide) PEO homopolymers to measure IMS drift times on three different IM-MS setups: a homemade drift tube (DT), a trapped (TIMS), and a traveling wave (T-Wave) IMS setup. The drift time evolutions were followed for increasing polymer DPs (masses) and charge states, and they are found to be comparable and reproducible on the three instruments. [Figure not available: see fulltext.

The Relationship between Bulk and Mobile Forms of Heavy Metals in Soils of Kursk

NASA Astrophysics Data System (ADS)

Nevedrov, N. P.; Protsenko, E. P.; Glebova, I. V.

2018-01-01

The contamination of Kursk urboecotopes by heavy metals (Pb, Cd, Zn, Cu, Ni) is considered. The relationships between the contents of bulk and mobile forms of heavy metal ions have been examined. The results of monitoring studies attest to a tendency for the accumulation of both bulk and mobile forms of heavy metals in the humus-accumulative horizon, except for bulk cadmium and mobile nickel. Linear and nonlinear regression models of the bulk contents of Pb, Cd, Zn, and Ni as dependent on the contents of their mobile forms have been developed. These models allow us to calculate the bulk content of heavy metal ions in the soils of urboecotopes using simpler methods of the extraction and laboratory determination of their mobile forms.

Mass spectrometry and tandem mass spectrometry of citrus limonoids.

PubMed

Tian, Qingguo; Schwartz, Steven J

2003-10-15

Methods for atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS/MS) of citrus limonoid aglycones and electrospray ionization tandem mass spectrometry (ESI-MS/MS) of limonoid glucosides are reported. The fragmentation patterns of four citrus limonoid aglycones (limonin, nomilin, obacunone, and deacetylnomilin) and six limonoid glucosides, that is, limonin 17-beta-D-glucopyranoside (LG), nomilin 17-beta-D-glucopyranoside (NG), nomilinic acid 17-beta-D-glucopyranoside (NAG), deacetyl nomilinic acid 17-beta-D-glucopyranoside (DNAG), obacunone 17-beta-D-glucopyranoside (OG), and obacunoic acid 17-beta-D-glucopyranoside (OAG) were investigated using a quadruple mass spectrometer in low-energy collisionally activated dissociation (CAD). The four limonoid aglycones and four limonoid glucosides (LG, OG, NAG, and DNAG) were purified from citrus seeds; the other two limonoid glucosides (NG and OAG) were tentatively identified in the crude extract of grapefruit seeds by ESI mass spectrometry in both positive and negative ion analysis. Ammonium hydroxide or acetic acid was added to the mobile phase to facilitate ionization. During positive ion APCI analysis of limonoid aglycones, protonated molecular ion, [M + H]+, or adduct ion, [M + NH3 + H]-, was formed as base peaks when ammonium hydroxide was added to the mobile phase. Molecular anions or adduct ions with acetic acid ([M + HOAc - H] and [M + HOAc]-) or a deprotonated molecular ion were produced during negative ion APCI analysis of limonoid aglycones, depending on the mobile-phase modifier used. Positive ion ESI-MS of limonoid glucosides produced adduct ions of [M + H + NH3]+, [M + Na]+, and [M + K]+ when ammonium hydroxide was added to the mobile phase. After collisionally activated dissociation (CAD) of the limonoid aglycone molecular ions in negative ion APCI analysis, fragment ions indicated structural information of the precursor ions, showing the presence of methyl, carboxyl, and oxygenated ring structure. CAD of the adduct ion [M + H + NH3]+ of limonoid glucosides produced the aglycone moiety corresponding to each glucoside. The combination of mass spectrometry and tandem mass spectrometry provides a powerful technique for identification and characterization of citrus limonoids.

A High-Pressure Hollow Cathode Discharge Source for Ion Mobility Spectrometers for In-Situ Detection of Organic Molecules on Mars

NASA Technical Reports Server (NTRS)

Beegle, L. W.; Noren, C.; Kanik, I.

2000-01-01

We have designed, constructed and begun testing of a new high-pressure (5-10 Torr) hollow cathode discharge source (HCDS) that can be utilized as an ionizer for ion mobility spectrometers as well as in a wide variety of mass analyzers.

Comprehensive lipidomic analysis of human plasma using multidimensional liquid- and gas-phase separations: Two-dimensional liquid chromatography-mass spectrometry vs. liquid chromatography-trapped-ion-mobility-mass spectrometry.

PubMed

Baglai, Anna; Gargano, Andrea F G; Jordens, Jan; Mengerink, Ynze; Honing, Maarten; van der Wal, Sjoerd; Schoenmakers, Peter J

2017-12-29

Recent advancements in separation science have resulted in the commercialization of multidimensional separation systems that provide higher peak capacities and, hence, enable a more-detailed characterization of complex mixtures. In particular, two powerful analytical tools are increasingly used by analytical scientists, namely online comprehensive two-dimensional liquid chromatography (LC×LC, having a second-dimension separation in the liquid phase) and liquid chromatography-ion mobility-spectrometry (LC-IMS, second dimension separation in the gas phase). The goal of the current study was a general assessment of the liquid-chromatography-trapped-ion-mobility-mass spectrometry (LC-TIMS-MS) and comprehensive two-dimensional liquid chromatography-mass spectrometry (LC×LC-MS) platforms for untargeted lipid mapping in human plasma. For the first time trapped-ion-mobility spectrometry (TIMS) was employed for the separation of the major lipid classes and ion-mobility-derived collision-cross-section values were determined for a number of lipid standards. The general effects of a number of influencing parameters have been inspected and possible directions for improvements are discussed. We aimed to provide a general indication and practical guidelines for the analyst to choose an efficient multidimensional separation platform according to the particular requirements of the application. Analysis time, orthogonality, peak capacity, and an indicative measure for the resolving power are discussed as main characteristics for multidimensional separation systems. Copyright © 2017 Elsevier B.V. All rights reserved.

Method for selective detection of explosives in mass spectrometer or ion mobility spectrometer at parts-per-quadrillion level

DOEpatents

Ewing, Robert G.; Atkinson, David A.; Clowers, Brian H.

2015-09-01

A method for selective detection of volatile and non-volatile explosives in a mass spectrometer or ion mobility spectrometer at a parts-per-quadrillion level without preconcentration is disclosed. The method comprises the steps of ionizing a carrier gas with an ionization source to form reactant ions or reactant adduct ions comprising nitrate ions (NO.sub.3.sup.-); selectively reacting the reactant ions or reactant adduct ions with at least one volatile or non-volatile explosive analyte at a carrier gas pressure of at least about 100 Ton in a reaction region disposed between the ionization source and an ion detector, the reaction region having a length which provides a residence time (tr) for reactant ions therein of at least about 0.10 seconds, wherein the selective reaction yields product ions comprising reactant ions or reactant adduct ions that are selectively bound to the at least one explosive analyte when present therein; and detecting product ions with the ion detector to determine presence or absence of the at least one explosive analyte.

Structure of alcohol cluster ions in the gas phase, according to spectrometry and ab initio calculations

NASA Astrophysics Data System (ADS)

Krisilov, A. V.; Lantsuzskaya, E. V.; Levina, A. M.

2017-01-01

Reduced ion mobility and scattering cross sections are calculated from experimentally obtained spectra of the ion mobility of linear aliphatic alcohols with carbon atom numbers from 2 to 9. A linear increase in the scattering cross sections as the molecular weight grows is found. According to the results from experiments and quantum chemical calculations, alcohol cluster ions do not form a compact structure. Neither are dipole moments compensated for during dimerization, in contrast to the aldehydes and ketones described earlier. It was concluded from ab initio calculations that charge delocalization in monomeric and dimeric ions of alcohols increases the dipole moment many times over.

Interpretation of inverted photocurrent transients in organic lead halide perovskite solar cells: proof of the field screening by mobile ions and determination of the space charge layer widths

DOE PAGES

Belisle, Rebecca A.; Nguyen, William H.; Bowring, Andrea R.; ...

2017-01-01

In Methyl Ammonium Lead Iodide (MAPI) perovskite solar cells, screening of the built-in field by mobile ions has been proposed as part of the cause of the large hysteresis observed in the current/voltage scans in many cells. Here, we show that photocurrent transients measured immediately (e.g. 100 μs) after a voltage step can provide direct evidence that this field screening exists. Just after a step to forward bias, the photocurrent transients are reversed in sign (i.e. inverted), and the magnitude of the inverted transients can be used to find an upper bound on the width of the space charge layersmore » adjacent to the electrodes. This in turn provides a lower bound on the mobile charge concentration, which we find to be ≳1 x 10 17 cm -3. Using a new photocurrent transient experiment, we show that the space charge layer thickness remains approximately constant as a function of bias, as expected for mobile ions in a solid electrolyte. We also discuss additional characteristics of the inverted photocurrent transients that imply either an unusually stable deep trapping, or a photo effect on the mobile ion conductivity.« less

Interpretation of inverted photocurrent transients in organic lead halide perovskite solar cells: proof of the field screening by mobile ions and determination of the space charge layer widths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belisle, Rebecca A.; Nguyen, William H.; Bowring, Andrea R.

In Methyl Ammonium Lead Iodide (MAPI) perovskite solar cells, screening of the built-in field by mobile ions has been proposed as part of the cause of the large hysteresis observed in the current/voltage scans in many cells. Here, we show that photocurrent transients measured immediately (e.g. 100 μs) after a voltage step can provide direct evidence that this field screening exists. Just after a step to forward bias, the photocurrent transients are reversed in sign (i.e. inverted), and the magnitude of the inverted transients can be used to find an upper bound on the width of the space charge layersmore » adjacent to the electrodes. This in turn provides a lower bound on the mobile charge concentration, which we find to be ≳1 x 10 17 cm -3. Using a new photocurrent transient experiment, we show that the space charge layer thickness remains approximately constant as a function of bias, as expected for mobile ions in a solid electrolyte. We also discuss additional characteristics of the inverted photocurrent transients that imply either an unusually stable deep trapping, or a photo effect on the mobile ion conductivity.« less

High-Performance Ion Mobility Spectrometry Using Hourglass Electrodynamic Funnel And Internal Ion Funnel

DOEpatents

Smith, Richard D.; Tang, Keqi; Shvartsburg, Alexandre A.

2004-11-16

A method and apparatus enabling increased sensitivity in ion mobility spectrometry/mass spectrometry instruments which substantially reduces or eliminates the loss of ions in ion mobility spectrometer drift tubes utilizing an hourglass electrodynamic ion funnel at the entrance to the drift tube and/or an internal ion funnel at the exit of the drift tube. An hourglass electrodynamic funnel is formed of at least an entry element, a center element, and an exit element, wherein the aperture of the center element is smaller than the aperture of the entry element and the aperture of the exit elements. Ions generated in a relatively high pressure region by an ion source at the exterior of the hourglass electrodynamic funnel are transmitted to a relatively low pressure region at the entrance of the hourglass funnel through a conductance limiting orifice. Alternating and direct electrical potentials are applied to the elements of the hourglass electrodynamic funnel thereby drawing ions into and through the hourglass electrodynamic funnel thereby introducing relatively large quantities of ions into the drift tube while maintaining the gas pressure and composition at the interior of the drift tube as distinct from those at the entrance of the electrodynamic funnel and allowing a positive gas pressure to be maintained within the drift tube, if desired. An internal ion funnel is provided within the drift tube and is positioned at the exit of said drift tube. The advantage of the internal ion funnel is that ions that are dispersed away from the exit aperture within the drift tube, such as those that are typically lost in conventional drift tubes to any subsequent analysis or measurement, are instead directed through the exit of the drift tube, vastly increasing the amount of ions exiting the drift tube.

Formation of iron complexs from trifluoroacetic acid based liquid chromatography mobile phases as interference ions in liquid chromatography/electrospray ionization mass spectrometric analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukla, Anil K.; Zhang, Rui; Orton, Daniel J.

Two unexpected singly charged ions at m/z 1103 and 944 have been observed in mass spectra obtained from electrospray ionization-mass spectrometric analysis of liquid chromatography effluents with mobile phases containing trifluoroacetic acid. Accurate mass measurement and tandem mass spectrometry studies revealed that these two ions are not due to any contamination from solvents and chemicals used for mobile and stationary phases or from the laboratory atmospheric environment. Instead these ions are clusters of trifluoroacetic acid formed in association with acetonitrile, water and iron from the stainless steel union used to connect the column with the electrospray tip and to applymore » high voltage; the molecular formulae are Fe+((OH)(H2O)2)9(CF3COOH)5 and Fe+((OH)(H2O)2)6 (CF3COOH)5.« less

Space charge effect in spectrometers of ion mobility increment with cylindrical drift chamber.

PubMed

Elistratov, A A; Sherbakov, L A

2007-01-01

We have amplified the model for the drift of ions under a non-uniform high-frequency electric field by taking space charge effect into account. By this means, we have investigated the effect of space charge on the dynamics of a single type of ions in a spectrometer of ion mobility increment with a cylindrical drift chamber. The counteraction of the space charge effect and the focusing effect is investigated. The output ion current saturation caused by the effect of the space charge is observed. The shape of the ion peak taking into consideration the space charge effect has been obtained. We show that the effect of the space charge is sufficient for the relative ion density greater than 10 ppt by order of magnitude (for a cylindrical geometry spectrometer with typical parameters).

A four dimensional separation method based on continuous heart-cutting gas chromatography with ion mobility and high resolution mass spectrometry.

PubMed

Lipok, Christian; Hippler, Jörg; Schmitz, Oliver J

2018-02-09

A two-dimensional GC (2D-GC) method was developed and coupled to an ion mobility-high resolution mass spectrometer, which enables the separation of complex samples in four dimensions (2D-GC, ion mobilility spectrometry and mass spectrometry). This approach works as a continuous multiheart-cutting GC-system (GC+GC), using a long modulation time of 20s, which allows the complete transfer of most of the first dimension peaks to the second dimension column without fractionation, in comparison to comprehensive two-dimensional gas chromatography (GCxGC). Hence, each compound delivers only one peak in the second dimension, which simplifies the data handling even when ion mobility spectrometry as a third and mass spectrometry as a fourth dimension are introduced. The analysis of a plant extract from Calendula officinales shows the separation power of this four dimensional separation method. The introduction of ion mobility spectrometry provides an additional separation dimension and allows to determine collision cross sections (CCS) of the analytes as a further physicochemical constant supporting the identification. A CCS database with more than 800 standard substances including drug-like compounds and pesticides was used for CCS data base search in this work. Copyright © 2017 Elsevier B.V. All rights reserved.

Measuring the effects of Coulomb repulsion via signal decay in an atmospheric pressure laser ionization ion mobility spectrometer.

PubMed

Ihlenborg, Marvin; Schuster, Ann-Kathrin; Grotemeyer, Juergen; Gunzer, Frank

2018-01-01

Using lasers in ion mobility spectrometry offers a lot of advantages compared to standard ionization sources. Especially, the ion yield can be drastically increased. It can, however, reach levels where the Coulomb repulsion leads to unwanted side effects. Here, we investigate how the Coulomb repulsion can be detected apart from the typical signal broadening by measuring effects created already in the reaction region and comparing them with corresponding finite element method simulations.

LC-IMS-MS Feature Finder

DOE Office of Scientific and Technical Information (OSTI.GOV)

2013-03-07

LC-IMS-MS Feature Finder is a command line software application which searches for possible molecular ion signatures in multidimensional liquid chromatography, ion mobility spectrometry, and mass spectrometry data by clustering deisotoped peaks with similar monoisotopic mass values, charge states, elution times, and drift times. The software application includes an algorithm for detecting multiple conformations and co-eluting species in the ion mobility dimension. LC-IMS-MS Feature Finder is designed to create an output file with detected features that includes associated information about the detected features.

Ring Current He Ion Control by Bounce Resonant ULF Waves

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Gerrard, Andrew J.; Lanzerotti, Louis J.; Soto-Chavez, Rualdo; Cohen, Ross J.; Manweiler, Jerry W.

2017-12-01

Ring current energy He ion (˜65 keV to ˜520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (˜9 h) of the spacecraft and is observed to be ˜50-100% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of tens of seconds. These periods correspond to the bounce resonant timescales of the ring current He ions being measured by RBSPICE. A statistical survey using the particle and field data for one full spacecraft precession period (approximately 2 years) shows that the wave and He ion flux variations are generally anticorrelated, suggesting the bounce resonant pitch angle scattering process as a major component in the scattering of He ions.

Deprotonation effect of tetrahydrofuran-2-carbonitrile buffer gas dopant in ion mobility spectrometry.

PubMed

Fernandez-Maestre, Roberto; Meza-Morelos, Dairo; Wu, Ching

2016-06-15

When dopants are introduced into the buffer gas of an ion mobility spectrometer, spectra are simplified due to charge competition. We used electrospray ionization to inject tetrahydrofuran-2-carbonitrile (F, 2-furonitrile or 2-furancarbonitrile) as a buffer gas dopant into an ion mobility spectrometer coupled to a quadrupole mass spectrometer. Density functional theory was used for theoretical calculations of dopant-ion interaction energies and proton affinities, using the hybrid functional X3LYP/6-311++(d,p) with the Gaussian 09 program that accounts for the basis set superposition error; analytes structures and theoretical calculations with Gaussian were used to explain the behavior of the analytes upon interaction with F. When F was used as a dopant at concentrations below 1.5 mmol m(-3) in the buffer gas, ions were not observed for α-amino acids due to charge competition with the dopant; this deprotonation capability arises from the production of a dimer with a high formation energy that stabilized the positive charge and created steric hindrance that deterred the equilibrium with analyte ions. F could not completely strip other compounds of their charge because they either showed steric hindrance at the charge site that deterred the approach of the dopant (2,4-lutidine, and DTBP), formed intramolecular bonds that stabilized the positive charge (atenolol), had high proton affinity (2,4-lutidine, DTBP, valinol and atenolol), or were inherently ionic (tetraalkylammonium ions). This selective deprotonation suggests the use of F to simplify spectra of complex mixtures in ion mobility and mass spectrometry in metabolomics, proteomics and other studies that generate complex spectra with thousands of peaks. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Ammonium Ion Binding to DNA G-Quadruplexes: Do Electrospray Mass Spectra Faithfully Reflect the Solution-Phase Species?

NASA Astrophysics Data System (ADS)

Balthasart, Françoise; Plavec, Janez; Gabelica, Valérie

2013-01-01

G-quadruplex nucleic acids can bind ammonium ions in solution, and these complexes can be detected by electrospray mass spectrometry (ESI-MS). However, because ammonium ions are volatile, the extent to which ESI-MS quantitatively could provide an accurate reflection of such solution-phase equilibria is unclear. Here we studied five G-quadruplexes having known solution-phase structure and ammonium ion binding constants: the bimolecular G-quadruplexes (dG4T4G4)2, (dG4T3G4)2, and (dG3T4G4)2, and the intramolecular G-quadruplexes dG4(T4G4)3 and dG2T2G2TGTG2T2G2 (thrombin binding aptamer). We found that not all mass spectrometers are equally suited to reflect the solution phase species. Ion activation can occur in the electrospray source, or in a high-pressure traveling wave ion mobility cell. When the softest instrumental conditions are used, ammonium ions bound between G-quartets, but also additional ammonium ions bound at specific sites outside the external G-quartets, can be observed. However, even specifically bound ammonium ions are in some instances too labile to be fully retained in the gas phase structures, and although the ammonium ion distribution observed by ESI-MS shows biases at specific stoichiometries, the relative abundances in solution are not always faithfully reflected. Ion mobility spectrometry results show that all inter-quartet ammonium ions are necessary to preserve the G-quadruplex fold in the gas phase. Ion mobility experiments, therefore, help assign the number of inner ammonium ions in the solution phase structure.[Figure not available: see fulltext.

A Platform for Real-time Acquisition and Analysis of Physiological Data in Hospital Emergency Departments

DTIC Science & Technology

2014-08-01

with the Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA 02114 USA (corresponding author; phone: 617 -726-2241; e-mail...programming interface ( API ). Algorithms are used to determine the reliability of waveform (e.g., electrocardiogram) and vital-sign data (e.g., heart rate...and comparing of real-time decision- support algorithms in mobile environments," Conf Proc IEEE Eng Med Biol Soc, vol. 2009 , pp. 3417-20, 2009 . [3

A critical review of ion mobility spectrometry for the detection of explosives and explosive related compounds.

PubMed

Ewing, R G; Atkinson, D A; Eiceman, G A; Ewing, G J

2001-05-10

Ion mobility spectrometry has become the most successful and widely used technology for the detection of trace levels of nitro-organic explosives on handbags and carry on-luggage in airports throughout the US. The low detection limits are provided by the efficient ionization process, namely, atmospheric pressure chemical ionization (APCI) reactions in negative polarity. An additional level of confidence in a measurement is imparted by characterization of ions for mobilities in weak electric fields of a drift tube at ambient pressure. Findings from over 30 years of investigations into IMS response to these explosives have been collected and assessed to allow a comprehensive view of the APCI reactions characteristic of nitro-organic explosives. Also, the drift tube conditions needed to obtain particular mobility spectra have been summarized. During the past decade, improvements have occurred in IMS on the understanding of reagent gas chemistries, the influence of temperature on ion stability, and sampling methods. In addition, commercial instruments have been refined to provide fast and reliable measurements for on-site detection of explosives. The gas phase ion chemistry of most explosives is mediated by the fragile CONO(2) bonds or the acidity of protons. Thus, M(-) or M.Cl(-) species are found with only a few explosives and loss of NO(2), NO(3) and proton abstraction reactions are common and complicating pathways. However, once ions are formed, they appear to have stabilities on time scales equal to or longer than ion drift times from 5-20 ms. As such, peak shapes in IMS are suitable for high selectivity and sensitivity.

Profiling the indole alkaloids in yohimbe bark with ultra-performance liquid chromatography coupled with ion mobility quadrupole time-of-flight mass spectrometry

USDA-ARS?s Scientific Manuscript database

An ultra-high performance liquid chromatography-ion mobility- quadrupole time-of-flight mass spectrometry (UHPLC-IM-QTOF-MS) method was developed for profiling the indole alkaloids in yohimbe bark. Many indole alkaloids with the yohimbine core structure, plus methylated, oxidized, and reduced speci...

Fundamental studies of gas phase ionic reactions by ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Giles, K.; Knighton, W. B.; Sahlstrom, K. E.; Grimsrud, E. P.

1995-01-01

Ion mobility spectrometry (IMS) provides a promising approach to the study of gas phase ionic reactions in buffer gases at unusually high pressures. This point is illustrated here by studies of the Sn2 nucleophilic displacement reaction, Cl(-) + CH3Br yields Br + CH3Br, using IMS at atmospheric pressure. The equilibrium clustering reaction, Cl(-)(CHCI3)(n - 1) + CHCI3 yields Cl(-)(CHCI3)(n), where n = 1 and 2, and the effect of clustering on the Sn2 reaction with CH3Br have also been characterized by this IMS-based kinetic method. Present problems and anticipated improvements in the application of ion mobility spectrometry to studies of other gas phase ionic processes are discussed.

FTP-Server for exchange, interpretation, and database-search of ion mobility spectra, literature, preprints and software

NASA Technical Reports Server (NTRS)

Baumbach, J. I.; Vonirmer, A.

1995-01-01

To assist current discussion in the field of ion mobility spectrometry, at the Institut fur Spectrochemie und angewandte Spektroskopie, Dortmund, start with 4th of December, 1994 work of an FTP-Server, available for all research groups at univerisities, institutes and research worker in industry. We support the exchange, interpretation, and database-search of ion mobility spectra through data format JCAMP-DS (Joint Committee on Atomic and Molecular Physical Data) as well as literature retrieval, pre-print, notice, and discussion board. We describe in general lines the entrance conditions, local addresses, and main code words. For further details, a monthly news report will be prepared for all common users. Internet email address for subscribing is included in document.

Measurement of drug facilitated sexual assault agents in simulated sweat by ion mobility spectrometry.

PubMed

Demoranville, Leonard T; Verkouteren, Jennifer R

2013-03-15

Ion mobility spectrometry has found widespread use for the detection of explosives and illicit drugs. The technique offers rapid results with high sensitivity and little sample preparation. As such, it is well suited for field deployed screening settings. Here the response of ion mobility spectrometers for three drug-facilitated sexual assault (DFSA) agents - flunitrazepam, ketamine, and MDMA - and related metabolites has been studied in the presence of a simulated sweat. While all three DFSA agents present certain challenges for qualitative identification, IMS can provide useful information to guide the early treatment and investigation of sexual assault cases. Used as a presumptive test, the identification of DFSA agents would later require confirmatory analysis by other techniques. Published by Elsevier B.V.

Experimental ion mobility measurements in Xe-CF4 mixtures

NASA Astrophysics Data System (ADS)

Cortez, A. F. V.; Kaja, M. A.; Escada, J.; Santos, M. A. G.; Veenhof, R.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.

2018-04-01

In this paper we present the results of the ion mobility measurements made in gaseous mixtures of xenon with carbon tetrafluoride (Xe-CF4) for pressures ranging from 6 to 10 Torr (8-10.6 mbar) and for low reduced electric fields in the 10 to 25 Td range (2.4-6.1 kVṡcm‑1ṡbar‑1), at room temperature. The time-of-arrival spectra revealed one or two peaks depending on the gas relative abundances, which were attributed to CF3+ and to Xe2+ ions. However, for Xe concentrations above 60%, only one peak remains (Xe2+). The reduced mobilities obtained from the peak centroid of the time-of-arrival spectra are presented for Xe concentrations in the 5%-95% range.

Detection of methamphetamine in the presence of nicotine using in situ chemical derivatization and ion mobility spectrometry.

PubMed

Ochoa, Mariela L; Harrington, Peter B

2004-02-15

The detection of methamphetamine in the presence of nicotine has been successfully accomplished using in situ chemical derivatization with propyl chloroformate as the derivatization reagent and ion mobility spectrometry (IMS). The rapid detection of methamphetamine is important for forensic scientists in order to establish a chain of evidence and link criminals to the crime scene. Nicotine is pervasive in clandestine drug laboratories from cigarette smoke residue. It has been demonstrated that nicotine obscures the methamphetamine peaks in ion mobility spectrometers due to their similar charge affinities and ion mobilities, which makes their detection a challenging task. As a consequence, false positive or negative responses may arise. In situ chemical derivatization poses as a sensitive, accurate, and reproducible alternative to remove the nicotine background when detecting nanogram amounts of methamphetamine. The derivatization agent was coated onto the sample disk, and the derivatization product corresponding to propyl methamphetamine carbamate was detected. In the present study, in situ chemical derivatization was demonstrated to be a feasible method to detect methamphetamine hydrochloride as the carbamate derivative, which was baseline-resolved from the nicotine peak. Alternating least squares (ALS) was used to model the datasets. A mixture containing both compounds revealed reduced mobilities of 1.61 cm(2)/V.s and 1.54 cm(2)/V.s for methamphetamine and nicotine, respectively. The reduced mobility of propyl methamphetamine carbamate was found at 1.35 cm(2)/V.s.

Ion mobility and conductivity in the M{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} (M=K, Rb) solid solutions with fluorite structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kavun, V. Ya., E-mail: kavun@ich.dvo.ru; Uvarov, N.F.; Slobodyuk, A.B.

Ionic mobility and conductivity in the K{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} and Rb{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} (x=0.05, 0.09) solid solutions with the fluorite structure have been investigated using the methods of {sup 19}F NMR, X-ray diffraction and impedance spectroscopy. Types of ionic motions in the fluoride sublattice of solid solutions have been established and temperature ranges of their realization have been determined (150–450 K). Diffusion of fluoride ions is a dominating type of ionic motions in the fluoride sublattice of solid solutions under study above 350 K. Due to high ionic conductivity, above 10{sup –3} S/cm at 450 K,more » these solid solutions can be used as solid electrolytes in various electrochemical devices and systems. - Graphical abstract: Temperature dependence of the concentration of mobile (2, 4) and immobile (1, 3) F ions in the K{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} solid solutions. - Highlights: • Studied the ion mobility, conductivity in M{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} solid solutions (M=K, Rb). • An analysis of {sup 19}F NMR spectra made it possible to identify types of ion mobility. • The main type of ion motion above 300 K in solid solutions is a diffusion of ions F{sup –}. • The ionic conductivity of the solid solutions studied more than 10{sup –3} S/cm at 450 K.« less

Identification of Lasso Peptide Topologies Using Native Nanoelectrospray Ionization-Trapped Ion Mobility Spectrometry-Mass Spectrometry.

PubMed

Dit Fouque, Kevin Jeanne; Moreno, Javier; Hegemann, Julian D; Zirah, Séverine; Rebuffat, Sylvie; Fernandez-Lima, Francisco

2018-04-17

Lasso peptides are a fascinating class of bioactive ribosomal natural products characterized by a mechanically interlocked topology. In contrast to their branched-cyclic forms, lasso peptides have higher stability and have become a scaffold for drug development. However, the identification and separation of lasso peptides from their unthreaded topoisomers (branched-cyclic peptides) is analytically challenging since the higher stability is based solely on differences in their tertiary structures. In the present work, a fast and effective workflow is proposed for the separation and identification of lasso from branched cyclic peptides based on differences in their mobility space under native nanoelectrospray ionization-trapped ion mobility spectrometry-mass spectrometry (nESI-TIMS-MS). The high mobility resolving power ( R) of TIMS resulted in the separation of lasso and branched-cyclic topoisomers ( R up to 250, 150 needed on average). The advantages of alkali metalation reagents (e.g., Na, K, and Cs salts) as a way to increase the analytical power of TIMS is demonstrated for topoisomers with similar mobilities as protonated species, efficiently turning the metal ion adduction into additional separation dimensions.

Ion mobility analyzer - quadrupole mass spectrometer system design

NASA Astrophysics Data System (ADS)

Cuna, C.; Leuca, M.; Lupsa, N.; Mirel, V.; Bocos-Bintintan, V.; Cuna, Stela; Cosma, V.; Tusa, Florina

2009-08-01

Because of their extremely high sensitivity for chemicals with elevated electronegativity or high proton affinity the ion mobility analysers are ideal for the ultra-trace detection of toxic or explosive chemicals, most of these situated often at concentration levels of sub-ppb (parts-per-billion). Ion mobility spectrometers (IMS) can be used to identify illicit drugs or environmental pollutants. Since resolution of an IMS is relatively low, to achieve an accurate identification of target analyte it is recommended to couple the IMS with a quadrupole mass spectrometer (QMS) or a time of flight mass spectrometer, acquiring in this way confirmatory information. This coupling is made through a specific interface. In this paper, an experimental model of such a tandem instrument, IMS-QMS is described. Accomplishment of this general purpose will be done, overcoming a series of specific issues. This implies the solving, using innovative solutions, of a series of complex issues: ensuring the stability of the ions beam generated by ion source; transfer with a good efficiency of the ionic current from IMS analyser to QMS; and realization of a special electronic circuitry which will be able to detect both positive and negative ions.

The hypertrehalosemic neuropeptides of cicadas are structural isomers-evidence by ion mobility mass spectrometry.

PubMed

König, Simone; Marco, Heather; Gäde, Gerd

2017-11-01

It has been known for more than 20 years that the neurosecretory glands of the cicadas, the corpora cardiaca, synthesize two isobaric peptides with hypertrehalosemic activity. Both decapeptides have exactly the same amino acid sequence (pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Asn-NH 2 ) and mass but differ in their retention time in reversed-phase liquid chromatography. A synthetic peptide with the same sequence elutes together with the second more hydrophobic peptide peak of the natural cicada extract. It is not clear what modification is causing the described observations. Therefore, in the current study, ion mobility separation in conjunction with high-resolution mass spectrometry was used to investigate this phenomenon as it was sensitive to changes in conformation. It detected different drift times in buffer gas for both the intact peptides and some of their fragment ions. Based on the ion mobility and fragment ion intensity of the corresponding ions, it is concluded that the region Pro 6 -Ser 7 -Trp 8 contains a structural feature differing from the L-amino acids present in the known peptide. Whether the conformer is the result of racemization or other biochemical processes needs to be further investigated.

Voltage sweep ion mobility spectrometry.

PubMed

Davis, Eric J; Williams, Michael D; Siems, William F; Hill, Herbert H

2011-02-15

Ion mobility spectrometry (IMS) is a rapid, gas-phase separation technique that exhibits excellent separation of ions as a standalone instrument. However, IMS cannot achieve optimal separation power with both small and large ions simultaneously. Similar to the general elution problem in chromatography, fast ions are well resolved using a low electric field (50-150 V/cm), whereas slow drifting molecules are best separated using a higher electric field (250-500 V/cm). While using a low electric field, IMS systems tend to suffer from low ion transmission and low signal-to-noise ratios. Through the use a novel voltage algorithm, some of these effects can be alleviated. The electric field was swept from low to high while monitoring a specific drift time, and the resulting data were processed to create a 'voltage-sweep' spectrum. If an optimal drift time is calculated for each voltage and scanned simultaneously, a spectrum may be obtained with optimal separation throughout the mobility range. This increased the resolving power up to the theoretical maximum for every peak in the spectrum and extended the peak capacity of the IMS system, while maintaining accurate drift time measurements. These advantages may be extended to any IMS, requiring only a change in software.

Effects of the Discharge Parameters on the Efficiency and Stability of Ambient Metastable-Induced Desorption Ionization

NASA Astrophysics Data System (ADS)

Zhang, Xiaotian; Chen, Chilai; Liu, Youjiang; Wang, Hongwei; Zhang, Lehua; Kong, Deyi; Mario, Chavarria

2015-12-01

Ionization efficiency is an important factor for ion sources in mass spectrometry and ion mobility spectrometry. Using helium as the discharge gas, acetone as the sample, and high-field asymmetric ion mobility spectrometry (FAIMS) as the ion detection method, this work investigates in detail the effects of discharge parameters on the efficiency of ambient metastable-induced desorption ionization (AMDI) at atmospheric pressure. The results indicate that the discharge power and gas flow rate are both significantly correlated with the ionization efficiency. Specifically, an increase in the applied discharge power leads to a rapid increase in the ionization efficiency, which gradually reaches equilibrium due to ion saturation. Moreover, when the discharge voltage is fixed at 2.1 kV, a maximum efficiency can be achieved at the flow rate of 9.0 m/s. This study provides a foundation for the design and application of AMDI for on-line detection with mass spectrometry and ion mobility spectrometry. supported by National Natural Science Foundation of China (No. 61374016), the Changzhou Science and Technology Support Program, China (No. CE20120081) and the External Cooperation Program of Chinese Academy of Sciences (No. GJHZ1218)

Corona discharge ionization of paracetamol molecule: Peak assignment

NASA Astrophysics Data System (ADS)

Bahrami, H.; Farrokhpour, H.

2015-01-01

Ionization of paracetamol was investigated using ion mobility spectrometry equipped with a corona discharge ionization source. The measurements were performed in the positive ion mode and three peaks were observed in the ion mobility spectrum. Experimental evidence and theoretical calculations were used to correlate the peaks to related ionic species of paracetamol. Two peaks were attributed to protonated isomers of paracetamol and the other peak was attributed to paracetamol fragment ions formed by dissociation of the N-C bond after protonation of the nitrogen atom. It was observed that three sites of paracetamol compete for protonation and their relative intensities, depending on the sample concentration. The ratio of ion products could be predicted from the internal proton affinity of the protonation sites at each concentration.

High Performance Ion Mobility Spectrometry Using Hourglass Electrodynamic Funnel And Internal Ion Funnel

DOEpatents

Smith, Richard D.; Tang, Keqi; Shvartsburg, Alexandre A.

2005-11-22

A method and apparatus enabling increased sensitivity in ion mobility spectrometry/mass spectrometry instruments which substantially reduces or eliminates the loss of ions in ion mobility spectrometer drift tubes utilizing a device for transmitting ions from an ion source which allows the transmission of ions without significant delay to an hourglass electrodynamic ion funnel at the entrance to the drift tube and/or an internal ion funnel at the exit of the drift tube. An hourglass electrodynamic funnel is formed of at least an entry element, a center element, and an exit element, wherein the aperture of the center element is smaller than the aperture of the entry element and the aperture of the exit elements. Ions generated in a relatively high pressure region by an ion source at the exterior of the hourglass electrodynamic funnel are transmitted to a relatively low pressure region at the entrance of the hourglass funnel through a conductance limiting orifice. Alternating and direct electrical potentials are applied to the elements of the hourglass electrodynamic funnel thereby drawing ions into and through the hourglass electrodynamic funnel thereby introducing relatively large quantities of ions into the drift tube while maintaining the gas pressure and composition at the interior of the drift tube as distinct from those at the entrance of the electrodynamic funnel and allowing a positive gas pressure to be maintained within the drift tube, if desired. An internal ion funnel is provided within the drift tube and is positioned at the exit of said drift tube. The advantage of the internal ion funnel is that ions that are dispersed away from the exit aperture within the drift tube, such as those that are typically lost in conventional drift tubes to any subsequent analysis or measurement, are instead directed through the exit of the drift tube, vastly increasing the amount of ions exiting the drift tube.

The mixed alkali effect in ionically conducting glasses revisited: a study by molecular dynamics simulation.

PubMed

Habasaki, Junko; Ngai, Kia L

2007-09-07

When more than two kinds of mobile ions are mixed in ionic conducting glasses and crystals, there is a non-linear decrease of the transport coefficients of either type of ion. This phenomenon is known as the mixed mobile ion effect or Mixed Alkali Effect (MAE), and remains an unsolved problem. We use molecular dynamics simulation to study the complex ion dynamics in ionically conducting glasses including the MAE. In the mixed alkali lithium-potassium silicate glasses and related systems, a distinct part of the van Hove functions reveals that jumps from one kind of site to another are suppressed. Although, consensus for the existence of preferential jump paths for each kind of mobile ions seems to have been reached amongst researchers, the role of network formers and the number of unoccupied ion sites remain controversial in explaining the MAE. In principle, these factors when incorporated into a theory can generate the MAE, but in reality they are not essential for a viable explanation of the ion dynamics and the MAE. Instead, dynamical heterogeneity and "cooperativity blockage" originating from ion-ion interaction and correlation are fundamental for the observed ion dynamics and the MAE. Suppression of long range motion with increased back-correlated motions is shown to be a cause of the large decrease of the diffusivity especially in dilute foreign alkali regions. Support for our conclusion also comes from the fact that these features of ion dynamics are common to other ionic conductors, which have no glassy networks, and yet they all exhibit the MAE.

Atmospheric Pressure Chemical Ionization Sources Used in The Detection of Explosives by Ion Mobility Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waltman, Melanie J.

2010-05-01

Explosives detection is a necessary and wide spread field of research. From large shipping containers to airline luggage, numerous items are tested for explosives every day. In the area of trace explosives detection, ion mobility spectrometry (IMS) is the technique employed most often because it is a quick, simple, and accurate way to test many items in a short amount of time. Detection by IMS is based on the difference in drift times of product ions through the drift region of an IMS instrument. The product ions are created when the explosive compounds, introduced to the instrument, are chemically ionizedmore » through interactions with the reactant ions. The identity of the reactant ions determines the outcomes of the ionization process. This research investigated the reactant ions created by various ionization sources and looked into ways to manipulate the chemistry occurring in the sources.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maimone, F., E-mail: f.maimone@gsi.de; Tinschert, K.; Endermann, M.

In order to increase the intensity of the highly charged ions produced by the Electron Cyclotron Resonance Ion Sources (ECRISs), techniques like the frequency tuning and the afterglow mode have been developed and in this paper the effect on the ion production is shown for the first time when combining both techniques. Recent experimental results proved that the tuning of the operating frequency of the ECRIS is a promising technique to achieve higher ion currents of higher charge states. On the other hand, it is well known that the afterglow mode of the ECRIS operation can provide more intense pulsedmore » ion beams in comparison with the continuous wave (cw) operation. These two techniques can be combined by pulsing the variable frequency signal driving the traveling wave tube amplifier which provides the high microwave power to the ECRIS. In order to analyze the effect of these two combined techniques on the ion source performance, several experiments were carried out on the pulsed frequency tuned CAPRICE (Compacte source A Plusiers Résonances Ionisantes Cyclotron Electroniques)-type ECRIS. Different waveforms and pulse lengths have been investigated under different settings of the ion source. The results of the pulsed mode have been compared with those of cw operation.« less

An Alternating Current Electroosmotic Pump Based on Conical Nanopore Membranes.

PubMed

Wu, Xiaojian; Ramiah Rajasekaran, Pradeep; Martin, Charles R

2016-04-26

Electroosmotic flow (EOF) is used to pump solutions through microfluidic devices and capillary electrophoresis columns. We describe here an EOF pump based on membrane EOF rectification, an electrokinetic phenomenon we recently described. EOF rectification requires membranes with asymmetrically shaped pores, and conical pores in a polymeric membrane were used here. We show here that solution flow through the membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the pore is rectified, and we previously showed that rectified currents yield EOF rectification. We have investigated the effect of both the magnitude and frequency of the voltage waveform on flow rate through the membrane, and we have measured the maximum operating pressure. Finally, we show that operating in AC mode offers potential advantages relative to conventional DC-mode EOF pumps.

Digitized detection of gamma-ray signals concentrated in narrow time windows for transient positron annihilation lifetime spectroscopy

NASA Astrophysics Data System (ADS)

Kinomura, A.; Suzuki, R.; Oshima, N.; O'Rourke, B. E.; Nishijima, T.; Ogawa, H.

2014-12-01

A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μs time window at a pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO2 layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.

Onboard software of Plasma Wave Experiment aboard Arase: instrument management and signal processing of Waveform Capture/Onboard Frequency Analyzer

NASA Astrophysics Data System (ADS)

Matsuda, Shoya; Kasahara, Yoshiya; Kojima, Hirotsugu; Kasaba, Yasumasa; Yagitani, Satoshi; Ozaki, Mitsunori; Imachi, Tomohiko; Ishisaka, Keigo; Kumamoto, Atsushi; Tsuchiya, Fuminori; Ota, Mamoru; Kurita, Satoshi; Miyoshi, Yoshizumi; Hikishima, Mitsuru; Matsuoka, Ayako; Shinohara, Iku

2018-05-01

We developed the onboard processing software for the Plasma Wave Experiment (PWE) onboard the Exploration of energization and Radiation in Geospace, Arase satellite. The PWE instrument has three receivers: Electric Field Detector, Waveform Capture/Onboard Frequency Analyzer (WFC/OFA), and the High-Frequency Analyzer. We designed a pseudo-parallel processing scheme with a time-sharing system and achieved simultaneous signal processing for each receiver. Since electric and magnetic field signals are processed by the different CPUs, we developed a synchronized observation system by using shared packets on the mission network. The OFA continuously measures the power spectra, spectral matrices, and complex spectra. The OFA obtains not only the entire ELF/VLF plasma waves' activity but also the detailed properties (e.g., propagation direction and polarization) of the observed plasma waves. We performed simultaneous observation of electric and magnetic field data and successfully obtained clear wave properties of whistler-mode chorus waves using these data. In order to measure raw waveforms, we developed two modes for the WFC, `chorus burst mode' (65,536 samples/s) and `EMIC burst mode' (1024 samples/s), for the purpose of the measurement of the whistler-mode chorus waves (typically in a frequency range from several hundred Hz to several kHz) and the EMIC waves (typically in a frequency range from a few Hz to several hundred Hz), respectively. We successfully obtained the waveforms of electric and magnetic fields of whistler-mode chorus waves and ion cyclotron mode waves along the Arase's orbit. We also designed the software-type wave-particle interaction analyzer mode. In this mode, we measure electric and magnetic field waveforms continuously and transfer them to the mission data recorder onboard the Arase satellite. We also installed an onboard signal calibration function (onboard SoftWare CALibration; SWCAL). We performed onboard electric circuit diagnostics and antenna impedance measurement of the wire-probe antennas along the orbit. We utilize the results obtained using the SWCAL function when we calibrate the spectra and waveforms obtained by the PWE.[Figure not available: see fulltext.

Optimization of a Differential Ion Mobility Spectrometry-Tandem Mass Spectrometry Method for High-Throughput Analysis of Nicotine and Related Compounds: Application to Electronic Cigarette Refill Liquids.

PubMed

Regueiro, Jorge; Giri, Anupam; Wenzl, Thomas

2016-06-21

Fast market penetration of electronic cigarettes is leading to an exponentially growing number of electronic refill liquids with different nicotine contents and an endless list of flavors. Therefore, rapid and simple methods allowing a fast screening of these products are necessary to detect harmful substances which can negatively impact the health of consumers. In this regard, the present work explores the capabilities of differential ion mobility spectrometry coupled to tandem mass spectrometry for high-throughput analysis of nicotine and 11 related compounds in commercial refill liquids for electronic cigarettes. The influence of main factors affecting the ion mobility separation, such as modifier types and concentration, separation voltage, and temperature, was systematically investigated. Despite small molecular weight differences among the studied compounds, a good separation was achieved in the ion mobility cell under the optimized conditions, which involved the use of ethanol as a polar gas-phase chemical modifier. Indeed, differential ion mobility was able to resolve (resolution >4) nicotine from its structural isomer anabasine without the use of any chromatographic separation. The quantitative performance of the proposed method was then evaluated, showing satisfactory precision (RSD ≤ 16%) and recoveries ranging from 85 to 100% for nicotine, and from 84 to 126% for the rest of the target analytes. Several commercial electronic cigarette refill liquids were analyzed to demonstrate the applicability of the method. In some cases, significant differences were found between labeled and measured levels of nicotine. Anatabine, cotinine, myosmine, and nornicotine were also found in some of the analyzed samples.

Combining Structural Probes in the Gas Phase - Ion Mobility- Resolved Action-FRET

NASA Astrophysics Data System (ADS)

Daly, Steven; MacAleese, Luke; Dugourd, Philippe; Chirot, Fabien

2018-01-01

In the context of native mass spectrometry, the development of gas-phase structural probes sensitive to the different levels of structuration of biomolecular assemblies is necessary to push forward conformational studies. In this paper, we provide the first example of the combination of ion mobility (IM) and Förster resonance energy transfer (FRET) measurements within the same experimental setup. The possibility to obtain mass- and mobility-resolved FRET measurements is demonstrated on a model peptide and applied to monitor the collision-induced unfolding of ubiquitin. [Figure not available: see fulltext.

Fast detection of toxic industrial compounds by laser ion mobility spectrometry

NASA Astrophysics Data System (ADS)

Oberhuettinger, Carola; Langmeier, Andreas; Oberpriller, Helmut; Kessler, Matthias; Goebel, Johann; Mueller, Gerhard

2009-05-01

Trace detection of toxic industrial compounds has been investigated with the help of a laser ion mobility spectrometer (LIMS). The LIMS was equipped with a tuneable UV laser source for enabling two-photon ionization of the analyte gases and an ion drift tube for the measurement of the ion mobility. Different aromatic and aliphatic hydrocarbons as well as amines were investigated. We find that the first class of molecules can be well ionized due to the delocalization of their valence electron shells and the second due to the presence of non-bonding electrons in lone-pair orbitals. Selectivity of detection is attained on the basis of molecule-specific photo-ionization and drift time spectra. Ion currents were found to scale linearly with the substance concentration over several orders of magnitude down to the detection limits in the ppt range. As besides toxic industrial compounds, similar electron configurations also occur in illicit drugs, toxins and pharmaceutical substances, LIMS can be applied in a variety of fields ranging from environmental analysis, air pollution monitoring, drug detection and chemical process monitoring.

Differential Ion Mobility Separations in up to 100 % Helium Using Microchips

PubMed Central

Shvartsburg, Alexandre A.; Ibrahim, Yehia M.; Smith, Richard D.

2014-01-01

The performance of differential IMS (FAIMS) analyzers is much enhanced by gases comprising He, especially He/N2 mixtures. However, electrical breakdown has limited the He fraction to ~50 %–75 %, depending on the field strength. By the Paschen law, the threshold field for breakdown increases at shorter distances. This allows FAIMS using chips with microscopic channels to utilize much stronger field intensities (E) than “full-size” analyzers with wider gaps. Here we show that those chips can employ higher He fractions up to 100 %. Use of He-rich gases improves the resolution and resolution/sensitivity balance substantially, although less than for full-size analyzers. The optimum He fraction is ~80 %, in line with first-principles theory. Hence, one can now measure the dependences of ion mobility on E in pure He, where ion-molecule cross section calculations are much more tractable than in other gases that form deeper and more complex interaction potentials. This capability may facilitate quantitative modeling of high-field ion mobility behavior and, thus, FAIMS separation properties, which would enable a priori extraction of structural information about the ions. PMID:24402673

Neural network recognition of chemical class information in mobility spectra obtained at high temperatures

NASA Technical Reports Server (NTRS)

Bell, S.; Nazarov, E.; Wang, Y. F.; Rodriguez, J. E.; Eiceman, G. A.

2000-01-01

A minimal neural network was applied to a large library of high-temperature mobility spectra drawn from 16 chemical classes including 154 substances with 2000 spectra at various concentrations. A genetic algorithm was used to create a representative subset of points from the mobility spectrum as input to a cascade-type back-propagation network. This network demonstrated that significant information specific to chemical class was located in the spectral region near the reactant ions. This network failed to generalize the solution to unfamiliar compounds necessitating the use of complete spectra in network processing. An extended back-propagation network classified unfamiliar chemicals by functional group with a mean for average values of 0.83 without sulfides and 0.79 with sulfides. Further experiments confirmed that chemical class information was resident in the spectral region near the reactant ions. Deconvolution of spectra demonstrated the presence of ions, merged with the reactant ion peaks that originated from introduced samples. The ability of the neural network to generalize the solution to unfamiliar compounds suggests that these ions are distinct and class specific.

Improved Analytical Performance of Negative 63Ni Ion Mobility Spectrometry for On-line Measurement of Propofol Using Dichloromethane as Dopant

NASA Astrophysics Data System (ADS)

Zhou, Qinghua; Hua, Lei; Wang, Changsong; Li, Enyou; Li, Haiyang

2015-01-01

On-line monitoring of propofol in exhaled air is a potential way to evaluate the anaesthesia depth for patients during surgery. In this study, a negative 63Ni ionization high resolution ion mobility spectrometer with Bradbury-Nielsen-Gate-Grid structure was built to measure propofol with reactant ions Cl-(H2O) n using dichloromethane as dopant. Instead of forming three propofol ions (M - H)-, M · O2 -, and (M2 - H)- with reactant ions O2 -(H2O) n , only product ion M · Cl- was produced when introducing dichloromethane gas. The peak-to-peak resolution ( R p-p) between reactant ions Cl-(H2O) n and product ion M · Cl- was 17.4, which was 1.6 times larger than that between O2 -(H2O) n and product ion. Furthermore, the linear response range using reactant ions Cl-(H2O) n was 3.5 times wider than that obtained with reactant ions O2 -(H2O) n .

Design of a TW-SLIM Module for Dual Polarity Confinement, Transport, and Reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garimella, Sandilya V. B.; Webb, Ian K.; Prabhakaran, Aneesh

2017-05-30

Here we describe instrumental approaches for performing dual polarity ion confinement, transport, ion mobility separations and reactions in Structures for Lossless Ion Manipulations (SLIM). Previous means of ion confinement in SLIM based upon rf- generated pseudopotentials and dc fields for lateral confinement cannot trap ions of opposite polarity simultaneously. Here we explore alternative approaches to provide lateral confinement of both ion polarities. Traveling wave ion mobility (IM) separations experienced by both polarities in such SLIM cause ions of both polarities migrate in the same directions and exhibit similar separations. The ion motion (and relative motion of the two polarities) undermore » both surfing and IM separation conditions are discussed. Strategies to separate the two populations to minimize reactive losses during transport are presented. A theoretical treatment of the time scales over which two populations (injected into a dc field-free region of the dual polarity SLIM device) interact is considered, and SLIM designs for allowing ion/ion interactions and other manipulations with dual polarities at 4 torr are presented.« less

Study on characteristic frequencies of ELF emissions and estimation of ion constituents in the vicinity of magnetic equator

NASA Astrophysics Data System (ADS)

Matsuda, S.; Kasahara, Y.; Goto, Y.

2012-12-01

The AKEBONO satellite has been operated continuously over 2 cycles of solar activity. Long-term observation data obtained by the AKEBONO satellite is very valuable to clarify plasma dynamics in the magnetosphere. Recently, the mechanism of wave-particle interaction around the radiation belt has attracted considerable attention. The ELF receiver, which is a sub-system of the VLF instruments onboard AKEBONO, measures waveforms below 50Hz for one component of electric field and three components of magnetic field, or waveforms below 100Hz for one component of electric and magnetic field, respectively. It was reported that ion cyclotron waves were observed near magnetic equator by the receiver [1] . It is well known that ion cyclotron wave generally propagates with a left-handed circularly polarization, but there exists right-handed polarized ion cyclotron wave below a characteristic frequency called 'crossover' in the presence of two or more kinds of ions such as oxygen and helium ions besides proton. As the crossover frequency can be derived theoretically from relative constituents of ions in plasma, it is possible to estimate the ion constituents by identifying the crossover frequency observationally. In this study, we analyze polarization of the ion cyclotron waves observed around the magnetic equator by the ELF receiver onboard AKEBONO, and report an example of ion cyclotron wave whose polarization changes from left-handed to right-handed at crossover frequency. As a next step, we estimate the ion constituents according to the polarization analysis. Furthermore, these phenomena sometimes have characteristic lower cut-off frequencies changing along the trajectories of Akebono. According to our work, it was found that the cutoff frequency is frequently in agreement with 1/n of proton's cyclotron frequency, where "n" is integer. The lower cut-off of ion cyclotron wave can be theoretically derived considering certain ion constituents of the background cold plasma. However, it remains several different interpretations depending on the species of ions and their ion constituents. In this study, we set up the following two hypotheses which shall satisfy dozens of such phenomena observed in 1989 and 1990: 1) Constituents of major ions in the plasmasphere (i.e., H^{+}, He^{+}) happened to coincide the condition that gives observed lower cut-off frequency along the trajectory. 2) There exists minor ions (i.e., D^{+}, T^{+}) that have cyclotron frequencies at 1/n of proton's cyclotron frequency. We examine the validity of the above hypotheses referring electron density and Dst index of the corresponding period. The present study could be a promising technique to estimate ion constituents from plasma wave observation by Akebono in the radiation belt. It is also noted that it can be also applicable to the ERG mission, which is expected to provide important clues for solving plasma dynamics in the Earth's radiation belt by means of integrated observation of electric and magnetic fields, particles and waves. [1] Y. Kasahara, A. Sawada, M. Yamamoto, I. Kimura, S. Kokubun, and K. Hayashi, Ion Cyclotron Emissions Observed by the Satellite Akebono in the vicinity of the Magnetic Equator, Radio Science, 27, 347-362, 1992.

Ligand induced structural isomerism in phosphine coordinated gold clusters revealed by ion mobility mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ligare, Marshall R.; Baker, Erin S.; Laskin, Julia

Structural isomerism in ligated gold clusters is revealed using electrospray ionization ion mobility spectrometry mass spectrometry. Phosphine ligated Au8 clusters are shown to adopt more “extended” type structures with increasing exchange of methyldiphenylphosphine (MePPh2) for triphenylphosphine (PPh3). These ligand-dependant structure-property relationships are critical to applications of clusters in catalysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burrows, T.A.; Thoma, P.J.

Two types of ion-mobility detectors were evaluated in both laboratory and field tests. Laboratory test results show that these detectors are highly sensitive to dynamite and pistol powder and have good false-alarm agent rejection. Field tests of these two detectors revealed that they would detect dynamite and Ball-C-Propellent in free air. However, neither of the ion-mobility detectors would detect these explosives if the explosives were concealed.

Distinguishing d - and l -aspartic and isoaspartic acids in amyloid β peptides with ultrahigh resolution ion mobility spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Xueyun; Deng, Liulin; Baker, Erin S.

2017-01-01

Ion mobility spectrometry (IMS) was utilized to separate Aβ peptide variants containing isomeric asparic and isoaspartic acid residues with either al- ord-form. The abundance of each variant is of great interest in Alzheimer's disease studies and also to evaluate how often these modifications are occurring in other environmental and biological samples.

Fast vaporization solid phase microextraction and ion mobility spectrometry: A new approach for determination of creatinine in biological fluids.

PubMed

Jafari, Mostafa; Ebrahimzadeh, Homeira; Banitaba, Mohamma Hossein

2015-11-01

In this work a rapid and simple method for creatinine determination in urine and plasma samples based on aqueous derivatization of creatinine and complete vaporization of sample (as low as 10 µL), followed by ion mobility spectrometry analysis has been proposed. The effect of four important parameters (extraction temperature, total volume of solution, desorption temperature and extraction time) on ion mobility signal has been studied. Under the optimized conditions, the quantitative response of ion mobility spectrometry for creatinine was linear in the range of 0-500 mg L(-1) with a detection limit of 0.6 mg L(-1) in urine and 0-250 mg L(-1) with a detection limit of 2.6 mg L(-1) in plasma sample. The limit of quantitation of creatinine was 2.1 mg L(-1) and 8.7 mg L(-1) in urine and plasma samples, respectively. The relative standard deviation of the method was found to be 13%. The method was successfully applied to the analysis of creatinine in biological samples, showing recoveries from 92% to 104% in urine and 101-110% in plasma samples. Copyright © 2015 Elsevier B.V. All rights reserved.

A novel four-dimensional analytical approach for analysis of complex samples.

PubMed

Stephan, Susanne; Jakob, Cornelia; Hippler, Jörg; Schmitz, Oliver J

2016-05-01

A two-dimensional LC (2D-LC) method, based on the work of Erni and Frei in 1978, was developed and coupled to an ion mobility-high-resolution mass spectrometer (IM-MS), which enabled the separation of complex samples in four dimensions (2D-LC, ion mobility spectrometry (IMS), and mass spectrometry (MS)). This approach works as a continuous multiheart-cutting LC system, using a long modulation time of 4 min, which allows the complete transfer of most of the first - dimension peaks to the second - dimension column without fractionation, in comparison to comprehensive two-dimensional liquid chromatography. Hence, each compound delivers only one peak in the second dimension, which simplifies the data handling even when ion mobility spectrometry as a third and mass spectrometry as a fourth dimension are introduced. The analysis of a plant extract from Ginkgo biloba shows the separation power of this four-dimensional separation method with a calculated total peak capacity of more than 8700. Furthermore, the advantage of ion mobility for characterizing unknown compounds by their collision cross section (CCS) and accurate mass in a non-target approach is shown for different matrices like plant extracts and coffee. Graphical abstract Principle of the four-dimensional separation.

Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling

NASA Astrophysics Data System (ADS)

Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

2016-03-01

Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H]2- ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H]3- ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H]2- ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H]3- ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.

Rapid analysis of pesticide residues in drinking water samples by dispersive solid-phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry.

PubMed

Zou, Nan; Gu, Kejia; Liu, Shaowen; Hou, Yanbing; Zhang, Jialei; Xu, Xiang; Li, Xuesheng; Pan, Canping

2016-03-01

An analytical method based on dispersive solid-phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass-mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4- to 48.7-fold (theoretical enrichment factor was 50-fold). The detection limits of pesticides were 0.01∼0.77 μg/kg. The linear range was 0.005-0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high-performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Child-Langmuir law applicability for a cathode sheath description of glow discharge in hydrogen

NASA Astrophysics Data System (ADS)

Lisovskiy, V. A.; Artushenko, K. P.; Yegorenkov, V. D.

2016-08-01

The present paper reveals that the Child-Langmuir law version with the constant ion mobility has to be applied for the cathode sheath description of the glow discharge in hydrogen. Using the analytical model we demonstrate that even in a high electric field the constant mobility law version rather than that for the constant ion mean free path has to hold in the case of impeded charge exchange and the dominant effect of polarization forces on the ion motion through the cathode sheath.

Detection of designer drugs in human hair by ion mobility spectrometry (IMS).

PubMed

Keller, T; Miki, A; Regenscheit, P; Dirnhofer, R; Schneider, A; Tsuchihashi, H

1998-06-08

Since its inception in the early 1970s under the name plasma chromatography, ion mobility spectrometry (IMS) has undergone great changes. It is now utilized more and more in forensic science laboratories where it is used to detect explosives and environmental pollutants [1-4] as well as its use in detecting drugs of abuse [5-8]. Although IMS is known for nearly 30 years now [9], relatively few cases of the application of ion mobility spectrometry to the analysis of human hair have been reported [10-12]. The authors report a new and quick method to rapidly screen and determine MDMA ('ecstasy', 'Adam') and MDEA ('Eve') in human hair. The proposed method using trihexylamine as internal standard resulted in a rapid procedure useful in screening human hair specimens for designer drugs.

Integrated Chemical and Microorganism Monitoring of Air Using Gas Chromatography/Ion Mobility Spectometry: Toward an Expanded-Use Volatile Organic Analyzer (VOA)

NASA Technical Reports Server (NTRS)

Eiceman, G. A.

1999-01-01

The work described in this research program originated with the choice by NASA of an ion mobility spectrometer for air quality monitoring on-board the international spacestation. Though the gas chromatograph-ion mobility spectrometer analyzer known as VOA met or exceeded expectations, limitations in the basic understanding of response and the utilization of foundational principles into usable technology was considered unacceptable. In this research program, a comprehensive model for the origins of mobility spectra was proposed, tested and verified. The principles considered responsible for the appearance of mobility spectra have now been elucidated through this project. This understanding has been applied in automated identification of mobility spectra using neural networks and routine procedures for this now exist. Finally, the limitation on linear range has been shown to be a technical limitation and not a fundamental limitation so that a hardware component was crafted to extend the linear range of a mobility spectrometer by 10X. This project has led to one Ph.D. dissertation and one MS thesis. In addition, over ten public presentations at professional meetings and six journal publications have resulted from this program of research. The findings are so plentiful that total analysis of the findings may require four to six years or more. The findings confirm that the decision to use VOA was sound and that the chemical and physical principles of mobility spectrometry are both understandable and predictable.

How Hot are Your Ions in TWAVE Ion Mobility Spectrometry?

PubMed Central

Merenbloom, Samuel I.; Flick, Tawnya G.; Williams, Evan R.

2012-01-01

Effective temperatures of ions during traveling wave ion mobility spectrometry (TWIMS) analysis were measured using singly protonated leucine enkephalin dimer as a chemical thermometer by monitoring dissociation of the dimer into monomer, as well as the subsequent dissociation of monomer into a-, b-, and y-ions, as a function of instrumental parameters. At fixed helium cell and TWIMS cell gas flow rates, the extent of dissociation does not vary significantly with either the wave velocity or wave height, except at low (<500 m/s) wave velocities that are not commonly used. Increasing the flow rate of nitrogen gas into the TWIMS cell and decreasing the flow rate of helium gas into the helium cell resulted in greater dissociation. However, the mobility distributions of the fragment ions formed by dissociation of the dimer upon injection into the TWIMS cell are nearly indistinguishable from those of fragment ions formed in the collision cell prior to TWIMS analysis for all TWIMS experiments. These results indicate that heating and dissociation occur when ions are injected into the TWIMS cell, and that the effective temperature subsequently decreases to a point at which no further dissociation is observed during the TWIMS analysis. An upper limit to the effective ion temperature of 449 K during TWIMS analysis is obtained at a helium flow rate of 180 mL/min, TWIMS flow rate of 80 mL/min and traveling wave height of 40 V, which is well below previously reported values. Effects of ion heating in TWIMS on gas-phase protein conformation are presented. PMID:22203576

Structure and mechanisms underlying ion transport in ternary polymer electrolytes containing ionic liquids

NASA Astrophysics Data System (ADS)

Mogurampelly, Santosh; Ganesan, Venkat

2017-02-01

We use all atom molecular dynamics simulations to investigate the influence of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) ionic liquid on the structure and transport properties of poly(ethylene oxide) (PEO) polymer electrolytes doped with LiPF6 salt. We observe enhanced diffusivities of the Li+, PF6-, and BMIM+ ions with increasing loading of the ionic liquid. Interplay between the different ion-ion and ion-polymer interactions is seen to lead to a destabilization of the Li-PF6 coordination and increase in the strength of association between the Li+ cations and the polymer backbone. As a consequence, the polymer segmental relaxation times are shown to be only moderately affected by the addition of ionic liquids. The ionic-liquid induced changes in the mobilities of Li+ ions are seen to be correlated to polymer segmental relaxation times. However, the mobilities of BMIM+ ions are seen to be more strongly correlated to the BMIM-PF6 ion-pair relaxation times.

Comparison of single-ion molecular dynamics in common solvents

NASA Astrophysics Data System (ADS)

Muralidharan, A.; Pratt, L. R.; Chaudhari, M. I.; Rempe, S. B.

2018-06-01

Laying a basis for molecularly specific theory for the mobilities of ions in solutions of practical interest, we report a broad survey of velocity autocorrelation functions (VACFs) of Li+ and PF6- ions in water, ethylene carbonate, propylene carbonate, and acetonitrile solutions. We extract the memory function, γ(t), which characterizes the random forces governing the mobilities of ions. We provide comparisons controlling for the effects of electrolyte concentration and ion-pairing, van der Waals attractive interactions, and solvent molecular characteristics. For the heavier ion (PF6-), velocity relaxations are all similar: negative tail relaxations for the VACF and a clear second relaxation for γ (t ), observed previously also for other molecular ions and with n-pentanol as the solvent. For the light Li+ ion, short time-scale oscillatory behavior masks simple, longer time-scale relaxation of γ (t ). But the corresponding analysis of the solventberg Li+(H2O)4 does conform to the standard picture set by all the PF6- results.

JLTV - Briefings to Industry, Ground Vehicle Power and Mobility (GVPM)

DTIC Science & Technology

2009-05-27

lithium ion battery cathodes, separators, and electrolytes. This effort shall also access the...manufacturability of the improved designs using the new materials. PAYOFF: Improved lithium ion battery power density Improved lithium ion battery energy...negative electrodes in lithium-ion batteries. PAYOFF: Better understanding of lithium - ion battery charging limitations Improved safety for

Selective ion accumulation in an ICP/ITMS using a filtered noise field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eiden, G.C.; Barinaga, C.J.; Koppenaal, D.W.

1995-12-31

Selective accumulation of ions in an ion trap mass spectrometer (ITMS) has been characterized using both single frequency and broadband resonant excitation. The goal of this work is to enhance selective accumulation of ions from plasmas and other external ion sources. The charge capacity of the ITMS is 10{sup 6} to 10{sup 7} ions, although the mass spectrum is distorted at much lower space charge. Detection of trace ions necessitates selective detection schemes such as selective trapping or optical detection. The authors report results of selective trapping studies for Sr, Y, and Zr solutions (100 ppb Y and 1 ppbmore » each Sr, Zr). {open_quotes}Background{close_quotes} ions in mass channels adjacent to the channel of interest is a worst case situation with respect to selective ejection and abundance sensitivity. Real samples will often have matrix ion m/z values much further removed from the m/z of the ions of interest. Thus, the authors also give results for a multielement solution. Ions from an inductively coupled plasma ion source are endcap injected into the ITMS. Broadband waveforms were generated by an HST-1000 (Teledyne MEC) instrument, using the filtered noise field (FNF) method. The experiment is controlled by the ITMS electronics and ICMS software. The sequence of experimental events is: ion injection at q{sub z} = 0.4 (typical), collisionally cool ions, set trapping potential for resonant excitation (q{sub z} = 0.2 to 0.6), analysis rf ramp.« less

Steepened magnetosonic waves in the high beta plasma surrounding Comet Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Tsurutani, B. T.; Smith, E. J.; Thorne, R. M.; Gosling, J. T.; Matsumoto, H.

1986-01-01

Studies of intense hydromagnetic waves at Giacobini-Zinner are extended to investigate the mode and direction of wave propagation. Simultaneous high-resolution measurements of electron density fluctuations demonstrate that long period waves propagate in the magnetosonic mode. Principal axis analyses of the long period waves and accompanying partial rotations show that the sum of the wave phase rotations is 360 deg, indicating that both are parts of the same wave oscillation. The time sequence of the steepened waveforms observed by ICE shows that the waves must propagate towards the Sun with Cph less than Vsw. Observations are consistent with wave generation by resonant ion ring or ion beam instability which predicts right-hand polarized waves propagating in the ion beam (solar) direction. The large amplitudes and small scale sizes of the cometary waves suggest that rapid pitch-angle scattering and energy transfer with energetic ions should occur. Since the waves are highly compressive, first-order Fermi acceleration is forecast.

Preparation, Separation, and Conformational Analysis of Differentially Sulfated Heparin Octasaccharide Isomers using Ion Mobility Mass Spectrometry

PubMed Central

Seo, Youjin; Andaya, Armann; Leary, Julie A.

2012-01-01

Heparin is a linear sulfated polysaccharide widely used in medicine because of its anticoagulant properties. The various sulfation and/or acetylation patterns on heparin impart different degrees of conformational change around the glycosidic bonds and subsequently alter its function as an anticoagulant, anticancer, or antiviral drug. Characterization of these structures is important for eventual elucidation of its function but presents itself as an analytical challenge due to the inherent heterogeneity of the carbohydrates. Heparin octasaccharide structural isomers of various sulfation patterns were investigated using ion mobility mass spectrometry (IMMS). In addition to distinguishing the isomers, we report the preparation and tandem mass spectrometry analysis for multiple sulfated or acetylated oligosaccharides. Herein, our data indicate that heparin octasaccharide isomers were separated based on their structural conformations in the ion mobility cell. Subsequent to this separation, isomers were further distinguished using product ions resulting from tandem mass spectrometry. Overall, IMMS analysis was used to successfully characterize and separate individual isomers and subsequently measure their conformations. PMID:22283665

Corona discharge ionization of paracetamol molecule: peak assignment.

PubMed

Bahrami, H; Farrokhpour, H

2015-01-25

Ionization of paracetamol was investigated using ion mobility spectrometry equipped with a corona discharge ionization source. The measurements were performed in the positive ion mode and three peaks were observed in the ion mobility spectrum. Experimental evidence and theoretical calculations were used to correlate the peaks to related ionic species of paracetamol. Two peaks were attributed to protonated isomers of paracetamol and the other peak was attributed to paracetamol fragment ions formed by dissociation of the N-C bond after protonation of the nitrogen atom. It was observed that three sites of paracetamol compete for protonation and their relative intensities, depending on the sample concentration. The ratio of ion products could be predicted from the internal proton affinity of the protonation sites at each concentration. Copyright © 2014 Elsevier B.V. All rights reserved.

Multigigahertz range-Doppler correlative processing in crystals

NASA Astrophysics Data System (ADS)

Harris, Todd L.; Babbitt, Wm. R.; Merkel, Kristian D.; Mohan, R. Krishna; Cole, Zachary; Olson, Andy

2004-06-01

Spectral-spatial holographic crystals have the unique ability to resolve fine spectral features (down to kilohertz) in an optical waveform over a broad bandwidth (over 10 gigahertz). This ability allows these crystals to record the spectral interference between spread spectrum waveforms that are temporally separated by up to several microseconds. Such crystals can be used for performing radar range-Doppler processing with fine temporal resolution. An added feature of these crystals is the long upper state lifetime of the absorbing rare earth ions, which allows the coherent integration of multiple recorded spectra, yielding integration gain and significant processing gain enhancement for selected code sets, as well as high resolution Doppler processing. Parallel processing of over 10,000 beams could be achieved with a crystal the size of a sugar cube. Spectral-spatial holographic processing and coherent integration of up to 2.5 Gigabit per second coded waveforms and of lengths up to 2047 bits has previously been reported. In this paper, we present the first demonstration of Doppler processing with these crystals. Doppler resolution down to a few hundred Hz for broadband radar signals can be achieved. The processing can be performed directly on signals modulated onto IF carriers (up to several gigahertz) without having to mix the signals down to baseband and without having to employ broadband analog to digital conversion.

Interpenetrating polymer network ion exchange membranes and method for preparing same

DOEpatents

Alexandratos, Spiro D.; Danesi, Pier R.; Horwitz, E. Philip

1989-01-01

Interpenetrating polymer network ion exchange membranes include a microporous polymeric support film interpenetrated by an ion exchange polymer and are produced by absorbing and polymerizing monomers within the support film. The ion exchange polymer provides ion exchange ligands at the surface of and throughout the support film which have sufficient ligand mobility to extract and transport ions across the membrane.

Transition metal impurities in the solid electrolyte LLZO (Li7La3Zr2O12) : Transport rates and their impact on Li-ion mobility

NASA Astrophysics Data System (ADS)

Yang, Sheng; Siegel, Donald

LLZO has many properties of an ideal solid electrolyte in lithium-ion batteries since it could enable the use of high voltage electrodes and hence enhance the energy density of lithium ion batteries. With supervalent cation doping such as Al3+, Ga3+ on the Li-site, the room temperature ionic conductivity of the cubic LLZO can accomplish high ionic conductivity up to 1mS/cm. However, some experiments suggest that mutual diffusion layers were formed between LLZO and cathode where transition metal (TM) diffused into LLZO, which could possibly lead to large interfacial resistance. In this study, we quantified the performance of LLZO after doping with cobalt, manganese, iron and nickel. In particular, we used molecular dynamics simulations with empirical Morse-type potentials to investigate the TM transport rates and their impact on Li-ion mobility. Our work indicates that TM impurities diffuse slower than Li-ion and they will result in a decrease in the Li-ion mobility by blocking Li-ion pathways. Our work shines light on the origin of interfacial resistance between LLZO and different cathodes. This work was supported by U.S. Department Energy's U.S.- China Clean Energy Research Center Clean Vehicles Consortium (CERC CVC), Grant No. DE-PI0000012.

Linking molecular models with ion mobility experiments. Illustration with a rigid nucleic acid structure

PubMed Central

D'Atri, Valentina; Porrini, Massimiliano; Rosu, Frédéric; Gabelica, Valérie

2015-01-01

Ion mobility spectrometry experiments allow the mass spectrometrist to determine an ion's rotationally averaged collision cross section ΩEXP. Molecular modelling is used to visualize what ion three-dimensional structure(s) is(are) compatible with the experiment. The collision cross sections of candidate molecular models have to be calculated, and the resulting ΩCALC are compared with the experimental data. Researchers who want to apply this strategy to a new type of molecule face many questions: (1) What experimental error is associated with ΩEXP determination, and how to estimate it (in particular when using a calibration for traveling wave ion guides)? (2) How to generate plausible 3D models in the gas phase? (3) Different collision cross section calculation models exist, which have been developed for other analytes than mine. Which one(s) can I apply to my systems? To apply ion mobility spectrometry to nucleic acid structural characterization, we explored each of these questions using a rigid structure which we know is preserved in the gas phase: the tetramolecular G-quadruplex [dTGGGGT]4, and we will present these detailed investigation in this tutorial. © 2015 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons Ltd. PMID:26259654

Analysis of explosives using corona discharge ionization combined with ion mobility spectrometry-mass spectrometry.

PubMed

Lee, Jihyeon; Park, Sehwan; Cho, Soo Gyeong; Goh, Eun Mee; Lee, Sungman; Koh, Sung-Suk; Kim, Jeongkwon

2014-03-01

Corona discharge ionization combined with ion mobility spectrometry-mass spectrometry (IMS-MS) was utilized to investigate five common explosives: cyclonite (RDX), trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotetramethylenetetranitramine (HMX), and 2,4-dinitrotoluene (DNT). The MS scan and the selected ion IMS analyses confirmed the identities of the existing ion species and their drift times. The ions observed were RDX·NO3(-), TNT(-), PETN·NO3(-), HMX·NO3(-), and DNT(-), with average drift times of 6.93 ms, 10.20 ms, 9.15 ms, 12.24 ms, 11.30 ms, and 8.89 ms, respectively. The reduced ion mobility values, determined from a standard curve calculated by linear regression of (normalized drift times)(-1) versus literature K0 values, were 2.09, 1.38, 1.55, 1.15, 1.25, and 1.60 cm(2) V(-1) s(-1), respectively. The detection limits were found to be 0.1 ng for RDX, 10 ng for TNT, 0.5 ng for PETN, 5.0 ng for HMX, and 10 ng for DNT. Simplified chromatograms were observed when nitrogen, as opposed to air, was used as the drift gas, but the detection limits were approximately 10 times worse (i.e., less sensitivity of detection). © 2013 Elsevier B.V. All rights reserved.

Influence of ion sterics on diffusiophoresis and electrophoresis in concentrated electrolytes

NASA Astrophysics Data System (ADS)

Stout, Robert F.; Khair, Aditya S.

2017-01-01

We quantify the diffusiophoresis and electrophoresis of a uniformly charged, spherical colloid in a binary electrolyte using modified Poisson-Nernst-Planck equations that account for steric repulsion between finite sized ions. Specifically, we utilize the Bikerman (Bik) lattice gas model and the Carnahan-Starling (CS) and Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) equations of state for monodisperse and polydisperse, respectively, hard spheres. We compute the phoretic mobility for weak applied fields using an asymptotic approach for thin diffuse layers, where ion steric effects are expected to be most prevalent. The thin diffuse layer limit requires λD/R →0 , where λD is the Debye screening length and R is the particle radius; this limit is readily attained for micron-sized colloids in concentrated electrolytic solutions. It is well known that the classic Poisson-Boltzmann (PB) model for pointlike, noninteracting ions leads to a prediction of a maximum in both the diffusiophoretic and electrophoretic mobilities with increasing particle zeta potential (at fixed λD/R ). In contrast, we find that ion sterics essentially eliminate this maximum (for reasonably attainable zeta potentials) and increase the mobility relative to PB. Next, we consider the more experimentally relevant case of a particle with a constant surface charge density and vary the electrolyte concentration, neglecting charge regulation on surface active sites. Rather surprisingly, there is little difference between the predictions of the four models (PB, Bik, CS, and BMCSL) for electrophoretic mobility in concentrated solutions, at reasonable surface charge densities (˜1 -10 μ C /cm2 ). This is because as the concentration increases, the zeta potential is reduced (to below the thermal voltage for concentrations above about 1 M) and therefore the diffuse layer structure is largely unaffected by ion sterics. For gradients of symmetric electrolytes (equal diffusivities, charge, and size) diffusiophoresis is also essentially unaffected by ion sterics, with a mobility that approaches zero with increasing concentration, just as in electrophoresis. For gradients of asymmetric electrolytes, the difference in diffusivities of the cation and anions leads to an induced electric field that acts on the charged particle. Importantly, we show that ion sterics leads to an excess contribution to the induced electric field, which increases rapidly with concentration. This increase overwhelms the accompanying decrease in zeta potential. The result is the diffusiophoretic mobility increases with concentration, rather than approaching zero. Therefore, diffusiophoresis could be an appealing alternative transport mechanism to electrophoresis in concentrated electrolyte solutions.

Characterization of applied fields for ion mobility in traveling wave based structures for lossless ion manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Prabhakaran Nair Syamala Amma, Aneesh; Garimella, Venkata BS

2018-03-21

Ion mobility (IM) is rapidly gaining attention for the analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM has limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. These can be readily obtainable in structures for lossless ion manipulations (SLIM), which are fabricated from electric fields that are generated by appropriate potentials applied to arrays of electrodes patterned on twomore » parallel surfaces. In this work we have investigated the relationship between the various SLIM variables, such as electrode dimensions, inter-surface gap, and the TW applied voltages, that directly impact the fields experienced by ions. Ion simulation and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric field. The variables explored impact both ion confinement and the observed IM resolution in Structures for Lossless Ion Manipulations (SLIM) modules.« less

Polymers for Traveling Wave Ion Mobility Spectrometry Calibration

NASA Astrophysics Data System (ADS)

Duez, Quentin; Chirot, Fabien; Liénard, Romain; Josse, Thomas; Choi, ChangMin; Coulembier, Olivier; Dugourd, Philippe; Cornil, Jérôme; Gerbaux, Pascal; De Winter, Julien

2017-07-01

One of the main issues when using traveling wave ion mobility spectrometry (TWIMS) for the determination of collisional cross-section (CCS) concerns the need for a robust calibration procedure built from referent ions of known CCS. Here, we implement synthetic polymer ions as CCS calibrants in positive ion mode. Based on their intrinsic polydispersities, polymers offer in a single sample the opportunity to generate, upon electrospray ionization, numerous ions covering a broad mass range and a large CCS window for different charge states at a time. In addition, the key advantage of polymer ions as CCS calibrants lies in the robustness of their gas-phase structure with respect to the instrumental conditions, making them less prone to collisional-induced unfolding (CIU) than protein ions. In this paper, we present a CCS calibration procedure using sodium cationized polylactide and polyethylene glycol, PLA and PEG, as calibrants with reference CCS determined on a home-made drift tube. Our calibration procedure is further validated by testing the polymer calibration to determine CCS of numerous different ions for which CCS are reported in the literature. [Figure not available: see fulltext.

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.

Ion mobility (IM) is rapidly gaining attention for the analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM has limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. These can be readily obtainable in structures for lossless ion manipulations (SLIM), which are fabricated from electric fields that are generated by appropriate potentials applied to arrays of electrodes patterned on twomore » parallel surfaces. In this work we have investigated the relationship between the various SLIM variables, such as electrode dimensions, inter-surface gap, and the TW applied voltages, that directly impact the fields experienced by ions. Ion simulation and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric field. The variables explored impact both ion confinement and the observed IM resolution in Structures for Lossless Ion Manipulations (SLIM) modules.« less

Improving Pulse Rate Measurements during Random Motion Using a Wearable Multichannel Reflectance Photoplethysmograph.

PubMed

Warren, Kristen M; Harvey, Joshua R; Chon, Ki H; Mendelson, Yitzhak

2016-03-07

Photoplethysmographic (PPG) waveforms are used to acquire pulse rate (PR) measurements from pulsatile arterial blood volume. PPG waveforms are highly susceptible to motion artifacts (MA), limiting the implementation of PR measurements in mobile physiological monitoring devices. Previous studies have shown that multichannel photoplethysmograms can successfully acquire diverse signal information during simple, repetitive motion, leading to differences in motion tolerance across channels. In this paper, we investigate the performance of a custom-built multichannel forehead-mounted photoplethysmographic sensor under a variety of intense motion artifacts. We introduce an advanced multichannel template-matching algorithm that chooses the channel with the least motion artifact to calculate PR for each time instant. We show that for a wide variety of random motion, channels respond differently to motion artifacts, and the multichannel estimate outperforms single-channel estimates in terms of motion tolerance, signal quality, and PR errors. We have acquired 31 data sets consisting of PPG waveforms corrupted by random motion and show that the accuracy of PR measurements achieved was increased by up to 2.7 bpm when the multichannel-switching algorithm was compared to individual channels. The percentage of PR measurements with error ≤ 5 bpm during motion increased by 18.9% when the multichannel switching algorithm was compared to the mean PR from all channels. Moreover, our algorithm enables automatic selection of the best signal fidelity channel at each time point among the multichannel PPG data.

Investigation of drift gas selectivity in high resolution ion mobility spectrometry with mass spectrometry detection.

PubMed

Matz, Laura M; Hill, Herbert H; Beegle, Luther W; Kanik, Isik

2002-04-01

Recent studies in electrospray ionization (ESI)/ion mobility spectrometry (IMS) have focussed on employing different drift gases to alter separation efficiency for some molecules. This study investigates four structurally similar classes of molecules (cocaine and metabolites, amphetamines, benzodiazepines, and small peptides) to determine the effect of structure on relative mobility changes in four drift gases (helium, nitrogen, argon, carbon dioxide). Collision cross sections were plotted against drift gas polarizability and a linear relationship was found for the nineteen compounds evaluated in the study. Based on the reduced mobility database, all nineteen compounds could be separated in one of the four drift gases, however, the drift gas that provided optimal separation was specific for the two compounds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belov, Mikhail E.; Anderson, Gordon A.; Smith, Richard D.

Data-dependent selective external ion ejection with improved resolution is demonstrated with a 3.5 tesla FTICR instrument employing DREAMS (Dynamic Range Enhancement Applied to Mass Spectrometry) technology. To correct for the fringing rf-field aberrations each rod of the selection quadrupole has been segmented into three sections, so that ion excitation and ejection was performed by applying auxiliary rf-only waveforms in the region of the middle segments. Two different modes of external ion trapping and ejection were studied with the mixtures of model peptides and a tryptic digest of bovine serum albumin. A mass resolution of about 100 has been attained formore » rf-only dipolar ejection in a quadrupole operating at a Mathieu parameter q of{approx} 0.45. LC-ESI-DREAMS-FTICR analysis of a 0.1 mg/mL solution of bovine serum albumin digest resulted in detection of 82 unique tryptic peptides with mass measurement errors lower than 5 ppm, providing 100% sequence coverage of the protein.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belov, Mikhail E.; Anderson, Gordon A.; Smith, Richard D.

Data-dependent selective external ion ejection with improved resolution is demonstrated with a 3.5 tesla FTICR instrument employing DREAMS (Dynamic Range Enhancement Applied to Mass Spectrometry) technology. To correct for the fringing rf-field aberrations each rod of the selection quadrupole has been segmented into three sections, so that ion excitation and ejection was performed by applying auxiliary rf-only waveforms in the region of the middle segments. Two different modes of external ion trapping and ejection were studied with the mixtures of model peptides and a tryptic digest of bovine serum albumin. A mass resolution of about 100 had been attained formore » rf-only dipolar ejection in a quadrupole operating at a Mathieu parameter q of ~0.45. LC-ESI-DREAMS-FTICR analysis of a 0.1 mg/mL solution of bovine serum albumin digest resulted in detection of 82 unique tryptic peptides with mass measurement errors lower than 5 ppm, providing 100 % sequence coverage of the protein.« less

DETECTORS AND EXPERIMENTAL METHODS: Equivalent properties of single event burnout induced by different sources

NASA Astrophysics Data System (ADS)

Yang, Shi-Yu; Cao, Zhou; Da, Dao-An; Xue, Yu-Xiong

2009-05-01

The experimental results of single event burnout induced by heavy ions and 252Cf fission fragments in power MOSFET devices have been investigated. It is concluded that the characteristics of single event burnout induced by 252Cf fission fragments is consistent to that in heavy ions. The power MOSFET in the “turn-off" state is more susceptible to single event burnout than it is in the “turn-on" state. The thresholds of the drain-source voltage for single event burnout induced by 173 MeV bromine ions and 252Cf fission fragments are close to each other, and the burnout cross section is sensitive to variation of the drain-source voltage above the threshold of single event burnout. In addition, the current waveforms of single event burnouts induced by different sources are similar. Different power MOSFET devices may have different probabilities for the occurrence of single event burnout.

Structured back gates for high-mobility two-dimensional electron systems using oxygen ion implantation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berl, M., E-mail: mberl@phys.ethz.ch; Tiemann, L.; Dietsche, W.

2016-03-28

We present a reliable method to obtain patterned back gates compatible with high mobility molecular beam epitaxy via local oxygen ion implantation that suppresses the conductivity of an 80 nm thick silicon doped GaAs epilayer. Our technique was optimized to circumvent several constraints of other gating and implantation methods. The ion-implanted surface remains atomically flat which allows unperturbed epitaxial overgrowth. We demonstrate the practical application of this gating technique by using magneto-transport spectroscopy on a two-dimensional electron system (2DES) with a mobility exceeding 20 × 10{sup 6} cm{sup 2}/V s. The back gate was spatially separated from the Ohmic contacts of the 2DES,more » thus minimizing the probability for electrical shorts or leakage and permitting simple contacting schemes.« less

Ion mobility-mass spectrometry as a tool to investigate protein-ligand interactions.

PubMed

Göth, Melanie; Pagel, Kevin

2017-07-01

Ion mobility-mass spectrometry (IM-MS) is a powerful tool for the simultaneous analysis of mass, charge, size, and shape of ionic species. It allows the characterization of even low-abundant species in complex samples and is therefore particularly suitable for the analysis of proteins and their assemblies. In the last few years even complex and intractable species have been investigated successfully with IM-MS and the number of publications in this field is steadily growing. This trend article highlights recent advances in which IM-MS was used to study protein-ligand complexes and in particular focuses on the catch and release (CaR) strategy and collision-induced unfolding (CIU). Graphical Abstract Native mass spectrometry and ion mobility-mass spectrometry are versatile tools to follow the stoichiometry, energetics, and structural impact of protein-ligand binding.

Environment applications for ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Ritchie, Robert K.; Rudolph, Andreas

1995-01-01

The detection of environmentally important polychlorinated aromatics by ion mobility spectrometry (IMS) was investigated. Single polychlorinated biphenyl (PCB) isomers (congeners) having five or more chlorine atoms were reliably detected in isooctane solution at levels of 35 ng with a Barringer IONSCAN ion mobility spectrometer operating in negative mode; limits of detection (LOD) were extrapolated to be in the low ng region. Mixtures of up to four PCB congeners, showing characteristic multiple peaks, and complex commercial mixtures of PCBs (Aroclors) were also detected. Detection of Aroclors in transformer oil was suppressed by the presence of the antioxidant BHT (2,6-di-t-butyl4-methylphenol) in the oil. The wood preservative pentachlorophenol (PCP) was easily detected in recycled wood shavings at levels of 52 ppm with the IONSCAN; the LOD was extrapolated to be in the low ppm region.

Collision induced unfolding of isolated proteins in the gas phase: past, present, and future.

PubMed

Dixit, Sugyan M; Polasky, Daniel A; Ruotolo, Brandon T

2018-02-01

Rapidly characterizing the three-dimensional structures of proteins and the multimeric machines they form remains one of the great challenges facing modern biological and medical sciences. Ion mobility-mass spectrometry based techniques are playing an expanding role in characterizing these functional complexes, especially in drug discovery and development workflows. Despite this expansion, ion mobility-mass spectrometry faces many challenges, especially in the context of detecting small differences in protein tertiary structure that bear functional consequences. Collision induced unfolding is an ion mobility-mass spectrometry method that enables the rapid differentiation of subtly-different protein isoforms based on their unfolding patterns and stabilities. In this review, we summarize the modern implementation of such gas-phase unfolding experiments and provide an overview of recent developments in both methods and applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Micro faraday-element array detector for ion mobility spectroscopy

DOEpatents

Gresham, Christopher A [Albuquerque, NM; Rodacy, Phillip J [Albuquerque, NM; Denton, M Bonner [Tucson, AZ; Sperline, Roger [Tucson, AZ

2004-10-26

An ion mobility spectrometer includes a drift tube having a collecting surface covering a collecting area at one end of the tube. The surface comprises a plurality of closely spaced conductive elements on a non-conductive substrate, each conductive element being electrically insulated from each other element. A plurality of capacitive transimpedance amplifiers (CTIA) adjacent the collecting surface are electrically connected to the plurality of elements, so charge from an ion striking an element is transferred to the capacitor of the connected CTIA. A controller counts the charge on the capacitors over a period of time.

Atmospheric Solid Analysis Probe Coupled to Ion Mobility Spectrometry-Mass Spectrometry, a Fast and Simple Method for Polyalphaolefin Characterization

NASA Astrophysics Data System (ADS)

Mendes Siqueira, Anna Luiza; Beaumesnil, Mathieu; Hubert-Roux, Marie; Loutelier-Bourhis, Corinne; Afonso, Carlos; Bai, Yang; Courtiade, Marion; Racaud, Amandine

2018-05-01

Polyalphaolefins (PAOs) are polymers produced from linear alpha olefins through catalytic oligomerization processes. The PAOs are known as synthetic high-performance base stock fluids used to improve the efficiency of many other synthetic products. In this study, we report the direct characterization of PAOs using atmospheric solid analysis probe (ASAP) coupled with ion mobility spectrometry-mass spectrometry (IMS-MS). We studied different PAOs grades exhibiting low- and high-viscosity index. Specific adjustments of the ASAP source parameters permitted the monitoring of ionization processes as three mechanisms could occur for these compounds: hydride abstraction, nitrogen addition, and/or the formation of [M-2H]+• ions. Several series of fragment ions were obtained, which allowed the identification of the alpha olefin used to synthesize the PAO. The use of the ion mobility separation dimension provides information on isomeric species. In addition, the drift time versus m/z plots permitted rapid comparison between PAO samples and to evidence their complexity. These 2D plots appear as fingerprints of PAO samples. To conclude, the resort to ASAP-IMS-MS provides a rapid characterization of the PAO samples in a direct analysis approach, without any sample preparation.

Next-Generation Terrestrial Laser Scanning to Measure Forest Canopy Structure

NASA Astrophysics Data System (ADS)

Danson, M.

2015-12-01

Terrestrial laser scanners (TLS) are now capable of semi-automatic reconstruction of the structure of complete trees or forest stands and have the potential to provide detailed information on tree architecture and foliage biophysical properties. The trends for the next generation of TLS are towards higher resolution, faster scanning and full-waveform data recording, with mobile, multispectral laser devices. The convergence of these technological advances in the next generation of TLS will allow the production of information for forest and woodland mapping and monitoring that is far more detailed, more accurate, and more comprehensive than any available today. This paper describes recent scientific advances in the application of TLS for characterising forest and woodland areas, drawing on the authors' development of the Salford Advanced Laser Canopy Analyser (SALCA), the activities of the Terrestrial Laser Scanner International Interest Group (TLSIIG), and recent advances in laser scanner technology around the world. The key findings illustrated in the paper are that (i) a complete understanding of system measurement characteristics is required for quantitative analysis of TLS data, (ii) full-waveform data recording is required for extraction of forest biophysical variables and, (iii) multi-wavelength systems provide additional spectral information that is essential for classifying different vegetation components. The paper uses a range of recent experimental TLS measurements to support these findings, and sets out a vision for new research to develop an information-rich future-forest information system, populated by mobile autonomous multispectral TLS devices.

Mixed-Isotope Labeling with LC-IMS-MS for Characterization of Protein–Protein Interactions by Chemical Cross-Linking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merkley, Eric D.; Baker, Erin S.; Crowell, Kevin L.

2013-02-20

Chemical cross-linking of proteins followed by proteolysis and mass spectrometric analysis of the resulting cross-linked peptides can provide insights into protein structure and protein-protein interactions. However, cross-linked peptides are by necessity of low stoichometry and have different physicochemical properties than linear peptides, routine unambiguous identification of the cross-linked peptides has remained difficult. To address this challenge, we demonstrated the use of liquid chromatography and ion mobility separations coupled with mass spectrometry in combination with a heavy-isotope labeling method. The combination of mixed-isotope cross-linking and ion mobility provided unique and easily interpretable spectral multiplet features for the intermolecular cross-linked peptides. Applicationmore » of the method to two different homodimeric proteins - SrfN, a virulence factor from Salmonella Typhimurium and SO_2176, a protein of unknown function from Shewanella oneidensis- revealed several cross-linked peptides from both proteins that were identified with a low false discovery rate (estimated using a decoy approach). A greater number of cross-linked peptides were identified using ion mobility drift time information in the analysis than when the data were summed across the drift time dimension before analysis. The identified cross-linked peptides migrated more quickly in the ion mobility drift tube than the unmodified peptides.« less

A compact high-resolution X-ray ion mobility spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinecke, T.; Kirk, A. T.; Heptner, A.

For the ionization of gaseous samples, most ion mobility spectrometers employ radioactive ionization sources, e.g., containing {sup 63}Ni or {sup 3}H. Besides legal restrictions, radioactive materials have the disadvantage of a constant radiation with predetermined intensity. In this work, we replaced the {sup 3}H source of our previously described high-resolution ion mobility spectrometer with 75 mm drift tube length with a commercially available X-ray source. It is shown that the current configuration maintains the resolving power of R = 100 which was reported for the original setup containing a {sup 3}H source. The main advantage of an X-ray source ismore » that the intensity of the radiation can be adjusted by varying its operating parameters, i.e., filament current and acceleration voltage. At the expense of reduced resolving power, the sensitivity of the setup can be increased by increasing the activity of the source. Therefore, the performance of the setup can be adjusted to the specific requirements of any application. To investigate the relation between operating parameters of the X-Ray source and the performance of the ion mobility spectrometer, parametric studies of filament current and acceleration voltage are performed and the influence on resolving power, peak height, and noise is analyzed.« less

Serpentine Ultralong Path with Extended Routing (SUPER) High Resolution Traveling Wave Ion Mobility-MS using Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Liulin; Webb, Ian K.; Garimella, Sandilya V. B.

Ion mobility (IM) separations have a broad range of analytical applications, but insufficient resolution limits many applications. Here we report on traveling wave (TW) ion mobility (IM) separations in a Serpentine Ultra-long Path with Extended Routing (SUPER) Structures for Lossless Ion Manipulations (SLIM) module in conjunction with mass spectrometry (MS). The extended routing utilized multiple passes was facilitated by the introduction of a lossless ion switch at the end of the ion path that either directed ions to the MS detector or to another pass through the serpentine separation region, providing theoretically unlimited TWIM path lengths. Ions were confined inmore » the SLIM by rf fields in conjunction with a DC guard bias, enabling essentially lossless TW transmission over greatly extended paths (e.g., ~1094 meters over 81 passes through the 13.5 m serpentine path). In this multi-pass SUPER TWIM provided resolution approximately proportional to the square root of the number of passes (or path length). More than 30-fold higher IM resolution for Agilent tuning mix m/z 622 and 922 ions (~340 vs. ~10) was achieved for 40 passes compared to commercially available drift tube IM and other TWIM-based platforms. An initial evaluation of the isomeric sugars Lacto-N-hexaose and Lacto-N-neohexaose showed the isomeric structures to be baseline resolved, and a new conformational feature for Lacto-N-neohexaose was revealed after 9 passes. The new SLIM SUPER high resolution TWIM platform has broad utility in conjunction with MS and is expected to enable a broad range of previously challenging or intractable separations.« less

Terahertz-Radiation-Enhanced Emission of Fluorescence from Gas Plasma

NASA Astrophysics Data System (ADS)

Liu, Jingle; Zhang, X.-C.

2009-12-01

We report the study of femtosecond laser-induced air plasma fluorescence under the illumination of terahertz (THz) pulses. Semiclassical modeling and experimental verification indicate that time-resolved THz radiation-enhanced emission of fluorescence is dominated by the electron kinetics and the electron-impact excitation of gas molecules or ions. We demonstrate that the temporal waveform of the THz field could be retrieved from the transient enhanced fluorescence, making omnidirectional, coherent detection available for THz time-domain spectroscopy.

Carrier mobility degradation due to high dose implantation in ultrathin unstrained and strained silicon-on-insulator films

NASA Astrophysics Data System (ADS)

Dupré, C.; Ernst, T.; Hartmann, J.-M.; Andrieu, F.; Barnes, J.-P.; Rivallin, P.; Faynot, O.; Deleonibus, S.; Fazzini, P. F.; Claverie, A.; Cristoloveanu, S.; Ghibaudo, G.; Cristiano, F.

2007-11-01

Based on electrical measurements and transmission electron microscopy (TEM) imaging, we propose an explanation for the electron and hole mobility degradation with gate length reduction in metal-oxide-semiconductor field effect transistors (MOSFETs). We demonstrate that ion implantation, normally used for source/drain doping, is responsible for transport degradation for short-channel devices. Implantation impact on electrons and holes mobility was investigated both on silicon-on-insulator (SOI) and tensile strained silicon-on-insulator (sSOI) substrates. Wafers with ultrathin Si films (from 8 to 35 nm) were Ge implanted at 3 keV and various concentrations (from 5×1014 to 2×1015 atoms cm-2), then annealed at 600 °C for 1 h. Secondary ion mass spectrometry enabled us to quantify the Ge-implanted atoms concentrations. The end-of-range defects impact on mobility was investigated with the pseudo-MOSFET technique. Measurements showed a mobility decrease as the implantation dose increased. We demonstrated that sSOI mobility is more sensitive to implantation than SOI mobility, without any implantation-induced strain relaxation in sSOI (checked using the ultraviolet Raman technique). A 36% (25%) holes (electrons) mobility degradation was measured for sSOI, while SOI presented a 21% mobility degradation for holes and 5% for electrons. Finally, the electrical results were compared with morphological studies. Plan-view TEM showed the presence of interstitial defects formed during ion implantation and annealing. The defect density was estimated to be two times higher in sSOI than in SOI, which is in full agreement with electrical results mentioned before. The results are relevant for the optimization of the source and drain regions of advanced nanoscale SOI and sSOI transistors.

The influence of addition of ion-pairing acid and organic modifier of the mobile phase on retention and migration of peptides in pressurized planar electrochromatography system with octadecyl silica-based adsorbent.

PubMed

Gwarda, Radosław Ł; Dzido, Tadeusz H

2018-07-13

In our previous papers we have investigated the influence of the mobile phase composition on mechanism of retention, selectivity and efficiency of peptide separation in various high-performance thin-layer chromatography (HPTLC) systems with commercially available silica-based adsorbents. We have also investigated the influence of pH of the mobile phase buffer on migration and separation of peptides in pressurized planar electrochromatography (PPEC). Here we investigate the influence of concentration of ion-pairing additive, and concentration and type of organic modifier of the mobile phase on migration of peptides in PPEC system with octadecyl silica-based adsorbent, and with the same set of the solutes as before. We compare our current results with the results obtained before for similar HPTLC and PPEC systems, and discuss the influence of particular variables on retention, electrophoretic mobility of solutes and electroosmotic flow of the mobile phase. We show, that the final selectivity of peptide separation results from co-influence of all the three factors mentioned. Concentration of organic modifier of the mobile phase, as well as concentration of ion-pairing additive, affect the retention, the electrophoretic mobility, and the electroosmotic flow simultaneously. This makes independent optimization of these factors rather difficult. Anyway PPEC offers much faster separation of peptides with quite different selectivity, in comparison to HPTLC, with similar adsorbents and similar mobile phase composition. However, we also present and discuss the issue of extensive tailing of peptide zones in the PPEC in comparison to similar HPTLC systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Determination of ammonia in ethylene using ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Cross, J. H.; Limero, T. F.; Lane, J. L.; Wang, F.

1997-01-01

A simple procedure to analyze ammonia in ethylene by ion mobility spectrometry is described. The spectrometer is operated with a silane polymer membrane., 63Ni ion source, H+ (H2O)n reactant ion, and nitrogen drift and source gas. Ethylene containing parts per billion (ppb) (v/v) concentrations of ammonia is pulled across the membrane and diffuses into the spectrometer. Preconcentration or preseparation is unnecessary, because the ethylene in the spectrometer has no noticeable effect on the analytical results. Ethylene does not polymerize in the radioactive source. Ethylene's flammability is negated by the nitrogen inside the spectrometer. Response to ammonia concentrations between 200 ppb and 1.5 ppm is near linear, and a detection limit of 25 ppb is calculated.

Physicochemical characteristics of LR3-IGF1 protein inclusion bodies: electrophoretic mobility studies.

PubMed

Wangsa-Wirawan, N D; O'Neill, B K; Middelberg, A P

2001-01-01

A knowledge of the physicochemical properties of inclusion bodies is important for the rational design of potential recovery processes such as flotation and precipitation. In this study, measurement of the size and electrophoretic mobility of protein inclusion bodies and cell debris was undertaken. SDS-PAGE analysis of protein inclusion bodies subjected to different cleaning regimes suggested that electrophoretic mobility provides a qualitative measure of protein inclusion body purity. Electrophoretic mobility as a function of electrolyte type and ionic strength was investigated. The presence of divalent ions produced a stronger effect on electrophoretic mobility compared with monovalent ions. The isoelectric point of cell debris was significantly lower than that for the inclusion bodies. Hence, the contaminating cell debris may be separated from inclusion bodies using flotation by exploiting this difference in isoelectric points. Separation by this method is simple, convenient, and a possible alternative to the conventional route of centrifugation.

A chemometric approach for characterization of serum transthyretin in familial amyloidotic polyneuropathy type I (FAP-I) by electrospray ionization-ion mobility mass spectrometry.

PubMed

Pont, Laura; Sanz-Nebot, Victoria; Vilaseca, Marta; Jaumot, Joaquim; Tauler, Roma; Benavente, Fernando

2018-05-01

In this study, we describe a chemometric data analysis approach to assist in the interpretation of the complex datasets from the analysis of high-molecular mass oligomeric proteins by ion mobility mass spectrometry (IM-MS). The homotetrameric protein transthyretin (TTR) is involved in familial amyloidotic polyneuropathy type I (FAP-I). FAP-I is associated with a specific TTR mutant variant (TTR(Met30)) that can be easily detected analyzing the monomeric forms of the mutant protein. However, the mechanism of protein misfolding and aggregation onset, which could be triggered by structural changes in the native tetrameric protein, remains under investigation. Serum TTR from healthy controls and FAP-I patients was purified under non-denaturing conditions by conventional immunoprecipitation in solution and analyzed by IM-MS. IM-MS allowed separation and characterization of several tetrameric, trimeric and dimeric TTR gas ions due to their differential drift time. After an appropriate data pre-processing, multivariate curve resolution alternating least squares (MCR-ALS) was applied to the complex datasets. A group of seven independent components being characterized by their ion mobility profiles and mass spectra were resolved to explain the observed data variance in control and patient samples. Then, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were considered for exploration and classification. Only four out of the seven resolved components were enough for an accurate differentiation. Furthermore, the specific TTR ions identified in the mass spectra of these components and the resolved ion mobility profiles provided a straightforward insight into the most relevant oligomeric TTR proteoforms for the disease. Copyright © 2018 Elsevier B.V. All rights reserved.

Ion Mobility Separation of Isomeric Carbohydrate Precursor Ions and Acquisition of their Independent Tandem Mass Spectra

PubMed Central

Zhu, Maolei; Bendiak, Brad; Clowers, Brian; Hill, Herbert H.

2010-01-01

The rapid separation of isomeric precursor ions of oligosaccharides prior to their analysis by MSn was demonstrated using an ambient pressure ion mobility spectrometer (IMS) interfaced with a quadrupole ion trap. Separations were not limited to specific types of isomers; representative isomers differing solely in the stereochemistry of sugars, in their anomeric configurations, and in their overall branching patterns and linkage positions could be resolved in the millisecond time frame. Physical separation of precursor ions permitted independent mass spectra of individual oligosaccharide isomers to be acquired to at least MS3, the number of stages of dissociation limited only practically by the abundance of specific product ions. IMS-MSn analysis was particularly valuable in the evaluation of isomeric oligosaccharides that yielded identical sets of product ions in MS/MS experiments, revealing pairs of isomers that would otherwise not be known to be present in a mixture if evaluated solely by MS dissociation methods alone. A practical example of IMS-MSn analysis of a set of isomers included within a single HPLC fraction of oligosaccharides released from bovine submaxillary mucin is described. PMID:19562326

vMon-mobile provides wireless connection to the electronic patient record

NASA Astrophysics Data System (ADS)

Oliveira, Pedro P., Jr.; Rebelo, Marina; Pilon, Paulo E.; Gutierrez, Marco A.; Tachinardi, Umberto

2002-05-01

This work presents the development of a set of tools to help doctors to continuously monitor critical patients. Real-time monitoring signals are displayed via a Web Based Electronic Patient Record (Web-EPR) developed at the Heart Institute. Any computer on the Hospital's Intranet can access the Web-EPR that will open a browser plug-in called vMon. Recently vMon was adapted to wireless mobile devices providing the same real-time visualization of vital signals of its desktop counterpart. The monitoring network communicates with the hospital network through a gateway using HL7 messages and has the ability to export waveforms in real time using the multicast protocol through an API library. A dedicated ActiveX component was built that establishes the streaming of the biomedical signals under monitoring and displays them on an Internet Explorer 5.x browser. The mobile version - called vMon-mobile - will parse the browser window and deliver it to a PDA device connected to a local area network. The result is a virtual monitor presenting real-time data on a mobile device. All parameters and signals acquired from the moment the patient is connected to the monitors are stored for a few days. The most clinically relevant information is added to patient's EPR.

Accelerated High-Resolution Differential Ion Mobility Separations Using Hydrogen

PubMed Central

Shvartsburg, Alexandre A.; Smith, Richard D.

2011-01-01

The resolving power of differential ion mobility spectrometry (FAIMS) was dramatically increased recently by carrier gases comprising up to 75% He or various vapors, enabling many new applications. However, the need for resolution of complex mixtures is virtually open-ended and many topical analyses demand yet finer separations. Also, the resolving power gains are often at the expense of speed, in particular making high-resolution FAIMS incompatible with online liquid-phase separations. Here, we report FAIMS employing hydrogen, specifically in mixtures with N2 containing up to 90% H2. Such compositions raise the mobilities of all ions and thus the resolving power beyond that previously feasible, while avoiding the electrical breakdown inevitable in He-rich mixtures. The increases in resolving power and ensuing peak resolution are especially significant at H2 fractions above ~50%. Higher resolution can be exchanged for acceleration of the analyses by up to ~4 times, at least. For more mobile species such as multiply-charged peptides, this exchange is presently forced by the constraints of existing FAIMS devices, but future designs optimized for H2 should consistently improve resolution for all analytes. PMID:22074292

Use of ion-mobility mass spectrometry (IMS-MS) to map polyoxometalate Keplerate clusters and their supramolecular assemblies.

PubMed

Robbins, Philip J; Surman, Andrew J; Thiel, Johannes; Long, De-Liang; Cronin, Leroy

2013-03-07

We present the high-resolution (HRES-MS) and ion-mobility (IMS-MS) mass spectrometry studies of icosahedral nanoscale polyoxometalate-based {L(30)}{(Mo)Mo(5)} Keplerate clusters, and demonstrate the use of IMS-MS to resolve and map intact nanoclusters, and its potential for the discovery of new structures, in this case the first gas phase observation of 'proto-clustering' of higher order Keplerate supramolecular aggregates.

Structural Investigation of Fluoridated POSS Cages Using Ion Mobility Mass Spectrometry and Molecular Mechanics (Preprint)

DTIC Science & Technology

2008-01-09

organic polymer. For example, the low surface energy properties of fluorinated POSS compounds have been used to augment both fluorinated and non... fluorinated polymers.10-13 Many POSS monomers have been successfully characterized using MALDI techniques14-16 in conjunction with ion mobility mass...nucleophilic attack, are shown in blue. Negative contours, showing susceptibility to electrophilic attack, are shown in red. The positive contour of

A novel approach to increasing cocaine detection confidence utilizing ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Jadamec, J. Richard; Su, Chih-Wu; Rigdon, Stephen; Norwood, Lavan

1995-01-01

When a positive detection of a narcotic occurs during the search of a vessel, a decision has to be made whether further intensive search is warranted. In terms of unwarranted delays of vessels and possible property damage, the accuracy of the analytical determination is very important. Analytical accuracy becomes critical when the data may be used in court actions as evidence. For this purpose, the U.S. Coast Guard has been investigating several confirmatory ion mobility spectrometry (IMS) field methods for the detection and identification of cocaine. This paper presents the findings of our investigations on the use of catalytic pyrolysis and base hydrolysis as confirmatory methods. The catalytic effects of various metals on the pyrolysis reaction are reported. In addition, the effects of several different ion mobility spectrometer sample transfer mediums and varying laboratory conditions on the base hydrolysis of the cocaine molecule are also be reported.

Portable Solid Phase Micro-Extraction Coupled with Ion Mobility Spectrometry System for On-Site Analysis of Chemical Warfare Agents and Simulants in Water Samples

PubMed Central

Yang, Liu; Han, Qiang; Cao, Shuya; Yang, Jie; Yang, Junchao; Ding, Mingyu

2014-01-01

On-site analysis is an efficient approach to facilitate analysis at the location of the system under investigation as it can result in more accurate, more precise and quickly available analytical data. In our work, a novel self-made thermal desorption based interface was fabricated to couple solid-phase microextraction with ion mobility spectrometry for on-site water analysis. The portable interface can be connected with the front-end of an ion mobility spectrometer directly without other modifications. The analytical performance was evaluated via the extraction of chemical warfare agents and simulants in water samples. Several parameters including ionic strength and extraction time have been investigated in detail. The application of the developed method afforded satisfactory recoveries ranging from 72.9% to 114.4% when applied to the analysis of real water samples. PMID:25384006

A flexible statistical model for alignment of label-free proteomics data – incorporating ion mobility and product ion information

PubMed Central

2013-01-01

Background The goal of many proteomics experiments is to determine the abundance of proteins in biological samples, and the variation thereof in various physiological conditions. High-throughput quantitative proteomics, specifically label-free LC-MS/MS, allows rapid measurement of thousands of proteins, enabling large-scale studies of various biological systems. Prior to analyzing these information-rich datasets, raw data must undergo several computational processing steps. We present a method to address one of the essential steps in proteomics data processing - the matching of peptide measurements across samples. Results We describe a novel method for label-free proteomics data alignment with the ability to incorporate previously unused aspects of the data, particularly ion mobility drift times and product ion information. We compare the results of our alignment method to PEPPeR and OpenMS, and compare alignment accuracy achieved by different versions of our method utilizing various data characteristics. Our method results in increased match recall rates and similar or improved mismatch rates compared to PEPPeR and OpenMS feature-based alignment. We also show that the inclusion of drift time and product ion information results in higher recall rates and more confident matches, without increases in error rates. Conclusions Based on the results presented here, we argue that the incorporation of ion mobility drift time and product ion information are worthy pursuits. Alignment methods should be flexible enough to utilize all available data, particularly with recent advancements in experimental separation methods. PMID:24341404

A flexible statistical model for alignment of label-free proteomics data--incorporating ion mobility and product ion information.

PubMed

Benjamin, Ashlee M; Thompson, J Will; Soderblom, Erik J; Geromanos, Scott J; Henao, Ricardo; Kraus, Virginia B; Moseley, M Arthur; Lucas, Joseph E

2013-12-16

The goal of many proteomics experiments is to determine the abundance of proteins in biological samples, and the variation thereof in various physiological conditions. High-throughput quantitative proteomics, specifically label-free LC-MS/MS, allows rapid measurement of thousands of proteins, enabling large-scale studies of various biological systems. Prior to analyzing these information-rich datasets, raw data must undergo several computational processing steps. We present a method to address one of the essential steps in proteomics data processing--the matching of peptide measurements across samples. We describe a novel method for label-free proteomics data alignment with the ability to incorporate previously unused aspects of the data, particularly ion mobility drift times and product ion information. We compare the results of our alignment method to PEPPeR and OpenMS, and compare alignment accuracy achieved by different versions of our method utilizing various data characteristics. Our method results in increased match recall rates and similar or improved mismatch rates compared to PEPPeR and OpenMS feature-based alignment. We also show that the inclusion of drift time and product ion information results in higher recall rates and more confident matches, without increases in error rates. Based on the results presented here, we argue that the incorporation of ion mobility drift time and product ion information are worthy pursuits. Alignment methods should be flexible enough to utilize all available data, particularly with recent advancements in experimental separation methods.

Selective detection of underivatized 2,4-dichlorophenoxyacetic acid in soil by supercritical fluid chromatography with ion mobility detection.

PubMed

Morrissey, M A; Hill, H H

1989-09-01

A simplified procedure was developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) in soils. Soil samples were separated by supercritical fluid chromatography after extraction without derivatization and without the use of column chromatography for cleanup. Interferences in the chromatographic separation were eliminated by using a tunably selective ion mobility detector. An atmospheric pressure ion formed by the free acid was selectively monitored so the detector could monitor 2,4-D in the presence of other electron-capturing compounds. For a randomly chosen soil sample, the level of 2,4-D detected was estimated at 500 ppb.

New high-efficiency ion-trap mobility detection system for narcotics

NASA Astrophysics Data System (ADS)

McGann, William J.

1997-02-01

A new patented Ion Trap Mobility Spectrometer design is presented. Conventional IMS designs typically operate below 0.1 percent efficiency. This is due primarily to electric field driven, sample ion discharge on a shutter grid. Since 99.9 percent of the sample ions generated in the reaction region are lost int his discharge process, the sensitivity of conventional systems is limited. The new design provides greater detection efficiency than conventional designs through the use of an 'ion trap' concept. The paper describes the plasma and sample ion dynamics in the reaction region of the new detector and discusses the advantages of utilizing a 'field-free' space to generate sample ions with high efficiency. Fast electronic switching is described which is used to perturb the field-free space and pulse the sample ions into the drift region for separation and subsequent detection using pseudo real-time software for analysis and display of the data. One application for this new detector is now being developed, a portable, hand-held system with switching capability for the detection of drugs and explosives. Preliminary ion spectra and sensitivity data are presented for cocaine and heroin using a hand sniffer configuration.

Isomer Information from Ion Mobility Separation of High-Mannose Glycan Fragments.

PubMed

Harvey, David J; Seabright, Gemma E; Vasiljevic, Snezana; Crispin, Max; Struwe, Weston B

2018-05-01

Extracted arrival time distributions of negative ion CID-derived fragments produced prior to traveling-wave ion mobility separation were evaluated for their ability to provide structural information on N-linked glycans. Fragmentation of high-mannose glycans released from several glycoproteins, including those from viral sources, provided over 50 fragments, many of which gave unique collisional cross-sections and provided additional information used to assign structural isomers. For example, cross-ring fragments arising from cleavage of the reducing terminal GlcNAc residue on Man 8 GlcNAc 2 isomers have unique collision cross-sections enabling isomers to be differentiated in mixtures. Specific fragment collision cross-sections enabled identification of glycans, the antennae of which terminated in the antigenic α-galactose residue, and ions defining the composition of the 6-antenna of several of the glycans were also found to have different cross-sections from isomeric ions produced in the same spectra. Potential mechanisms for the formation of the various ions are discussed and the estimated collisional cross-sections are tabulated. Graphical Abstract ᅟ.

Techniques for Microwave Near-Field Quantum Control of Trapped Ions

DTIC Science & Technology

2013-01-31

counts. Each DDS (Analog Devices AD9858) can generate signals at frequencies to 400 MHz with a frequency resolution of 0.233 Hz and phase resolution...fast, two- channel DAC is used to generate arbitrary waveforms with a 50-MHz update rate, a voltage range from −10 V to 10 V, and a resolution of 0.305...mV. This DAC is programed via USB and triggered by the data acquisition FPGA . We use three DDS modules as sources for three frequency octupling

Protonation of caffeine: A theoretical and experimental study

NASA Astrophysics Data System (ADS)

Bahrami, Hamed; Tabrizchi, Mahmoud; Farrokhpour, Hossein

2013-03-01

Protonation of caffeine was examined by ion mobility spectrometry equipped with two ionization sources, corona discharge (CD) and UV photoionization. Three peaks were observed in ion mobility spectrum by simultaneously running the two ionization sources. Experimental and theoretical evidence was collected to link the observed peaks to caffeine related ionic species. One peak was attributed to the M+ ion while the other two were assigned to different protonated isomers of caffeine. In the case of CD ionization source, it was observed that different sites of caffeine compete for protonation and their relative intensities, depends on the sample concentration as well as the nature of the reactant ions. The new concept of "internal proton affinity" (IPA) was defined to express the tendency of holding the added proton for each atom in a molecule.

Dynamic multiplexed analysis method using ion mobility spectrometer

DOEpatents

Belov, Mikhail E [Richland, WA

2010-05-18

A method for multiplexed analysis using ion mobility spectrometer in which the effectiveness and efficiency of the multiplexed method is optimized by automatically adjusting rates of passage of analyte materials through an IMS drift tube during operation of the system. This automatic adjustment is performed by the IMS instrument itself after determining the appropriate levels of adjustment according to the method of the present invention. In one example, the adjustment of the rates of passage for these materials is determined by quantifying the total number of analyte molecules delivered to the ion trap in a preselected period of time, comparing this number to the charge capacity of the ion trap, selecting a gate opening sequence; and implementing the selected gate opening sequence to obtain a preselected rate of analytes within said IMS drift tube.

Digitized detection of gamma-ray signals concentrated in narrow time windows for transient positron annihilation lifetime spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinomura, A., E-mail: a.kinomura@aist.go.jp; Suzuki, R.; Oshima, N.

2014-12-15

A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μs time window at amore » pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO{sub 2} layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.« less

System Design of One-chip Wave Particle Interaction Analyzer for SCOPE mission.

NASA Astrophysics Data System (ADS)

Fukuhara, Hajime; Ueda, Yoshikatsu; Kojima, Hiro; Yamakawa, Hiroshi

In past science spacecrafts such like GEOTAIL, we usually capture electric and magnetic field waveforms and observe energetic eletron and ion particles as velocity distributions by each sensor. We analyze plasma wave-particle interactions by these respective data and the discussions are sometimes restricted by the difference of time resolution and by the data loss in desired regions. One-chip Wave Particle Interaction Analyzer (OWPIA) conducts direct quantitative observations of wave-particle interaction by direct 'E dot v' calculation on-board. This new instruments have a capability to use all plasma waveform data and electron particle informations. In the OWPIA system, we have to calibrate the digital observation data and transform the same coordinate system. All necessary calculations are processed in Field Programmable Gate Array(FPGA). In our study, we introduce a basic concept of the OWPIA system and a optimization method for each calculation functions installed in FPGA. And we also discuss the process speed, the FPGA utilization efficiency, the total power consumption.

Next-generation fiber lasers enabled by high-performance components

NASA Astrophysics Data System (ADS)

Kliner, D. A. V.; Victor, B.; Rivera, C.; Fanning, G.; Balsley, D.; Farrow, R. L.; Kennedy, K.; Hampton, S.; Hawke, R.; Soukup, E.; Reynolds, M.; Hodges, A.; Emery, J.; Brown, A.; Almonte, K.; Nelson, M.; Foley, B.; Dawson, D.; Hemenway, D. M.; Urbanek, W.; DeVito, M.; Bao, L.; Koponen, J.; Gross, K.

2018-02-01

Next-generation industrial fiber lasers enable challenging applications that cannot be addressed with legacy fiber lasers. Key features of next-generation fiber lasers include robust back-reflection protection, high power stability, wide power tunability, high-speed modulation and waveform generation, and facile field serviceability. These capabilities are enabled by high-performance components, particularly pump diodes and optical fibers, and by advanced fiber laser designs. We summarize the performance and reliability of nLIGHT diodes, fibers, and next-generation industrial fiber lasers at power levels of 500 W - 8 kW. We show back-reflection studies with up to 1 kW of back-reflected power, power-stability measurements in cw and modulated operation exhibiting sub-1% stability over a 5 - 100% power range, and high-speed modulation (100 kHz) and waveform generation with a bandwidth 20x higher than standard fiber lasers. We show results from representative applications, including cutting and welding of highly reflective metals (Cu and Al) for production of Li-ion battery modules and processing of carbon fiber reinforced polymers.

E/N effects on K0 values revealed by high precision measurements under low field conditions

NASA Astrophysics Data System (ADS)

Hauck, Brian C.; Siems, William F.; Harden, Charles S.; McHugh, Vincent M.; Hill, Herbert H.

2016-07-01

Ion mobility spectrometry (IMS) is used to detect chemical warfare agents, explosives, and narcotics. While IMS has a low rate of false positives, their occurrence causes the loss of time and money as the alarm is verified. Because numerous variables affect the reduced mobility (K0) of an ion, wide detection windows are required in order to ensure a low false negative response rate. Wide detection windows, however, reduce response selectivity, and interferents with similar K0 values may be mistaken for targeted compounds and trigger a false positive alarm. Detection windows could be narrowed if reference K0 values were accurately known for specific instrumental conditions. Unfortunately, there is a lack of confidence in the literature values due to discrepancies in the reported K0 values and their lack of reported error. This creates the need for the accurate control and measurement of each variable affecting ion mobility, as well as for a central accurate IMS database for reference and calibration. A new ion mobility spectrometer has been built that reduces the error of measurements affecting K0 by an order of magnitude less than ±0.2%. Precise measurements of ±0.002 cm2 V-1 s-1 or better have been produced and, as a result, an unexpected relationship between K0 and the electric field to number density ratio (E/N) has been discovered in which the K0 values of ions decreased as a function of E/N along a second degree polynomial trend line towards an apparent asymptote at approximately 4 Td.

Negative corona discharge-ion mobility spectrometry as a detection system for low density extraction solvent-based dispersive liquid-liquid microextraction.

PubMed

Ebrahimi, Amir; Jafari, Mohammad T

2015-03-01

This paper deals with a method based on negative corona discharge ionization ion mobility spectrometry (NCD-IMS) for the analysis of ethion (as an organophosphorus pesticide). The negative ions such as O2(-) and NO(x)(-) were eliminated from the background spectrum to increase the instrument sensitivity. The method was used to specify the sample extracted via dispersive liquid-liquid microextraction (DLLME) based on low density extraction solvent. The ion mobility spectrum of ethion in the negative mode and the reduced mobility value for its ion peak are firstly reported and compared with those of the positive mode. In order to combine the low density solvent DLLME directly with NCD-IMS, cyclohexane was selected as the extraction solvent, helping us to have a direct injection up to 20 µL solution, without any signal interference. The method was exhaustively validated in terms of sensitivity, enrichment factor, relative recovery, and repeatability. The linear dynamic range of 0.2-100.0 µg L(-1), detection limit of 0.075 µg L(-1), and the relative standard deviation (RSD) of about 5% were obtained for the analysis of ethion through this method. The average recoveries were calculated about 68% and 92% for the grape juice and underground water, respectively. Finally, some real samples were analyzed and the feasibility of the proposed method was successfully verified by the efficient extraction of the analyte using DLLME before the analysis by NCD-IMS. Copyright © 2014 Elsevier B.V. All rights reserved.

Direct Liquid Sampling for Corona Discharge Ion Mobility Spectrometry.

PubMed

Sabo, Martin; Malásková, Michaela; Harmathová, Olga; Hradski, Jasna; Masár, Marián; Radjenovic, Branislav; Matejčík, Štefan

2015-07-21

We present a new technique suitable for direct liquid sampling and analysis by ion mobility spectrometry (IMS). The technique is based on introduction of a droplet stream to the IMS reaction region. The technique was successfully used to detect explosives dissolved in methanol and oil as well as to analyze amino acids and dipeptides. One of the main advantages of this technique is its ability to analyze liquid samples without the requirement of any special solution.

Practical application of in silico fragmentation based residue screening with ion mobility high-resolution mass spectrometry.

PubMed

Kaufmann, Anton; Butcher, Patrick; Maden, Kathry; Walker, Stephan; Widmer, Mirjam

2017-07-15

A screening concept for residues in complex matrices based on liquid chromatography coupled to ion mobility high-resolution mass spectrometry LC/IMS-HRMS is presented. The comprehensive four-dimensional data (chromatographic retention time, drift time, mass-to-charge and ion abundance) obtained in data-independent acquisition (DIA) mode was used for data mining. An in silico fragmenter utilizing a molecular structure database was used for suspect screening, instead of targeted screening with reference substances. The utilized data-independent acquisition mode relies on the MS E concept; where two constantly alternating HRMS scans (low and high fragmentation energy) are acquired. Peak deconvolution and drift time alignment of ions from the low (precursor ion) and high (product ion) energy scan result in relatively clean product ion spectra. A bond dissociation in silico fragmenter (MassFragment) supplied with mol files of compounds of interest was used to explain the observed product ions of each extracted candidate component (chromatographic peak). Two complex matrices (fish and bovine liver extract) were fortified with 98 veterinary drugs. Out of 98 screened compounds 94 could be detected with the in silico based screening approach. The high correlation among drift time and m/z value of equally charged ions was utilized for an orthogonal filtration (ranking). Such an orthogonal ion mobility based filter removes multiply charged ions (e.g. peptides and proteins from the matrix) as well as noise and artefacts. Most significantly, this filtration dramatically reduces false positive findings but hardly increases false negative findings. The proposed screening approach may offer new possibilities for applications where reference compounds are hardly or not at all commercially available. Such areas may be the analysis of metabolites of drugs, pyrrolizidine alkaloids, marine toxins, derivatives of sildenafil or novel designer drugs (new psychoactive substances). Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Ion Mobility-Derived Collision Cross Section As an Additional Measure for Lipid Fingerprinting and Identification

PubMed Central

2014-01-01

Despite recent advances in analytical and computational chemistry, lipid identification remains a significant challenge in lipidomics. Ion-mobility spectrometry provides an accurate measure of the molecules’ rotationally averaged collision cross-section (CCS) in the gas phase and is thus related to ionic shape. Here, we investigate the use of CCS as a highly specific molecular descriptor for identifying lipids in biological samples. Using traveling wave ion mobility mass spectrometry (MS), we measured the CCS values of over 200 lipids within multiple chemical classes. CCS values derived from ion mobility were not affected by instrument settings or chromatographic conditions, and they were highly reproducible on instruments located in independent laboratories (interlaboratory RSD < 3% for 98% of molecules). CCS values were used as additional molecular descriptors to identify brain lipids using a variety of traditional lipidomic approaches. The addition of CCS improved the reproducibility of analysis in a liquid chromatography-MS workflow and maximized the separation of isobaric species and the signal-to-noise ratio in direct-MS analyses (e.g., “shotgun” lipidomics and MS imaging). These results indicate that adding CCS to databases and lipidomics workflows increases the specificity and selectivity of analysis, thus improving the confidence in lipid identification compared to traditional analytical approaches. The CCS/accurate-mass database described here is made publicly available. PMID:25495617

Ion mobility spectrometer, spectrometer analyte detection and identification verification system, and method

DOEpatents

Atkinson, David A.

2002-01-01

Methods and apparatus for ion mobility spectrometry and analyte detection and identification verification system are disclosed. The apparatus is configured to be used in an ion mobility spectrometer and includes a plurality of reactant reservoirs configured to contain a plurality of reactants which can be reacted with the sample to form adducts having varying ion mobilities. A carrier fluid, such as air or nitrogen, is used to carry the sample into the spectrometer. The plurality of reactants are configured to be selectively added to the carrier stream by use inlet and outlet manifolds in communication with the reagent reservoirs, the reservoirs being selectively isolatable by valves. The invention further includes a spectrometer having the reagent system described. In the method, a first reactant is used with the sample. Following a positive result, a second reactant is used to determine whether a predicted response occurs. The occurrence of the second predicted response tends to verify the existence of a component of interest within the sample. A third reactant can also be used to provide further verification of the existence of a component of interest. A library can be established of known responses of compounds of interest with various reactants and the results of a specific multi-reactant survey of a sample can be compared against the library to determine whether a component detected in the sample is likely to be a specific component of interest.

Multi-capillary column-ion mobility spectrometry: a potential screening system to differentiate virgin olive oils.

PubMed

Garrido-Delgado, Rocío; Arce, Lourdes; Valcárcel, Miguel

2012-01-01

The potential of a headspace device coupled to multi-capillary column-ion mobility spectrometry has been studied as a screening system to differentiate virgin olive oils ("lampante," "virgin," and "extra virgin" olive oil). The last two types are virgin olive oil samples of very similar characteristics, which were very difficult to distinguish with the existing analytical method. The procedure involves the direct introduction of the virgin olive oil sample into a vial, headspace generation, and automatic injection of the volatiles into a gas chromatograph-ion mobility spectrometer. The data obtained after the analysis by duplicate of 98 samples of three different categories of virgin olive oils, were preprocessed and submitted to a detailed chemometric treatment to classify the virgin olive oil samples according to their sensory quality. The same virgin olive oil samples were also analyzed by an expert's panel to establish their category and use these data as reference values to check the potential of this new screening system. This comparison confirms the potential of the results presented here. The model was able to classify 97% of virgin olive oil samples in their corresponding group. Finally, the chemometric method was validated obtaining a percentage of prediction of 87%. These results provide promising perspectives for the use of ion mobility spectrometry to differentiate virgin olive oil samples according to their quality instead of using the classical analytical procedure.

Experimental ion mobility measurements in Xe-C2H6

NASA Astrophysics Data System (ADS)

Perdigoto, J. M. C.; Cortez, A. F. V.; Veenhof, R.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.

2017-10-01

In this paper we present the results of the ion mobility measurements made in gaseous mixtures of xenon (Xe) with ethane (C2H6) for pressures ranging from 6 to 10 Torr (8-10.6 mbar) and for low reduced electric fields in the 10 Td to 25 Td range (2.4-6.1 kVṡcm-1ṡ bar-1), at room temperature. The time of arrival spectra revealed two peaks throughout the entire range studied which were attributed to ion species with 3-carbons (C3H5+, C3H6+ C3H8+ and C3H9+) and with 4-carbons (C4H7+, C4H9+ and C4H10+). Besides these, and for Xe concentrations above 70%, a bump starts to appear at the right side of the main peak for reduced electric fields higher than 20 Td, which was attributed to the resonant charge transfer of C2H6+ to C2H6 that affects the mobility of its ion products (C3H8+ and C3H9+). The time of arrival spectra for Xe concentrations of 20%, 50%, 70% and 90% are presented, together with the reduced mobilities as a function of the Xe concentration calculated from the peaks observed for the low reduced electric fields and pressures studied.

Sensitive detection of trimethylamine based on dopant-assisted positive photoionization ion mobility spectrometry.

PubMed

Cheng, Shasha; Li, Haitao; Jiang, Dandan; Chen, Chuang; Zhang, Tan; Li, Yong; Wang, Haitao; Zhou, Qinghua; Li, Haiyang; Tan, Mingqian

2017-01-01

Biogenic amines are degradation products generated through enzymatic and microbial processes during food spoilage, which may pose a health hazard to consumers at elevated levels. Trimethylamine (TMA) is a good target for the detection of biogenic amines due to its volatility and fishy odor. In this study, we developed a stand-alone dopant-assisted positive photoionization ion mobility spectrometry (DAPP-IMS) for rapid and sensitive detection of TMA. Response of TMA was enhanced by the addition of dopants and characteristic product ions with reduced mobility 2.26cm 2 V -1 s -1 were formed. 2-Butaone was chosen as the dopant for better separation between reagent ion peak and TMA product ion peak as well as higher sensitivity and the limit of detections (LODs) for TMA standard sample was 1ppb. The potential application of DAAP-IMS was evaluated by the detection of TMA generated by oyster and shrimp during 4°C storage. Analysis of two kinds of seafood showed the same characteristic peak to TMA standard sample, and the intensity of TMA increased over the storage time. The results of this study testify to the potential of DAPP-IMS for qualitative and quantitative determination of TMA in real food samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Transport Properties of Anatase-TiO2 Polycrystalline-Thin-Film Field-Effect Transistors with Electrolyte Gate Layers

NASA Astrophysics Data System (ADS)

Horita, Ryohei; Ohtani, Kyosuke; Kai, Takahiro; Murao, Yusuke; Nishida, Hiroya; Toya, Taku; Seo, Kentaro; Sakai, Mio; Okuda, Tetsuji

2013-11-01

We have fabricated anatase-TiO2 polycrystalline-thin-film field-effect transistors (FETs) with poly(vinyl alcohol) (PVA), ion-liquid (IL), and ion-gel (IG) gate layers, and have tried to improve the response to gate voltage by varying the concentration of mobile ions in these electrolyte gate layers. The increase in the concentration of mobile ions by doping NaOH into the PVA gate layer or reducing the gelator in the IG gate layer markedly increases the drain-source current and reduces the driving gate voltage, which show that the mobile ions in the PVA, IL, and IG gate layers cause the formation of electric double layers (EDLs), which act as nanogap capacitors. In these TiO2-EDL-FETs, the slow formation of EDLs and the oxidation reaction at the interface between the surface of the TiO2 film and the electrolytes cause unideal FET properties. In the optimized IL and IG TiO2-EDL-FETs, the driving gate voltage is less than 1 V and the ON/OFF ratios of the transfer characteristics are about 1×104 at RT, and the nearly metallic state is realized at the interface purely by applying a gate voltage.

Design of a TW-SLIM Module for Dual Polarity Confinement, Transport, and Reactions

NASA Astrophysics Data System (ADS)

Garimella, Sandilya V. B.; Webb, Ian K.; Prabhakaran, Aneesh; Attah, Isaac K.; Ibrahim, Yehia M.; Smith, Richard D.

2017-07-01

Here we describe instrumental approaches for performing dual polarity ion confinement, transport, ion mobility separations, and reactions in structures for lossless ion manipulations (SLIM). Previous means of ion confinement in SLIM, based upon rf-generated pseudopotentials and DC fields for lateral confinement, cannot trap ions of opposite polarity simultaneously. Here we explore alternative approaches to provide simultaneous lateral confinement of both ion polarities. Traveling wave ion mobility (IM) separations experienced in such SLIM cause ions of both polarities to migrate in the same directions and exhibit similar separations. The ion motion (and relative motion of the two polarities) under both surfing and IM separation conditions are discussed. In surfing conditions the two polarities are transported losslessly and non-reactively in their respective potential minima (higher absolute voltage regions confine negative polarities, and lower absolute potential regions are populated by positive polarities). In separation mode, where ions roll over an overtaking traveling wave, the two polarities can interact during the rollovers. Strategies to minimize overlap of the two ion populations to prevent reactive losses during separations are presented. A theoretical treatment of the time scales over which two populations (injected into a DC field-free region of the dual polarity SLIM device) interact is considered, and SLIM designs for allowing ion/ion interactions and other manipulations with dual polarities at 4 Torr are presented.

Mobility and fluorescence of barium ions in xenon gas for the exo experiment

NASA Astrophysics Data System (ADS)

Benitez Medina, Julio Cesar

The Enriched Xenon Observatory (EXO) is an experiment which aims to observe the neutrinoless double beta decay of 136Xe. The measurement of this decay would give information about the absolute neutrino mass and whether or not the neutrino is its own antiparticle. Since this is a very rare decay, the ability to reject background events by detecting the barium ion daughter from the double beta decay would be a major advantage. EXO is currently operating a detector with 200 kg of enriched liquid xenon, and there are plans to build a ton scale xenon detector. Measurements of the purity of liquid xenon in our liquid xenon test cell are reported. These results are relevant to the research on detection of single barium ions by our research group at Colorado State University. Details of the operation of the purity monitor are described. The effects of using a purifier, recirculation and laser ablation on the purity of liquid xenon are discussed. Mobility measurements of barium in xenon gas are reported for the first time. The variation of mobility with xenon gas pressure suggests that a significant fraction of molecular ions are formed when barium ions interact with xenon gas at high pressures. The measured mobility of Ba+ in Xe gas at different pressures is compared with the predicted theoretical value, and deviations are explained by a model that describes the fraction of molecular ions in Xe gas as a function of pressure. The results are useful for the analysis of experiments of fluorescence of Ba+ in xenon gas. It is also important to know the mobility of the ions in order to calculate the time they interact with an excitation laser in fluorescence experiments and in proposed 136 Ba+ daughter detection schemes. This thesis presents results of detection of laser induced fluorescence of Ba+ ions in Xe gas. Measurements of the pressure broadening of the excitation spectra of Ba+ in xenon gas are presented. Nonradiative decays due to gas collisions and optical pumping affect the number of fluorescence counts detected. A model that treats the barium ion as a three level system is used to predict the total number of fluorescence counts and correct for optical pumping. A pressure broadening coefficient for Ba+ in xenon gas is extracted and limits for p-d and d-s nonradiative decay rates are extracted. Although fluorescence is reduced significantly at 5-10 atm xenon pressure, the measurements in this thesis indicate that it is still feasible to detect 136Ba+ ions directly in high pressure xenon gas, e.g. in a double beta decay detector.

Development and Evaluation of a Reverse-Entry Ion Source Orbitrap Mass Spectrometer

NASA Astrophysics Data System (ADS)

Poltash, Michael L.; McCabe, Jacob W.; Patrick, John W.; Laganowsky, Arthur; Russell, David H.

2018-05-01

As a step towards development of a high-resolution ion mobility mass spectrometer using the orbitrap mass analyzer platform, we describe herein a novel reverse-entry ion source (REIS) coupled to the higher-energy C-trap dissociation (HCD) cell of an orbitrap mass spectrometer with extended mass range. Development of the REIS is a first step in the development of a drift tube ion mobility-orbitrap MS. The REIS approach retains the functionality of the commercial instrument ion source which permits the uninterrupted use of the instrument during development as well as performance comparisons between the two ion sources. Ubiquitin (8.5 kDa) and lipid binding to the ammonia transport channel (AmtB, 126 kDa) protein complex were used as model soluble and membrane proteins, respectively, to evaluate the performance of the REIS instrument. Mass resolution obtained with the REIS is comparable to that obtained using the commercial ion source. The charge state distributions for ubiquitin and AmtB obtained on the REIS are in agreement with previous studies which suggests that the REIS-orbitrap EMR retains native structure in the gas phase.

Extending the frontiers of mass spectrometric instrumentation and methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schieffer, Gregg Martin

2010-01-01

The focus of this dissertation is two-fold: developing novel analysis methods using mass spectrometry and the implementation and characterization of a novel ion mobility mass spectrometry instrumentation. The novel mass spectrometry combines ion trap for ion/ion reactions coupled to an ion mobility cell. The long term goal of this instrumentation is to use ion/ion reactions to probe the structure of gas phase biomolecule ions. The three ion source - ion trap - ion mobility - qTOF mass spectrometer (IT - IM - TOF MS) instrument is described. The analysis of the degradation products in coal (Chapter 2) and the imagingmore » plant metabolites (Appendix III) fall under the methods development category. These projects use existing commercial instrumentation (JEOL AccuTOF MS and Thermo Finnigan LCQ IT, respectively) for the mass analysis of the degraded coal products and the plant metabolites, respectively. The coal degradation paper discusses the use of the DART ion source for fast and easy sample analysis. The sample preparation consisted of a simple 50 fold dilution of the soluble coal products in water and placing the liquid in front of the heated gas stream. This is the first time the DART ion source has been used for analysis of coal. Steven Raders under the guidance of John Verkade came up with the coal degradation projects. Raders performed the coal degradation reactions, worked up the products, and sent them to me. Gregg Schieffer developed the method and wrote the paper demonstrating the use of the DART ion source for the fast and easy sample analysis. The plant metabolite imaging project extends the use of colloidal graphite as a sample coating for atmospheric pressure LDI. DC Perdian and I closely worked together to make this project work. Perdian focused on building the LDI setup whereas Schieffer focused on the MSn analysis of the metabolites. Both Perdian and I took the data featured in the paper. Perdian was the primary writer of the paper and used it as a chapter in his dissertation. Perdian and Schieffer worked together to address the revisions and publish it in Rapid Communications in Mass Spectrometry Journal.« less

Understanding the conductive channel evolution in Na:WO3-x-based planar devices

NASA Astrophysics Data System (ADS)

Shang, Dashan; Li, Peining; Wang, Tao; Carria, Egidio; Sun, Jirong; Shen, Baogen; Taubner, Thomas; Valov, Ilia; Waser, Rainer; Wuttig, Matthias

2015-03-01

An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07545e

Atmospheric ions and germination of uredospores of Puccinia striiformis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharp, E.L.

1967-06-09

Atmospheric ions, identified by mobility characteristics, were associated with germination of lyophilized uredospores of Puccinia striiformis West. at Bozeman, Montana. Ions of intermediate size were highest in concentration, and percentage germination of spores was lowest during periods conducive to air pollution. In duplicate experiments at an isolated site near Barrow, Alaska, essentially all atmospheric ions were small ions and the fungus spores were consistently germinated near maximum.

Influence of nanoparticle-ion and nanoparticle-polymer interactions on ion transport and viscoelastic properties of polymer electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mogurampelly, Santosh; Sethuraman, Vaidyanathan; Pryamitsyn, Victor

We use atomistic simulations to probe the ion conductivities and mechanical properties of polyethylene oxide electrolytes containing Al{sub 2}O{sub 3} nanoparticles. We specifically study the influence of repulsive polymer-nanoparticle and ion-nanoparticle interactions and compare the results with those reported for electrolytes containing the polymorph β-Al{sub 2}O{sub 3} nanoparticles. We observe that incorporating repulsive nanoparticle interactions generally results in increased ionic mobilities and decreased elastic moduli for the electrolyte. Our results indicate that both ion transport and mechanical properties are influenced by the polymer segmental dynamics in the interfacial zones of the nanoparticle in the ion-doped systems. Such effects were seenmore » to be determined by an interplay between the nanoparticle-polymer, nanoparticle-ion, and ion-polymer interactions. In addition, such interactions were also observed to influence the number of dissociated ions and the resulting conductivities. Within the perspective of the influence of nanoparticles on the polymer relaxation times in ion-doped systems, our results in the context of viscoelastic properties were consistent with the ionic mobilities. Overall, our results serve to highlight some issues that confront the efforts to use nanoparticle dispersions to simultaneously enhance the conductivity and the mechanical strength of polymer electrolyte.« less

Lifetimes and stabilities of familiar explosives molecular adduct complexes during ion mobility measurements

PubMed Central

McKenzie, Alan; DeBord, John Daniel; Ridgeway, Mark; Park, Melvin; Eiceman, Gary; Fernandez-Lima, Francisco

2015-01-01

Trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) was utilized for the separation and identification of familiar explosives in complex mixtures. For the first time, molecular adduct complex lifetimes, relative stability, binding energies and candidate structures are reported for familiar explosives. Experimental and theoretical results showed that the adduct size and reactivity, complex binding energy and the explosive structure tailors the stability of the molecular adduct complex. TIMS flexibility to adapt the mobility separation as a function of the molecular adduct complex stability (i.e., short or long IMS experiments / low or high IMS resolution) permits targeted measurements of explosives in complex mixtures with higher confidence levels. PMID:26153567

Importance of pH-regulated charge density on the electrophoresis of soft particles

NASA Astrophysics Data System (ADS)

Gopmandal, Partha P.; Ohshima, H.

2017-02-01

The present study deals with the electrophoresis of spherical soft particles consisting of an ion and liquid-penetrable but liquid-flow-impenetrable inner core surrounded by an ion and fluid-penetrable polyelectrolyte layer. The inner core is considered to be dielectric and bearing basic functional group coated with polyelectrolyte layer containing acidic functional group. An approximate expression for the electrophoretic mobility of such a particle is obtained under a low potential limit. The electrophoretic behaviour of the undertaken particle is investigated for a wide range of bulk pH values and electrolyte concentrations. Our study also indicates some remarkable features of the electrophoresis e.g., occurrence of zero mobility, mobility reversal etc.

Metal-induced crystallization of amorphous zinc tin oxide semiconductors for high mobility thin-film transistors

NASA Astrophysics Data System (ADS)

Hwang, Ah Young; Kim, Sang Tae; Ji, Hyuk; Shin, Yeonwoo; Jeong, Jae Kyeong

2016-04-01

Transition tantalum induced crystallization of amorphous zinc tin oxide (a-ZTO) was observed at low temperature annealing of 300 °C. Thin-film transistors (TFTs) with an a-ZTO channel layer exhibited a reasonable field-effect mobility of 12.4 cm2/V s, subthreshold swing (SS) of 0.39 V/decade, threshold voltage (VTH) of 1.5 V, and ION/OFF ratio of ˜107. A significant improvement in the field-effect mobility (up to ˜33.5 cm2/V s) was achieved for crystallized ZTO TFTs: this improvement was accomplished without compromising the SS, VTH, or ION/OFF ratio due to the presence of a highly ordered microstructure.

Investigating the role of ion-pair strategy in regulating nicotine release from patch: Mechanistic insights based on intermolecular interaction and mobility of pressure sensitive adhesive.

PubMed

Li, Qiaoyun; Wan, Xiaocao; Liu, Chao; Fang, Liang

2018-07-01

The aim of this study was to prepare a drug-in-adhesive patch of nicotine (NIC) and use ion-pair strategy to regulate drug delivery rate. Moreover, the mechanism of how ion-pair strategy regulated drug release was elucidated at molecular level. Formulation factors including pressure sensitive adhesives (PSAs), drug loading and counter ions (C 4 , C 6 , C 8 , C 10 , and C 12 ) were screened. In vitro release experiment and in vitro transdermal experiment were conducted to determine the rate-limiting step in drug delivery process. FT-IR and molecular modeling were used to characterize the interaction between drug and PSA. Thermal analysis and rheology study were conducted to investigate the mobility variation of PSA. The optimized patch prepared with NIC-C 8 had the transdermal profile fairly close to that of the commercial product (p > 0.05). The release rate constants (k) of NIC, NIC-C 4 and NIC-C 10 were 21.1, 14.4 and 32.4, respectively. Different release rates of NIC ion-pair complexes were attributed to the dual effect of ion-pair strategy on drug release. On one hand, ion-pair strategy enhanced the interaction between drug and PSA, which inhibited drug release. On the other hand, using ion-pair strategy improved the mobility of PSA, which facilitated drug release. Drug release behavior was determined by combined effect of two aspects above. These conclusions provided a new idea for us to regulate drug release behavior from patch. Copyright © 2018 Elsevier B.V. All rights reserved.

Determination of Collision Cross Sections Using a Fourier Transform Electrostatic Linear Ion Trap Mass Spectrometer

NASA Astrophysics Data System (ADS)

Dziekonski, Eric T.; Johnson, Joshua T.; Lee, Kenneth W.; McLuckey, Scott A.

2018-02-01

Collision cross sections (CCSs) were determined from the frequency-domain linewidths in a Fourier transform electrostatic linear ion trap. With use of an ultrahigh-vacuum precision leak valve and nitrogen gas, transients were recorded as the background pressure in the mass analyzer chamber was varied between 4× 10-8 and 7 × 10-7 Torr. The energetic hard-sphere ion-neutral collision model, described by Xu and coworkers, was used to relate the recorded image charge to the CCS of the molecule. In lieu of our monoisotopically isolating the mass of interest, the known relative isotopic abundances were programmed into the Lorentzian fitting algorithm such that the linewidth was extracted from a sum of Lorentzians. Although this works only if the isotopic distribution is known a priori, it prevents ion loss, preserves the high signal-to-noise ratio, and minimizes the experimental error on our homebuilt instrument. Six tetraalkylammonium cations were used to correlate the CCS measured in the electrostatic linear ion trap with that measured by drift-tube ion mobility spectrometry, for which there was an excellent correlation ( R 2 ≈ 0.9999). Although the absolute CCSs derived with our method differ from those reported, the extracted linear correlation can be used to correct the raw CCS. With use of [angiotensin II]2+ and reserpine, the corrected CCSs (334.9 ± 2.1 and 250.1 ± 0.5, respectively) were in good agreement with the reported ion mobility spectrometry CCSs (335 and 254.3, respectively). With sufficient signal-to-noise ratio, the CCSs determined are reproducible to within a fraction of a percent, comparable to the uncertainties reported on dedicated ion mobility instruments.

Ion transport in sub-5-nm graphene nanopores.

PubMed

Suk, Myung E; Aluru, N R

2014-02-28

Graphene nanopore is a promising device for single molecule sensing, including DNA bases, as its single atom thickness provides high spatial resolution. To attain high sensitivity, the size of the molecule should be comparable to the pore diameter. However, when the pore diameter approaches the size of the molecule, ion properties and dynamics may deviate from the bulk values and continuum analysis may not be accurate. In this paper, we investigate the static and dynamic properties of ions with and without an external voltage drop in sub-5-nm graphene nanopores using molecular dynamics simulations. Ion concentration in graphene nanopores sharply drops from the bulk concentration when the pore radius is smaller than 0.9 nm. Ion mobility in the pore is also smaller than bulk ion mobility due to the layered liquid structure in the pore-axial direction. Our results show that a continuum analysis can be appropriate when the pore radius is larger than 0.9 nm if pore conductivity is properly defined. Since many applications of graphene nanopores, such as DNA and protein sensing, involve ion transport, the results presented here will be useful not only in understanding the behavior of ion transport but also in designing bio-molecular sensors.

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

DOE PAGES

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.; ...

2018-03-26

Ion mobility (IM) is rapidly gaining attention for the separation and analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM separations have limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. Both of these can be readily obtained in Structures for Lossless Ion Manipulations (SLIM), which are fabricated from arrays of electrodes patterned on two parallel surfaces where potentials aremore » applied to generate appropriate electric fields between the surfaces. Here we have investigated the relationship between the primary SLIM variables, such as electrode dimensions, inter-surface gap, and the applied TW voltages, that directly impact the fields experienced by ions. Ion trajectory simulations and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric fields on IM resolution. The variables explored impact both ion confinement and the observed IM resolution using SLIM modules.« less

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.

Ion mobility (IM) is rapidly gaining attention for the separation and analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM separations have limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. Both of these can be readily obtained in Structures for Lossless Ion Manipulations (SLIM), which are fabricated from arrays of electrodes patterned on two parallel surfaces where potentials aremore » applied to generate appropriate electric fields between the surfaces. Here we have investigated the relationship between the primary SLIM variables, such as electrode dimensions, inter-surface gap, and the applied TW voltages, that directly impact the fields experienced by ions. Ion trajectory simulations and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric fields on IM resolution. The variables explored impact both ion confinement and the observed IM resolution using SLIM modules.« less

Ion Conductivity and Sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bychkov, E.; Tveryanovich, Y.; Vlasov, Y.

2005-03-02

Ionic transport in glasses was discovered in the 19th century following the classical work of Warburg (1884). Since then, considerable progress has been achieved in both theoretical understanding and practical applications of ion-conducting vitreous systems (see Frischat, 1975; Malugani and Robert, 1980; Ribes, Barrau and Souquet, 1980; Kennedy and Yang, 1987; Vlasov and Bychkov, 1987; Hayashi, Tatsumisago and Minami, 1999; Doremus, 1962 and references therein). Nevertheless, this topic and especially the ion-conducting mechanisms in disordered solids need additional study using traditional macroscopic methods (ac and dc electrical conductivity, tracer diffusion, and ion transport number measurements), as well as advanced structuralmore » techniques on third generation synchrotron light sources and spallation neutron sources over a large range of the scattering vector Q. This approach led to the discovery of important features: in particular, different transport regimes at low and high mobile ion content that are closely related to a competition between the stochastic scenario and a non-random distribution of the mobile ions in the glass network. Well-known experimental findings such as compositional dependence of the Haven ratio H{sub R}, interpreted earlier by a number of drastically different ion transport models, can also be explained using a unified approach. Many of the new experimental results were obtained for silver and copper chalcogenide glasses which appear to be useful model materials, in part because of a large accessible composition domain, as well as coverage of five orders of magnitude in the mobile cation content, and corresponding dramatic changes in the ionic transport up to 10 orders of magnitude.« less

Test of GET Electronics for the CHIMERA and FARCOS multi-detectors

NASA Astrophysics Data System (ADS)

De Luca, S.; Acosta, L.; Auditore, L.; Boiano, C.; Cardella, G.; Castoldi, A.; D'Andrea, M.; De Filippo, E.; Dell'Aquila, D.; Fichera, F.; Gnoffo, B.; Guazzoni, C.; Lanzalone, G.; Lombardo, I.; Martorana, N. S.; Minniti, T.; Norella, S.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Quattrocchi, L.; Rizzo, F.; Russotto, P.; Saccà, G.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

2017-11-01

In this paper we present the results of the tests on the new digital electronics GET (General Electronics for Tpc), which will be used for the readout of the CsI(Tl) detectors of CHIMERA (Charged Heavy Ion Mass and Energy Resolving Array) and for the new correlator FARCOS (Femtoscope ARray for COrrelations and Spectroscopy). The new electronics allows us to digitize the full waveform of the signals produced by the detector. Among its features it is worth noticing the compactness and low power consumption (5W for 256 channels). Tests have been performed with pulsers, radioactive sources and ion beams. With such electronics very good results in energy resolution and isotope separation of the detected fragments were obtained, by using both hardware and software filters.

Digital Rise-Time Discrimination of Pulses from the Tigress Integrated Plunger Silicon PIN Diode Wall

NASA Astrophysics Data System (ADS)

Voss, P.; Henderson, R.; Andreoiu, C.; Ashley, R.; Ball, G. C.; Bender, P. C.; Chester, A.; Cross, D. S.; Drake, T. E.; Garnsworthy, A. B.; Hackman, G.; Ketelhut, S.; Krücken, R.; Miller, D.; Rajabali, M. M.; Starosta, K.; Svensson, C. E.; Tardiff, E.; Unsworth, C.; Wang, Z.-M.

Electromagnetic transition rate measurements play an important role in characterizing the evolution of nuclear structure with increasing proton-neutron asymmetry. At TRIUMF, the TIGRESS Integrated Plunger device and its suite of ancillary detector systems have been implemented for charged-particle tagging and light-ion identification in coincidence with gamma-ray spectroscopy for Doppler-shift lifetime studies and low-energy Coulomb excitation measurements. Digital pulse-shape analysis of signals from these ancillary detectors for particle identification improves the signal-to-noise ratio of gamma-ray energy spectra. Here, we illustrate the reaction-channel selectivity achieved by utilizing digital rise-time discrimination of waveforms from alpha particles and carbon ions detected with silicon PIN diodes, thereby enhancing gamma-ray line-shape signatures for precision lifetime studies.

Soft ionization device with characterization systems and methods of manufacture

NASA Technical Reports Server (NTRS)

Hartley, Frank T. (Inventor)

2004-01-01

Various configurations of characterization systems such as ion mobility spectrometers and mass spectrometers are disclosed that are coupled to an ionization device. The ionization device is formed of a membrane that houses electrodes therein that are located closer to one another than the mean free path of the gas being ionized. Small voltages across the electrodes generate large electric fields which act to ionize substantially all molecules passing therethrough without fracture. Methods to manufacture the mass spectrometer and ion mobility spectrometer systems are also described.

Storage Reliability of Missile Materiel Program. Storage Reliability Analysis Summary Report. Volume 1. Electrical and Electronic Devices

DTIC Science & Technology

1976-05-01

since the platinum silicide and titanium metals also offer very low mobility to the alkaline ions, the BLSJ . is inert to sodium . Inversion and...gettering agents for sodium ions, thus making the cont&-nination far less mobile. The stability of the structural and electrical properties of the oxide...to be an effective barrier to sodium migration. In Beam Lead Sealed ,unction (BLSJ) devices, the silicon nitride seals the devices from sodium and

Storage Reliability of Missile Materiel Program. Storage Reliability Analysis Summary Report. Volume 1. Electrical and Electronic Devices

DTIC Science & Technology

1978-01-01

silicon nitride seals the devices from sodium and since the platinum silicide and titanium metals also offer very low mobility to the alkaline ions, the...of bipolar devices. These materials act as gettering agents for sodium ions, thus making the contamination far less mobile. The stability of the...parameter instability. Silicon nitride has been shown to be an effective barrier to sodium migration. In Beam Lead Sealed Junction (BLSJ) devices, the

Ion Mobility Separation of Variant Histone Tails Extending to the “Middle-down” Range

PubMed Central

Shvartsburg, Alexandre A.; Zheng, Yupeng; Smith, Richard D.; Kelleher, Neil L.

2012-01-01

Differential ion mobility spectrometry (FAIMS) can baseline-resolve multiple variants of post-translationally modified peptides extending to the 3 - 4 kDa range, which differ in the localization of a PTM as small as acetylation. Essentially orthogonal separations for different charge states expand the total peak capacity in proportion to the number of observed states that increases for longer polypeptides. This might enable resolving localization variants for yet larger peptides and even intact proteins. PMID:22559289

Analysis of psilocybin and psilocin in Psilocybe subcubensis Guzmán by ion mobility spectrometry and gas chromatography-mass spectrometry.

PubMed

Keller, T; Schneider, A; Regenscheit, P; Dirnhofer, R; Rücker, T; Jaspers, J; Kisser, W

1999-01-11

A new method has been developed for the rapid analysis of psilocybin and/or psilocin in fungus material using ion mobility spectrometry. Quantitative analysis was performed by gas chromatography-mass spectrometry after a simple one-step extraction involving homogenization of the dried fruit bodies of fungi in chloroform and derivatization with MSTFA. The proposed methods resulted in rapid procedures useful in analyzing psychotropic fungi for psilocybin and psilocin.

Community Seismic Network (CSN)

NASA Astrophysics Data System (ADS)

Clayton, R. W.; Heaton, T. H.; Kohler, M. D.; Cheng, M.; Guy, R.; Chandy, M.; Krause, A.; Bunn, J.; Olson, M.; Faulkner, M.

2011-12-01

The CSN is a network of low-cost accelerometers deployed in the Pasadena, CA region. It is a prototype network with the goal of demonstrating the importance of dense measurements in determining the rapid lateral variations in ground motion due to earthquakes. The main product of the CSN is a map of peak ground produced within seconds of significant local earthquakes that can be used as a proxy for damage. Examples of this are shown using data from a temporary network in Long Beach, CA. Dense measurements in buildings are also being used to determine the state of health of structures. In addition to fixed sensors, portable sensors such as smart phones are also used in the network. The CSN has necessitated several changes in the standard design of a seismic network. The first is that the data collection and processing is done in the "cloud" (Google cloud in this case) for robustness and the ability to handle large impulsive loads (earthquakes). Second, the database is highly de-normalized (i.e. station locations are part of waveform and event-detection meta data) because of the mobile nature of the sensors. Third, since the sensors are hosted and/or owned by individuals, the privacy of the data is very important. The location of fixed sensors is displayed on maps as sensor counts in block-wide cells, and mobile sensors are shown in a similar way, with the additional requirement to inhibit tracking that at least two must be present in a particular cell before any are shown. The raw waveform data are only released to users outside of the network after a felt earthquake.

Contribution of capillary electrophoresis to an integrated vision of humic substances size and charge characterizations

DOE Office of Scientific and Technical Information (OSTI.GOV)

D'Orlye, Fanny; Reiller, Pascal E.

2014-02-15

The physicochemical properties of three different humic substances (HS) are probed using capillary zone electrophoresis in alkaline carbonate buffers, pH 10. Special attention is drawn to the impact of the electrolyte ionic strength and counter-ion nature, chosen within the alkali-metal series, on HS electrophoretic mobility. Taylor-Aris dispersion analysis provides insights into the hydrodynamic radius (R-H) distributions of HS. The smallest characterized entities are of nano-metric dimensions, showing neither ionic strength- nor alkali-metal-induced aggregation. These results are compared with the entities evidenced in dynamic light scattering measurements, the size of which is two order of magnitude higher, ca. 100 nm. Themore » extended Onsager model provides a reasonable description of measured electrophoretic mobilities in the ionic strength range 1-50 mM, thus allowing the estimation of limiting mobilities and ionic charge numbers for the different HS samples. An unexpected HS electrophoretic mobility increase (in absolute value) is observed in the order Li{sup +} ≤ Na{sup +} ≤ K{sup +} ≤ Cs{sup +} and discussed either in terms of retarding forces or in terms of ion-ion interactions. (authors)« less

Ion size effects on the electrokinetics of spherical particles in salt-free concentrated suspensions

NASA Astrophysics Data System (ADS)

Roa, Rafael; Carrique, Felix; Ruiz-Reina, Emilio

2012-02-01

In this work we study the influence of the counterion size on the electrophoretic mobility and on the dynamic mobility of a suspended spherical particle in a salt-free concentrated colloidal suspension. Salt-free suspensions contain charged particles and the added counterions that counterbalance their surface charge. A spherical cell model approach is used to take into account particle-particle electro-hydrodynamic interactions in concentrated suspensions. The finite size of the counterions is considered including an entropic contribution, related with the excluded volume of the ions, in the free energy of the suspension, giving rise to a modified counterion concentration profile. We are interested in studying the linear response of the system to an electric field, thus we solve the different electrokinetic equations by using a linear perturbation scheme. We find that the ionic size effect is quite important for moderate to high particles charges at a given particle volume fraction. In addition for such particle surface charges, both the electrophoretic mobility and the dynamic mobility suffer more important changes the larger the particle volume fraction for each ion size. The latter effects are more relevant the larger the ionic size.

Electrospray Ionization/Ion Mobility Spectrometer/Cylindrical Ion Trap Mass Spectrometer System for In-Situ Detection of Organic Compounds

NASA Technical Reports Server (NTRS)

Kanik, I.; Johnson, P. V.; Beegle, L. W.; Cooks, R. G.; Laughlin, B. C.; Hill, H. H.

2003-01-01

The potential of an Electrospray Ionization/Ion Mobility Spectrometer/Cylindrical Ion Trap Mass Spectrometer (ESI/IMS/CIT-MS) as an analytical instrument for analyzing material extracted from rock and soil samples as part of a suite of instruments on the proposed 2009 Mars Science Lander (MSL) will be demonstrated. This instrument will be able to identify volatile compounds as well as resident organic molecules on the parts-per-billion (ppb) level. Also, it will be able to obtain an inventory of chemical species on the surface of Mars which will result in a better understanding of ongoing surface chemistry. Finally, questions relevant to biological processes will be answered with the complete inventory of surface and near surface organic molecules that the ESI/IMS/CIT is capable of performing.

Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells

PubMed Central

Atia, Jolene; McCloskey, Conor; Shmygol, Anatoly S.; Rand, David A.; van den Berg, Hugo A.; Blanks, Andrew M.

2016-01-01

Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the ‘conductance repertoire’ being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors) consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations. PMID:27105427

Low frequency AC waveform generator

DOEpatents

Bilharz, Oscar W.

1986-01-01

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Study of Biological Effects of Low Energy Ion Implantation on Tomato and Radish Breeding

NASA Astrophysics Data System (ADS)

Liang, Qiuxia; Huang, Qunce; Cao, Gangqiang; Ying, Fangqing; Liu, Yanbo; Huang, Wen

2008-04-01

Biological effects of 30 keV low energy nitrogen ion implantation on the seeds of five types of tomato and one type of radish were investigated. Results showed that low energy ions have different effects on different vegetables. The whole dose-response curve of the germination ratio did not take on "the shape of saddle", but was a rising and falling waveform with the increase or decrease in ion implantation. In the vegetable of Solanaceae, two outstanding aberrant plants were selected from M1 of Henan No.4 tomato at a dose of 7 × 1017 nitrogen ions/cm2, which had thin-leaves, long-petal and nipple tip fruit stably inherited to M7. Furthermore the analysis of the isozyme showed that the activity of the mutant tomato seedling was distinct in quantity and color. In Raphanus sativus L., the aberrances were obvious in the mutant of radish 791 at a dose of 5 × 1017 nitrogen ions/cm2, and the weight of succulent root and the volume of growth were over twice the control's. At present, many species for breeding have been identified in the field and only stable species have been selected for the experiment of production. It is evident that the low energy ion implantation technology has clear effects on vegetables' genetic improvement.

Cross Sections and Transport Properties of BR- Ions in AR

NASA Astrophysics Data System (ADS)

Jovanovic, Jasmina; Stojanovic, Vladimir; Raspopovic, Zoran; Petrovic, Zoran

2014-10-01

We have used a combination of a simple semi-analytic theory - Momentum Transfer Theory (MTT) and exact Monte Carlo (MC) simulations to develop Br- in Ar momentum transfer cross section based on the available data for reduced mobility at the temperature T = 300 K over the range 10 Td <= E / N <= 300 Td. At very low energies, we have extrapolated obtained cross sections towards Langevin's cross section. Also, we have extrapolated data to somewhat higher energies based on behavior of similar ions in similar gases and by the addition of the total detachment cross section that was used from the threshold around 7.7 eV. Relatively complete set was derived which can be used in modeling of plasmas by both hybrid, particle in cell (PIC) and fluid codes. A good agreement between calculated and measured ion mobilities and longitudinal diffusion coefficients is an independent proof of the validity of the cross sections that were derived for the negative ion mobility data. In addition to transport coefficients we have also calculated the net rate coefficients of elastic scattering and detachment. Author acknowledge Ministry of Education, Science and Technology, Proj. Nos. 171037 and 410011.

Selection and preliminary evaluation of three structures as potential solid conductors of alkali ions: Two hollandites, a titanate, and a tungstate

NASA Technical Reports Server (NTRS)

Singer, J.; Kautz, H. E.; Fielder, W. L.; Fordyce, J. S.

1973-01-01

Utilization of crystal-chemical criteria has suggested three structure types in which alkali ions may be mobile: (1)hollandites K(x)Mg(x/2)Ti(8-x/2)O16 and K(x)Al(x)Ti(8-x)O16 for 1.6 less than or equal to x less than or equal to 2.0 tungstate K2W4013; and (3) sodium hexatitante Na2Ti6O13. Each is a tunnel structure. An electrical screening procedure, previously tested on beta-alumina, has indicated high K(+) ion mobility in the hollandites and in the tungstate, but not in the hexatitanate. Specimens were polycrystalline disks near 90 percent of theoretical density. The ac conductivity calculated from dielectric and capacitance measurements has been attributed to ion mobility. This ac conductivity was up to 0.01/ohm-cm for hollandites and about 0.0001/ohm-cm for the tungstate, with approximate activation energies of 21 to 25 and 16 kJ/mole (5 to 6 and 4 kcal/mole), respectively. Electronic conduction and chemical reactivity have eliminated the tungstate from further consideration. The hollandites have been considered worthy of further development and evaluation.

Toward artifact-free data in Hadamard transform-based double multiplexing of ion mobility-Orbitrap mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tummalacherla, Meghasyam; Garimella, Sandilya V. B.; Prost, Spencer A.

The integration of ion mobility spectrometry (IMS) with trap-based mass spectrometer (MS) such as Orbitrap using the dual gate approach suffers from low duty cycle. Efforts to improve the duty cycle involve the utilization of Hadamard transform based double multiplexing which significantly improve the signal to noise ratio and duty cycle of the ion mobility – Orbitrap mass spectrometry (IM – Orbitrap MS) platform. However, significant fluctuations in ion intensity and the temporal shifts in the encoded data give rise to artifacts and noise in the demultiplexed data which significantly reduce the data quality and negate the benefits of multiplexing.more » We propose a new approach that identifies the true IM peaks and helps in eliminating the artifacts in the demultiplexed data leading to a decrease in false positives in subsequent data processing. The algorithm takes an analytical approach to first identify the position of the IM peak in the temporal domain, and then demultiplex and identify the true data making it easier for subsequent data processing. After the application of the algorithm, the quality of the IM-Orbitrap MS measurements was greatly improved because of the reduction in artifacts.« less

Miniaturized low-cost ion mobility spectrometer for fast detection of chemical warfare agents.

PubMed

Zimmermann, Stefan; Barth, Sebastian; Baether, Wolfgang K M; Ringer, Joachim

2008-09-01

Ion mobility spectrometry (IMS) is a well-known method for detecting hazardous compounds in air. Typical applications are the detection of chemical warfare agents, highly toxic industrial compounds, explosives, and drugs of abuse. Detection limits in the low part per billion range, fast response times, and simple instrumentation make this technique more and more popular. In particular, there is an increasing demand for miniaturized low-cost IMS for hand-held devices and air monitoring of public areas by sensor networks. In this paper, we present a miniaturized aspiration condenser type ion mobility spectrometer for fast detection of chemical warfare agents. The device is easy to manufacture and allows single substance identification down to low part per billion-level concentrations within seconds. The improved separation power results from ion focusing by means of geometric constraints and fluid dynamics. A simple pattern recognition algorithm is used for the identification of trained substances in air. The device was tested at the German Armed Forces Scientific Institute for Protection Technologies-NBC-Protection. Different chemical warfare agents, such as sarin, tabun, soman, US-VX, sulfur mustard, nitrogen mustard, and lewisite were tested. The results are presented here.

Application of design of experiments for formulation development and mechanistic evaluation of iontophoretic tacrine hydrochloride delivery.

PubMed

Patel, Niketkumar; Jain, Shashank; Madan, Parshotam; Lin, Senshang

2016-11-01

The objective of this investigation is to develop mathematical equation to understand the impact of variables and establish statistical control over transdermal iontophoretic delivery of tacrine hydrochloride. In addition, possibility of using conductivity measurements as a tool of predicting ionic mobility of the participating ions for the application of iontophoretic delivery was explored. Central composite design was applied to study effect of independent variables like current strength, buffer molarity, and drug concentration on iontophoretic tacrine permeation flux. Molar conductivity was determined to evaluate electro-migration of tacrine ions with application of Kohlrausch's law. The developed mathematic equation not only reveals drug concentration as the most significant variable regulating tacrine permeation, followed by current strength and buffer molarity, but also is capable to optimize tacrine permeation with respective combination of independent variables to achieve desired therapeutic plasma concentration of tacrine in treatment of Alzheimer's disease. Moreover, relative higher mobility of sodium and chloride ions was observed as compared to estimated tacrine ion mobility. This investigation utilizes the design of experiment approach and extends the primary understanding of imapct of electronic and formulation variables on the tacrine permeation for the formulation development of iontophoretic tacrine delivery.

Review on Ion Mobility Spectrometry. Part 1: Current Instrumentation

PubMed Central

Cumeras, R.; Figueras, E.; Davis, C.E.; Baumbach, J.I.; Gràcia, I.

2014-01-01

Ion Mobility Spectrometry (IMS) is a widely used and ‘well-known’ technique of ion separation in gaseous phase based on the differences of ion mobilities under an electric field. All IMS instruments operate with an electric field that provides space separation, but some IMS instruments also operate with a drift gas flow which provides also a temporal separation. In this review we will summarize the current IMS instrumentation. IMS techniques have received an increased interest as new instrumentation has become available to be coupled with mass spectrometry (MS). For each of the eight types of IMS instruments reviewed it is mentioned whether they can be hyphenated with MS and whether they are commercially available. Finally, out of the described devices, the six most-consolidated ones are compared. The current review article is followed by a companion review article which details the IMS hyphenated techniques (mainly gas chromatography and mass spectrometry) and the factors that make the data from an IMS device change as function of device parameters and sampling conditions. These reviews will provide the reader with an insightful view of the main characteristics and aspects of the IMS technique. PMID:25465076

Li-ion site disorder driven superionic conductivity in solid electrolytes: a first-principles investigation of β-Li 3PS 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phani Dathar, Gopi Krishna; Balachandran, Janakiraman; Kent, Paul R. C.

The attractive safety and long-term stability of all solid-state batteries has added a new impetus to the discovery and development of solid electrolytes for lithium batteries. Recently several superionic lithium conducting solid electrolytes have been discovered. All the superionic lithium containing compounds (β-Li 3PS 4 and Li 10GeP 2S 12 and oxides, predominantly in the garnet phase) have partially occupied sites. This naturally begs the question of understanding the role of partial site occupancies (or site disorder) in optimizing ionic conductivity in these family of solids. In this paper, we find that for a given topology of the host lattice,more » maximizing the number of sites with similar Li-ion adsorption energies, which gives partial site occupancy, is a natural way to increase the configurational entropy of the system and optimize the conductivity. For a given topology and density of Li-ion adsorption sites, the ionic conductivity is maximal when the number of mobile Li-ions are equal to the number of mobile vacancies, also the very condition for achieving maximal configurational entropy. We demonstrate applicability of this principle by elucidating the role of Li-ion site disorder and the local chemical environment in the high ionic conductivity of β-Li 3PS 4. In addition, for β-Li 3PS 4 we find that a significant density of vacancies in the Li-ion sub-lattice (~25%) leads to sub-lattice melting at (~600 K) leading to a molten form for the Li-ions in an otherwise solid anionic host. This gives a lithium site occupancy that is similar to what is measured experimentally. We further show that quenching this disorder can improve conductivity at lower temperatures. As a consequence, we discover that (a) one can optimize ionic conductivity in a given topology by choosing a chemistry/composition that maximizes the number of mobile-carriers i.e. maximizing both mobile Li-ions and vacancies, and (b) when the concentration of vacancies becomes significant in the Li-ion sub-lattice, it becomes energetically as well as entropically favorable for it to remain molten well below the bulk decomposition temperature of the solid. Finally, this principle may already apply to several known superionic conducting solids.« less

Li-ion site disorder driven superionic conductivity in solid electrolytes: a first-principles investigation of β-Li 3PS 4

DOE PAGES

Phani Dathar, Gopi Krishna; Balachandran, Janakiraman; Kent, Paul R. C.; ...

2016-12-09

The attractive safety and long-term stability of all solid-state batteries has added a new impetus to the discovery and development of solid electrolytes for lithium batteries. Recently several superionic lithium conducting solid electrolytes have been discovered. All the superionic lithium containing compounds (β-Li 3PS 4 and Li 10GeP 2S 12 and oxides, predominantly in the garnet phase) have partially occupied sites. This naturally begs the question of understanding the role of partial site occupancies (or site disorder) in optimizing ionic conductivity in these family of solids. In this paper, we find that for a given topology of the host lattice,more » maximizing the number of sites with similar Li-ion adsorption energies, which gives partial site occupancy, is a natural way to increase the configurational entropy of the system and optimize the conductivity. For a given topology and density of Li-ion adsorption sites, the ionic conductivity is maximal when the number of mobile Li-ions are equal to the number of mobile vacancies, also the very condition for achieving maximal configurational entropy. We demonstrate applicability of this principle by elucidating the role of Li-ion site disorder and the local chemical environment in the high ionic conductivity of β-Li 3PS 4. In addition, for β-Li 3PS 4 we find that a significant density of vacancies in the Li-ion sub-lattice (~25%) leads to sub-lattice melting at (~600 K) leading to a molten form for the Li-ions in an otherwise solid anionic host. This gives a lithium site occupancy that is similar to what is measured experimentally. We further show that quenching this disorder can improve conductivity at lower temperatures. As a consequence, we discover that (a) one can optimize ionic conductivity in a given topology by choosing a chemistry/composition that maximizes the number of mobile-carriers i.e. maximizing both mobile Li-ions and vacancies, and (b) when the concentration of vacancies becomes significant in the Li-ion sub-lattice, it becomes energetically as well as entropically favorable for it to remain molten well below the bulk decomposition temperature of the solid. Finally, this principle may already apply to several known superionic conducting solids.« less

Gaseous phase ion detection method based on laser-induced fluorescence for ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Guo, Kaitai; Ni, Kai; Ou, Guangli; Zhang, Xiaoguo; Yu, Quan; Qian, Xiang; Wang, Xiaohao

2015-08-01

Ion mobility spectrometry (IMS) is widely used in the field of chemical composition analysis. Faraday cup is the most classical method to detect ions for IMS in the atmospheric pressure. However, the performance of Faraday plate was limited by many kinds of factors, including interfering electromagnetic waves, thermal(Johnson) noise, induced current , gain bandwidth product, etc. There is a theoretical limit in detection of ions at ambient condition which is approximately 106 ions per second. In this paper, we introduced a novel way using laser-induced fluorescence (LIF) to bypass the limitation of Faraday plate. Fluorescent ions which were selected by IMS get excited when they fly through the laser excitation area. The fluorescence emitted by the excited ions was captured exponentially and amplified through proper optoelectronic system. Rhodamine 6G (R6G) was selected as the fluorochrome for the reason that excitation wavelength, emission wavelength, and fluorescence quantum yield were more appropriate than others. An orthometric light path is designed to eliminate the adverse impact which was caused by induced laser. The experiment result shows that a fluorescence signal from the sample ions of the IMS could be observed. Compared with Faraday plate, the LIF-IMS may find a potential application in more system at the atmosphere condition.

Atmospheric ions, boreal forests and impacts on climate

NASA Astrophysics Data System (ADS)

Manninen, H. E.; Nieminen, T.; Franchin, A.; Järvinen, E.; Kontkanen, J.; Hirsikko, A.; Hõrrak, U.; Mirme, A.; Tammet, H.; Kerminen, V.-M.; Petäjä, T.; Kulmala, M.

2012-04-01

Aerosol particles play an important role in the Earth's atmosphere and in the climate system: They scatter and absorb solar radiation, facilitate chemical processes, and serve as seeds for cloud formation. The aerosol particles have direct cooling and warming effects on climate (IPCC, 2007). Secondary new particle formation (NPF) is a globally important source of aerosol particles (Kulmala and Kerminen, 2008). Currently, the mechanisms of particle formation and the vapors participating in this process are, however, not truly understood. Several formation and growth mechanisms have been proposed for the very first steps of the process: homogeneous, heterogeneous, ion-induced and kinetic nucleation and activation type cluster growth. Small ions are part of the atmospheric aerosol spectrum, and in atmospheric sciences study of ion-aerosol interactions is essential. Small ions are small molecular clusters carrying a net electric charge. They are produced by ionisation of molecules in the air. Typically the small ion concentrations vary in the range of 100-2000 cm-3 in both polarities (Hirsikko et al., 2011). Ion-induced NPF is limited by the ion production rate, which typically is around 10 ion pairs cm-3s-1 in the boundary layer over the ground. The ion production rate has strong spatial and temporal dependence. The ionisation mechanisms change with altitude: radon and gamma radiation from the ground and galactic cosmic rays dominate close to the Earth's surface, while higher in the free troposphere cosmic rays become the main driving factor. In order to fully explain atmospheric NPF and subsequent growth, we need to measure directly the very initial steps of the formation processes. Air ion spectrometers measure the mobility distributions of charged aerosol particles in the mobility diameter range of 0.8-42 nm (Mirme et al., 2007; Tammet et al., 2011). Neutral cluster and air ion spectrometers measure additionally the mobility distribution of neutral particles larger than 2 nm in diameter by charging the aerosol sample with unipolar corona chargers (Manninen et al., 2009). According to earlier studies, the atmospheric nucleation and cluster activation take place at the mobility diameter range of 1.5-2 nm. Therefore, the ion spectrometers allow direct measurements at exactly the size where atmospheric nucleation takes place. The results indicate that the ion-induced nucleation contributes ~1-30% to the NPF events in most atmospheric conditions (Manninen et al., 2010). In other words, neutral particle formation seems to dominate over ion-mediated mechanisms, at least in the boreal forest conditions. Acknowledgements. This research was supported by the Academy of Finland Center of Excellence program (project number 1118615). Hirsikko, A. et al.: Atmospheric ions and nucleation: a review of observations, Atmos. Chem. Phys., 11, 767-798, 2011. IPCC, Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK and New York, NY, USA, 996 pp, 2007. Kulmala, M., and Kerminen, V.-M.: On the growth of atmospheric nanoparticles, Atmos. Res., 90, 132-150, 2008. Manninen, H.E. et al.: Long-term field measurements of charged and neutral clusters using Neutral cluster and Air Ion Spectrometer (NAIS). Boreal Env. Res. 14, 591-605, 2009. Manninen, H.E. et al., EUCAARI ion spectrometer measurements at 12 European sites - analysis of new particle formation events, Atmos. Chem. Phys., 10, 7907-7927, 2010. Mirme, A. et al.: A Wide-range multi-channel Air Ion Spectrometer, Boreal Environ. Res., 12, 247-264, 2007. Tammet, H.: Symmetric inclined grid mobility analyzer for the measurement of charged clusters and fine nanoparticles in atmospheric air. Aerosol Science and Technology, 45, 468 - 479, 2011.

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gahan, D.; Hopkins, M. B.; Dolinaj, B.

2008-03-15

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupledmore » plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies - 500 kHz to 30 MHz, and rf bias waveforms - sinusoidal, square, and dual frequency.« less

Intrinsic H+ ion mobility in the rabbit ventricular myocyte

PubMed Central

Vaughan-Jones, R D; Peercy, B E; Keener, J P; Spitzer, K W

2002-01-01

The intrinsic mobility of intracellular H+ ions was investigated by confocally imaging the longitudinal movement of acid inside rabbit ventricular myocytes loaded with the acetoxymethyl ester (AM) form of carboxy-seminaphthorhodafluor-1 (carboxy-SNARF-1). Acid was diffused into one end of the cell through a patch pipette filled with an isotonic KCl solution of pH 3.0. Intracellular H+ mobility was low, acid taking 20-30 s to move 40 μm down the cell. Inhibiting sarcolemmal Na+-H+ exchange with 1 mm amiloride had no effect on this time delay. Net Hi+ movement was associated with a longitudinal intracellular pH (pHi) gradient of up to 0.4 pH units. Hi+ movement could be modelled using the equations for diffusion, assuming an apparent diffusion coefficient for H+ ions (DappH) of 3.78 × 10−7 cm2 s−1, a value more than 300-fold lower than the H+ diffusion coefficient in a dilute, unbuffered solution. Measurement of the intracellular concentration of SNARF (≈400 μM) and its intracellular diffusion coefficient (0.9 × 10−7 cm2 s−1) indicated that the fluorophore itself exerted an insignificant effect (between 0.6 and 3.3 %) on the longitudinal movement of H+ equivalents inside the cell. The longitudinal movement of intracellular H+ is discussed in terms of a diffusive shuttling of H+ equivalents on high capacity mobile buffers which comprise about half (≈11 mm) of the total intrinsic buffering capacity within the myocyte (the other half being fixed buffer sites on low mobility, intracellular proteins). Intrinsic Hi+ mobility is consistent with an average diffusion coefficient for the intracellular mobile buffers (Dmob) of ≈9 × 10−7 cm2 s−1. PMID:12015426

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toczydlowska, Diana; Kedra-Krolik, Karolina; Nejbert, Krzysztof

The role of surface electrostatics on the reductive dissolution of iron (III) oxides is poorly understood, despite its importance in controlling the amount of mobilized iron. We report the potentiometric titration of the a; y -Fe2O3 oxides exposed to reductants and complexing ligands (Fe(II), ascorbate, oxalate, malonate). We monitored in situ surface and potentials, the ratio of mobilized ferric to ferrous ions, and periodically analyzed nanoparticle crystal structure using X-ray diffraction. We found that addition of Fe2+ ions produces a response consistent with the iron solubilityactivity curve, whereas the presence of ascorbate significantly decreases the amount of mobilized Fe(III) duemore » to reduction to Fe(II). In addition, XRD analysis proved that y-Fe2O3 particles remain structurally unchanged along the titration pathway despite iron cycling between aqueous and solid reservoirs. Our studies, suggest that the surface redoxactivity of iron oxides is primarily governed by the balance between Fe(III) and Fe(II) ions in aqueous phase, which may be easily altered by complexing and reducing agents.« less

Coupling Front-End Separations, Ion Mobility Spectrometry, and Mass Spectrometry For Enhanced Multidimensional Biological and Environmental Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Xueyun; Wojcik, Roza; Zhang, Xing

Ion mobility spectrometry (IMS) is a widely used analytical technique for rapid molecular separations in the gas phase. IMS alone is useful, but its coupling with mass spectrometry (MS) and front-end separations has been extremely beneficial for increasing measurement sensitivity, peak capacity of complex mixtures, and the scope of molecular information in biological and environmental sample analyses. Multiple studies in disease screening and environmental evaluations have even shown these IMS-based multidimensional separations extract information not possible with each technique individually. This review highlights 3-dimensional separations using IMS-MS in conjunction with a range of front-end techniques, such as gas chromatography (GC),more » supercritical fluid chromatography (SFC), liquid chromatography (LC), solid phase extractions (SPE), capillary electrophoresis (CE), field asymmetric ion mobility spectrometry (FAIMS), and microfluidic devices. The origination, current state, various applications, and future capabilities for these multidimensional approaches are described to provide insight into the utility and potential of each technique.« less

IMS applications analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

RODACY,PHILIP J.; REBER,STEPHEN D.; SIMONSON,ROBERT J.

This report examines the market potential of a miniature, hand-held Ion Mobility Spectrometer. Military and civilian markets are discussed, as well as applications in a variety of diverse fields. The strengths and weaknesses of competing technologies are discussed. An extensive Ion Mobility Spectrometry (IMS) bibliography is included. The conclusions drawn from this study are: (1) There are a number of competing technologies that are capable of detecting explosives, drugs, biological, or chemical agents. The IMS system currently represents the best available compromise regarding sensitivity, specificity, and portability. (2) The military market is not as large as the commercial market, butmore » the military services are more likely to invest R and D funds in the system. (3) Military applications should be addressed before commercial applications are addressed. (4) There is potentially a large commercial market for rugged, hand-held Ion Mobility Spectrometer systems. Commercial users typically do not invest R and D funds in this type of equipment rather, they wait for off-the-shelf availability.« less

Lithium-ion battery electrolyte mobility at nano-confined graphene interfaces

PubMed Central

Moeremans, Boaz; Cheng, Hsiu-Wei; Hu, Qingyun; Garces, Hector F.; Padture, Nitin P.; Renner, Frank Uwe; Valtiner, Markus

2016-01-01

Interfaces are essential in electrochemical processes, providing a critical nanoscopic design feature for composite electrodes used in Li-ion batteries. Understanding the structure, wetting and mobility at nano-confined interfaces is important for improving the efficiency and lifetime of electrochemical devices. Here we use a Surface Forces Apparatus to quantify the initial wetting of nanometre-confined graphene, gold and mica surfaces by Li-ion battery electrolytes. Our results indicate preferential wetting of confined graphene in comparison with gold or mica surfaces because of specific interactions of the electrolyte with the graphene surface. In addition, wetting of a confined pore proceeds via a profoundly different mechanism compared with wetting of a macroscopic surface. We further reveal the existence of molecularly layered structures of the confined electrolyte. Nanoscopic confinement of less than 4–5 nm and the presence of water decrease the mobility of the electrolyte. These results suggest a lower limit for the pore diameter in nanostructured electrodes. PMID:27562148

Profiling the indole alkaloids in yohimbe bark with ultra-performance liquid chromatography coupled with ion mobility quadrupole time-of-flight mass spectrometry.

PubMed

Sun, Jianghao; Baker, Andrew; Chen, Pei

2011-09-30

An ultra-performance liquid chromatography/ion mobility quadrupole time-of-flight mass spectrometry (UPLC/IM-QTOF-MS) method was developed for profiling the indole alkaloids in yohimbe bark. Many indole alkaloids with the yohimbine or ajmalicine core structure, plus methylated, oxidized and reduced species, were characterized. Common fragments and mass differences are described. It was shown that the use of IMS could provide another molecular descriptor, i.e. molecular shape by rotationally averaged collision cross-section; this is of great value for identification of constituents when reference materials are usually not available. Using the combination of high resolution (~40000) accurate mass measurement with time-aligned parallel (TAP) fragmentation, MS(E) (where E represents collision energy), ion mobility mass spectrometry (IMS) and UPLC chromatography, a total 55 indole alkaloids were characterized and a few new indole alkaloids are reported for the first time. Published in 2011 by John Wiley & Sons, Ltd.

Crosslinking by ligands to surface immunoglobulin triggers mobilization of intracellular 45Ca2+ in B lymphocytes

PubMed Central

1979-01-01

Detailed studies of steady-state ion fluxes in murine lymphocytes were used to examine for possible ionic changes generated by surface Ig, the antigen receptor of B lymphocytes. When bound by ligands, surface Ig triggered the mobilization and release of 45Ca2+ from the cell interior by a transmembrane process requiring crosslinking of the bound receptors. This ionic event was unique for two reasons: (a) it did not occur when other common lymphocyte surface macromolecules were bound with rabbit anti-lymphocyte antibodies; and (b) it was not accompanied by a general perturbation of lymphocyte ionic properties such as a change in 42K+ fluxes nor did it depend on the presence of extracellular ions. Capping of surface Ig shares the same time sequence, dose response, requirement for crosslinking, and lack of dependence on extracellular ions. These correlations suggest that mobilization of intracellular Ca2+ may represent an early ionic signal for the contractile activation of lymphocytes that generates capping of surface Ig. PMID:315942

Coupling Front-End Separations, Ion Mobility Spectrometry, and Mass Spectrometry For Enhanced Multidimensional Biological and Environmental Analyses

PubMed Central

Zheng, Xueyun; Wojcik, Roza; Zhang, Xing; Ibrahim, Yehia M.; Burnum-Johnson, Kristin E.; Orton, Daniel J.; Monroe, Matthew E.; Moore, Ronald J.; Smith, Richard D.; Baker, Erin S.

2017-01-01

Ion mobility spectrometry (IMS) is a widely used analytical technique for rapid molecular separations in the gas phase. Though IMS alone is useful, its coupling with mass spectrometry (MS) and front-end separations is extremely beneficial for increasing measurement sensitivity, peak capacity of complex mixtures, and the scope of molecular information available from biological and environmental sample analyses. In fact, multiple disease screening and environmental evaluations have illustrated that the IMS-based multidimensional separations extract information that cannot be acquired with each technique individually. This review highlights three-dimensional separations using IMS-MS in conjunction with a range of front-end techniques, such as gas chromatography, supercritical fluid chromatography, liquid chromatography, solid-phase extractions, capillary electrophoresis, field asymmetric ion mobility spectrometry, and microfluidic devices. The origination, current state, various applications, and future capabilities of these multidimensional approaches are described in detail to provide insight into their uses and benefits. PMID:28301728

Classification of ion mobility spectra by functional groups using neural networks

NASA Technical Reports Server (NTRS)

Bell, S.; Nazarov, E.; Wang, Y. F.; Eiceman, G. A.

1999-01-01

Neural networks were trained using whole ion mobility spectra from a standardized database of 3137 spectra for 204 chemicals at various concentrations. Performance of the network was measured by the success of classification into ten chemical classes. Eleven stages for evaluation of spectra and of spectral pre-processing were employed and minimums established for response thresholds and spectral purity. After optimization of the database, network, and pre-processing routines, the fraction of successful classifications by functional group was 0.91 throughout a range of concentrations. Network classification relied on a combination of features, including drift times, number of peaks, relative intensities, and other factors apparently including peak shape. The network was opportunistic, exploiting different features within different chemical classes. Application of neural networks in a two-tier design where chemicals were first identified by class and then individually eliminated all but one false positive out of 161 test spectra. These findings establish that ion mobility spectra, even with low resolution instrumentation, contain sufficient detail to permit the development of automated identification systems.

Unusual Complex Formation and Chemical Reaction of Haloacetate Anion on the Exterior Surface of Cucurbit[6]uril in the Gas Phase

NASA Astrophysics Data System (ADS)

Choi, Tae Su; Ko, Jae Yoon; Heo, Sung Woo; Ko, Young Ho; Kim, Kimoon; Kim, Hugh I.

2012-10-01

Noncovalent interactions of cucurbit[6]uril (CB[6]) with haloacetate and halide anions are investigated in the gas phase using electrospray ionization ion mobility mass spectrometry. Strong noncovalent interactions of monoiodoacetate, monobromoacetate, monochloroacetate, dichloroacetate, and trichloroacetate on the exterior surface of CB[6] are observed in the negative mode electrospray ionization mass spectra. The strong binding energy of the complex allows intramolecular SN2 reaction of haloacetate, which yields externally bound CB[6]-halide complex, by collisional activation. Utilizing ion mobility technique, structures of exteriorly bound CB[6] complexes of haloacetate and halide anions are confirmed. Theoretically determined low energy structures using density functional theory (DFT) further support results from ion mobility studies. The DFT calculation reveals that the binding energy and conformation of haloacetate on the CB[6] surface affect the efficiency of the intramolecular SN2 reaction of haloacetate, which correlate well with the experimental observation.

Signatures of Mechanically Interlocked Topology of Lasso Peptides by Ion Mobility-Mass Spectrometry: Lessons from a Collection of Representatives

NASA Astrophysics Data System (ADS)

Fouque, Kevin Jeanne Dit; Lavanant, Hélène; Zirah, Séverine; Hegemann, Julian D.; Zimmermann, Marcel; Marahiel, Mohamed A.; Rebuffat, Sylvie; Afonso, Carlos

2017-02-01

Lasso peptides are characterized by a mechanically interlocked structure, where the C-terminal tail of the peptide is threaded and trapped within an N-terminal macrolactam ring. Their compact and stable structures have a significant impact on their biological and physical properties and make them highly interesting for drug development. Ion mobility - mass spectrometry (IM-MS) has shown to be effective to discriminate the lasso topology from their corresponding branched-cyclic topoisomers in which the C-terminal tail is unthreaded. In fact, previous comparison of the IM-MS data of the two topologies has yielded three trends that allow differentiation of the lasso fold from the branched-cyclic structure: (1) the low abundance of highly charged ions, (2) the low change in collision cross sections (CCS) with increasing charge state and (3) a narrow ion mobility peak width. In this study, a three-dimensional plot was generated using three indicators based on these three trends: (1) mean charge divided by mass (ζ), (2) relative range of CCS covered by all protonated molecules (ΔΩ/Ω) and (3) mean ion mobility peak width (δΩ). The data were first collected on a set of twenty one lasso peptides and eight branched-cyclic peptides. The indicators were obtained also for eight variants of the well-known lasso peptide MccJ25 obtained by site-directed mutagenesis and further extended to five linear peptides, two macrocyclic peptides and one disulfide constrained peptide. In all cases, a clear clustering was observed between constrained and unconstrained structures, thus providing a new strategy to discriminate mechanically interlocked topologies.

Automated Cough Assessment on a Mobile Platform

PubMed Central

2014-01-01

The development of an Automated System for Asthma Monitoring (ADAM) is described. This consists of a consumer electronics mobile platform running a custom application. The application acquires an audio signal from an external user-worn microphone connected to the device analog-to-digital converter (microphone input). This signal is processed to determine the presence or absence of cough sounds. Symptom tallies and raw audio waveforms are recorded and made easily accessible for later review by a healthcare provider. The symptom detection algorithm is based upon standard speech recognition and machine learning paradigms and consists of an audio feature extraction step followed by a Hidden Markov Model based Viterbi decoder that has been trained on a large database of audio examples from a variety of subjects. Multiple Hidden Markov Model topologies and orders are studied. Performance of the recognizer is presented in terms of the sensitivity and the rate of false alarm as determined in a cross-validation test. PMID:25506590

Use of CDMA access technology in mobile satellite systems

NASA Technical Reports Server (NTRS)

Ramasastry, Jay; Wiedeman, Bob

1995-01-01

Use of Code Division Multiple Access (CDMA) technology in terrestrial wireless systems is fairly well understood. Similarly, design and operation of Power Control in a CDMA-based system in a terrestrial environment is also well established. Terrestrial multipath characteristics, and optimum design of the CDMA receiver to deal with multipath and fading conditions are reliably established. But the satellite environment is different. When the CDMA technology is adopted to the satellite environment, other design features need to be incorporated (for example; interleaving, open-loop and closed-loop power control design, diversity characteristics) to achieve comparable level of system performance. In fact, the GLOBALSTAR LEO/MSS system has incorporated all these features. Contrary to some published reports, CDMA retains the advantages in the satellite environment that are similar to those achieved in the terrestrial environment. This document gives a description of the CDMA waveform and other design features adopted for mobile satellite applications.

Microearthquake streaks and seismicity triggered by slow earthquakes on the mobile south flank of Kilauea Volcano, Hawai'i

USGS Publications Warehouse

Wolfe, C.J.; Brooks, B.A.; Foster, J.H.; Okubo, P.G.

2007-01-01

We perform waveform cross correlation and high precision relocation of both background seismicity and seismicity triggered by periodic slow earthquakes at Kilauea Volcano's mobile south flank. We demonstrate that the triggered seismicity dominantly occurs on several preexisting fault zones at the Hilina region. Regardless of the velocity model employed, the relocated earthquake epicenters and triggered seismicity localize onto distinct fault zones that form streaks aligned with the slow earthquake surface displacements determined from GPS. Due to the unknown effects of velocity heterogeneity and nonideal station coverage, our relocation analyses cannot distinguish whether some of these fault zones occur within the volcanic crust at shallow depths or whether all occur on the decollement between the volcano and preexisting oceanic crust at depths of ???8 km. Nonetheless, these Hilina fault zones consistently respond to stress perturbations from nearby slow earthquakes. Copyright 2007 by the American Geophysical Union.

Low frequency ac waveform generator

DOEpatents

Bilharz, O.W.

1983-11-22

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Ion mobility spectrometry–mass spectrometry (IMS–MS) for on- and offline analysis of atmospheric gas and aerosol species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krechmer, Jordan E.; Groessl, Michael; Zhang, Xuan

Measurement techniques that provide molecular-level information are needed to elucidate the multiphase processes that produce secondary organic aerosol (SOA) species in the atmosphere. Here we demonstrate the application of ion mobility spectrometry-mass spectrometry (IMS–MS) to the simultaneous characterization of the elemental composition and molecular structures of organic species in the gas and particulate phases. Molecular ions of gas-phase organic species are measured online with IMS–MS after ionization with a custom-built nitrate chemical ionization (CI) source. This CI–IMS–MS technique is used to obtain time-resolved measurements (5 min) of highly oxidized organic molecules during the 2013 Southern Oxidant and Aerosol Study (SOAS)more » ambient field campaign in the forested SE US. The ambient IMS–MS signals are consistent with laboratory IMS–MS spectra obtained from single-component carboxylic acids and multicomponent mixtures of isoprene and monoterpene oxidation products. Mass-mobility correlations in the 2-D IMS–MS space provide a means of identifying ions with similar molecular structures within complex mass spectra and are used to separate and identify monoterpene oxidation products in the ambient data that are produced from different chemical pathways. Water-soluble organic carbon (WSOC) constituents of fine aerosol particles that are not resolvable with standard analytical separation methods, such as liquid chromatography (LC), are shown to be separable with IMS–MS coupled to an electrospray ionization (ESI) source. The capability to use ion mobility to differentiate between isomers is demonstrated for organosulfates derived from the reactive uptake of isomers of isoprene epoxydiols (IEPOX) onto wet acidic sulfate aerosol. As a result, controlled fragmentation of precursor ions by collisionally induced dissociation (CID) in the transfer region between the IMS and the MS is used to validate MS peak assignments, elucidate structures of oligomers, and confirm the presence of the organosulfate functional group.« less

Ion mobility spectrometry–mass spectrometry (IMS–MS) for on- and offline analysis of atmospheric gas and aerosol species

DOE PAGES

Krechmer, Jordan E.; Groessl, Michael; Zhang, Xuan; ...

2016-07-25

Measurement techniques that provide molecular-level information are needed to elucidate the multiphase processes that produce secondary organic aerosol (SOA) species in the atmosphere. Here we demonstrate the application of ion mobility spectrometry-mass spectrometry (IMS–MS) to the simultaneous characterization of the elemental composition and molecular structures of organic species in the gas and particulate phases. Molecular ions of gas-phase organic species are measured online with IMS–MS after ionization with a custom-built nitrate chemical ionization (CI) source. This CI–IMS–MS technique is used to obtain time-resolved measurements (5 min) of highly oxidized organic molecules during the 2013 Southern Oxidant and Aerosol Study (SOAS)more » ambient field campaign in the forested SE US. The ambient IMS–MS signals are consistent with laboratory IMS–MS spectra obtained from single-component carboxylic acids and multicomponent mixtures of isoprene and monoterpene oxidation products. Mass-mobility correlations in the 2-D IMS–MS space provide a means of identifying ions with similar molecular structures within complex mass spectra and are used to separate and identify monoterpene oxidation products in the ambient data that are produced from different chemical pathways. Water-soluble organic carbon (WSOC) constituents of fine aerosol particles that are not resolvable with standard analytical separation methods, such as liquid chromatography (LC), are shown to be separable with IMS–MS coupled to an electrospray ionization (ESI) source. The capability to use ion mobility to differentiate between isomers is demonstrated for organosulfates derived from the reactive uptake of isomers of isoprene epoxydiols (IEPOX) onto wet acidic sulfate aerosol. As a result, controlled fragmentation of precursor ions by collisionally induced dissociation (CID) in the transfer region between the IMS and the MS is used to validate MS peak assignments, elucidate structures of oligomers, and confirm the presence of the organosulfate functional group.« less

Ion mobility spectrometry-mass spectrometry (IMS-MS) for on- and offline analysis of atmospheric gas and aerosol species

NASA Astrophysics Data System (ADS)

Krechmer, Jordan E.; Groessl, Michael; Zhang, Xuan; Junninen, Heikki; Massoli, Paola; Lambe, Andrew T.; Kimmel, Joel R.; Cubison, Michael J.; Graf, Stephan; Lin, Ying-Hsuan; Budisulistiorini, Sri H.; Zhang, Haofei; Surratt, Jason D.; Knochenmuss, Richard; Jayne, John T.; Worsnop, Douglas R.; Jimenez, Jose-Luis; Canagaratna, Manjula R.

2016-07-01

Measurement techniques that provide molecular-level information are needed to elucidate the multiphase processes that produce secondary organic aerosol (SOA) species in the atmosphere. Here we demonstrate the application of ion mobility spectrometry-mass spectrometry (IMS-MS) to the simultaneous characterization of the elemental composition and molecular structures of organic species in the gas and particulate phases. Molecular ions of gas-phase organic species are measured online with IMS-MS after ionization with a custom-built nitrate chemical ionization (CI) source. This CI-IMS-MS technique is used to obtain time-resolved measurements (5 min) of highly oxidized organic molecules during the 2013 Southern Oxidant and Aerosol Study (SOAS) ambient field campaign in the forested SE US. The ambient IMS-MS signals are consistent with laboratory IMS-MS spectra obtained from single-component carboxylic acids and multicomponent mixtures of isoprene and monoterpene oxidation products. Mass-mobility correlations in the 2-D IMS-MS space provide a means of identifying ions with similar molecular structures within complex mass spectra and are used to separate and identify monoterpene oxidation products in the ambient data that are produced from different chemical pathways. Water-soluble organic carbon (WSOC) constituents of fine aerosol particles that are not resolvable with standard analytical separation methods, such as liquid chromatography (LC), are shown to be separable with IMS-MS coupled to an electrospray ionization (ESI) source. The capability to use ion mobility to differentiate between isomers is demonstrated for organosulfates derived from the reactive uptake of isomers of isoprene epoxydiols (IEPOX) onto wet acidic sulfate aerosol. Controlled fragmentation of precursor ions by collisionally induced dissociation (CID) in the transfer region between the IMS and the MS is used to validate MS peak assignments, elucidate structures of oligomers, and confirm the presence of the organosulfate functional group.

Online hydrogen/deuterium exchange performed in the ion mobility cell of a hybrid mass spectrometer.

PubMed

Nagy, Kornél; Redeuil, Karine; Rezzi, Serge

2009-11-15

The present paper describes the performance of online, gas-phase hydrogen/deuterium exchange implemented in the ion mobility cell of a quadrupole time-of-flight mass spectrometer. Deuterium oxide and deuterated methanol were utilized to create deuterated vapor that is introduced into the ion mobility region of the mass spectrometer. Hydrogen/deuterium exchange occurs spontaneously in the milliseconds time frame without the need of switching the instrument into ion mobility mode. The exchange was studied in case of low molecular weight molecules and proteins. The observed number of exchanged hydrogens was equal to the number of theoretically exchangeable hydrogens for all low molecular weight compounds. This method needs only minimal instrumental modifications, is simple, cheap, environment friendly, compatible with ultraperformance liquid chromatography, and can be implemented on commercially available instruments. It does not compromise choice of liquid chromatographic solvents and accurate mass or parallel-fragmentation (MS(E)) methods. The performance of this method was compared to that of conventional alternatives where the deuterated solvent is introduced into the cone gas of the instrument. Although the degree of exchange was similar between the two methods, the "cone gas method" requires 10 times higher deuterated solvent volumes (50 muL/min) and offers reduced sensitivity in the tandem mass spectrometry (MS/MS) mode. The presented method is suggested as a standard future element of mass spectrometers to aid online structural characterization of unknowns and to study conformational changes of proteins with hydrogen/deuterium exchange.

Ion Mobility Derived Collision Cross Sections to Support Metabolomics Applications

PubMed Central

2015-01-01

Metabolomics is a rapidly evolving analytical approach in life and health sciences. The structural elucidation of the metabolites of interest remains a major analytical challenge in the metabolomics workflow. Here, we investigate the use of ion mobility as a tool to aid metabolite identification. Ion mobility allows for the measurement of the rotationally averaged collision cross-section (CCS), which gives information about the ionic shape of a molecule in the gas phase. We measured the CCSs of 125 common metabolites using traveling-wave ion mobility-mass spectrometry (TW-IM-MS). CCS measurements were highly reproducible on instruments located in three independent laboratories (RSD < 5% for 99%). We also determined the reproducibility of CCS measurements in various biological matrixes including urine, plasma, platelets, and red blood cells using ultra performance liquid chromatography (UPLC) coupled with TW-IM-MS. The mean RSD was < 2% for 97% of the CCS values, compared to 80% of retention times. Finally, as proof of concept, we used UPLC–TW-IM-MS to compare the cellular metabolome of epithelial and mesenchymal cells, an in vitro model used to study cancer development. Experimentally determined and computationally derived CCS values were used as orthogonal analytical parameters in combination with retention time and accurate mass information to confirm the identity of key metabolites potentially involved in cancer. Thus, our results indicate that adding CCS data to searchable databases and to routine metabolomics workflows will increase the identification confidence compared to traditional analytical approaches. PMID:24640936

Isomer Information from Ion Mobility Separation of High-Mannose Glycan Fragments

NASA Astrophysics Data System (ADS)

Harvey, David J.; Seabright, Gemma E.; Vasiljevic, Snezana; Crispin, Max; Struwe, Weston B.

2018-05-01

Extracted arrival time distributions of negative ion CID-derived fragments produced prior to traveling-wave ion mobility separation were evaluated for their ability to provide structural information on N-linked glycans. Fragmentation of high-mannose glycans released from several glycoproteins, including those from viral sources, provided over 50 fragments, many of which gave unique collisional cross-sections and provided additional information used to assign structural isomers. For example, cross-ring fragments arising from cleavage of the reducing terminal GlcNAc residue on Man8GlcNAc2 isomers have unique collision cross-sections enabling isomers to be differentiated in mixtures. Specific fragment collision cross-sections enabled identification of glycans, the antennae of which terminated in the antigenic α-galactose residue, and ions defining the composition of the 6-antenna of several of the glycans were also found to have different cross-sections from isomeric ions produced in the same spectra. Potential mechanisms for the formation of the various ions are discussed and the estimated collisional cross-sections are tabulated. [Figure not available: see fulltext.

Detection of aqueous phase chemical warfare agent degradation products by negative mode ion mobility time-of-flight mass spectrometry [IM(tof)MS].

PubMed

Steiner, Wes E; Harden, Charles S; Hong, Feng; Klopsch, Steve J; Hill, Herbert H; McHugh, Vincent M

2006-02-01

The use of negative ion monitoring mode with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer [IM(tof)MS] to detect chemical warfare agent (CWA) degradation products from aqueous phase samples has been determined. Aqueous phase sampling used a traditional electrospray ionization (ESI) source for sample introduction and ionization. Certified reference materials (CRM) of CWA degradation products for the detection of Schedule 1, 2, or 3 toxic chemicals or their precursors as defined by the chemical warfare convention (CWC) treaty verification were used in this study. A mixture of six G-series nerve related CWA degradation products (EMPA, IMPA, EHEP, IHEP, CHMPA, and PMPA) and their related collision induced dissociation (CID) fragment ions (MPA and EPA) were found in each case to be clearly resolved and detected using the IM(tof)MS instrument in negative ion monitoring mode. Corresponding ions, masses, drift times, K(o) values, and signal intensities for each of the CWA degradation products are reported.

Using corona discharge-ion mobility spectrometry for detection of 2,4,6-Trichloroanisole.

PubMed

Lichvanová, Zuzana; Ilbeigi, Vahideh; Sabo, Martin; Tabrizchi, Mahmoud; Matejčík, Stefan

2014-09-01

In this work possible application of the corona discharge-ion mobility spectrometer (CD-IMS) for detection of 2,4,6-Trichloroanisole (TCA) has been investigated. We applied CD-IMS interfaced with orthogonal acceleration time of flight mass spectrometer (CD-IMS-oaTOF) to study the ion processes within the CD-IMS technique. The CD-IMS instrument was operated in two modes, (i) standard and (ii) reverse flow modes resulting in different chemical ionisation schemes by NO3(-)(HNO3)n (n=0,1,2) and O2(-)(H2O)n (n=0,1,2), respectively. The O2(-)(H2O)n ionisation was associated with formation of Cl(-) and (TCA-CH3)(-) ions from TCA. The NO3(-)(HNO3)n ionisation, resulted in formation of NO3(-)(HNO3)(TCA-Cl) adduct ions. Limit of detection (LOD) for TCA was determined in gas (100 ppb) and solid phases (150 ng). Copyright © 2014 Elsevier B.V. All rights reserved.

Numerical modeling of field-assisted ion-exchanged channel waveguides by the explicit consideration of space-charge buildup.

PubMed

Mrozek, Piotr

2011-08-01

A numerical model explicitly considering the space-charge density evolved both under the mask and in the region of optical structure formation was used to predict the profiles of Ag concentration during field-assisted Ag(+)-Na(+) ion exchange channel waveguide fabrication. The influence of the unequal values of diffusion constants and mobilities of incoming and outgoing ions, the value of a correlation factor (Haven ratio), and particularly space-charge density induced during the ion exchange, on the resulting profiles of Ag concentration was analyzed and discussed. It was shown that the incorporation into the numerical model of a small quantity of highly mobile ions other than exclusively Ag(+) and Na(+) may considerably affect the range and shape of calculated Ag profiles in the multicomponent glass. The Poisson equation was used to predict the electric field spread evolution in the glass substrate. The results of the numerical analysis were verified by the experimental data of Ag concentration in a channel waveguide fabricated using a field-assisted process.

Broadband ion mobility deconvolution for rapid analysis of complex mixtures.

PubMed

Pettit, Michael E; Brantley, Matthew R; Donnarumma, Fabrizio; Murray, Kermit K; Solouki, Touradj

2018-05-04

High resolving power ion mobility (IM) allows for accurate characterization of complex mixtures in high-throughput IM mass spectrometry (IM-MS) experiments. We previously demonstrated that pure component IM-MS data can be extracted from IM unresolved post-IM/collision-induced dissociation (CID) MS data using automated ion mobility deconvolution (AIMD) software [Matthew Brantley, Behrooz Zekavat, Brett Harper, Rachel Mason, and Touradj Solouki, J. Am. Soc. Mass Spectrom., 2014, 25, 1810-1819]. In our previous reports, we utilized a quadrupole ion filter for m/z-isolation of IM unresolved monoisotopic species prior to post-IM/CID MS. Here, we utilize a broadband IM-MS deconvolution strategy to remove the m/z-isolation requirement for successful deconvolution of IM unresolved peaks. Broadband data collection has throughput and multiplexing advantages; hence, elimination of the ion isolation step reduces experimental run times and thus expands the applicability of AIMD to high-throughput bottom-up proteomics. We demonstrate broadband IM-MS deconvolution of two separate and unrelated pairs of IM unresolved isomers (viz., a pair of isomeric hexapeptides and a pair of isomeric trisaccharides) in a simulated complex mixture. Moreover, we show that broadband IM-MS deconvolution improves high-throughput bottom-up characterization of a proteolytic digest of rat brain tissue. To our knowledge, this manuscript is the first to report successful deconvolution of pure component IM and MS data from an IM-assisted data-independent analysis (DIA) or HDMSE dataset.

Re-electrospraying splash-landed proteins and nanoparticles.

PubMed

Benner, W Henry; Lewis, Gregory S; Hering, Susanne V; Selgelke, Brent; Corzett, Michelle; Evans, James E; Lightstone, Felice C

2012-03-06

FITC-albumin, Lsr-F, or fluorescent polystyrene latex particles were electrosprayed from aqueous buffer and subjected to dispersion by differential electrical mobility at atmospheric pressure. A resulting narrow size cut of singly charged molecular ions or particles was passed through a condensation growth tube collector to create a flow stream of small water droplets, each carrying a single ion or particle. The droplets were splash landed (impacted) onto a solid or liquid temperature controlled surface. Small pools of droplets containing size-selected particles, FITC-albumin, or Lsr-F were recovered, re-electrosprayed, and, when analyzed a second time by differential electrical mobility, showed increased homogeneity. Transmission electron microscopy (TEM) analysis of the size-selected Lsr-F sample corroborated the mobility observation.

Mobility Peak Tailing Reduction in a Differential Mobility Analyzer (DMA) Coupled with a Mass Spectrometer and Several Ionization Sources

NASA Astrophysics Data System (ADS)

Amo-Gonzalez, Mario; Fernandez de la Mora, Juan

2017-08-01

The differential mobility analyzer (DMA) is a narrow-band linear ion mobility filter operating at atmospheric pressure. It combines in series with a quadrupole mass spectrometer (Q-MS) for mobility/mass analysis, greatly reducing chemical noise in selected ion monitoring. However, the large flow rate of drift gas ( 1000 L/min) required by DMAs complicates the achievement of high gas purity. Additionally, the symmetry of the drying counterflow gas at the interface of many commercial MS instruments, is degraded by the lateral motion of the drift gas at the DMA entrance slit. As a result, DMA mobility peaks often exhibit tails due to the attachment of impurity vapors, either (1) to the reagent ion within the separation cell, or (2) to the analyte of interest in the ionization region. In order to greatly increase the noise-suppression capacity of the DMA, we describe various vapor-removal schemes and measure the resulting increase in the tailing ratio, ( TR = signal at the peak maximum over signal two half-widths away from this maximum). Here we develop a low-outgassing DMA circuit connected to a mass spectrometer, and test it with three ionization sources (APCI, Desolvating-nano ESI, and Desolvating low flow SESI). While prior TR values were in the range 100-1000, the three new sources achieve TR 105. The SESI source has been optimized for maximum sensitivity, delivering an unprecedented gain for TNT of 190 counts/fg, equivalent to an ionization efficiency of one out of 140 neutral molecules.

Threshold for ion movements in wood cell walls below fiber saturation observed by X-ray fluorescence microscopy (XFM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zelinka, Samuel L.; Gleber, Sophie-Charlotte; Vogt, Stefan

Diffusion of chemicals and ions through the wood cell wall plays an important role in wood damage mechanisms. In the present work, free diffusion of ions through wood secondary walls and middle lamellae has been investigated as a function of moisture content (MC) and anatomical direction. Various ions (K, Cl, Zn, Cu) were injected into selected regions of 2 mu m thick wood sections with a microinjector and then the ion distribution was mapped by means of X-ray fluorescence microscopy with submicron spatial resolution. The MC of the wood was controlled in situ by means of climatic chamber with controlledmore » relative humidity (RH). For all ions investigated, there was a threshold RH below which the concentration profiles did not change. The threshold RH depended upon ionic species, cell wall layer, and wood anatomical orientation. Above the threshold RH, differences in mobility among ions were observed and the mobility depended upon anatomical direction and cell wall layer. These observations support a recently proposed percolation model of electrical conduction in wood. The results contribute to understanding the mechanisms of fungal decay and fastener corrosion that occur below the fiber saturation point.« less

Development and Evaluation of a Reverse-Entry Ion Source Orbitrap Mass Spectrometer.

PubMed

Poltash, Michael L; McCabe, Jacob W; Patrick, John W; Laganowsky, Arthur; Russell, David H

2018-05-23

As a step towards development of a high-resolution ion mobility mass spectrometer using the orbitrap mass analyzer platform, we describe herein a novel reverse-entry ion source (REIS) coupled to the higher-energy C-trap dissociation (HCD) cell of an orbitrap mass spectrometer with extended mass range. Development of the REIS is a first step in the development of a drift tube ion mobility-orbitrap MS. The REIS approach retains the functionality of the commercial instrument ion source which permits the uninterrupted use of the instrument during development as well as performance comparisons between the two ion sources. Ubiquitin (8.5 kDa) and lipid binding to the ammonia transport channel (AmtB, 126 kDa) protein complex were used as model soluble and membrane proteins, respectively, to evaluate the performance of the REIS instrument. Mass resolution obtained with the REIS is comparable to that obtained using the commercial ion source. The charge state distributions for ubiquitin and AmtB obtained on the REIS are in agreement with previous studies which suggests that the REIS-orbitrap EMR retains native structure in the gas phase. Graphical Abstract ᅟ.

Numerical simulation of ion transport in an atmosphere-to-vacuum interface taking into account gas dynamics and space charge.

PubMed

Skoblin, Michael G; Chudinov, Alexey V; Sulimenkov, Ilia V; Brusov, Vladimir S; Makarov, Alexander A; Wouters, Eloy R; Kozlovskiy, Viacheslav I

2017-08-01

A two-step approach was developed for the study of ion transport in an atmospheric pressure interface. In the first step, the flow in the interface was numerically simulated using the standard gas dynamic package ANSYS CFX 15.0. In the second step, the calculated fields of pressure, temperature, and velocity were imported into a custom-built software application for simulation of ion motion under the influence of both gas dynamic and electrostatic forces. To account for space charge effects in axially symmetric interfaces an analytical expression was used for the Coulomb force. For all other types of interfaces, an iterative approach for the Coulomb force computation was developed. The simulations show that the influence of the space charge is the main contributor to the loss of ion current in the heated capillary. In addition, the maximum ion current which can be transmitted through the heated capillary (0.58 mm inner diameter and 58.5 mm length) is limited to ∼6 nA for ions with m/z = 508 Da and with reduced ion mobility 1.05 cm 2 V -1 s -1 . This limit remains practically constant and independent of the ion current at the entrance of the capillary. For a particular ion type, this limit depends on its m/z ratio and ion mobility.

Proton-driven amide bond-cleavage pathways of gas-phase peptide ions lacking mobile protons.

PubMed

Bythell, Benjamin J; Suhai, Sándor; Somogyi, Arpád; Paizs, Béla

2009-10-07

The mobile proton model (Dongre, A. R., Jones, J. L., Somogyi, A. and Wysocki, V. H. J. Am. Chem. Soc. 1996, 118 , 8365-8374) of peptide fragmentation states that the ionizing protons play a critical role in the gas-phase fragmentation of protonated peptides upon collision-induced dissociation (CID). The model distinguishes two classes of peptide ions, those with or without easily mobilizable protons. For the former class mild excitation leads to proton transfer reactions which populate amide nitrogen protonation sites. This enables facile amide bond cleavage and thus the formation of b and y sequence ions. In contrast, the latter class of peptide ions contains strongly basic functionalities which sequester the ionizing protons, thereby often hindering formation of sequence ions. Here we describe the proton-driven amide bond cleavages necessary to produce b and y ions from peptide ions lacking easily mobilizable protons. We show that this important class of peptide ions fragments by different means from those with easily mobilizable protons. We present three new amide bond cleavage mechanisms which involve salt-bridge, anhydride, and imine enol intermediates, respectively. All three new mechanisms are less energetically demanding than the classical oxazolone b(n)-y(m) pathway. These mechanisms offer an explanation for the formation of b and y ions from peptide ions with sequestered ionizing protons which are routinely fragmented in large-scale proteomics experiments.

The effects of CO2 on the negative reactant ions of IMS

NASA Technical Reports Server (NTRS)

Spangler, Glenn E.

1995-01-01

In the presence of CO2, the negative reactant ions of ion mobility spectrometry (IMS) are ion clusters of CO4(-) and CO3(-). Methyl salicylate is ionized by the CO4(-)(H2O(n))(N2(m)) reactant ions, but not by the CO3(-)(H2O(n))(N2(m)) reactant ions. While the CO4(-) ions are formed by direct association, the CO3(-) ions require additional energy to be formed. The additional energy is provided by either excited neutral gas molecules in a metastable state or UV (ultraviolet) radiation.

A photoelectric technique for measuring lightning-channel propagation velocities from a mobile laboratory

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Rust, W. David

1989-01-01

The present device for lightning channel propagation-velocity determination employs eight photodetectors mounted behind precision horizontal slits in the focal plane of a photographic camera lens. The eight photodetector pulses, IRIG-B time, and slow and fast electric field-change waveforms are recorded on a 14-track analog tape recorder. A comparison of the present results with those obtained by a streaking camera shows no significant differences between the velocities obtained from the same strokes with the two systems; neither is there any difference in pulse characteristics or in the velocities calculated from them.

Making Shock Waves in Microfluidics: The Physics and Applications of Isotachophoresis

NASA Astrophysics Data System (ADS)

Santiago, Juan

2007-11-01

Microfluidics lies at the interfaces between engineering, chemistry, and biology, and aims to develop chemical laboratories on a chip. An important technique is on-chip capillary electrophoresis which has been applied to a wide range of chemical and biochemical assay applications over the last decade. Perhaps the best way of improving the sensitivity of on-chip electrophoresis is to integrate an online sample preconcentration method. At Stanford, we are developing methods to concentrate ions into small volumes using a method called isotachophoresis (ITP). In ITP, sample ions are injected between the high mobility co-ions of a leading electrolyte (LE) and the low mobility co-ions of a trailing electrolyte (TE). Upon application of an electric field, the disparate ion mobilities of the LE and TE cause sample species to segregate and focus into a series of narrow self-sharpening zones which migrate at equal velocity (hence ``isotacho''). ITP-type processes have been studied and used for more than 60 years, and yet there remain significant challenges in the robust modeling of these transport processes and the creation of widely applicable assays. We use ITP to create sample ion concentration ``shock waves'' in microchannels. These concentration waves can be integrated with on-chip electrophoresis for high sensitivity assays, and novel modes of operation. The talk will summarize the basic physics of ITP, experimental studies of ITP, models of ITP, and the development of novel ITP-assays with unprecedented sensitivity and new functionality. For example, using leading-to-sample ion concentration ratios of 10^15 and local electric fields of ˜4 kV/cm, we can achieve order one micron wide ITP zones. We can achieve million fold preconcentration in 120 s and can detect 100 attomolar sample concentrations (to our knowledge the highest demonstrated sensitivity for an electrophoresis-related assay). We have also developed a method that uses ITP to separate, indirectly detect, and identify the electrophoretic mobilities of unlabeled (non-fluorescent) analytes using surrogate fluorescent molecules. Our goal is the development of novel on-chip ITP assays which expand the design space of microfluidic devices.

Travelling-wave ion mobility mass spectrometry and negative ion fragmentation of hybrid and complex N-glycans

PubMed Central

Harvey, David J.; Scarff, Charlotte A.; Edgeworth, Matthew; Pagel, Kevin; Thalassinos, Konstantinos; Struwe, Weston B.; Crispin, Max; Scrivens, Jim

2016-01-01

Nitrogen cross sections of hybrid and complex glycans released from the glycoproteins IgG, gp120 (from human immunodeficiency virus), ovalbumin, α1-acid glycoprotein, thyroglobulin and fucosylated glycoproteins from the human parotid gland were measured with a travelling-wave ion mobility mass spectrometer using dextran as the calibrant. The utility of this instrument for isomer separation was also investigated. Some isomers, such as Man3GlcNAc3 from chicken ovalbumin and Man3GlcNAc3Fuc1 from thyroglobulin could be partially resolved and identified by their negative ion fragmentation spectra. Several other larger glycans, however, although existing as isomers, produced only asymmetric rather than separated arrival time distributions (ATDs). Nevertheless, in these cases, isomers could often be detected by plotting extracted fragment ATDs of diagnostic fragment ions from the negative ion spectra obtained in the transfer cell of the Waters Synapt mass spectrometer. Coincidence in the drift times of all fragment ions with an overall asymmetric ATD profile usually suggested that separations were due to conformers or anomers, whereas symmetrical ATDs of fragments showing differences in drift times indicated isomer separation. Although some significant differences in cross sections were found for the smaller isomeric glycans, the differences found for the larger compounds were usually too small to be analytically useful. Possible correlations between cross sections and structural types were also investigated and it was found that complex glycans tended to have slightly smaller cross sections than high-mannose glycans of comparable molecular weight. In addition, biantennary glycans containing a core fucose and/or a bisecting GlcNAc residue fell on different mobility-m/z trend lines to those glycans not so substituted with both of these substituents contributing to larger cross sections. PMID:27477117

Development of large-surface Nafion-metal composite actuator and its electrochemical characterization

NASA Astrophysics Data System (ADS)

Noh, Taegeun; Tak, Yong Suk; Nam, Jaedo; Jeon, Jaewook; Kim, Hunmo; Choi, Hyoukryeol; Bae, Sang Sik

2001-07-01

Behaviors of nafion-based actuators are significantly affected by interfacial area between electrode and polymer electrolyte. Replication method was utilized to manufacture a large surface-area composite actuator. Etched aluminum foil was used as a template for replication using liquid nafion solution. Measurement of double layer charging and scanning electron microscopy indicated that interfacial area was greatly increased by replication method. Higher surface area induced a better bending performance of ionic polymer metal composite (IPMC). In parallel, the effect of cations on IPMC was interpreted with constant current experiment, linear sweep voltammetry and electrochemical impedance spectroscopy. For univalent cations, ion size is the most influencing parameter on ionic mobility inside membrane. However, ion-ion interaction affects an ionic mobility for divalent cations.

Proton-transfer-reaction/ion-mobility-spectrometer and method of using the same

NASA Technical Reports Server (NTRS)

Kanik, Isik (Inventor); Beegle, Luther W. (Inventor)

2004-01-01

A high-pressure hollow cathode ionizer is combined with an ion-mobility-spectrometer (IMS) for the detection of trace amounts of organic compounds in gas. The ionizer uses H.sub.3 0.sup.+, ions which do not react with air to ionize the organic compounds and the organic compounds are soft ionized. The ionized organic compounds are detected in the IMS at levels of parts per billion and identified using calibrated reference tables. Applications include but are not limited to the fields of: (1) medicine as a breath analyzer for detection of lung cancer, diabetes, liver cirrhosis, (2) law enforcement in drug interdiction and explosives detection, (3) food monitoring and control, (4) environmental monitoring and (5) space applications.

Scintillations associated with bottomside sinusoidal irregularities in the equatorial F region

NASA Technical Reports Server (NTRS)

Basu, S.; Basu, S.; Valladares, C. E.; Dasgupta, A.; Whitney, H. E.

1986-01-01

Multisatellite scintillation observations and spaced receiver drift measurements are presented for a category of equatorial F region plasma irregularities characterized by nearly sinusoidal waveforms in the ion number density. The observations were made at Huancayo, Peru, and the measurements at Ancon, Peru, associated with irregularities observed by the Atmospheric-Explorer-E satellite on a few nights in December 1979. Utilizing ray paths to various geostationary satellites, it was found that the irregularities grow and decay almost simultaneously in long-lived patches extending at least 1000 km in the east-west direction.

Indirect ultraviolet detection of alkaline earth metal ions using an imidazolium ionic liquid as an ultraviolet absorption reagent in ion chromatography.

PubMed

Liu, Yong-Qiang; Yu, Hong

2017-04-01

A convenient and versatile method was developed for the separation and detection of alkaline earth metal ions by ion chromatography with indirect UV detection. The chromatographic separation of Mg 2+ , Ca 2+ , and Sr 2+ was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid as the mobile phase, in which the imidazolium ionic liquid acted as an UV-absorption reagent. The effects of imidazolium ionic liquids, detection wavelength, acids in the mobile phase, and column temperature on the retention of Mg 2+ , Ca 2+ , and Sr 2+ were investigated. The main factors influencing the separation and detection were the background UV absorption reagent and the concentration of hydrogen ion in ion chromatography with indirect UV detection. The successful separation and detection of Mg 2+ , Ca 2+ , and Sr 2+ within 14 min were achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.06, 0.12, and 0.23 mg/L, respectively. A new separation and detection method of alkaline earth metal ions by ion chromatography with indirect UV detection was developed, and the application range of ionic liquids was expanded. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tandem differential mobility analysis-mass spectrometry reveals partial gas-phase collapse of the GroEL complex.

PubMed

Hogan, Christopher J; Ruotolo, Brandon T; Robinson, Carol V; Fernandez de la Mora, Juan

2011-04-07

A parallel-plate differential mobility analyzer and a time-of-flight mass spectrometer (DMA-MS) are used in series to measure true mobility in dry atmospheric pressure air for mass-resolved electrosprayed GroEL tetradecamers (14-mers; ~800 kDa). Narrow mobility peaks are found (2.6-2.9% fwhm); hence, precise mobilities can be obtained for these ions without collisional activation, just following their generation by electrospray ionization. In contrast to previous studies, two conformers are found with mobilities (Z) differing by ~5% at charge state z ~ 79. By extrapolating to small z, a common mobility/charge ratio Z(0)/z = 0.0117 cm(2) V(-1) s(-1) is found for both conformers. When interpreted as if the GroEL ion surface were smooth and the gas molecule-protein collisions were perfectly elastic and specular, this mobility yields an experimental collision cross section, Ω, 11% smaller than in an earlier measurement, and close to the cross section, A(C,crystal), expected for the crystal structure (determined by a geometric approximation). However, the similarity between Ω and A(C,crystal) does not imply a coincidence between the native and gas-phase structures. The nonideal nature of protein-gas molecule collisions introduces a drag enhancement factor, ξ = 1.36, with which the true cross section A(C) is related to Ω via A(C) = Ω/ξ. Therefore, A(C) for GroEL 14-mer ions determined by DMA measurements is 0.69A(C,crystal). The factor 1.36 used here is based on the experimental Stokes-Millikan equation, as well as on prior and new numerical modeling accounting for multiple scattering events via exact hard-sphere scattering calculations. Therefore, we conclude that the gas-phase structure of the GroEL complex as electrosprayed is substantially more compact than the corresponding X-ray crystal structure.

Dielectric Modulation of Ion Transport near Interfaces

NASA Astrophysics Data System (ADS)

Antila, Hanne S.; Luijten, Erik

2018-03-01

Ion mobility and ionic conductance in nanodevices are known to deviate from bulk behavior, a phenomenon often attributed to surface effects. We demonstrate that dielectric mismatch between the electrolyte and the surface can qualitatively alter ionic transport in a counterintuitive manner. Instead of following the polarization-induced modulation of the concentration profile, mobility is enhanced or reduced by changes in the ionic atmosphere near the interface and affected by a polarization force parallel to the surface. In addition to revealing this mechanism, we explore the effect of salt concentration and electrostatic coupling.

The role of ion mobility spectrometry-mass spectrometry in the analysis of protein reference standards.

PubMed

Pritchard, Caroline; O'Connor, Gavin; Ashcroft, Alison E

2013-08-06

To achieve comparability of measurement results of protein amount of substance content between clinical laboratories, suitable reference materials are required. The impact on measurement comparability of potential differences in the tertiary and quaternary structure of protein reference standards is as yet not well understood. With the use of human growth hormone as a model protein, the potential of ion mobility spectrometry-mass spectrometry as a tool to assess differences in the structure of protein reference materials and their interactions with antibodies has been investigated here.

49 CFR 175.10 - Exceptions for passengers, crewmembers, and air operators.

Code of Federal Regulations, 2014 CFR

2014-10-01

... mobility aid equipped with a lithium ion battery, when carried as checked baggage, provided— (i) The lithium ion battery must be of a type that successfully passed each test in the UN Manual of Tests and... the movement of baggage, mail, service items, or other cargo; (v) Where a lithium ion battery-powered...

49 CFR 175.10 - Exceptions for passengers, crewmembers, and air operators.

Code of Federal Regulations, 2013 CFR

2013-10-01

... mobility aid equipped with a lithium ion battery, when carried as checked baggage, provided— (i) The lithium ion battery must be of a type that successfully passed each test in the UN Manual of Tests and... the movement of baggage, mail, service items, or other cargo; (v) Where a lithium ion battery-powered...

77 FR 31274 - Hazardous Materials: Harmonization With the United Nations Recommendations on the Transport of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-25

... (ICAO) Dangerous Goods Panel (DGP) regarding certain lithium ion battery-powered mobility aids (e.g... devices on an aircraft and providing for the intentional removal of a lithium ion battery from a device... limit lithium ion batteries used to power portable electronic devices and medical devices to 160 watt...

Discontinuous model with semi analytical sheath interface for radio frequency plasma

NASA Astrophysics Data System (ADS)

Miyashita, Masaru

2016-09-01

Sumitomo Heavy Industries, Ltd. provide many products utilizing plasma. In this study, we focus on the Radio Frequency (RF) plasma source by interior antenna. The plasma source is expected to be high density and low metal contamination. However, the sputtering the antenna cover by high energy ion from sheath voltage still have been problematic. We have developed the new model which can calculate sheath voltage wave form in the RF plasma source for realistic calculation time. This model is discontinuous that electronic fluid equation in plasma connect to usual passion equation in antenna cover and chamber with semi analytical sheath interface. We estimate the sputtering distribution based on calculated sheath voltage waveform by this model, sputtering yield and ion energy distribution function (IEDF) model. The estimated sputtering distribution reproduce the tendency of experimental results.

Atypical Particle Heating at a Supercritical Interplanetary Shock

NASA Technical Reports Server (NTRS)

Wilson, Lynn B., III

2010-01-01

We present the first observations at an interplanetary shock of large amplitude (> 100 mV/m pk-pk) solitary waves and large amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

Supercritical fluid chromatographic resolution of water soluble isomeric carboxyl/amine terminated peptides facilitated via mobile phase water and ion pair formation.

PubMed

Patel, M A; Riley, F; Ashraf-Khorassani, M; Taylor, L T

2012-04-13

Both analytical scale and preparative scale packed column supercritical fluid chromatography (SFC) have found widespread applicability for chiral separations of multiple polar pharmaceutical candidates. However, SFC is rapidly becoming an achiral technique. More specifically, ion pair SFC is finding greater utility for separation of ionic analytes such as amine salts and organic sulfonates. The key to this success is, in part, the incorporation of additives such as trifluoroacetic acid and ammonium acetate into the mobile phase in association with a wide variety of both bonded silica stationary phases and high purity bare silica. Ion pairing SFC coupled with evaporative light scattering detection and mass spectrometric detection is presented here for the separation of water soluble, uncapped, isomeric peptide pairs that differ in amino acid arrangement. The separation is best achieved on either diol-bonded silica or bare silica with 1-5% (w/w) water as a significant ingredient in the mobile phase. Nitrogenous stationary phases such as 2-ethylpyridine, which had been very successful for the separation of capped peptides failed to yield the desired separation regardless of the mobile phase composition. A HILIC type retention mechanism is postulated for the separation of both isomeric uncapped peptide pairs. Copyright © 2012 Elsevier B.V. All rights reserved.

Room-temperature detection of mobile impurities in compound semiconductors by transient ion drift

NASA Astrophysics Data System (ADS)

Lyubomirsky, Igor; Rabinal, M. K.; Cahen, David

1997-05-01

We show that the transient ion drift (TID) method, which is based on recording junction capacitance under constant reverse bias [A. Zamouche, T. Heiser, and A. Mesli, Appl. Phys. Lett. 66, 631 (1995)], can be used not only for measurements of the diffusion coefficient of mobile impurities, but also to estimate the concentration of mobile species as part of the total dopant density. This is illustrated for CdTe, contaminated by Cu, and intentionally doped by Li or Ag and for CuInSe2. We show also that, with some restrictions, the TID method can be used if the mobile ions are major dopants. This is demonstrated using Schottky barriers on CdTe, and p-n junction devices in (Hg,Cd)Te, and CuInSe2. The values that we obtain for the diffusion coefficients (for Li, Ag, and Cu in CdTe and for Cu in CuInSe2) agree well with measured or extrapolated values, obtained by other methods, as reported in the literature. Furthermore, we could distinguish between diffusion and chemical reactions of dopants, as demonstrated for the case of Cu in CdTe and Ag-doped (Hg,Cd)Te. In the former case this allows us to separate copper-free from contaminated CdTe samples.

A strategy for identification and structural characterization of compounds from Gardenia jasminoides by integrating macroporous resin column chromatography and liquid chromatography-tandem mass spectrometry combined with ion-mobility spectrometry.

PubMed

Wang, Lu; Liu, Shu; Zhang, Xueju; Xing, Junpeng; Liu, Zhiqiang; Song, Fengrui

2016-06-24

In this paper, an analysis strategy integrating macroporous resin (AB-8) column chromatography and high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) combined with ion mobility spectrometry (IMS) was proposed and applied for identification and structural characterization of compounds from the fruits of Gardenia jasminoides. The extracts of G. jasminoides were separated by AB-8 resin column chromatography combined with reversed phase liquid chromatography (C18 column) and detected by electrospray ionization tandem mass spectrometry. Additionally, ion mobility spectrometry (IMS) was employed as a supplementary separation technique to discover previously undetected isomers from the fruits of G. jasminoides. A total of 71 compounds, including iridoids, flavonoids, triterpenes, monoterpenoids, carotenoids and phenolic acids were identified by the characteristic high resolution mass spectrometry and the ESI-MS/MS fragmentations. In conclusion, the IMS-MS technique achieved the separation of isomers in crocin-3 and crocin-4 according to their acquired mobility drift times differing from classical analysis by mass spectrometry. The proposed strategy can be used as a highly sensitive and efficient procedure for identification and separation isomeric components in extracts of herbal medicines. Copyright © 2016 Elsevier B.V. All rights reserved.

Improvement of a device for detection and characterization of certain atmospheric pollutants. Final report. Perfectionnement d'un appareillage de detection et de caracterisation de certains pollutants atmospheriques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tesseyre, Y.

The study allowed development of an original measuring system for mobility, involving simultaneously a repulsive electrical field and a continuous gas flow. It made it possible to define a model to calculate ionic transparency of grates, taking into account electrical fields below and above them, ion mobility, speed of gas flow and geometric transparency. Calculation of the electrical field proceeded in a plane-plane system, taking into account the space load and diffusion; a graphic method was developed to determine the field, thus avoiding numerical integration of the diffusion equation. The tracings of the mobility spectra obtained in different gases mademore » it possible to determine characteristic discrete mobility values comparable to those observed by other more sophisticated systems for measuring mobilities, such as the flight time systems. Detection of pollutants in weak concentration in dry air was shown. However, the presence of water vapor in the air forms agglomerates around the ions formed, reducing resolution of the system and making it less applicable under normal atmospheric conditions.« less

Comprehensive Gas-Phase Peptide Ion Structure Studies Using Ion Mobility Techniques: Part 2. Gas-Phase Hydrogen/Deuterium Exchange for Ion Population Estimation.

PubMed

Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Tafreshian, Amirmahdi; Valentine, Stephen J

2017-05-01

Gas-phase hydrogen/deuterium exchange (HDX) using D 2 O reagent and collision cross-section (CCS) measurements are utilized to monitor the ion conformers of the model peptide acetyl-PAAAAKAAAAKAAAAKAAAAK. The measurements are carried out on a home-built ion mobility instrument coupled to a linear ion trap mass spectrometer containing electron transfer dissociation (ETD) capabilities. ETD is utilized to obtain per-residue deuterium uptake data for select ion conformers, and a new algorithm is presented for interpreting the HDX data. Using molecular dynamics (MD) production data and a hydrogen accessibility scoring (HAS)-number of effective collisions (NEC) model, hypothetical HDX behavior is attributed to various in-silico candidate (CCS match) structures. The HAS-NEC model is applied to all candidate structures, and non-negative linear regression is employed to determine structure contributions resulting in the best match to deuterium uptake. The accuracy of the HAS-NEC model is tested with the comparison of predicted and experimental isotopic envelopes for several of the observed c-ions. It is proposed that gas-phase HDX can be utilized effectively as a second criterion (after CCS matching) for filtering suitable MD candidate structures. In this study, the second step of structure elucidation, 13 nominal structures were selected (from a pool of 300 candidate structures) and each with a population contribution proposed for these ions. Graphical Abstract ᅟ.