Ion Mobility Spectrometry

High-resolution real-time particle mass measurements have not been achievable because the enormous amount of kinetic energy imparted to the particles upon expansion into vacuum competes with and overwhelms the forces applied to the charged particles within the mass spectrometer. It is possible to reduce the kinetic energy of a collimated particulate ion beam through collisions with a buffer gas while radially constraining their motion using a quadrupole guide or trap over a limited mass range. Controlling the pressure drop of the final expansion into a quadrupole trap permits a much broader mass range at the cost of sacrificing collimation. To achieve high-resolution mass analysis of massive particulate ions, an efficient trap with a large tolerance for radial divergence of the injected ions was developed that permits trapping a large range of ions for on-demand injection into an awaiting mass analyzer. The design specifications required that frequency of the trapping potential be adjustable to cover a large mass range and the trap radius be increased to increase the tolerance to divergent ion injection. The large-radius linear quadrupole ion trap was demonstrated by trapping singly-charged bovine serum albumin ions for on-demand injection into a mass analyzer. Additionally, this work demonstrates the ability to measure an electrophoretic mobility cross section (or ion mobility) of singly-charged intact proteins in the low-pressure regime. This work represents a large step toward the goal of high-resolution analysis of intact proteins, RNA, DNA, and viruses. (J Am Soc Mass Spectrom 2008, 19, 1942-1947) © 2008 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry E ver since the mass spectrometer was introduced, scientists have looked for ways to increase the mass range. The greatest advances came with the introduction of electrospray ionization (ESI) [1] and matrix-assisted laser desorption ionization (MALDI) [2]. These techniques permitted the production of massive ions in vacuum for subsequent mass analysis. Yet even with the advance of large ion production into the megadalton (MDa) range, the working range of mass spectrometers remained in the tens of kilodalton (kDa) range. The working range defines the range of mass-tocharge ratios where the spectrometer yields the most useful information; in other words, the range with the highest resolution, sensitivity, and mass accuracy.The working range limitation results from the kinetic energy imparted to the large ions during expansion into vacuum. Liu et al. [3] measured the centerline velocity of particles exiting their aerodynamic lens system through a 2-Torr expansion into vacuum. By extrapolating their results to zero particle diameter (mass), the kinetic energy of the particles traveling along the centerline of the expansion was found to be roughly linear yielding ϳ13.5, 85.3, and 530 eV for 10, 100, and 1000 kDa molecules. This result shows that even a lowpressure expansion can impart enough kinetic energy into large ions to compete ...

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“…One may obtain the reduced ion mobility, K 0 , related to ion-neutral collisions using the following relation [10]:…”

Section: Resultsmentioning

confidence: 99%

“…The resulting ion mobility of BSA is 1300 cm 2 V Ϫ1 s Ϫ1 Ϯ 10%. The equation governing gas-phase ion transport in an electric field is given by [10]:…”

Section: Resultsmentioning

confidence: 99%

Trapping of intact, singly-charged, bovine serum albumin ions injected from the atmosphere with a 10-cm diameter, frequency-adjusted linear quadrupole ion trap

Koizumi

Whitten

Reilly

2008

J. Am. Soc. Mass Spectrom.

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“…E in the LPPI source is about 15 V/cm. This gives v Ϸ 5700 cm/s and for a source length of 1 cm gives a drift time of about 0.18 ms] [16]. Table 1 lists the compounds used in this work and the media (e.g., air or solvent) and concentrations in which they were introduced into the LPPI/MS system.…”

Section: Methodsmentioning

confidence: 99%

“…Assuming a value of E a ϭ ⌬H ϭ 0.6 eV ( Table 4) and assuming that the effective kT in eq 11 from thermal (about 0.03-0.04 eV) and ion acceleration energy (about 0.06 eV) is 0.075 eV, we obtain a value of t e ϳ 0.3 ms. Given that the residence time of ions in the LPPI source is about 0.2 ms 16 and that t e will be larger if E a Ͼ ⌬H, it is possible that equilibrium is not fully achieved in the LPPI source used here.…”

Section: Kinetics Considerationsmentioning

confidence: 99%

Mechanism of [M + H]⁺ formation in photoionization mass spectrometry

Syage¹

2004

J. Am. Soc. Mass Spectrom.

150

157

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In this paper we examine the mechanism of [M ϩ H] ϩ (henceforth MH ϩ ) formation by direct photoionization. Based on comparisons of the relative abundance of M ϩ and MH ϩ ions for photoionization of a variety of compounds M as vapor in air versus in different solvents, we conclude that the mechanism is M ϩ h 3 M ϩ ϩ e Ϫ followed by the reaction M ϩ ϩ S 3 MH ϩ ϩ S(ϪH). The principal evidence for molecular radical ion formation M ϩ followed by hydrogen atom abstraction from protic solvent S are: (1) Nearly exclusive formation of M ϩ for headspace ionization of M in air, (2) significant relative abundance of MH ϩ in the presence of protic solvents (e.g., CH 3 OH, H 2 O, c-hexane), but not in aprotic solvents (e.g., CCl 4-), (3) observation of induced equilibrium oscillations in the abundance of MH ϩ and M ϩ , and (4) correlation of the ratio of MH ϩ /M ϩ to reaction length in the photoionization source. Thermodynamic models are advanced that explain the qualitative dependence of the MH ϩ /M ϩ equilibrium ratio on the properties of solvent S and analyte M. Though the hydrogen abstraction reaction is endothermic in most cases, it is shown that the equilibrium constant is still expected to be much greater than unity in most of the cases studied due to the very slow reverse reaction involving the very low abundant MH ϩ and S(ϪH) species. (J Am Soc Mass Spectrom 2004, 15, 1521-1533

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“…4 Traditionally, this task has been accomplished either by using pulsed ionization sources, such as matrix-assisted laser desorption ionization (MALDI), 5 or by sampling from continuous ion sources produced by radioactive 4 or electrospray ionization (ESI). 6, 7 Because multiple IMS experiments are often averaged to improve signal-to-noise ratio (SNR) and analytical confidence, it is paramount that the spatial and temporal distributions of each ion packet be highly reproducible.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Ion Utilization Efficiency Using an Electrodynamic Ion Funnel Trap as an Injection Mechanism for Ion Mobility Spectrometry

et al. 2008

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Conventional ion mobility spectrometers that sample ion packets from continuous sources have traditionally been constrained by an inherently low duty cycle. As such, ion utilization efficiencies have been limited to <1% in order to maintain instrumental resolving power. Using a modified electrodynamic ion funnel, we demonstrated the ability to accumulate, store, and eject ions in conjunction with ion mobility spectrometry (IMS), which elevated the charge density of the ion packets ejected from the ion funnel trap (IFT) and provided a considerable increase in the overall ion utilization efficiency of the IMS instrument. A 7-fold increase in signal intensity was revealed by comparing continuous ion beam current with the amplitude of the pulsed ion current in IFT-IMS experiments using a Faraday plate. Additionally, we describe the IFT operating characteristics using a time-of-flight mass spectrometer attached to the IMS drift tube.

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Ion Mobility Spectrometry

Cited by 641 publications

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Trapping of intact, singly-charged, bovine serum albumin ions injected from the atmosphere with a 10-cm diameter, frequency-adjusted linear quadrupole ion trap

Trapping of intact, singly-charged, bovine serum albumin ions injected from the atmosphere with a 10-cm diameter, frequency-adjusted linear quadrupole ion trap

Mechanism of [M + H]⁺ formation in photoionization mass spectrometry

Enhanced Ion Utilization Efficiency Using an Electrodynamic Ion Funnel Trap as an Injection Mechanism for Ion Mobility Spectrometry

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Ion Mobility Spectrometry

Cited by 641 publications

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Trapping of intact, singly-charged, bovine serum albumin ions injected from the atmosphere with a 10-cm diameter, frequency-adjusted linear quadrupole ion trap

Trapping of intact, singly-charged, bovine serum albumin ions injected from the atmosphere with a 10-cm diameter, frequency-adjusted linear quadrupole ion trap

Mechanism of [M + H]+ formation in photoionization mass spectrometry

Enhanced Ion Utilization Efficiency Using an Electrodynamic Ion Funnel Trap as an Injection Mechanism for Ion Mobility Spectrometry

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Mechanism of [M + H]⁺ formation in photoionization mass spectrometry