Field-corrected ion cell for ion cyclotron resonance

Hanson, Curtiss D.; Castro, Mauro E.; Kerley, Eric L.; Russell, David H.

doi:10.1021/ac00204a018

Cited by 68 publications

(27 citation statements)

References 33 publications

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“…the trapping voltage) as well as RF fields used for excitation can create problems for mass analysis, and uniformity of both these types of field is called for. Various solutions have been proposed to deal with the axial trapping field (21,22). In the late 1980s, Wang and Marshall used a grounded mesh just in front of the axial trapping electrodes (23).…”

Section: Fig 7 Ion Motion Within An Icr Cellmentioning

confidence: 99%

Fourier Transform Mass Spectrometry

Ščigelová

Hornshaw

Giannakopulos

et al. 2011

Molecular & Cellular Proteomics

182

137

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Mass spectrometers have been used for a long time in a variety of biological applications. Recent years, however, have witnessed a significant increase in the employment of mass spectrometers such as of time-of-flight, Fourier transform ion cyclotron resonance (FTICR) 1 , and Orbitrap, which provide accurate mass of analytes over wide mass range. The FTICR and Orbitrap analyzers outperform any other commonly used mass spectrometer with respect to the maximum mass resolution and accuracy routinely achievable even for small numbers of ions. Both these mass spectrometers share certain features, such as an image current detection system and the application of Fourier transform mathematical operations for generating mass spectra from time domain transients produced by the image current. Consequently, they are often referred to as Fourier transform-based mass spectrometers (FTMS).The combination of FTMS with ion preselection and fragmentation devices and their coupling to reversed-phase liquid chromatography (LC) represents a ubiquitous approach to both small molecule and proteomic analyses. Multidimensional LC separations have an important role to play in proteomics applications for reducing sample complexity, and complement well the high dynamic range of detection in an acquisition offered by FTMS instruments.The current article does not intend to be an exhaustive review paper on FTMS techniques; it is intended as teaching material for scientists without a physics background to assist them with understanding the mass spectrometry tools they are called to use in their everyday laboratory work. Thus, only the fundamental aspects of FTMS which are useful to a nonphysicist are introduced. The discussion then focuses on examples of where this technology can be applied and what are the benefits as well as limitations of this technology for practical proteomic applications.Need for High Resolution and Mass Accuracy-The mass accuracy is the ratio of the m/z measurement error to the true m/z, usually quoted in parts per million (ppm). The mass resolving power (resolution) is the measure of the ability to distinguish two peaks of slightly different m/z, herein understood as full width at half maximum (FWHM). Linearity of detection and very high fidelity in the determination of frequency are inherent to FTMS and allow very high resolving power, mass accuracy, and dynamic range to be achieved. But why would one need high mass accuracy and high resolution?The benefit of measuring a compound's mass with adequately high accuracy can directly determine its elemental composition. Accurate mass thus acts as a powerful "filter" useful for confirming the identity of a compound or even identification of an unknown. This is illustrated in Fig. 1 showing the fragmentation (tandem mass spectrometry (MS/MS)) spectrum of flavonoid quercetin (m/z 303). Mass deviation of less than 3 ppm for any detected fragment together with the richness of the fragmentation spectra itself enable confirming the elemental composition of the starting compound a...

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Section: Fig 7 Ion Motion Within An Icr Cellmentioning

confidence: 99%

Fourier Transform Mass Spectrometry

Ščigelová

Hornshaw

Giannakopulos

et al. 2011

Molecular & Cellular Proteomics

182

137

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“…Attempts to derive the magnitude of this frequency shift quantitatively within the framework of the simple physical models of this paper, give rise to three possible approaches. What is desired is the average Coulomb radial force on the particular ion which we assume gives the frequency shift via Eqns (14) and (15). Unfortunately, the average radial force is infinite for rl = r, (Fig.…”

Section: Choice Of Modelmentioning

confidence: 99%

Simple physical models for coulomb‐induced frequency shifts and coulomb‐induced inhomogenous broadening for like and unlike ions in fourier transform ion cyclotron resonance mass spectrometry

Chen

Comisarow

1991

Rapid Comm Mass Spectrometry

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Two simple models which correspond more closely to physical reality than some prior models are proposed to account for the Coulomb-induced frequency shifts to lower frequency, which have been observed in Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The first model consists of two different-mass point charges which undergo cyclotron orbits with the same orbit centers at their respective cyclotron frequencies. The model predicts that each excited cyclotron motion should induce a negative frequency shift in the other's cyclotron motion. The model predicts a zero frequency shift for ions of the same mass. The physical hasis for the Coulomb-induced shift is most easily seen in a coordinate frame which rotates at the cyclotron motion of the ion whose frequency is shifted. It is noted that a prior model for Coulomb-induced frequency shifts is more appropriate for scanning ICR than FT-ICR and the reason is described for the correctness of the predictions of this less appropriate model. A second model, the line model, is created by extension of the point model. The line model gives rise to a position-dependent frequency shift which is synonymous with inhomogeneous Coulomb broadening. When a non-quadrupolar electrostatic trapping field is included in the model, 'like' ions become 'unlike' and Coulomb-shifting and Coulomb-broadening apply, as for 'like' ions. The analysis predicts that ICR cells which are designed to have negligible trapping fields over most of their volume will be less sensitive to Coulomb shifting/hroadening than ordinary ICR cells.

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“…Second, the experimentally measured ICR frequencies of ions vary with the VTRs (22,25,26). It has been shown that "screened" (26) and "field-corrected" (8,27) The failure of these pulsed-valve experiments is in part due to inefficient cooling of desorbed ions. In order to have sufficient numbers of gas phase collisions for translational cooling of desorbed ions, a large dose of reagent gas must be introduced into the ion cell.…”

mentioning

confidence: 99%

Laser desorption studies of high mass biomolecules in Fourier-transform ion cyclotron resonance mass spectrometry.

Solouki

Russell

1992

Proc. Natl. Acad. Sci. U.S.A.

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Matrix-assisted laser desorption ionization is used to obtain Fourier-transform ion cyclotron resonance mass spectra of model peptides (e.g., gramicidin S, angiotensin I, renin substrate, melittin, and bovine insulin). Matrix-assisted laser desorption ionization yields ions having appreciable kinetic energies. Two methods for trapping the high kinetic energy ions are described: (') the ion signal for [M + H]+ ions is shown to increase with increasing trapping voltages, and (ii) collisional relaxation is used for the detection of [M + H]+ ions of bovine insulin.Ionization methods such as californium plasma desorption (1), matrix-assisted laser desorption (MALD) (2), and electrospray ionization (ESI) (3) have greatly expanded the role of mass spectrometry of high mass biomolecules. Biomolecules having molecular masses >100,000 Da can be ionized to yield a single-charged (e.g., [M + H]+) or multiple-charged (e.g., [M + nH]n+) ion. Although most of the MALD and ESI work has utilized time-of-flight, quadrupole mass spectrometers and/or quadrupole ion traps, MALD (4) and ESI are adaptable to Fourier-transform ion cyclotron resonance (FT-ICR). The advantage of FTICR (and the quadrupole ion trap) is that tandem mass spectrometry experiments [e.g., collision-induced dissociation and photodissociation (5)] and ion molecule reactions can be implemented for structural characterization. The best high mass performance [-60,000 mass resolution at m/z 6000 (6)] of FTICR has been achieved with laser desorption ionization of nonpolar polymers. McLafferty and coworkers (7) have made considerable progress with the development of ESI for FTICR, and a highsensitivity ESI/FTICR system was recently described.* Several groups (9, 10) have suggested that the performance of FTICR with biological molecules (samples that have relatively low ionization probabilities) and molecular masses greater than -2500 Da may be adversely affected by inefficient trapping of the ions or inherent limitations of the ion detection. For example, the mass resolution for samples with molecular masses greater than -2500 Da is far less than the theoretically predicted values (11). On the basis of our experience with desorption ionization and high mass FTICR, we suggested that the major problem with high-resolution FTICR at high mass is due to the high kinetic energies of desorbed ions (9). We have recently evaluated two experimental methods for improving the trapping efficiency of high mass ions: (i) the effects of increasing the electric trapping field and (ii) the effects of collisional relaxation of the laser-desorbed species prior to trapping the ions in the ion cyclotron resonance (ICR) cell. In this article we present the results from both experimental methods. The results show that increasing the trapping potentials improves the ion trapping efficiency, but detection of [M + H]+ ions of bovine insulin (m/z = 5734) requires collisional relaxation of ions prior to their introduction into the ion cell. MATERIALS AND METHODSFTICR Mass Spectrometer. The...

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Field-corrected ion cell for ion cyclotron resonance

Cited by 68 publications

References 33 publications

Fourier Transform Mass Spectrometry

Fourier Transform Mass Spectrometry

Simple physical models for coulomb‐induced frequency shifts and coulomb‐induced inhomogenous broadening for like and unlike ions in fourier transform ion cyclotron resonance mass spectrometry

Laser desorption studies of high mass biomolecules in Fourier-transform ion cyclotron resonance mass spectrometry.

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