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Szalwinski LJ, Holden DT, Morato NM, Cooks RG. 2D MS/MS Spectra Recorded in the Time Domain Using Repetitive Frequency Sweeps in Linear Quadrupole Ion Traps. Anal Chem 2020; 92:10016-10023. [PMID: 32578980 DOI: 10.1021/acs.analchem.0c01719] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ion trap mass spectrometers have emerged as powerful on-site analytical platforms, in spite of limited mass resolution, due to their compatibility with ambient ionization methods and ready implementation of tandem mass spectrometry (MS/MS). When operated at constant trapping voltage, ions can be activated at their secular frequencies and all MS/MS experiments can be performed, including the two-dimensional tandem mass scan (2D MS/MS scan) in which all precursor ions and their subsequent product ions are both identified and correlated. In the new method of performing this 2D MS/MS experiment presented here, the precursor ions are excited by a nonlinear (inverse Mathieu q) frequency sweep while the resulting product ions are identified by their ejection time within a repeating orthogonally applied nonlinear (inverse Mathieu q) frequency sweep. This resulting compact representation contains the total fragmentation behavior of a collection of ionized compounds and captures detailed chemical information efficiently (typically in 1 s). The approach is implemented using a simple single mass analyzer instrument. This methodology was tested on three different multicomponent mixtures: drugs of abuse, peptides, and fentanyl analogs. The data are compared with those obtained by more common MS/MS scan methods.
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Affiliation(s)
- Lucas J Szalwinski
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Dylan T Holden
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Nicolás M Morato
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - R Graham Cooks
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
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2
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Snyder DT, Szalwinski LJ, St John Z, Cooks RG. Two-Dimensional Tandem Mass Spectrometry in a Single Scan on a Linear Quadrupole Ion Trap. Anal Chem 2019; 91:13752-13762. [PMID: 31592640 DOI: 10.1021/acs.analchem.9b03123] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
A two-dimensional tandem mass spectrometry (2D MS/MS) scan has been developed for the linear quadrupole ion trap. Precursor ions are mass-selectively excited using a nonlinear ac frequency sweep at constant rf voltage, while simultaneously, all product ions of the excited precursor ions are ejected from the ion trap using a broad-band waveform. The fragmentation time of the precursor ions correlates with the precursor m/z value (the first mass dimension) and also with the ejection time of the product ions, allowing the correlation between precursor and product ions. Additionally, the second mass dimension (product ions' m/z values) is recovered through fast Fourier transform of each mass spectral peak, revealing either intentionally introduced "frequency tags" or the product ion micropacket frequencies, both of which can be converted to product ion m/z through the classical Mathieu parameters, thereby revealing a product ion mass spectrum for every precursor ion without prior isolation. We demonstrate the utility of this method for analyzing a broad range of structurally related precursor ions, including chemical warfare agent simulants, fentanyls and other opioids, amphetamines, cathinones, antihistamines, and tetracyclic antidepressants.
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Affiliation(s)
- Dalton T Snyder
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Lucas J Szalwinski
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Zachary St John
- Department of Chemistry , The College of New Jersey , Ewing Township , New Jersey 08618 , United States
| | - R Graham Cooks
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
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3
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Lu X, Ni K, Yu Q, Xu W, Qian X, Wang X. Reducing mass peak instability caused by the phase changes of RF and AC signals in a rectilinear ion-trap analyzer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:034103. [PMID: 28372366 DOI: 10.1063/1.4979073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
For an ion trap with resonance ejection, peak intensity and peak position of the acquired mass spectra are affected by the phase difference between the radio frequency (RF) and auxiliary alternating current (AC) potentials. To ensure measurement stability, RF and AC phase-locking is commonly used in commercial ion trap mass spectrometers. In this study, a compact electronic control system was developed to accurately regulate the RF and AC phases and was employed in a photoionization rectilinear ion trap (RIT) mass spectrometer. We found that the phase-locking method was defective in multicomponent analysis because the optimal RF and AC phase difference was usually different for different m/z peaks. After studying and characterizing the relationship between the peaks and the RF and AC phases, a correction method based on data processing was used to improve the peaks' stability and accuracy. The results show that the fluctuations of both peak intensity and peak position were significantly reduced and that the instrument presented satisfying reproducibility and quantitative ability.
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Affiliation(s)
- Xinqiong Lu
- Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Kai Ni
- Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Quan Yu
- Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Wenchao Xu
- Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Xiang Qian
- Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Xiaohao Wang
- Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
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Nikolić D, Madzunkov SM, Darrach MR. Computer Modeling of an Ion Trap Mass Analyzer, Part I: Low Pressure Regime. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:2115-2124. [PMID: 26286456 DOI: 10.1007/s13361-015-1236-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 07/21/2015] [Accepted: 07/23/2015] [Indexed: 06/04/2023]
Abstract
We present the multi-particle simulation program suite Computational Ion Trap Analyzer (CITA) designed to calculate the ion trajectories within a Paul quadrupole ion trap developed by the Jet Propulsion Laboratory (JPL). CITA uses an analytical expression of the electrodynamic field, employing up to six terms in multipole expansion and a modified velocity-Verlet method to numerically calculate ion trajectories. The computer code is multithreaded and designed to run on shared-memory architectures. CITA yields near real-time simulations with full propagation of 26 particles per second per core. As a consequence, a realistic numbers of trapped ions (100+ million) can be used and their trajectories modeled, yielding a representative prediction of mass spectrometer analysis of trace gas species. When the model is compared with experimental results conducted at low pressures using the conventional quadrupole and dipole excitation modes, there is an excellent agreement with the observed peak shapes. Owing to the program's efficiency, CITA has been used to explore regions of trapping stability that are of interest to experimental research. These results are expected to facilitate a fast and reliable modeling of ion dynamics in miniature quadrupole ion trap and improve the interpretation of observed mass spectra. Graphical Abstract ᅟ.
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Affiliation(s)
- Dragan Nikolić
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA, 91109, USA.
| | - Stojan M Madzunkov
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA, 91109, USA
| | - Murray R Darrach
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA, 91109, USA
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5
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Wu G, Cooks RG, Ouyang Z, Yu M, Chappell WJ, Plass WR. Ion trajectory simulation for electrode configurations with arbitrary geometries. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:1216-28. [PMID: 16793279 DOI: 10.1016/j.jasms.2006.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 05/09/2006] [Accepted: 05/10/2006] [Indexed: 05/10/2023]
Abstract
A multi-particle ion trajectory simulation program ITSIM 6.0 is described, which is capable of ion trajectory simulations for electrode configurations with arbitrary geometries. The electrode structures are input from a 3D drawing program AutoCAD and the electric field is calculated using a 3D field solver COMSOL. The program CreatePot acts as interface between the field solver and ITSIM 6.0. It converts the calculated electric field into a field array file readable by ITSIM 6.0 and ion trajectories are calculated by solving Newton's equation using Runge-Kutta integration methods. The accuracy of the field calculation is discussed for the ideal quadrupole ion trap in terms of applied mesh density. Electric fields of several different types of devices with 3D geometry are simulated, including ion transport through an ion optical system as a function of pressure. Ion spatial distributions, including the storage of positively charged ions only and simultaneous storage of positively/negatively charged ions in commercial linear ion traps with various geometries, are investigated using different trapping modes. Inelastic collisions and collision induced dissociation modeled using RRKM theory are studied, with emphasis on the fragmentation of n-butylbenzene inside an ideal quadrupole ion trap. The mass spectrum of 1,3-dichlorobenzene is simulated for the rectilinear ion trap device and good agreement is observed between the simulated and the experimental mass spectra. Collisional cooling using helium at different pressures is found to affect mass resolution in the rectilinear ion trap.
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Affiliation(s)
- Guangxiang Wu
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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6
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Goeringer DE, Viehland LA, Danailov DM. Prediction of collective characteristics for ion ensembles in quadrupole ion traps without trajectory simulations. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:889-902. [PMID: 16731002 DOI: 10.1016/j.jasms.2006.03.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Revised: 03/27/2006] [Accepted: 03/27/2006] [Indexed: 05/09/2023]
Abstract
Fundamental aspects are presented of a two-temperature moment theory for quadrupole ion traps developed via transformation of the Boltzmann equation. Solutions of the moment equations correspond to changes in the ensemble average for any function of ion velocity, because the Boltzmann equation reflects changes to an ion distribution as a whole. The function of primary interest in this paper is the ion effective temperature and its behavior during ion storage and resonance excitation. Calculations suggest that increases in ion effective temperature during resonance excitation are due primarily to power absorption from the main RF trapping field rather than from the dipolar excitation signal. The dipolar excitation signal apparently serves mainly to move ions into regions of the ion trap where the RF electric field, and thus ion RF heating, is greater than near the trap center. Both ideal and non-ideal ion trap configurations are accounted for in the moment equations by incorporating parameterized variables a and q , which are modified versions of the commonly used forms for the DC and AC ring voltages, and b and d , which are new forms that account for the voltages applied to the endcaps. Besides extending the applicability of the moment equations to non-ideal quadrupole ion traps, the modified versions of the parameterized variables can have additional utility. Calculation of the spatial dependence of ion secular oscillation frequencies is demonstrated as an example.
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Affiliation(s)
- Douglas E Goeringer
- Organic and Biological Mass Spectrometry Group, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
| | - Larry A Viehland
- Division of Science, Chatham College, Pittsburgh, Pennsylvania, USA
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7
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Dobson G, Murrell J, Despeyroux D, Wind F, Tabet JC. Investigation into factors affecting precision in ion trap mass spectrometry using different scan directions and axial modulation potential amplitudes. JOURNAL OF MASS SPECTROMETRY : JMS 2004; 39:1295-1304. [PMID: 15472990 DOI: 10.1002/jms.686] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Electrospray ionization mass spectra obtained from different scan directions are observed to be dependent on the axial modulation potential amplitudes used for resonant ejection and on the positive deviation caused by higher even-multipole fields present in most commercial ion traps. The axial modulation voltage influences the dissociation of ions during resonant ejection and the observed mass shifts. The higher even-multipole fields in commercial ion traps are known to influence resonant ejection from the ion trap and can cause a loss in mass resolution for peaks in reverse scan mass spectra compared with that obtained by the forward scan. However, along with the dissociation of ions during resonant ejection causing a loss in resolution, the possibility of resolving an isotopic distribution is also shown to be influenced by the mass shifts caused by the space charge. These mass shifts differ depending on the scan direction employed. A significant loss in resolution can also result from resonant ejection using non-optimal axial modulation voltages. We also present results showing the ejection of ions at betaz = 1/2 using the reverse scan mode without the axial modulation voltage. Ion ejection at betaz = 1/2 is uncommon in commercial (stretched ion traps) with the conventional analytical scan without the use of a frequency of the axial modulation voltage corresponding to this non-linear resonance.
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Affiliation(s)
- G Dobson
- Université Pierre et Marie Curie, Laboratoire de Chimie Structurale Organique et Biologique, CNRS UMR 7613, 4 Place Jussieu, 75005 Paris Cedex 05, France
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8
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Viehland LA, Goeringer DE. Kinetic theory of radio frequency quadrupole ion traps. I. Trapping of atomic ions in a pure atomic gas. J Chem Phys 2004; 120:9090-103. [PMID: 15267845 DOI: 10.1063/1.1691405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A kinetic theory based on the Boltzmann equation is developed for the trapping of atomic ions in a radio-frequency quadrupole ion trap containing enough neutral atoms that ion-neutral collisions cannot be ignored. The collisions are treated at the same level of sophistication and detail as is used to deal with the time- and space-dependent electric fields in the trap. As a result, microscopic definitions are obtained for the damping and stochastic forces that originate from such collisions. These definitions contrast with corresponding phenomenological terms added ad hoc in previous treatments to create damped Mathieu and Langevin equations, respectively. Furthermore, the theory indicates that either collisional cooling or heating of the ions is possible, depending upon details of the ion-neutral mass ratios and interaction potential. The kinetic theory is not dependent on any special assumptions about the electric field strengths, the ion-neutral interaction potentials, or the ion-neutral mass ratio. It also provides an ab initio way to describe the ion kinetic energies, temperatures, and other properties by a series of successive approximations.
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Affiliation(s)
- Larry A Viehland
- Division of Science, Chatham College, Pittsburgh, Pennsylvania 15232, USA
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9
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Riter LS, Peng Y, Noll RJ, Patterson GE, Aggerholm T, Cooks RG. Analytical performance of a miniature cylindrical ion trap mass spectrometer. Anal Chem 2002; 74:6154-62. [PMID: 12510733 DOI: 10.1021/ac0204956] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The analytical performance of a fieldable cylindrical ion trap (CIT)-based miniature mass spectrometer is described. A detailed description of the instrument itself is to be found in the immediately preceding paper (Patterson, G. E.; Guymon, A. J.; Riter, L S.; Everly, M.; Griep-Raming, J.; Laughlin, B. C.; Ouyang, Z.; Cooks, R. G., Miniature Cylindrical Ion Trap Mass Spectrometer, Anal. Chem. 2002, 24, 6145-6153). Applications employing the MS/MS and MSn capabilities of the miniature instrument and analytical performance criteria are given here. The limit of detection for methyl salicylate, introduced as the pure vapor, is estimated as 1 pg. The resolution, R = m/delta m, where delta m, measured as full width at half-maximum, is estimated as 100. Monitoring of organic compounds in air is performed using a permeation membrane introduction device coupled to the mass spectrometer. Water monitoring is performed using an external membrane introduction mass spectrometry (MIMS) system, with acetophenone and toluene serving as model compounds. Data are given for chemical warfare agent simulants, methyl salicylate, and dimethyl methyl phosphonate (DMMP) in air. On-line detection of menthol vapor emitted from a cough drop is reported. Methyl salicylate in air gives a recognizable mass spectrum at 400 ppb in the ambient system, while use of a heated membrane brings the detection limit down to 10 ppb.
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Affiliation(s)
- Leah S Riter
- Chemistry Department, Purdue University, West Lafayette, Indiana 47907, USA
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10
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Plass WR, Gill LA, Bui HA, Cooks RG. Ion Mobility Measurement by Dc Tomography in an Rf Quadrupole Ion Trap. J Phys Chem A 2000. [DOI: 10.1021/jp994356c] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Wolfgang R. Plass
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
| | - Lynn A. Gill
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
| | - Huy A. Bui
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
| | - R. Graham Cooks
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
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11
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Visual representations of simulated three-dimensional ion trajectories in an ion trap mass spectrometer. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0168-1176(96)04416-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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12
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Makarov AA. Resonance Ejection from the Paul Trap: A Theoretical Treatment Incorporating a Weak Octapole Field. Anal Chem 1996; 68:4257-63. [DOI: 10.1021/ac960653r] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Qin J, Chait BT. Matrix-assisted laser desorption ion trap mass spectrometry: efficient trapping and ejection of ions. Anal Chem 1996; 68:2102-7. [PMID: 9027225 DOI: 10.1021/ac951162u] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The present paper explores the coupling of a matrix-assisted laser desorption/ionization (MALDI) ion source with an ion trap mass analyzer, with particular emphasis on the development of methods for improving the efficiency of ion trapping and ejection. A technique is described for directly measuring, for the first time, the trapping efficiency of peptide ions produced in a remote external MALDI ion source. The technique was used to devise an improved scheme for trapping, which yielded efficiencies as high as 39%. An improved understanding of the resonant ejection process led us to a new resonant ejection parameter set that increased the ejection efficiency by 1 order of magnitude over more conventionally used parameter sets and allowed for marked improvements in the mass resolution of ions with m/z > 2500. The presently described improvements in the efficiencies of ion trapping and ejection together with improved methods for isolating and fragmenting ions (Qin, J.; Chait, B.T.Anal. Chem., following article in this tissue) lay the foundation for highly sensitive MALDI ion trap mass spectrometry of proteins (Qin, J.; et al. Anal. Chem. 1996, 68, 1784-1791).
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Affiliation(s)
- J Qin
- Rockefeller University, New York, New York 10021, USA
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14
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Affiliation(s)
- A L Burlingame
- Department of Pharmaceutical Chemistry, University of California, San Francisco 94143-0446, USA
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15
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Jonscher KR, Yates JR. Mixture analysis using a quadrupole mass filter/quadrupole ion trap mass spectrometer. Anal Chem 1996; 68:659-67. [PMID: 8999740 DOI: 10.1021/ac950978s] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A hybrid tandem mass spectrometer is constructed by interfacing a quadrupole mass filter (Q) to a quadrupole ion trap mass spectrometer (QITMS) and is evaluated for the analysis of mixtures. The mass filter is set to selectively inject ions of a particular m/z or, in scanning mode, to sequentially inject ions into the QITMS for subsequent manipulation and detection. Performance of the instrument is demonstrated using a mixture of ions created by electron impact ionization of perfluorotributylamine (FC-43) and peptide ions generated by pulsed Cs+ bombardment. Resulting data are compared to those obtained by utilizing only the ion trap. Molecular weight, fragmentation, and high-resolution analyses for the sequentially injected mass-filtered peptides show improved performance over similar measurements employing only the ion trap mass spectrometer. Performance is optimized when ions are not rf-isolated in the QITMS. Using the hybrid, a resolution of 33,200 is achieved for angiotensin I. Dramatic reduction of space charge-induced signal suppression is demonstrated for LSIMS of Glu-fibrinopeptide B. 'On-the-fly' collision-induced dissociation is performed for m/z 502 from FC-43, where fragmentation is induced by increasing the ion injection energy. Collision-induced dissociation efficiencies for fragmentation of angiotensin I by resonance excitation are investigated as a function of cooling time for different modes of operation of the hybrid. A current limitation of the instrument is the time required to port the data for acquisition.
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Affiliation(s)
- K R Jonscher
- Department of Molecular Biotechnology, University of Washington, Seattle 98195-7730, USA
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16
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Cleven CD, Cooks RG, Garrett AW, Nogar NS, Hemberger PH. Radial Distributions and Ejection Times of Molecular Ions in an Ion Trap Mass Spectrometer: A Laser Tomography Study of Effects of Ion Density and Molecular Type. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp951667o] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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17
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Doroshenko VM, Cotter RJ. Effect of phase locking AC and RF voltages for high mass analysis in a quadrupole ion trap mass spectrometer. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 1996; 10:1921-1926. [PMID: 9004528 DOI: 10.1002/rcm.1290101502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Experiments on the influence of locking the AC and RF frequency phases on the mass resolution and line position in the mass spectra from a quadrupole ion trap mass spectrometer were carried out at low ejection values of beta z to investigate the possibility of using this effect for high mass analysis. At a typical mass scan rate of 1000 u/s the improvement for the mass resolution in these experiments did not exceed 10-20% at beta z = 0.25 compared with 200-250% at beta z = 0.5. However, without phase locking, the mass resolution at beta z = 0.25 was about two times higher than that at beta z = 0.5. Thus, the absolute values for the mass resolution observed without phase-locked AC and RF frequencies at beta z = 0.25 were about the same as at beta z = 0.5 with phase locking. This observation was explained by a significant negative contribution to the mass resolution of the ion microoscillations along the trajectory at the fundamental RF frequency which is different for the cases of beta z = 0.25 and beta z = 0.5.
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Affiliation(s)
- V M Doroshenko
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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18
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Parks JH, Szöke A. Simulation of collisional relaxation of trapped ion clouds in the presence of space charge fields. J Chem Phys 1995. [DOI: 10.1063/1.469766] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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19
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Londry F, March R. Systematic factors affecting high mass-resolution and accurate mass assignment in a quadrupole ion trap. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0168-1176(95)04153-c] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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20
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Cox K, Cleven C, Cooks R. Mass shifts and local space charge effects observed in the quadrupole ion trap at higher resolution. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0168-1176(95)04152-b] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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21
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Julian RK, Nappi M, Weil C, Cooks RG. Multiparticle simulation of ion motion in the ion trap mass spectrometer: Resonant and direct current pulse excitation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 1995; 6:57-70. [PMID: 24222061 DOI: 10.1016/1044-0305(94)00087-g] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/1993] [Revised: 08/22/1994] [Accepted: 08/22/1994] [Indexed: 06/02/2023]
Abstract
A PC-based program that simulates the behavior of a collection of ions is extended to include the effects of collisions with the buffer gas and enhanced visualization methods. The simulations are based on the quadrupole field associated with the actual ion trap electrode structure. Ionization is simulated in such a way as to distribute ionization events randomly over rf phase angles and yield a realistic collection of stored ions. The effects of buffer gas collisions on ion motion during both mass-selective instability and resonance ejection scans are found to include the expected dampening of spatial excursions as well as limitation of the kinetic energy of trapped ions. In both experiments, ion ejection occurs over a number of secular cycles in the vicinity of the theoretical instability point. Activation via a resonant ac signal or a short dc pulse is shown to result in phase-locking of the ions as well as the expected increase in the size of the excursions in the z direction and in ion kinetic energy. Collisions cause dephasing and loss of kinetic energy. Radial dc activation is compared with activation in the axial direction. Experimental data for dc pulse activation of the n-butylbenzene molecular ion are analyzed in phase space and the onset of surface-induced dissociation is correlated with changes in the experimental m/z 91 to m/z 92 fragment ion ratio. Poincaré sections are shown for resonantly excited ions and their value in demonstrating improvement of the resolution of these experiments over conventional mass-selective instability scans is shown.
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Affiliation(s)
- R K Julian
- Department of Chemistry, Purdue Uruverslty, 1393 Brown Bufldmg, Rec Room 2494, 47907, West Lafayette, IN
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22
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Grosshans PB, Chen R, Limbach PA, Marshall AG. Linear excitation and detection in Fourier transform ion cyclotron resonance mass spectrometry. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0168-1176(94)90034-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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23
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Eiden G, Garrett A, Cisper M, Nogar N, Hemberger P. An improved method for capturing laser desorbed ions in an ion trap mass spectrometer: dynamic r.f. trapping. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0168-1176(94)04013-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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24
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Williams JD, Cooks RG, Syka JE, Hemberger PH, Nogar NS. Determination of positions, velocities, and kinetic energies of resonantly excited ions in the quadrupole ion trap mass spectrometer by laser photodissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 1993; 4:792-797. [PMID: 24227464 DOI: 10.1016/1044-0305(93)80037-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/1993] [Revised: 06/15/1993] [Accepted: 06/15/1993] [Indexed: 06/02/2023]
Abstract
The effects on ion motion caused by the application of a resonance AC dipole voltage to the end-cap electrodes of the quadrupole ion trap are described. An excimer laser is used to photodissociate benzoyl ions, and its triggering is phase locked to the AC voltage to follow the motion of the ion cloud as a function of the phase angle of the AC signal. Resonantly excited ions maintain a coherent motion in the presence of He buffer gas, which dissipates energy from the ions via collisions. Maximum ion displacements, which depend upon the potential well depth (q z value), occur twice each AC cycle. Axial components of ion velocities are determined by differentiating the displacements of the distributions with respect to time. The experimental data show that these velocities are maximized when the ion cloud passes through zero axial displacement, and they compare favorably with results calculated using a simple harmonic oscillator model. Axial components of ion kinetic energies are low (<5 eV) under the chosen experimental conditions. At low values of q2 (≈ 0.2), the width of the ion distribution increases as the ion cloud approaches the center of the trap and decreases as it approaches the end-cap electrodes. This effect is created by compaction of the ion trajectories when ion velocities are decreased.
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Affiliation(s)
- J D Williams
- Department of Chemistry, Purdue University, 47907, West Lafayette, Indiana, USA
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