Calibration of an audio-frequency ion trap mass spectrometer

Cai, Yong; Peng, Wen-Ping; Kuo, S.-J.; Chang, Huan‐Cheng

doi:10.1016/s1387-3806(01)00558-9

Cited by 20 publications

(12 citation statements)

References 32 publications

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“…8,26,27 Six different types of chromatographic packing materials were characterized: they included 4.6 μm porous silica particles with pore sizes of 100 and 300 Å, the C 1 (trimethylsilane), C 4 (propyldimethylsilane), C 8 (octyldimethylsilane), and C 18 (octadecyldimethylsilane) bonded 4.6 μm porous silica particles with pore size of 100 Å from Agela Technologies Inc. (Tianjin, China). The structures of the chemicals bonded onto the silica surfaces are shown in Figure 1.…”

Section: ' Experimental Sectionmentioning

confidence: 99%

Characterization of Column Packing Materials in High-Performance Liquid Chromatography by Charge-Detection Quadrupole Ion Trap Mass Spectrometry

Xiong

Zhou²,

Chen³

et al. 2011

Anal. Chem.

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This article reports an application of charge-detection quadrupole ion trap mass spectrometry (CD-ITMS) to characterize the column packing materials in high-performance liquid chromatography (HPLC). Both the mean mass and the mass distribution of the packing materials are obtained and used to calculate the specific surface area of unbonded silica, the carbon load of the bonded silica, and their particle size distributions. The obtained specific surface areas and carbon loads are consistent with those measured independently by nitrogen sorption and elemental analysis respectively, whereas the derived size distributions show better resolution than that measured by a laser particle size analyzer. Furthermore, we evaluate the uniformity of particle size, which is the key parameter for column efficiency of the liquid chromatography by analyzing the mass distribution of the packing materials at the top and bottom of the column. A broader mass distribution, which yields decreased column efficiency, is observed for the column top because of the excessive use of the column. Our results suggest that CD-ITMS can serve as an alternative means for the characterization of the packing materials in HPLC and is potentially useful for column quality control.

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Section: ' Experimental Sectionmentioning

confidence: 99%

Characterization of Column Packing Materials in High-Performance Liquid Chromatography by Charge-Detection Quadrupole Ion Trap Mass Spectrometry

Xiong

Zhou²,

Chen³

et al. 2011

Anal. Chem.

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“…When a buffer gas was first used to improve the resolution of the mass spectrum by Stafford et al [4], the stability boundary would move towards the positive direction on q-axis as bath gas pressure increase [2,5,6]. For the particle under the background at about 40 mTorr, the delay ejection also occurred at a large q value in the audio-frequency ion trap mass spectrometer [7][8][9][10][11].In practical traps, however, the electric field distribution is nonlinear, and the main causes contributing to field distortions are the misalignment of the trap [12], the truncation of electrodes [12], and the space charge [13,14]. As the existence of high order terms in electric field, the stability boundary deviates from the ideal value and the equation of motion for the ions will be nonlinear Mathieu equation.…”

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confidence: 99%

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Characteristics of stability boundary and frequency in nonlinear ion trap mass spectrometer

Zhou

Zhu

Xiong

et al. 2010

J. Am. Soc. Mass Spectrom.

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In this article, the Poincare-Lighthill-Kuo (PLK) method is used to derive an analytical expression on the stability boundary and the ion trajectory. A multipole superposition model mainly including octopole component is adopted to represent the inhomogeneities of the field. In this method, both the motional displacement and secular frequency of ions have been expanded to asymptotic series by the scale of nonlinear term , which represents a weak octopole field. By solving the zero and first-order approximate equations, it is found that a frequency shift exists between the ideal and nonlinear conditions. The motional frequency of ions in nonlinear ion trap depends on not only Mathieu parameters, a and q, but also the percentage of the nonlinear field and the initial amplitude of ions. In the same trap, ions have the same mass-to-charge ratio (m/z) but they have different initial amplitudes or velocities. Consequently, they will be ejected at different time through after a mass-selective instability scan. The influences on the mass resolution in quadrupole ion trap, which is coupled with positive or negative octopole fields, have been discussed respectively. where u is the related motional frequency in the axial and radial direction, ⍀ is the frequency of the driven radio-frequency (rf) potential, ␤ u is a parameter dependent on Mathieu parameters a u and q u , and the subscript u refers to axial and radial coordinates. Boundary ejection methods take the advantage of ejecting ions with a mass-selective instability scan, with which the rf amplitude is scanned linearly to cause the secular frequency of ions to increase until they become unstable [2-4], when the ions reach the boundary at a ϭ 0, q eject ϭ 0.908, ␤ z is equal to one, the ion has reached its stability limit. When a buffer gas was first used to improve the resolution of the mass spectrum by Stafford et al. [4], the stability boundary would move towards the positive direction on q-axis as bath gas pressure increase [2,5,6]. For the particle under the background at about 40 mTorr, the delay ejection also occurred at a large q value in the audio-frequency ion trap mass spectrometer [7][8][9][10][11].In practical traps, however, the electric field distribution is nonlinear, and the main causes contributing to field distortions are the misalignment of the trap [12], the truncation of electrodes [12], and the space charge [13,14]. As the existence of high order terms in electric field, the stability boundary deviates from the ideal value and the equation of motion for the ions will be nonlinear Mathieu equation.Most papers [15][16][17][18][19] deal with the time-dependent nonlinear terms with the method of pseudopotential well approximation [20].Using this approximation, high order terms become time-independent, and the nonlinear Mathieu equation is a normal nonlinear equation known as Duffing equation. The solution of such kind of equations has been well-studied [21]. When q u Ͻ 0.4 [2,22], this approximation accords well with the physical truth, some useful...

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“…The most widely discussed distortion is the "stretched" ion trap [2], which has the end cap electrodes moved out so that the distance to the end cap, z 0 , is increased over that of an ideal field, z 0 ϭ r 0 ⁄ ͙ 2, where r 0 is the distance from the center to the ring electrode. It has been argued that the addition of higher order multipole fields of the correct sign to 3-D traps improves MS/MS efficiency [1c, 1f, 2], and allows faster ejection at the stability boundary [2,3], to give higher scan speeds and improved mass resolution.There is increasing interest in using linear quadrupoles as ion traps, both as stand alone mass analyzers with radial [4] or axial [5] ejection, or in combination with other mass analyzers (for a recent review see [6]). …”

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Ion excitation in a linear quadrupole ion trap with an added octopole field

Michaud

Frank

Ding

et al. 2005

J. Am. Soc. Mass Spectrom.

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Modeling of ion motion and experimental investigations of ion excitation in a linear quadrupole trap with a 4% added octopole field are described. The results are compared with those obtained with a conventional round rod set. Motion in the effective potential of the rod set can explain many of the observed phenomena. The frequencies of ion oscillation in the x and y directions shift with amplitude in opposite directions as the amplitudes of oscillation increase. Excitation profiles for ion fragmentation become asymmetric and in some cases show bistable behavior where the amplitude of oscillation suddenly jumps between high and low values with very small changes in excitation frequency. Experiments show these effects. Ions are injected into a linear trap, stored, isolated, excited for MS/MS, and then mass analyzed in a time-of-flight mass analyzer. Frequency shifts between the x and y motions are observed, and in some cases asymmetric excitation profiles and bistable behavior are observed. Higher MS/MS efficiencies are expected when an octopole field is added. MS/MS efficiencies (N 2 collision gas) have been measured for a conventional quadrupole rod set and a linear ion trap with a 4% added octopole field. Efficiencies are chemical compound dependent, but when an octopole field is added, efficiencies can be substantially higher than with a conventional rod set, particularly at pressures of 1.4 ϫ 10 Ϫ4 torr or less. . The most widely discussed distortion is the "stretched" ion trap [2], which has the end cap electrodes moved out so that the distance to the end cap, z 0 , is increased over that of an ideal field, z 0 ϭ r 0 ⁄ ͙ 2, where r 0 is the distance from the center to the ring electrode. It has been argued that the addition of higher order multipole fields of the correct sign to 3-D traps improves MS/MS efficiency [1c, 1f, 2], and allows faster ejection at the stability boundary [2,3], to give higher scan speeds and improved mass resolution.There is increasing interest in using linear quadrupoles as ion traps, both as stand alone mass analyzers with radial [4] or axial [5] ejection, or in combination with other mass analyzers (for a recent review see [6]).There is also interest in trapping and exciting ions for MS/MS at the relatively low pressures typical for operation of the last mass analyzing quadrupole in triple quadrupole systems, ca. 3 ϫ 10 Ϫ5 torr [7]. Addition of higher multipoles to a linear ion trap might be expected to provide benefits similar to those seen with 3-D traps. Douglas and coworkers [8] have shown that an octopole field can be added to a linear quadrupole by using rod sets with rods equally spaced from the central axis but with one pair of rods different in diameter than the other pair, as shown in Figure 1. The electric potential within this rod set is given to a good approximation bywhere x is the distance from the center towards a smaller rod, y is the distance from the center towards a larger rod, r 0 is the distance from the center to any rod, and U and V rf are the amplitudes...

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Calibration of an audio-frequency ion trap mass spectrometer

Cited by 20 publications

References 32 publications

Characterization of Column Packing Materials in High-Performance Liquid Chromatography by Charge-Detection Quadrupole Ion Trap Mass Spectrometry

Characterization of Column Packing Materials in High-Performance Liquid Chromatography by Charge-Detection Quadrupole Ion Trap Mass Spectrometry

Characteristics of stability boundary and frequency in nonlinear ion trap mass spectrometer

Ion excitation in a linear quadrupole ion trap with an added octopole field

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