A two-dimensional quadrupole ion trap mass spectrometer

Schwartz, Jae C.; Senko, Michael W.; Syka, John E. P.

doi:10.1016/s1044-0305(02)00384-7

Cited by 684 publications

(744 citation statements)

References 23 publications

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“…The experiments described here were done with balanced rf applied to the rods. Figure 3 shows the results of an experiment to measure the frequencies and peak shapes for depletion of protonated reserpine ions and formation of fragment ions with dipole excitation applied between the larger ( 4 in the effective potential, shows a shift up from 55.44 kHz of 1.11 kHz to 56.55 kHz, and for excitation between the larger rods a shift down of 1.24 kHz to 54.20 kHz. These shifts are approximately equal in magnitude and of opposite sign as expected from eq 14.…”

Section: Axis Potentialmentioning

confidence: 99%

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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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Section: Axis Potentialmentioning

confidence: 99%

“…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]). …”

mentioning

confidence: 99%

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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“…. Both approaches yield high quality mass spectra and offer advantages over conventional three-dimensional ion traps, such as greater ion capacity, higher trapping efficiencies, less mass discrimination, and reduced effects of space charge [1,3]. In certain cases, linear ion trap mass spectrometers can be incorporated into the ion path of triple quadrupoles yielding an instrument that combines the strengths of both platforms [1,4].…”

mentioning

confidence: 99%

Mass selective axial ion ejection from a linear quadrupole ion trap

Londry¹,

Hager²

2003

J. Am. Soc. Mass Spectrom.

193

218

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The electric fields responsible for mass-selective axial ejection (MSAE) of ions trapped in a linear quadrupole ion trap have been studied using a combination of analytic theory and computer modeling. Axial ejection occurs as a consequence of the trapped ions' radial motion, which is characterized by extrema that are phase-synchronous with the local RF potential. As a result, the net axial electric field experienced by ions in the fringe region, over one RF cycle, is positive. This axial field depends strongly on both the axial and radial ion coordinates. The superposition of a repulsive potential applied to an exit lens with the diminishing quadrupole potential in the fringing region near the end of a quadrupole rod array can give rise to an approximately conical surface on which the net axial force experienced by an ion, averaged over one RF cycle, is zero. This conical surface has been named the cone of reflection because it divides the regions of ion reflection and ion ejection. Once an ion penetrates this surface, it feels a strong net positive axial force and is accelerated toward the exit lens. As a consequence of the strong dependence of the axial field on radial displacement, trapped thermalized ions can be ejected axially from a linear ion trap in a mass-selective way when their radial amplitude is increased through a resonant response to an auxiliary signal. . Both approaches yield high quality mass spectra and offer advantages over conventional three-dimensional ion traps, such as greater ion capacity, higher trapping efficiencies, less mass discrimination, and reduced effects of space charge [1,3]. In certain cases, linear ion trap mass spectrometers can be incorporated into the ion path of triple quadrupoles yielding an instrument that combines the strengths of both platforms [1,4]. Ions are trapped radially in these devices by the RF quadrupole field and axially by static DC potentials at the ends of the quadrupole rod array, in contrast to conventional Paul traps in which ions are trapped by a three-dimensional RF quadrupole field. Radial mass-selective ion ejection occurs when the RF voltage is ramped in the presence of a sufficiently intense auxiliary AC voltage. The auxiliary AC resonance-ejection voltage is applied radially and the ions emerge from the linear ion trap through slots cut in the quadrupole rods [3]. Radial ejection requires that the RF field be of high quality over the entire length of the ion trap [3] in order to preserve mass spectral resolution, since resolution depends on the fidelity of the secular frequency of the trapped ions. Thus, very high mechanical precision is required in fabrication of the quadrupole rods in order to maintain the same secular frequency over the length of the device. Of course, the greater the length of the linear ion trap, the more difficult it is to maintain the high degree of mechanical precision. In addition, considerable care must be taken to ensure that the ions that are intended to be ejected radially from the linear ion trap are isolated as ...

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“…There are two opposite principles. One is increasing RF amplitude to trap large m/z ions, [28] especially in the case of metal clusters due to the large m/z ion. The trapping efficiency for m/z 988 Au 6 Ag(C)(L 1 ) 6 3+ (black solid line) and m/z Au 8 (L 2 ) 3 (L 3 ) 2 2+ is shown in Supplementary Fig.…”

Section: +mentioning

confidence: 99%

Studying mass spectrometric behaviors of {Au₆Ag₂(C)[PPh₂(4‐CH₃‐Py)]₆}(BF₄)₄ and {Au₈[(PPh₃)₂O]₃(PPh₃)₂}(NO₃)₂ by electrospray time‐of‐flight mass spectrometry and electrospray ion trap mass spectrometry

Yang

Chen

et al. 2016

Rapid Comm Mass Spectrometry

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RATIONALE: Mass spectrometry (MS) has been recognized as a powerful technique to detect accurate chemical information about metal clusters. Maintaining metal clusters intact, which is a great challenge in MS analysis, was achieved in this work by choosing a suitable mass analyzer and carefully optimizing analysis parameters. METHODS: Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) and electrospray ion trap mass spectrometry (ESI-IT-MS) were applied to characterize the synthesized ligand-protected metal clusters [Au 6 . Three kinds of buffer gas (helium, mass: 2; nitrogen, mass: 28; argon, mass: 40) and various radiofrequency (RF) amplitudes (from 70 to 330) were chosen to study the fragmentation rate during the "collision cooling" process in the ion trap analyzer. RESULTS: In the ESI-TOF-MS analysis, metal clusters 1 and 2 were mainly observed as intact clusters, which were Au 6 Ag 2 (C)(L 1 ) 6 (BF 4 ) 2 2+ , Au 6 Ag 2 (C)(L 1 ) 6 (BF 4 ) 3+ , Au 6 Ag 2 (C)(L 1 ) 6 4+ for 1 and Au 8 (L 2 ) 3 (L 3 ) 2 2+ for 2. While, in the ESI-IT-MS analysis, only fragments could be found, such as, Au 6 (L 2 ) 3 2+ for 2. It is obvious that the two kinds of mass analyzers caused different MS behaviors of metal clusters. In the ion trap (IT) mass analyzer, particularly, "collision cooling" was contributing to further dissociation of fragile compounds, in which a higher RF amplitude and a larger mass buffer gas led to more fragmentation. CONCLUSION: In this work, intact metal clusters were obtained in ESI-TOF-MS, instead of ESI-IT-MS, in which the "collision cooling" process caused more cluster dissociation. It was concluded that the analyzer in ESI-TOF-MS is "softer" than that in ESI-IT-MS for metal clusters. Copyright © 2016 John Wiley & Sons, Ltd.Metal clusters composed by metal cores and organic ligands have brought about an upsurge in research because of their interesting properties, such as catalysis, [1][2][3] chirality, [4,5] electrical conductivity, [6,7] luminescence, [8][9][10] C-H activation, [11] and so on. The properties of metal clusters depend on their structures, chemical compositions, and bondings. Recently, more and more metal clusters are studied by mass spectrometry (MS), since MS not only provides the exact molecular mass and isotopic patterns to characterize their composition, [12][13][14][15][16][17] but also gives insights into their chemical behaviors in solution, such as ligand exchange and the growth mechanism. [18][19][20] However, due to the weak non-covalent interactions, such as coordination bond and metal-metal bond, metal clusters are easily decomposed in MS analysis, and it is challenging to obtain information about their intact clusters. It is well known that fragments of metal clusters can be produced in the ionization processes. The ionization methods causing less degrees of dissociation of the analyzed compound are always reported as being ''soft'' ionization methods, including electrospray ionization (ESI), [12,13,17,19,20] matrix-assisted laser desorption (MALDI), [...

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A two-dimensional quadrupole ion trap mass spectrometer

Cited by 684 publications

References 23 publications

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

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

Mass selective axial ion ejection from a linear quadrupole ion trap

Studying mass spectrometric behaviors of {Au₆Ag₂(C)[PPh₂(4‐CH₃‐Py)]₆}(BF₄)₄ and {Au₈[(PPh₃)₂O]₃(PPh₃)₂}(NO₃)₂ by electrospray time‐of‐flight mass spectrometry and electrospray ion trap mass spectrometry

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A two-dimensional quadrupole ion trap mass spectrometer

Cited by 684 publications

References 23 publications

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

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

Mass selective axial ion ejection from a linear quadrupole ion trap

Studying mass spectrometric behaviors of {Au6Ag2(C)[PPh2(4‐CH3‐Py)]6}(BF4)4 and {Au8[(PPh3)2O]3(PPh3)2}(NO3)2 by electrospray time‐of‐flight mass spectrometry and electrospray ion trap mass spectrometry

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Studying mass spectrometric behaviors of {Au₆Ag₂(C)[PPh₂(4‐CH₃‐Py)]₆}(BF₄)₄ and {Au₈[(PPh₃)₂O]₃(PPh₃)₂}(NO₃)₂ by electrospray time‐of‐flight mass spectrometry and electrospray ion trap mass spectrometry