Evidence of isomerization during ion isolation in the quadrupole ion trap

Hart, Kevin J.; McLuckey, Scott A.; Glish, Gary L.

doi:10.1016/1044-0305(92)85010-h

Cited by 10 publications

(6 citation statements)

References 10 publications

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“…In principal, it should be possible to convert a less stable isomer to a more stable (thermodynamic) species by careful ion activation, provided the barrier for isomerization is less than the energy required for decomposition. 71 Recently, we demonstrated the efficient isomerization of (C2H5)SiH2+ to (CH3)2-SiH+ by collisional activation by using an "off-resonance" electric field pulse. 72 In this case, the two SiC2H7+ isomers were distinguished by reaction with ethene-da and methanol.…”

Section: Fe+=si(ch3)2 Hamentioning

confidence: 99%

Generation, characterization, and properties of iron-silylene and iron-silene cationic complexes in the gas phase

Jacobson¹,

Bakhtiar²

1993

J. Am. Chem. Soc.

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Section: Fe+=si(ch3)2 Hamentioning

confidence: 99%

Generation, characterization, and properties of iron-silylene and iron-silene cationic complexes in the gas phase

Jacobson¹,

Bakhtiar²

1993

J. Am. Chem. Soc.

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“…The isolation of high-mass ions is normally achieved through a combination of reverse and forward radio frequency (rf) scans incorporating resonant ejection . It is necessary to exercise care during this step since the isolation process can induce excitation and unwanted fragmentation of the isolated ion species . Such excitation can be an especially serious problem for the internally hot ions produced by MALDI .…”

mentioning

confidence: 99%

“…1 It is necessary to exercise care during this step since the isolation process can induce excitation and unwanted fragmentation of the isolated ion species. 2 Such excitation can be an especially serious problem for the internally hot ions produced by MALDI. 3 We show here by direct measurement that an isolation efficiency close to unity can be achieved for MALDI-generated peptide ions.…”

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confidence: 99%

Matrix-Assisted Laser Desorption Ion Trap Mass Spectrometry: Efficient Isolation and Effective Fragmentation of Peptide Ions

Qin

Chait

1996

Anal. Chem.

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Effective analysis of the sequence of peptides using matrix-assisted laser desorption/ionization (MALDI) tandem ion trap mass spectrometry requires efficient mass isolation and the ability to induce extensive sequence-specific fragmentation. The present paper describes a new excitation scheme, which we term red-shifted off-resonance large-amplitude excitation (RSORLAE), that can deposit higher amounts of internal energy in ions than is feasible with conventional resonant excitation. The new method provides an effective means for inducing fragmentation of MALDI-produced peptide ions with m/z values up to 3500. Prior to excitation, it is necessary to isolate ions of interest with high efficiency. We demonstrate that isolation efficiencies of > 95% can be achieved by careful design of the rf scan functions used during ion isolation. In particular, sudden transitions in the amplitude of the rf field (from low to high amplitudes) must be avoided. The combined improvements in the efficiency for ion isolation and the efficacy of ion activation make MALDI tandem ion trap mass spectrometry a practical tool for the characterization of proteins with high sensitivity.

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“…Typical pressures were 2 X 10-7 torr for the sample and 7 X 10-4 torr for the He bath gas . For CI and ion-molecule reactions with methane, the methane pressure was 1.0 X 10- 5 torr.…”

Section: Mass Spectrometrymentioning

confidence: 99%

“…To support further the assignment of C 6Ht as phenylium ion, the structure of the C 7Hj product ion was determined. There are at least three possible isomers for C 7Hj (tropylium, benzyl, and tolyl), whose unique reactivities with neutral molecules make them distinguishable [5,[13][14][15][16][17][18]. Benzyl ions react with xylene, tolyl ions react with methane, and tropylium is unreactive with both [5,13,14,17].…”

Section: Metastable Ionsmentioning

confidence: 99%

Reaction from isomeric parent ions in the dissociation of dimethylpyrroles

Lin

Asam

Glish

1996

J. Am. Soc. Mass Spectrom.

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The major dissociation pathways of the [M-H](+) (loss of NH3 or CH4) and the [M+H](+) (loss of NH3 or CH3) ions from dimethylpyrroles have been determined to occur from isomeric parent ions. For the [M-H](+) ion (formed by loss of a methyl hydrogen), loss of NH3 leads to the formation of the phenylium ion and is preceded by consecutive carbon ring expansions followed by a ring contraction to form protonated aniline. Loss of CH4 occurs after the first carbon ring expansion, which forms protonated picoline. The relative partitioning between the two dissociation paths depends upon the internal energy content of the parent ion; the highest point on the potential energy surface is the second ring expansion step. The [M+H](+) ion reacts through a similar pathway via dihydro analogs of picoline and aniline. The proposed reaction pathways are supported by results of semiempirical molecular orbital calculations.

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Evidence of isomerization during ion isolation in the quadrupole ion trap

Cited by 10 publications

References 10 publications

Generation, characterization, and properties of iron-silylene and iron-silene cationic complexes in the gas phase

Generation, characterization, and properties of iron-silylene and iron-silene cationic complexes in the gas phase

Matrix-Assisted Laser Desorption Ion Trap Mass Spectrometry: Efficient Isolation and Effective Fragmentation of Peptide Ions

Reaction from isomeric parent ions in the dissociation of dimethylpyrroles

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