Mass Spectrometry of Free Radicals

Sablier, Michel; Fujii, Toshihiro

doi:10.1021/cr010295e

Cited by 61 publications

(67 citation statements)

References 506 publications

(1,209 reference statements)

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“…Mass spectrometry can be applied successfully for the detection of radicals [16]. The challenge in using this technique is to ionize the radicals selectively in the presence of interfering species.…”

Section: Radical Detection By Threshold Ionizationmentioning

confidence: 99%

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Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

Horn

Ihmann

et al. 2006

Review of Scientific Instruments

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Abstract:A newly developed apparatus combining a Molecular Beam Mass Spectrometer (MBMS) and a catalytic wall reactor is described. The setup has been developed for in situ studies of high temperature catalytic reactions (> 1000 • C), which involve besides surface reactions also gas phase reactions in their mechanism. The goal is to identify gas phase radicals by threshold ionization. A tubular reactor, made from the catalytic material, is positioned in a vacuum chamber. Expansion of the gas through a 100 µm sampling orifice in the reactor wall into differentially pumped nozzle, skimmer and collimator chambers leads to formation of a molecular beam. A quadrupole MS with electron impact ion source designed for molecular beam inlet and threshold ionization measurements is used as analyzer. The sampling time from nozzle to detector is estimated to be less than 10 ms. A detection time resolution of up to 20 ms can be reached. The temperature of the reactor is measured by pyrometry. Besides a detailed description of the setup components and the physical background of the method, this article presents measurements showing the performance of the apparatus. After deriving shape and width of the energy spread of the ionizing electrons from measurements on N 2 and He we estimated the detection limit in threshold ionization measurements using binary mixtures of CO in N 2 to be in the range of several hundred ppm. Mass spectra and threshold ionization measurements recorded during catalytic partial oxidation of methane at 1250 • C on a P t catalyst are presented. The detection of CH 3 · radicals is successfully demonstrated.

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Section: Radical Detection By Threshold Ionizationmentioning

confidence: 99%

“…It can be shown by means of thermodynamics, that the ionization energy of the corresponding radical X· is always lower than the appearance energy of X + from XY by an amount equal to the dissociation enthalpy (∆ d H) of the X − Y bond [16]:…”

Section: Radical Detection By Threshold Ionizationmentioning

confidence: 99%

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

Horn

Ihmann

et al. 2006

Review of Scientific Instruments

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“…One of the greatest advantages of IAMS is that it can be used to directly analyze gaseous compounds. The features that allow this system to detect the intermediate free radicals and novel molecular species produced in various plasmas have been extensively explored [3][4][5], and IAMS techniques can be used to identify and quantify compounds and mixtures under plasma [6,7] and pyrolysis [8,9] conditions. To extend the ion attachment technique to ion trap mass spectrometry [10] or time of flight mass spectrometry [11] has been realized.…”

Section: Introductionmentioning

confidence: 99%

Design and Performance of a Compact Li⁺ Ion Attachment Mass Spectrometry System with an Atmospheric Sampling Device

Takahashi

Nakamura

Fujii

2012

J. Am. Soc. Mass Spectrom.

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This report describes the development of a compact ion attachment mass spectrometry system. A single turbomolecular pump was employed to fill the basic requirements for vacuum conditions simply and cost-effectively, without the need for a differential pumping stage. A Li + ion source was placed in the first of two vacuum chambers; a 0.4 mm aperture allowed the product ions to enter the second chamber for mass analysis. With the present system, any chemical species, including radical intermediates, can be detected at atmospheric pressure in real-time. The minimum detectable amount (at S/N=3) of toluene was around 1.3×10 -12 g/s with a linearity greater than 10 4 . For illustrative purposes, we tested the system on laboratory air and on aroma compounds in the headspace of the Yuzu plant, Citrus junos.

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“…In other words, carbocationic chemistry is observed predominantly from a alkyl disulfide, a source of free radicals. 9 The major products were N-tert-butylacetamide (3) from tert-butyl cation, which was isolated in 80% yield, and thianthrene (Th, 95%) by reducing of Th + .…”

mentioning

confidence: 99%

“…In support of the reluctant oxidation of 5, it should be noted that the ionization potential (IP) of Th is near 7.90 eV, 11,12 while the IP of 5 is 8.25 eV. 9 Since Th has not enough oxidation potential (1.3 V) to oxidize 5 rapidly the small amounts of 5 can reasonably be expected to survive long enough to yield 4.…”

mentioning

confidence: 99%

The First Example of Cation Radical Induced Desulfurization from Disulfides.

Park

Lee

2003

ChemInform

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Mass Spectrometry of Free Radicals

Cited by 61 publications

References 506 publications

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

Design and Performance of a Compact Li⁺ Ion Attachment Mass Spectrometry System with an Atmospheric Sampling Device

The First Example of Cation Radical Induced Desulfurization from Disulfides.

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Mass Spectrometry of Free Radicals

Cited by 61 publications

References 506 publications

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

Design and Performance of a Compact Li+ Ion Attachment Mass Spectrometry System with an Atmospheric Sampling Device

The First Example of Cation Radical Induced Desulfurization from Disulfides.

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Design and Performance of a Compact Li⁺ Ion Attachment Mass Spectrometry System with an Atmospheric Sampling Device