In-beam electron impact mass spectrometry ofN-carbobenzoxy derivatives of oligopeptides composed of leucine and isoleucine

Ohashi, Mamoru; Tsujimoto, Kazuo; Tamura, Shigeki; Nakayama, Noboru; Okumura, Yasuaki; Sakurai, Atsushi

doi:10.1002/bms.1200070404

Cited by 7 publications

(1 citation statement)

References 26 publications

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“…Pyrolysis mass spectrometry was investigated (5) as a means of characterizing the compounds. The use of in-beam or extended-probe techniques to study apparently nonvolatile and thermally unstable compounds is now commonplace and well documented in the literature (6)(7)(8)(9)(10)(11)(12)(13)(14). Using this technique, ammonia-positive and methane-negative ion desorption CI of penicillins was reported (15); however, this report did not include any electron ionization (EI) data.…”

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confidence: 99%

In-Beam Electron Ionization Mass Spectra of Penicillins

Ohashi

Barron

Benson

1983

Journal of Pharmaceutical Sciences

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mentioning

confidence: 99%

In-Beam Electron Ionization Mass Spectra of Penicillins

Ohashi

Barron

Benson

1983

Journal of Pharmaceutical Sciences

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Matrix‐Assisted in‐Beam Mass Spectra of Thermally Fragile Molecules

Liu

Hsieh

1986

J Chinese Chemical Soc

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In‐beam and matrix‐isolation techniques have been used in the mass spectral studies of several categories of biologically significant compounds. These include amino acids, quaternary ammonium salts, vitamins and nucleosides. Molecular ions and/or (M+H)+ions are obtained, together with useful fragmentations, all of which are valuable in structural elucidations. Spectra obtained by this version of the in‐beam technique are similar but not identical with those obtained by field desorption and secondary ion mass spectrometry. Ammonium and sodium chlorides, ammonium sulfate, p‐toluenesulfonic and hydrochloric acids can all be used as a room temperature matrix. The detection limits for vitamin E and 2′‐deoxyguanosine have been determined as 1 ngand 5 μg, respectively.

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Thermal degradation of O‐acyl oximes under electron impact ionization conditions

Horiyama

Suwa

Yamaki

et al. 1995

Rapid Comm Mass Spectrometry

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Thermal degradation of 0-acyl oximes under electron impact ionization (EI) conditions has been examined. The EI mass spectra gave fragment ions originating from thermal degradation, as well as molecular ions M" and normal fragment ions due to unimolecular decomposition of the M" ions. The fragment ions due to thermal degradation of 0-acyl oximes were identified by using fast-atom bombardment (FAB) mass spectrometry with a liquid matrix together with the collision-induced dissociation (CID) technique. While the FAB mass spectra of 0-acyl oximes gave, preferentially, M+' ions together with some characteristic fragment ions, as well as the molecular related ions [M + HI+ and [M -HI+, the spectra showed little evidence of the fragment ions which may originate from thermal degradation under EI conditions. The CID spectra of selected M" ions formed by electron impact also showed little of such fragment ions. The thermal degradation was directly confirmed by measuring the FAB mass spectra of 0-acyl oximes that had been heated in a sealed sample tube.Although electron impact ionization mass spectrometry (EI-MS) is a most popular method for the structure elucidation of organic compounds, it is limited to the analysis of thermally stable compounds. EI, chemical ionization, field ionization, and other methods, which require a heating process to vaporize sample materials before ionization, will possibly bring about thermal degradation, so it is expected that EI mass spectra of organic compounds may contain fragment ions originating from both normal fragmentation and thermal degradation even when the mass spectra give a definite peak due to M+' ions. The formation of Mf' ions and the thermal degradation of analytes may occur competitively under EI conditions,' and it is difficult to separate completely those fragments that originate from thermal degradation or isomerization and those from fragmentation of normal M+' ions.Since 1970, a number of techniques that inhibit thermal degradation of analytes have been developed. 1-5 In 1981, fast-atom bombardment (FAB) and liquid secondary ion mass spectrometry (LSIMS) were developed as more simple and milder ionization method^.^,' Takayama et a1.* have demonstrated that by using the FAB method, thermal isomerization of flavanones could be avoided. Aplin et aL9 have described that in the sequence study of amino acids the breakdown of protecting groups and diketopiperazine, which is formed by cyclization of amino acid, is due to thermal reaction under EI conditions. The oxime derivatives are well known as antiinflammatory, antipyretic, fungicidal, and parasiticidal active compounds.", l1 The 0-acyl oximes used in this work were synthesized for the purpose of development of a series of nonsteroidal anti-inflammatory drugs. l2 It is important to examine the thermal behavior of drugs in connection with their stability. In the present paper, we examine the thermal degradation and degradation sites of 0-acyl oximes under EI conditions by using FAB, collision-induced dissociation (CID), and ...

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In-beam electron impact mass spectrometry ofN-carbobenzoxy derivatives of oligopeptides composed of leucine and isoleucine

Cited by 7 publications

References 26 publications

In-Beam Electron Ionization Mass Spectra of Penicillins

In-Beam Electron Ionization Mass Spectra of Penicillins

Matrix‐Assisted in‐Beam Mass Spectra of Thermally Fragile Molecules

Thermal degradation of O‐acyl oximes under electron impact ionization conditions

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