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Volume 53 (2005)
- Issue 6 Pages 305-
- Issue 5 Pages 241-
- Issue 4 Pages 183-
- Issue 3 Pages 89-
- Issue 2 Pages 53-
- Issue 1 Pages 1-
Volume 53, Issue 4
Displaying 1-6 of 6 articles from this issue
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INTEGRATED PAPER
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Shuji KATO2005 Volume 53 Issue 4 Pages 183-202
Published: 2005
Released on J-STAGE: April 05, 2006
JOURNAL FREE ACCESSGas phase ion chemistry using the selected ion flow tube (SIFT) technique is discussed with the focus on fundamental studies on ion structure, energetics, reactivity, and dynamics: Laser-induced fluorescence (LIF) kinetics/dynamics of N2+(v) ions (vibrationally state-selected ion-molecule reactions; energy transfer processes), mechanisms of prototypical organic ion reactions (SN2 nucleophilic substitution and kinetic isotope effects; hydrogen/deuterium exchange; isotope effects in termolecular association), and ion-molecule reactions with biological implications (SN2 reactions at a nitrogen center; ECO2 elimination reactions of alkyl hydroperoxides). Anion chemistry of small nitroalkanes is also presented. A powerful combination of SIFT and negative ion photoelectron spectroscopy is used to study thermochemistry and structure of energetic and exotic ions (alkyl peroxides; anionic derivatives of diazo and azole compounds, cyclooctatetraene, and cyclopentanone). Finally, some of the new directions in SIFT research are discussed, i.e., reactions of ions with polyatomic organic radicals, and chemical ionization mass spectrometry with new detection schemes.View full abstractDownload PDF (1232K)
REGULAR PAPERS
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—Formation and Stability of C10 and C2nH2 (n =2–5)—Yoshiyasu KATO, Tomonari WAKABAYASHI, Takamasa MOMOSE, Tadamasa SHIDA2005 Volume 53 Issue 4 Pages 203-210
Published: 2005
Released on J-STAGE: April 05, 2006
JOURNAL FREE ACCESSThe products from laser ablated graphite under the flow of H2 and He buffer gases were analyzed by time-of-flight (TOF) mass spectroscopy in combination with one-photon ionization of an energy of 10.5 eV/photon. By changing the time interval between the ablation laser pulse and the photoionization laser pulse it was found that the neutral clusters ablated from the graphite have three distinctly different velocities for one and the same value of m/z, which was detected as three separate bunches of TOF mass peaks. The effect of changing the time interval was examined extensively. As a result, it was found that the first component that appeared earlier in the ionization region consisted of various bared carbon clusters Cn with n≥6 and hydrocarbons CnHm with n≥4 and m=1 through 4 while the second and third components that arrived later were C10 and C2nH2 (n=2 through 5) only. This persistence of C10 and C2nH2 at longer delay times was attributed to the robustness of these clusters against collisions occurring in ablated plumes. It was inferred that the robustness is due to the chemical inertness of a monocyclic form for C10 and of a linear polyynic form, H(-C≡C)n-H, for C2nH2. In the He buffer gas heated to 600 K the yield of the third (slowest) component of C10 enhanced drastically, which indicates that thermal collisions in plumes favor the production of this monocycle, which further suggests that the monocycle may play a crucial role in the formation of C60, known as a favored product in hot plumes of ablated graphite.View full abstractDownload PDF (856K) -
Tadashi ARII2005 Volume 53 Issue 4 Pages 211-216
Published: 2005
Released on J-STAGE: April 05, 2006
JOURNAL FREE ACCESSA new evolved gas analysis-mass spectrometry (EGA-MS) equipped with a skimmer interface system and a pressure control function (PCF) has been developed successfully. The skimmer interface system based upon jet separator principle is constructed between a sample chamber surrounded by an electrical furnace and a vacuum chamber. Although the skimmer type is principally more excellent than a capillary type, it is a significant problem that the sensitivity of EGA-MS falls with increasing the temperature. The fall of detection sensitivity of EGA-MS depending on temperature rising has been remarkably improved by introducing the pressure control function (PCF). As the result of evaluating PCF by using the thermal decomposition of calcium oxalate monohydrate, the ionic intensities of the evolved gases increased more than twice. The new EGA-MS was applied to the thermal decomposition of zinc acetylacetonate monohydrate and polymethylmethacrylate (PMMA). It was confirmed that the more sensitive and precise gas analysis which prevented condensation of evolution gases and/or generation of by-products can be performed, by comparing with the capillary interface system of TG-MS.View full abstractDownload PDF (498K) -
Mayuko ISHIDA, Masayoshi IMAGAWA, Takao SHIMIZU, Ryo TAGUCHI2005 Volume 53 Issue 4 Pages 217-226
Published: 2005
Released on J-STAGE: April 05, 2006
JOURNAL FREE ACCESSIn the current studies, we examined the molecular species of lysophosphatidic acids (lysoPAs) and their precursors in human plasma. We first examined the extraction of phospholipids under highly acidic conditions, which have been reported to allow high recovery of lysoPAs. Capillary liquid chromatography/electrospray ionization mass spectrometry (LC/ESIMS) revealed a variety of phospholipids, including lysophosphatidylethanolamines (lysoPEs), lysoPAs, and lysophosphatidylmethanols (lysoPMEs). However, we found that most of lysoPMEs and part of lysophosphatidylcholines (lysoPCs), lysoPEs, and lysoPAs were artifacts generated by hydrolysis under acidic extraction conditions. In contrast, a solid phase method was effective for the extraction of lysophospholipids, including lysoPAs. Analysis of the solid phase-extracted lipids obtained from plasma by LC/ESIMS (C18 column), followed by neutral loss scanning and product ion scanning, indicated that acyl 16 : 0, 18 : 0, 18 : 1, 18 : 2, 20 : 4, and 22 : 6 lysoPEs are present in human plasma. Furthermore, following incubation of plasma at 37°C, there was an increase in lysoPAs. On the other hand, the levels of some molecular species of lysoPCs and lysoPEs were reduced, indicating that lysoPCs and lysoPEs are precursors of lysoPAs in human plasma.View full abstractDownload PDF (1033K)
COMMUNICATION
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Hiroaki SUZUKI, Tohru YAMAGAKI, Kazuo TACHIBANA2005 Volume 53 Issue 4 Pages 227-229
Published: 2005
Released on J-STAGE: April 05, 2006
JOURNAL FREE ACCESSThe combination of harmine and ammonium chloride is a useful matrix in detecting the chloride ion adducts of neutral oligosaccharides in negative-ion MALDI-TOF mass spectra. Sandwich method is the best way to prepare the mixed crystals of matrix, analyte, and additive on the target. Changing the molar ratio of ammonium chloride additive from 0 to five times the amount of harmine matrix, the relative intensity of the chloride ion adducts of the analyte molecules to the deprotonated matrix molecular ion ( [Analyte+Cl]-/ [Matrix-H]-) increases logarithmically. A ratio of several times the amount of additive to matrix works most effectively in the formation and detection of the chloride ion adducts of the neutral oligosaccharides as opposed to an amount of additive that is on the same order as the analytes.View full abstractDownload PDF (158K)
REVIEW
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Shuichi SHIMMA, Mitsutoshi SETOU2005 Volume 53 Issue 4 Pages 230-238
Published: 2005
Released on J-STAGE: April 05, 2006
JOURNAL FREE ACCESSImaging mass spectrometry is a novel visualization method for a spatial distribution of biomolecules. This technology is regarded as a next generation mass spectrometry. Therefore many institutes study with several approaches and report on this new technology. We review the recent progress of imaging mass spectrometry presented at the 52nd ASMS conference 2004, and propose a new technology mass-microscope emerging from high resolution imaging mass spectrometry.View full abstractDownload PDF (2051K)
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