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Volume 52, Issue 1
Displaying 1-8 of 8 articles from this issue
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REGULAR PAPER
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Masahiko TSUCHIYA, Takashi TASHIRO, Atsushi SHIGIHARA2004 Volume 52 Issue 1 Pages 1-12
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSStudies of water clusters under atmospheric pressure are very important. In previous methods, however, clusters existing in vacuum at low temperature have been measured. Therefore, the size distributions of observed cluster ions are likely different from those existing at normal conditions. Liquid ionization (LPI) mass spectrometry we have developed provides information about hydrogen-bonded clusters in a gas phase and also at the liquid surface at ambient temperature under atmospheric pressure. Thus, LPI-MS was applied to study water clusters in gas phases. The results indicated that the sizes of water clusters in vapor increased with the temperature of liquid water and those in the air increased with the relative humidity, while they decreased with increasing the temperature of the gas phase. In general, the size distribution of water clusters shows one smooth envelope, except for a few magic numbered clusters. Adiabatic condensation is negligible to occur in this method and thus, LPI mass spectra give useful information about clusters in gas phases under the normal conditions.View full abstractDownload PDF (452K) -
Shoji OKUNO, Ryuichi ARAKAWA, Yoshinao WADA2004 Volume 52 Issue 1 Pages 13-20
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSUnderstanding ion-molecular reactions is suggested to be essential to delineating the mechanisms of matrix-assisted laser desorption/ionization (MALDI) and related ionization methods. To examine the implications of matrix-analyte reactions in the reduction observed in MALDI, copper(II) chloride and riboflavin were analyzed by desorption/ionization on porous silicon (DIOS) mass spectrometry. This system does not require a matrix for soft laser desorption/ionization. The two susbstances were reduced by DIOS as well, and the reduction of riboflavin was accelerated using water as a solvent, as reported in MALDI. The results indicated that target-analyte electron transfer occurs in LDI, although the possibility of matrix-analyte electron transfer in MALDI cannot be excluded.View full abstractDownload PDF (266K) -
Minoru ISHIKAWA, Tomoyo HONDA, Hidefumi YOSHII, Toshihiko IKEDA, Haruo ...2004 Volume 52 Issue 1 Pages 21-28
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSAfter oral administration of 14C-labeled gemfibrozil to male dogs, ten metabolites of gemfibrozil, designated as dog metabolite (DM)-1, DM-2, DM-3, DM-4, DM-5-1, DM-5-2, DM-6, DM-7, DM-8, and DM-9, were detected in the urine. Structural analysis of these metabolites by mass spectrometry and tandem mass spectrometry in various ionization modes demonstrated that DM-1, DM-2, DM-3, DM-4, DM-5-1, DM-5-2, and DM-6 were previously unreported metabolites of gemfibrozil. With the exception of DM-8 and DM-9, the gemfibrozil metabolites in dog urine were conjugated metabolites produced by glucuronidation at the carboxylic acid group and the phenolic hydroxyl group generated metabolically or by sulfo-conjugation at the phenolic hydroxyl group. Interestingly, DM-1 and DM-2 were demonstrated to be unique, doubly conjugated forms of DM-9. In DM-1, glucuronidation had occurred at both the carboxylic acid group and phenolic hydroxyl group. In DM-2, sulfo-conjugation at the phenolic hydroxyl group and glucuronidation at the carboxylic acid group had occurred. Therefore, the dogs were found to possess enzymatic mechanisms that glucuronidate or sulfo-conjugate already conjugated metabolites, converting water-soluble metabolites to hydrophilic metabolites.View full abstractDownload PDF (294K)
NOTE
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Toshiyuki SHINOZUKA, Mitsuhiro SHIBATA, Tatsuaki YAMAGUCHI2004 Volume 52 Issue 1 Pages 29-32
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSThis study involved the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) to determine the molecular weight distribution of the humic substances, humic acid (HA), and fulvic acid (FA), extracted from peat and soil. The results of MALDI-TOF-MS were compared with the conventional method of high performance size exclusion chromatography (HPSEC) for determining the molecular size distribution of the humic substances. The number-average molecular weight (Mn) of peat-based HA, peat-based FA, soil-based HA, and soil-based FA evaluated by MALDI-TOF-MS were 3,700, 2,900, 10,500, and 9,700, respectively. These results indicate that FA has a lower molecular weight than HA in samples of the same origin, and peat-based HA and FA have considerably lower molecular weights than soil-based HA and FA.View full abstractDownload PDF (129K)
REVIEW
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Ryuichi ARAKAWA, Shoji OKUNO, Yoshinao WADA2004 Volume 52 Issue 1 Pages 33-38
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSThe soft laser desorption/ionization represented by matrix-assisted laser desorption/ionization is currently an indispensable method of analyzing a wide variety of compounds including biopolymers, synthetic polymers, endocrine disruptors, and metal complexes. In order to make the best of its potentials, a number of related techniques have been developed, being focused on sample preparation, matrix usage, sample targets, and mass analyzers. This review collects noticeable advances in these topics to suggest the directions of further investigation.View full abstractDownload PDF (179K)
REGULAR PAPER
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Yoshikazu ADACHI, Tomoyuki TAKAHASHI2004 Volume 52 Issue 1 Pages 39-44
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSThis paper presents a liquid chromatography-electrospray ionization-mass spectrometric (LC-MS) screening and identification procedures for drugs and toxic substances from forensic biological materials such as postmortem blood, urine, and tissues (so-called general unknown screening or systematic toxicological analysis). Gas chromatoraphy-mass spectrometry (GC-MS) has been the method of choice for toxicological analysis of volatile substances while non-volatile and/or thermally labile substances need LC-MS for identification. To develop the LC-MS procedures for forensic analysis, mass spectra library and retention indices, like in the case of GC-GM, are required. Retention indices were determined according to the retention times on the chromatographic separation using a Waters Symmetry C18 (particle size 3.5 μm), 2.1 mm × 150 mm column with a gradient of methanol and 10 mM ammonium acetate (pH 6.8) delivered at a 0.2 mL/min flow rate. Retention times of substances were then converted to retention indices based on those of uracil, phenol, methylparaben (methyl-p-hydroxybenzoate), ethylparaben (ethyl-p-hydroxybenzoate), propylparaben (propyl-p-hydroxybenzoate), butylparaben (butyl-p-hydroxybenzoate), and heptylparaben (heptyl-p-hydroxybenzoate) in the retention index standard mixture. Mass spectra library was made applying two different cone voltages (20 V and 60 V) both in the positive and negative ion modes for in-source fragmentation due to collision-induced dissociation. Mass spectra obtained presented the molecular-related ion and number of specific fragment ions sufficient for identification. The combination of the retention index, molecular-related ion and fragment ions has made LC-MS a preferred method for general unknown screening in the field of forensic toxicology to GC-MS.View full abstractDownload PDF (181K)
TECHNICAL REPORT
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Satoko TOKIWA, Toshikazu NISHIDE, Akio HASHIZUME, Nobuyoshi MIYABAYASH ...2004 Volume 52 Issue 1 Pages 45-50
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSPattern coefficients (PC) of H2O using temperature programmed desorption mass spectrometry (TPDMS) were determined by using TPD curves of m/z 1, 16, 17, and 18 generated from H2O adsorbed on silica gels. TPD curves of m/z 1, 16, 17, and 18, which corresponded to H2O and its fragments were obtained by a quadrupole mass spectrometer (QMS) equipped with the TPDMS apparatus. The H2O pattern coefficients for m/z 1, 16, 17, and 18 were determined to be 16.8, 2.12, 26.4, and 100, respectively. The values were different from those supplied by QMS company especially for m/z 1. Our PC data determined for the TPDMS reasonably explain the TPD curves for CaC2O4·H2O.View full abstractDownload PDF (194K)
COMMUNICATION
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Koki HIIZUMI, Fumiyuki NAKAGAWA, Kazuo FUJITA, Masayumi ISHIDA, Keiich ...2004 Volume 52 Issue 1 Pages 51-54
Published: 2004
Released on J-STAGE: October 28, 2005
JOURNAL FREE ACCESSThe gas-phase clustering reaction, OCS+(OCS)n-1+OCS=OCS+(OCS)n, was investigated using a pulsed-electron beam high-pressure mass spectrometer. The bond energies of OCS+(OCS) and OCS+(OCS)2 were determined to be 23.9 and 7.8 kcal/mol, respectively. The sudden drop of the bond energies OCS+(OCS)→OCS+(OCS)2 indicates the covalent bond formation in the dimer cation (OCS)2+ and the interaction in the trimer cluster ion (OCS)2+ … OCS is mainly electrostatic.View full abstractDownload PDF (172K)
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