All issues
Volume 44 (1996)
- Issue 6 Pages 563-
- Issue 5 Pages 501-
- Issue 4 Pages 461-
- Issue 3 Pages 293-
- Issue 2 Pages 105-
- Issue 1 Pages 1-
Volume 44, Issue 5
Displaying 1-3 of 3 articles from this issue
- |<
- <
- 1
- >
- >|
INTEGRATED PAPER
-
Mitsuo TAKAYAMA1996 Volume 44 Issue 5 Pages 501-530
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSSome ideas have been presented to understand ion formation under matrix fast atom bombardment (FAB) conditions. A state of hydrogen-bonding hydrophilic solvation, named “quasi-preformed state”, has been introduced to explain the ion formation reflecting condensed-phase, and the both “quasi-preformed state” and a state of “preformed ion” have been defined on the basis of the Bjerrum's proposition for ion-pairs in solution. Some examples of preformed ion have been described. The extents of electronic excitation leading to the formation of molecular ions M+·, under matrix FAB conditions, have been examined by detecting FAB-induced fluorescence from a thin layer of alkali-halides (LiCl, NaCl, KCl, and CsCl), and by using some compounds of which ionization energies are known. The results obtained indicate that matrix FAB conditions are sufficient in energy for M+· formation (by about 10 eV electronic excitation) and are insufficient for M2+ formation (by about 20 eV electronic excitation). The mechanisms of the formation of various ions, [M+H]+, [M+Na]+, [M-H]+, M+·, M-·, and [M-H]-, under matrix FAB conditions have been described. A model for FAB ionization, named “cavity” model, has been introduced to deal quantitatively with the rate of ion formation or ion yields from matrix surface. The “cavity” model requires that the ion formation occurs in both processes, i) the collision cascade reflecting condensed-phase and ii) the ion/molecule reactions reflecting gas-phase. The influence of fast atom species (He, Ar, and Xe) on the ion yields which may directly relate to the size of cavity or crater has been examined by comparing with the spectral patterns in the gas-phase FAB mass spectra of m-nitrobenzyl alcohol. It has been roughly estimated that a “cavity” formed with Ar or Xe beam contains several 100 molecules.View full abstractDownload PDF (1911K)
REGULAR PAPERS
-
Mitsuo TAKAYAMA, Kenzo HIRAOKA, Hisao NAKATA1996 Volume 44 Issue 5 Pages 531-541
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSMass spectra of methyl stearate (1) obtained under low energy (8-13 eV) electron ionization (EI) conditions showed intense [M+H]+ ions and abundant fragment ions in the positive-ion mode, and intense [M-H]- ions and characteristic fragment ions in the negative-ion mode. Positive-ion mass spectra of 1 under 8-13 eV/EI conditions showed an interesting ion at m/z 75 which may originate from a McLafferty rearrangement reaction of the [M+H]+ ions, an even electron species. The detailed experimental conditions to reproduce these spectra have been explored. It was found that the most important condition is the introduction into the ionizing cell of a relatively high-pressure sample vapor from a liquid state, similar to a spray process, and that the abundant fragment ions come from the [M+H]+ ions. Possible mechanisms are discussed to explain the formation of [M+H]+, [M-H]-, and abundant fragment ions under the 8-13 eV/EI conditions. Furthermore, unusual ion species such as [M+K]+, [M+Na]+, [M+H]+, [M-H]+, K+, and Na+ were observed in the mass spectrum of 1 obtained at the lowest energy (2 eV) EI conditions, suggesting that thermal surface ionization occurred on the Re filament.View full abstractDownload PDF (621K) -
Toshitaka OHSHITA, Reona MIYAMOTO, Keizo HARAFUJI1996 Volume 44 Issue 5 Pages 543-551
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSAfter opium ingestion, it is possible to obtain the same analytical results with regard to the presence of morphine in the urine sample as after abuse of diacetylmorphine (heroin). Therefore, it is difficult to determine the abused drug only from the fact of morphine presence in the urine sample. This study was aimed at examining whether the abused drug could be determined from urine samples by detection of morphine and its analogs. Morphine and its analogs in the human urine samples were directly extracted and the extracts were analyzed by capillary GC and identified mass spectrometrically by full mass spectra. In the results, the urine samples were classified into 3 groups: 1) heroin with 6-acetylmorphine or 6-acetylmorphine, 2) thebaine with desmethylpapaverine or desmethylpapaverine, 3) others.
The above data suggest that our method is capable of detecting morphine and its analogs in the urine samples, and giving useful informations for determination of the abused drugs.View full abstractDownload PDF (552K)
- |<
- <
- 1
- >
- >|