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Volume 47 (1999)
- Issue 6 Pages 319-
- Issue 5 Pages 289-
- Issue 4 Pages 251-
- Issue 3 Pages 97-
- Issue 2 Pages 67-
- Issue 1 Pages 2-
Volume 47, Issue 5
Displaying 1-5 of 5 articles from this issue
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INTEGRATED PAPER
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Atsumu HIRABAYASHI1999 Volume 47 Issue 5 Pages 289-296
Published: 1999
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSSonic spray ionization technique has been developed as an interface in LC/MS and CE/MS. In this technique, a solution from a capillary is sprayed with a sonic gas flow coaxial to the capillary, and gas-phase ions and charged droplets are formed under atmospheric pressure. The amount of the produced ions depends on the gas velocity and has a maximum at the sonic velocity. The origin of the charged species cannot be ascribed to the traditional models of friction electrification, electrical double layer formed near the capillary surface, or statistical charging. An explanation is proposed based on nonuniformity of positive and negative ion concentrations near the solution surface caused by the surface potential. Based on the explanation, we have modified our technique to regulate the nonuniformity by applying an external electric field to the solution surface. Then, the ion amount is found to be dramatically enhanced and multiply-charged ions are readily formed. The analysis of the droplets produced from a nonvolatile solution also shows that the abundance of the droplets having charge numbers close to the Layleigh limit increases as the external electric field increases. These results suggest that ions are readily formed from solutions having a very wide range of chemical properties and flow rates, since highly-charged droplets are produced from the solutions by the shear stress due to the sonic gas flow.View full abstractDownload PDF (860K)
REGULAR PAPERS
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Yasuhide NAITO1999 Volume 47 Issue 5 Pages 297-303
Published: 1999
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSTrajectories of an ion undergoing sustained off-resonance irradiation (SORI) in Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) were examined by means of computer simulations, which take account of non-uniform excitation and trapping electric fields within a cubic FTICR ion-trap. The equation of motion used for the simulations also contains a friction term proportional to the ionic velocity, reflecting a collisional damping of the motion (viscous drag model). The relationship between the initial position of the excited ion and the translational energy was explored; to give a practical index of the collision energy in SORI-collisional activation. The translational energy appears to be independent of the initial z-displacement of the ion. In contrast, the initial magnetron radius represented by the initial x-displacement is a sensitive factor for the translational energy. It is suggested that a diffusion of a trapped ion cloud in the course of a trapping may affect the precision of the collision energy in a controlled SORI-collisional activation. This trajectory simulation can provide a better insight into the energetic property of SORI than a conventional theoretical approach based on a statistical kinetics and a uniform electric field, and may be an effective tool to estimate an availability of collision energy range unless scattering of activated ions becomes a dominant process in the SORI dynamics.View full abstractDownload PDF (855K) -
Ikuo SAKAI, Tadakuni TAJIMA1999 Volume 47 Issue 5 Pages 304-309
Published: 1999
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSCollision activated dissociation (CAD) spectra and metastable ion (MI) spectra of the [C5H8O2]+· ions from various esters of angeric acid and tigric acid have been studied. The [C5H8O2]+· ions formed upon the McLafferty rearrangement from the precursor esters of these acids were identified as the same structures of the molecular ions directly produced by electron impact ionization of angeric acid and tigric acid respectively on the basis of CAD spectral evidence. The cis-trans isomerization of the acids can occur during ionization or subsequent fragmentation of the lower internal energy ions which proceed via unimolecular metastable decompositions. We have provided an example that the isomeric ions can be distinguished by the ion abundance enhancement by high energy collisional activation on the specific fragmentation reactions of the [C5H8O2]+· ions.View full abstractDownload PDF (508K) -
Yutaka TAKAHASHI, Tetsuo HIGUCHI, Osamu SEKIGUCHI, Chinatsu TANAKA, Sa ...1999 Volume 47 Issue 5 Pages 310-314
Published: 1999
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSUnimolecular metastable decompositions of ionized 2-hydroxy-2-methylpropanoic acid, (CH3)2C(OH)COOH (2), and its methyl ester, (CH3)2C(OH)COOCH3 (1), have been investigated by means of mass-analyzed ion kinetic energy (MIKE) spectrometry and D-labeling technique. The abundances of the molecular ions of 1 and 2 are too weak to measure their MIKE spectra. The source-generated m/z 59 ions, (CH3)2C+(OH), decompose into the ions at m/z 41 and 31 by losing H2O and C2H4, respectively, in the metastable time window. The ion abundance ratio ([m/z 31]/[m/z 41]) was 1.6 for 1 and was 2.2 for 2. This contrasts to the case of CH3CH2C+(OH) from 2-hydroxybutanoic acid, CH3CH2CH(OH)COOH (5) which leads predominantly to H2O loss ([m/z 31]/[m/z 41] is 0.12). A partial hydrogen exchange between the hydroxyl and methyl groups occurs prior to the H2O and C2H4 losses from the m/z 59 ion for 1, but the extents are different from each other. The extent of the exchange increases with decreasing the mean internal energy of the precursor ion. Most of the [M-ĊH3]+ ions at m/z 103 and 89 for 1 and 2 decompose into the ions at m/z 75 and 61, respectively, by the loss of CO. These reactions occur through a 1,2-skeletal rearrangement of OCH3 or OH. In the MIKE spectrum, the abundance of ion with a low value of ΣΔHf is larger than that with a high ΣΔHf (ΣΔHf is the sum of heats of formation of the fragment ion and the neutral species lost.). In contrast with the case of methyl and ethyl 2-hydroxypropanoates, CH3CH(OH)COOCH3 (3) and CH3CH(OH)COOCH2CH3 (4), which are isomers of 2 and 1, so-called double hydrogen atom migration was absent in the cases of 1 and 2.View full abstractDownload PDF (441K)
COMMUNICATION
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Jun FUTAMI, Isao NISHI, Yoshio EN1999 Volume 47 Issue 5 Pages 315-317
Published: 1999
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSThe discriminative measurement method of the dynamic metabolic change of an administered glucose and a pre-reserved carbohydrate is clearly demonstrated during the prolonged exercise (75 W bicycle ergometer work). The administered glucose is an ordinary commercial available medical use. The isotopic abundance difference ratio of the glucose is as high as 20‰ comparing to that of the expired CO2 before the administration. This paper proposed the discriminative measurement method and showed a trail measurement for inspecting the method.View full abstractDownload PDF (238K)
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