JMSSJ On-line Abstracts, Vol.47, No.5 (1999)

Sonic Spray Ionization and Ion Formation Processes

Atsumu HIRABAYASHI^* (^*Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo 185-8601, Japan)

J. Mass Spectrom. Soc. Jpn., 47(5), 289-296, 1999

Sonic spray ionization technique has been developed as an interface in LC/MS and CE/MS. In this tech-nique, 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, orsta-tistical 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.

Computational Assessment of Sustained Off-Resonance Irradiation (SORI) in a Cubic FTICR Ion-Trap

Yasuhide NAITO^*,** (^*The Institute of Physical and Chemical Research, RIKEN, 2-1 Hirosawa, Wako-shi 351-0198, Japan, ^**Present Address: Japan Advanced Institute of Science and Technology, JAIST, School of Materials Science, 1-1 Asahi-dai, Tatsunokuchi, Ishikawa 923-1292, Japan)

J. Mass Spectrom. Soc. Jpn., 47(5), 297-303, 1999

Trajectories 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). There lationship between the initial position of theex-citedion and the translational energy was explored; to give apractical 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.

Tandem Mass Spectrometric Studies on the [C₅H₈O₂]^{+ ·} Ions from Angeric Acid and Tigric

Ikuo SAKAI^a) and Tadakuni TAJIMA^b) (^a)Toray Research Center, Inc., 1111 Tebiro, Kamakura 248-8555, Japan, Present Address: Koriyama Women's University, 3-25-2 Kaisei, Koriyama 963-8851, Japan, ^b)Toray Research Center, Inc., 1111 Tebiro, Kamakura 248-8555, Japan)

J. Mass Spectrom. Soc. Jpn., 47(5), 304-309, 1999

Collision 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.

Unimolecular Metastable Decomposition of Ionized 2-Hydroxy-2-methylpropanoic Acid and Its Methyl Ester

Yutaka TAKAHASHI,^*a) Tetsuo HIGUCHI,^a) Osamu SEKIGUCHI,^*b) Chinatsu TANAKA,^b) Satoshi NAKAJIMA,^b) and Susumu TAJIMA^*b) (^a)MS Application Laboratory, Application and Research Center, JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-0021, Japan, ^b)Chemistry and Materials Science, Gunma National College of Technology, 580 Toribamachi, Maebashi, Gunma 371-0845, Japan)

J. Mass Spectrom. Soc. Jpn., 47(5), 310-314, 1999

Unimolecular 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-hydroxy-butanoic 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-CH₃]⁺ 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 SDH_f is larger than that with a high SDH_f (SDH_f 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)COOCH₂CH ₃ (4), which are isomers of 2 and 1, so-called double hydrogen atom migration was absent in the cases of 1 and 2.

Measurement Method of Carbohydrate Metabolism during Prolonged Exercise by Monitoring ¹³CO₂ as Tracer

Jun FUTAMI,^*a) Isao NISHI,^b) and Yoshio EN^c) (^*a)Department of Economic Informatics, Faculty of Economics, Higashi Nippon International University, 37 Suganezawa, Kamata, Taira, Iwaki-city, Fukushima 970-8567, Japan, ^b)Department of Electronics and Computer, Faculty of Science and Engineering, Science University of Tokyo in Ymaguchi, 1-1-1 Daigakudori, Onoda-city, Yamaguchi 756-0884, Japan, ^c)Institute of Exercise Physiology, Nippon Sport Science University, 7-1-1 Fukasawa, Setagaya-ku, Tokyo 158-8508, Japan)

J. Mass Spectrom. Soc. Jpn., 47(5), 315-317, 1999

The 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.