JMSSJ On-line Abstracts, Vol.49, No.4 (2001)

Prediction of Cleavage Sites for Polymers in SIMS by MO Calculations

English

Kazunaka ENDO ( Department of Chemistry, Faculty of Science, Kanazawa University (Kanazawa 920-1192, Japan) )

J. Mass Spectrom. Soc. Jpn., 49(4), 135-143, 2001

The cleavage sites of representative polymers in time-of-flight(TOF)- and static(S)-secondary ion mass spectrometry (SIMS) can be estimated from the two-center bond energies of the electric neutral model oligomers by semiempirical MO calculations using the AM1 method in MOPAC software. The cleavage of the intramolecular bonds may be classified into three cases; a) the scission can occur in any bonds [polyethylene, poly-(vinyl methyl ether), polyacrylonitrile, poly(vinyl alcohol)], b) the cleavage of the main chain occur in any bonds, after pendant groups break first [poly(vinyl chloride), poly(acrylamide)], c) the main chain carbons with the pendant group break in any bonds of the main chain [poly(vinyl floride), poly(tetrafluoroethylene)]. Examples of the cleavage are also used in secondary positive-ion fragment spectra of conductive polymers. Furthermore, we analyze the decomposition process of nitrocellulose (NC) due to X-ray induced surface damage by the MO calculations using the electric neutral dimer model. The scission of NO₂ groups in the NC is confirmed from the TOF-SIMS measurement.

Peak Shape and Kinetic Energy Release in Charge Inversion Mass Spectrometry

Japanese, English Abstract

Shigeo HAYAKAWA^*a), Masayoshi MORI^a), Nobuaki WATANABE^a), Keizo FUJII^a), Kazuo ARAKAWA^b), and Norio MORISHITA^b) ( ^*a) College of Integrated Arts and Sciences, Osaka Prefecture University (1-1, Gakuencho, Sakai, Osaka 599-8531, Japan) ^b) Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute (1233, Watanuki, Takasaki, Gunma 370-1292, Japan) )

J. Mass Spectrom. Soc. Jpn., 49(4), 144-149, 2001

A trapezoidal peak shape of dissociative ions is observed in the charge inversion mass spectra. The relation between the kinetic energy release (KER) and the peak shape was simulated. Dissociation with a specific KER value having very narrow distribution for both ionic and neutral species affords the trapezoidal peak shape in a mass spectrum. The KER value was evaluated from the full width at half maximum (FWHM) of the trapezoidal peak associated with the CH₃O^- ions formed from CH₃OH⁺ ions in the charge inversion mass spectrum. The KER value showed the good agreement with that evaluated from the velocity distribution of H atom formed from the photo-dissociation of neutral methanol. This agreement demonstrated that the excited neutral methanol dissociated predominantly into the methoxy radical and the hydrogen atom, and that charge inversion mass spectrometry gave the dissociation of energy-selected neutral species.

Microanalysis of Phospholipids of Mammalian Cells by Liquid Chromatography/Electrospray Ionization-Mass Spectrometry

Japanese, English Abstract

Mayuko ISHIDA^*a), Jun HAYAKAWA^a), Masayoshi IMAGAWA^a), and Ryo TAGUCHI^a) (^*a) Faculty of Pharmaceutical Sciences, Nagoya City University (3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-0027, Japan) )

J. Mass Spectrom. Soc. Jpn., 49(4), 150-160, 2001

A fast and sensitive analytical method of phospholipids by capillary liquid chromatography/electrospray ionization-mass spectrometry was applied to the analysis of individual molecular species of phospholipids in mammalian cells with or without previous treatment with phospholipases. Using a quadrupole mass spectrometer, we selected a simultaneous analysis method under four different functions for detection of positive and negative molecular related ions as well as fragment ions. In the analysis of the elution patterns of the phospholipids, a two-dimensional map revealed to be very useful. By the treatment with phospholipases A or phospholipases C, significant decrease of substrate phospholipids in extracted lipid mixture or cells. Increase of products, such as lyso-phospholipids, and diglycerides or ceramides were effectively determined. Especially by the treatment with PLA₁ or PLA₂, accumulation of specific molecular species of lyso-phospholipids, either unsaturated or saturated, were respectively detected. Application of anion exchange column was also examined for effective separation and identification of acidic phospholipids, such as phosphatidylinositol, phosphatidylglycerol, phosphatidylserine, phosphatidic acid, and their lyso-forms. Analyses of these acidic lyso-phospholipids are very important to elucidate their function as lipid mediators.

Effects of Solvents and Additives on Liquid Ionization Mass Spectra of Dialkyl Peroxides

Japanese, English Abstract

Yoshiyuki MOCHIDA,^*a) Gorou ARAI,^a) Shigeo NAKAMURA,^a) and Masahiko TSUCHIYA ^b)(^*a) Department of Applied Chemistry, Faculty of Engineering, Kanagawa University (3-27-1, Rokkaku-bashi, Kanagawa-ku, Yokohama 221-8686, Japan) ^b) Present address: 4-37-27, Kugayama, Suginami-ku, Tokyo, 168-0082, Japan.)

J. Mass Spectrom. Soc. Jpn., 49(4), 161-170, 2001

Appropriate solvents and additives were investigated for liquid ionization (LPI) mass spectra of dialkylperoxides having one peroxy group, such as di-t-butyl peroxide (BB), t-butyl cumyl peroxide (BC), dicumyl peroxide (CC), and having two peroxy groups, such as 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane (BAB), a,a'-bis-(t-butyl peroxy)diisopropyl benzene (BPB), 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne-3 (BYB). When each sample was dissolved only in a solvent (e.g., ethanol, hexane, octane, or toluene), abundant hydrated protonated molecules [M+H+H₂O]⁺ were observed for all samples, but peaks corresponding to protonated molecules [M+H]+ were weak, except for BAB. Addition of butanol to alkane (solvent) increased the abundance of [M+H]⁺, with decrease of [M+H+H₂O]⁺ for BAB, BPB, and BYB. For these compounds (having two peroxy groups), the addition of butanol (BuOH) to the suitable solvent, such as toluene, was effective for producing dominant adduct ions [M+H+BuOH]⁺ with few [M+H+H₂O]⁺. The addition of ethylamine (EA) to any solvent examined was also effective for producing adduct ions [M+H+EA]⁺ for all dialkylperoxides. It is interesting that BB having a symmetric structure gave dominant molecular ions M^{+ ·} even in the ionization condition like LPI. The addition of p-cresol (PC) to a suitable solvent was useful for BB and BAB (both symmetric structures) to produce dominant molecular adduct ions like [M+PC]^{+ ·}. LPI-MS is useful not only for determining relative molecular mass of dialkylperoxides but also for investigating the effects of solvents and various kinds of additives.