JMSSJ On-line Abstracts, Vol.50, No.6 (2002)

Negative Chemical Ionization Mass Spectrometric Study on the Dissociative Electron Attachment to Halogenated Ethane

Seiko NAKAGAWA^a),  (^a)Tokyo Metropolitan Industrial Technology Research Institute Radiation Laboratory (Fukazawa ,Setagaya-ku ,Tokyo 158-0081 ,Japan ))

J. Mass Spectrom. Soc. Jpn., 50(6),286-289, 2002

  The temperature dependence for the formation of negative ions from Cl₂BrC-CBrCl₂, FClBrC-CBrF₂, and ClBr₂C-CF₃ was studied using negative chemical ionization mass spectrometry. Halide ions and halogen molecular anions were observed. The intensity ratios between the halide ions and halogen molecular anions were almost equal to F₂BrC-CBrF₂. Halogen molecular anions are produced from halogen atoms presented by each C atom: the four-center elimination. The temperature dependence of the ion intensity ratios, Br^-/Cl^- and Br₂^-/BrCl^-, suggests that the strength of the bonding energy of the C-Cl relative to C-Br increases in the order of Cl₂BrC-CBrCl₂<FClBrC-CBrF₂<ClBr₂C-CF₃.

Matrix Effects on the Chiral Recognition Determined by the Relative Peak Intensity of Diastereomeric Host-Guest Complex Ions Using the FAB Mass Spectrometry/Enantiomer Labeled Guest Method

Motohiro SHIZUMA,^*a) Hitoshi YAMADA,^b) Hiroshi ADACHI,^c) Yoshio TAKAI,^b) Tokuji TAKEDA,^a) and Masami SAWADAb)(^*a) Technochemistry Department, Osaka Municipal Technical Research Institute (1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),290-295, 2002

  The FAB mass spectrometry (MS)/enantiomer labeled (EL) guest method is one of the useful technique to easily evaluate chiral discrimination ability of a chiral host (H) toward chiral guests (G_R⁺, G_S-dn⁺). In this paper, the matrix dependency of the relative peak intensity (IRIS) of the diastereomeric host-guest complex ions [(H+G_R)⁺ and (H+G_S-dn)⁺] was investigated (host, MeFruNys; guest, Phe-O-iPr⁺). The IRIS values of spectra measured using NBA, NPOE, and DTDE matrices agreed almost with the ratio of concentrations of the complex ions calculated from the association constants (K_R and K_S) in chloroform at 298 K. While, the IRIS values of spectra using glycerol matrix reached almost unity. It was assumed that the IRIS values depend upon the matrices used since the difference of solvation ability of the matrices affects the actual concentration of the guest concerning in the complexation. And then, it was recommended that NBA is the best matrix for chiral recognition mass spectrometry studies.

Study of Electron Impact Ionization Cross-sections of Sodium-containing Molecules

Jintao HUANG,^*a) Tomohiro FURUKAWA,^a) Kazumi AOTO,^a) and Michio YAMAWAKI^b)(Graduate School of Engineering, Yamanashi University (^*a) Oarai Engineering Center, Japan Nuclear Cycle Development Institute (4002 Narita, Oarai-machi, Ibaraki, 311-1393, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),296-300, 2002

Ion/molecule reactions in octafluorocyclobutane (c-C₄F₈) were studied using a high-pressure mass spectrometer. The thermochemical stabilities of the cluster ions of halide ions (X^-) with c-C₄F₈ were measured. While the F^- ion forms a covalent bond with c-C₄F₈, the interaction between other halide ions with c-C₄F₈ is mainly electrostatic. Theoretical calculation revealed that the halide ions interact not with the lowest unoccupied molecular orbital but with the next lowest unoccupied molecular orbital of the c-C₄F₈ molecule in the most stable cluster ions X^- (c-C₄F₈). The electron affinity of c-C₄F₈ was measured to be 24.2±2.3 kcal/mol (1.05±0.10 eV) by observing the equilibria for reaction of SF₆^-+c-C₄F₈ = c-C₄F₈^-+SF_6- While the sound equilibrium for that reaction was established in the temperature region from 350 K down to the lowest temperature measured (150 K), that was not established in the higher temperature region above 350 K. This was attributed to the existence of an isomer for c-C₄F₈^- whose electron detachment energy is smaller than 1.05 ev. By the measurement of thermochemical stabilitries of [(O2)m(c-C₄F₈)n]- (m+n = 1-3), the lower electron affinity of c-C4F8 was determined to be 12.0±1.2 kcal/mol (0.52±0.05 eV). The lower limit of the proton affinity of c-C₄F₈ was estimated to be 130 kcal/mol.

Proof of Inclusion Complex Formation between Cyclophane and Aromatic Guests by Fast Atom Bombardment Mass Spectrometry

Koichi METORI,^*a) Yumiko KIMURA,^a) and Muneharu MIYAKE^a)(^*a) College of Pharmacy, Nihon University (7-7-1 Narashinodai, Funabashi, Chiba 274-8555, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),301-303, 2002

  Some obstacles for the analysis of host-guest complexes by proton nuclear magnetic resonance (¹H NMR) are the problem of requiring for a large excess of host, high concentration and high solubility of host and guest in order to get a good resolution. By ¹H NMR spectrometry it is very difficult to detect the complex which the peaks of guest become overlapped by host peaks. Our primary purpose in this report is to judge if fast atom bombardment mass spectrometry (FAB-MS) is a suitable measurement tool for the determination of the host-guest complex stoichiometry in stead of ¹H NMR spectrometry.

Susceptible Region of Myoglobins to In-source Decay Using Matrix-assisted Laser Desorption/Ionization Coupled with Delayed Extraction Reflectron Time-of-Flight Mass Spectrometer

Mitsuo TAKAYAMA*(* Graduate School of Integrated Science, Yokohama City University (22-2 Seto, Kanazawa-ku, Yokohama 236-0027, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),304-310, 2002

  The susceptibility to in-source decay (ISD) in myoglobin, using matrix-assisted laser desorption/ionization (MALDI) coupled with a delayed extraction reflectron time-of-flight (TOF) mass spectrometer, has been described from the standpoint of secondary structures. The ISD data of three different myoglobins showed a common intense product of c35 ion originated from the cleavage of amine bond N-C_α at Gly35-His36 or Ser35-His36 residues. It is suggested that the relatively abundant formation of c35 ion in Gly35-His36 or Ser35-His36 residues is not due to the presence of His36 residue, but due to a turn region between helices in secondary structure of myoglobins.

Development of Quantitative Chiral Recognition Mass Spectrometry

Masami SAWADA(* Materials Analysis Center, The Institute of Scientific and Industrial Research, Osaka University (8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),311-329, 2002

  The developments of our quantitative chiral recognition studies in the host-guest complexations between chiral crown ethers and chiral amino acid esters by FAB, ESI, and MALDI mass spectrometry have been described. Both the enantiomer labeled (EL)-guest method and the EL-host method, which had been previously proposed by us, were successfully advanced. The relative peak intensity (IRIS) values of the diastereomeric host-guest complex ions appeared in mass spectra were especially noted, and their use to chiral recognition was illustrated. Generally, the former method was used to chiral recognition ability-determination of a given host, and the latter one was used to enantiomeric excess (e.e.)-determination of a given guest. Through the manuscript, emphasis has been put on the finding that one can detect correctly the concentration ratio of the two diastereomeric host-guest complex ions formed in a matrix solution by FAB mass spectrometry and then, that FABMS is a powerful tool for detecting chiral host-guest interactions in the host-guest complexation systems. Recent ,e.e.-determination methods by ESI mass spectrometry etc. were also summarized.

Polar Derivatization of 5α-Dihydrotestosterone and Sensitive Analysis by Semimicro-LC/ESI-MS

Yumiko NAKAGAWA and Yutaka HASHIMOTO(^a) Pharmaceuticals Group, Nippon Kayaku Co., Ltd. (3-31-12 Shimo, Kita-ku, Tokyo 115-8588, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),330-336, 2002

  Polar derivatization method for electrospray ionization mass spectrometry (ESI-MS) was developed and applied to the sensitive analysis of 5α-dihydrotestosterone (DHT) in prostate and plasma. Rat prostate was dissolved with alkaline solution and DHT in the prostate was extracted by solid phase extraction, and derivatized to the N-methylpyridinium-DHT as a polar derivative. The N-methylpyridinium derivative of DHT was purified by solid-phase extraction using Bond Elut C18, and determined by a semimicro-LC/ESI-MS with selected reaction monitoring (SRM). Linear responses of the N-methylpyridinium derivative of DHT were observed for analyte concentration from 5 to 100 pg/tube. DHT values were 12.0±3.8 ng/g tissue in rat prostates, 171.7±127.2 pg/mL in rat plasma and 286.2±123.5 pg/mL in human plasma.

The Characteristics of In-source Decay in Mass Spectrometric Degradation Methods - Hydrogen-Attachment Dissociation (HAD) -

Mitsuo TAKAYAMA(* Graduate School of Integrated Science, Yokohama City University (22-2 Seto, Kanazawa-ku, Yokohama 236-0027, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),337-349, 2002

  In-source decay (ISD) combined with matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometer (TOF MS) has been described by comparing with conventional mass spectrometric degradation (MSD) methods such as collision-induced dissociation (CID) and post-source decay (PSD). The ISD characteristic is the formation of c- and (z+2)-ions originated from the N-C_α bond cleavage on the peptide backbone, while the CID and PSD processes are the CO-NH bond cleavage which brings about b- and y-ion. Furthermore, the ISD processes occurring with 337 nm laser photon irradiation for peptide or protein proceed resulting in the formation of hyper-valent radical species via intermolecular hydrogen transfer between matrix and analyte molecules following the non-ergodic N-C_α bond cleavage. The non-ergodic N-C_α bond cleavage occurs in the MALDI ion source within nanosecond order, as an α-cleavage initiated with radical site at the carbonyl carbon. The MALDI-ISD method has been applied to three peptides and five proteins.

Time-of-Flight Studies of Secondary Ions Produced by 400 eV

Makoto WATANABE, Daisuke EGUCHI, Tetsuya SATO, and Kenzo HIRAOKA(^a) Graduate School of Engineering, Yamanashi University (4-3-11 Takeda, Kofu 400-8511, Japan) ^*b) Clean Energy Research Center, Yamanashi University (4-3-11 Takeda, Kofu 400-8511, Japan))

J. Mass Spectrom. Soc. Jpn., 50(6),350-352, 2002

  Secondary ions produced by 400 eV He⁺ ion impact on Ar, Kr, and Xe thin films deposited on a silicon substrate at 8 K were measured as a function of film thickness using a time-of-flight secondary-ion mass spectrometer. For Ar, the cluster ions Ar_n⁺ up to n=4 as well as the monomer ion (n=1) were observed and they showed characteristic film-thickness dependence with increase of the film thickness up to 200 monolayers. This is due to the momentum transfer in the elastic collision between the incident He+ ion and the matrix Ar atoms and also to the relaxation of electronic excitations (e.g., holes and excitons) to phonons resulting in the film erosion. In contrast, neither dimer nor cluster ions were detected for solid Kr and Xe films. This is due to the less efficient momentum transfer in the elastic collision between He⁺ and Rg's (Rg=Kr and Xe) and also to the efficient electronic energy migration in solid Kr and Xe. The C⁺ ions originating from the carbonic contaminants on the silicon substrate were found to be sensitized by the deposition of rare gas films. The penetration depths of the primary ion He⁺ through the rare gas films increase in the order of Ar<Kr<Xe.