Toshihiro Fujii

Alkali-metal ion/molecule association reactions and their applications to mass spectrometry

This review will be concerned primarily with thermal alkali-metal ion association reactions of the general type: A+ + M + N reversible (A + M)+ + N. Where A denotes a positively charged alkali metal ion, M is neutral species and N works as a third body. As indicated, most association reactions are reversible, and the A-M bond derives primarily from electrostatic forces whose energy (affinity) is typically 50 kcal/mol or less, often much less. The review includes reaction mechanism, instrumentation, and application to mass spectrometry, together with reaction rates and alkali ion affinities of the classified compounds.

Lead isotope ratios of airborne particulate matter as tracers of long‐range transport of air pollutants around Japan

The use of airborne lead isotope ratios as tracers of long-range transport of air pollutants in the Asian region was evaluated using air trajectory analysis. Airborne particulate matter was collected in various seasons from 1988 to 1991 at the Oki Islands located between the Asian continent and Japan. Air masses coming from Japan had lead isotope ratios nearly equal to those measured on mainland Japan. Air masses from the Asian continent had less radiogenic isotope ratios than those from Japan. Trajectory analysis showed that these less radiogenic values could be used to further subdivide Asian air masses as having come from one of three regions: the southern part of the Korean Peninsula, north China, and Russia. The isotope ratios of the samples classified into three regions were close to previously reported values measured in each region, except for those assigned to Korea, where it is believed that the ratios are currently changing. It was concluded that lead isotope ratios were reliable tracers of the long-range transport of air pollutants, especially when used in conjunction with air trajectory analysis.

Torsional barrier, ionization potential, and electron affinity of biphenyl—A theoretical study

The structure and torsional barriers at 0° and 90° for biphenyl were studied by both ab initio and density functional methods by using various levels of theory with different basis sets. The torsional angle (φ) calculated at the MP2/6-311+G(2d,2p) level was 42.1°, while φ calculated using various density functionals with different basis sets was close to 40°. In contrast with the ab initio results, the torsional barrier at 0° [ΔE0=E(φ=0°)−E(equilibrium)] obtained using various density functionals coincided well with experimental values. The torsional barrier ratio (ΔE90/ΔE0) obtained at the B3LYP/cc-pVTZ level, 1.0988, agreed well with the experimental value, 1.0833, whereas it was 0.416 at the MP2/6-311G(d,p) level. Structural studies on biphenyl ions showed that the biphenyl cation has a nonplanar (φ=19°) structure whereas its anionic counterpart has a planar structure. The ionization potential obtained at the B3LYP/6-311+G(2d,2p) level was 7.86 eV. Contrary to an earlier study, a positive electron affi...

A novel method for detection of radical species in the gas phase: usage of Li+ ion attachment to chemical species

Abstract This report describes a new method for detection and identification of intermediate radical species in the gas phase. It provides mass spectra of quasi-molecular ions formed by lithium-ion attachment to the radical species (R) under high pressure. Results are obtained in the form of a mass spectrometric trace of Li + adduct radicals. As an example, the method was applied to the study of the microwave discharge in i -butane/He and was successfully used for the qualitative analysis of the compositions of hydrocarbon radicals in the discharge. Various kinds of hydrocarbon radicals, such as C n H 2 n −1 and C n H 2 n +1 (where n =2–6), were identified.

Surface ionization mass spectrometry of organic compounds. I. Nitrogen-containing aliphatic organic compounds

Abstract The surface ionization mass spectra of thirty nitrogen-containing aliphatic organic compounds, which are classified by the functional group, were measured using a quadrupole mass spectrometer with the thermionic source being a rhenium oxide emitter. The spectra are presented in the form of a table, which includes relative sensitivity, possible ion composition and the optimum emitter temperature along with the classified compound. The results are interpreted in terms of the three modes of ion formation, i.e. molecular surface ionization, dissociative surface ionization and associative surface ionization. The surface ionization mass spectrometry is particularily well suited to the application of alkylamines, aminoalcohols, quaternary ammonium salts nd hydrazines, which exhibit an intense molecular ion, together with diagnostic ions for structural determinations.

Determination of monoterpene hydrocarbons in the atmosphere

Abstract A gas chromatographic—mass spectrometric technique for the analysis of trace concentrations (sub-ppb*) of monoterpenes in the air is descrbed. Samples wre collected on Tenax GC adsorbent and thermally desorded onto the analytical column for separation and detection by selected ion monitoring. Experimental results are given for different kinds of forests in the Tsukuba district of Japan. The diurnal variation of the monoterpene concentration in the atmosphere was also measured in a pine forest.

Ion attachment mass spectrometry combined with infrared image furnace for thermal analysis: evolved gas analysis studies.

A well-established ion attachment mass spectrometer (IAMS) is combined with an in-house single-atom infrared image furnace (IIF) specifically for thermal analysis studies. Besides the detection of many chemical species at atmospheric pressure, including free radical intermediates, the ion attachment mass spectrometer can also be used for the analysis of products emanating from temperature-programmed pyrolysis. The performance and applicability of the IIF-IAMS is illustrated with poly(tetrafluoroethylene) (PTFE) samples. The potential of the system for the analysis of oxidative pyrolysis is also considered. Temperature-programmed decomposition of PTFE gave constant slopes of the plots of temperature versus signal intensity in a defined region and provided an apparent activation energy of 28.8 kcal/mol for the PTFE decomposition product (CF(2))(3). A brief comparison with a conventional pyrolysis gas chromatography/mass spectrometry system is also given.

Simultaneous measurements and determinations of stable carbon and nitrogen isotope ratios, and organic carbon and nitrogen contents in biological samples by coupling of a small quadrupole mass spectrometer and modified carbon-nitrogen elemental analyzer

Abstract A simple and rapid method for simultaneous measurements of 13 C/ 12 C and 15 N/ 14 N ratios and organic C and N contents in biological samples at microgram levels by coupling of QMS and modified CHN elemental analyzer was examined for the use of stable carbon and nitrogen isotope as a tracer. Monitoring of CO 2 (m/z=44 and 45) and N 2 (m/z=28 and 29) ion currents due to the combustion product gas by the elemental analyzer allows simultaneous measurements of both isotope ratios within 0.5 % at 10–500 microgram. Organic C and N contents were determined within 5–12 % relative standard deviation at the same levels, depending upon the combustion conditions.

Surface ionization of volatile organic compounds on a hot rhenium filament. A potentially valuable ionization technique in organic mass spectrometry

Abstract Positive thermionic emission of twelve volatile organic compounds from a Re filament exposed to oxygen has been studied by use of mass spectrometry. The results are interpreted in terms of a simple model which involves formation of surface reaction products followed by surface ionization. The newly defined relative sensitivity (A torr −1 ), the maximum ion currents of the base peak emitted per torr of sample molecules, varies very widely from sample to sample. A pressure of 1.1 × 10 −7 torr of trimethylamine yields an (M-H) + ion current of 9.4 × 10 −6 A as determined using the mass spectrometer with an ion multiplier at a gain of 5 × 10 3 , which is 230 times greater than that of a conventional electron bombardment peak.

Analysis of N-containing Hydrocarbon Species Produced by a CH4/N2 Microwave Discharge: Simulation of Titan’s Atmosphere

We report the production of gaseous hydrocarbons, nitriles, and amines in a continuous-flow microwave (MW) plasma discharge excited in a 10% CH4+90% N2 mixture at a pressure of 20 torr. The product analysis was made by Li+ ion attachment mass spectrometry (Li+MS), which is suitable for identifying neutral species in the plasma, since Li+MS provides only molecular ions without any fragmentation. Since these experiments are, by design, potentially relevant to the atmospheric chemistry in Titans stratosphere, the products were compared to those obtained from spacecraft observation and laboratory simulations. Our experiments detected more than 70 gaseous species, including 24 nitriles, 10 amines, and possibly some hydrazines. All the species found by the Voyager fly-by of Titan were detected in our simulation system. There was good agreement between our MW plasma and previous simulation experiments. These results suggest that MW discharge plasma may be a valid simulation of processes that occur in planetary atmospheres.