Mass spectrometer studies

A number of papers concerned with the decomposition behaviour of organic halogen compounds in the mass spectrometer and related systems is to be found in the journal Organic Mass Spectrometry. For example, in the case of fluoro-compounds, McCarthy has discussed mass spectral correlations for fluorinated alkanes studies by other workers have included those on aromatic fluoro-com-pounds , fluorine-containing dimethyl esters , and tetrafluoroethanes . In the same journal, studies on other halogen compounds include dichlorocyclo-propanes , norbornyl chlorides and bromides , j8-phenylethyl bromides , and chloro-substituted benzynes . 

Studies reported in other journals and publications have included those on fluoroaliphatics fluoroaromatics hexafluoro- 

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Yoder R (2003) Electrospray ionisation mass spectrometer study ofdioctyitin compounds in solution. Report provided to Risk Policy Analysts Ltd by the European Tin Stabilisers Association, May. 

A qualitative comparison of the results from the gas chromatography - mass spectrometer study of the different hydrocarbons from the wood materials, did not show significant differences between results from one method to the other. As far as can be judged it is mainly the amount of each component that differs between the small scale test methods and full scale fire tests. 

Atkinson, R., B. J. Finlayson, and J. N. Pitts, Jr. Photoionization mass spectrometer studies of gas phase ozone-olefin reactions. J. Amer. Chem. Soc. 95 7592-7599, 1973. 

Mass spectrometer studies of oxidant additions to fluoro- and chlorocarbon gases have demonstrated that the relative reactivity of atoms with unsaturate species in a glow discharge follows the sequence F -- O > Cl > Br (41), Of course, the most reactive species present will preferentially undergo saturation reactions that reduce polymer formation and that may increase halogen atom concentration. Ultimately, determination of the relative reactivity of the plasma species allows prediction of the primary atomic etchants in a plasma of specific composition. 

A. Me Ilroy, T.D. Hain, H.A. Michelsen, and T.A. Cool. A Laser and Molecular Beam Mass Spectrometer Study of Low-Pressure Dimethyl Ether Flames. Proc. Combust. Inst., 28 1647-1653, 2000. 

Early mass-spectrometer studies (Hogg and Kebarle, 1965 Hogg et al., 1966 Searles and Kebarle, 1968), confirmed later by different groups and techniques (Payzant et al., 1973 Fehsenfeld and Ferguson, 1973 Tang and Casdeman, 1975) of the competitive solvation of NHa by water and ammonia vapors had shown that NHs molecules were taken up preferentially to water, up to an addition of four molecules in the first solvation shell, while water seemed to be preferred over ammonia in the second solvation shell. 

The steps (1 )-(5) represent the likely radical reaction sequence, but it is possible that ionic species, such as those observed in mass spectrometer studies are involved in the primary stage of the reaction. In the case of carbon tetrachloride these would be CCls, Cl, CCl" " and CCI2 as well as the negative ion Cl . 

An enthalpy of sublimation at 298.15 K of 52.1 kcal mol was chosen to fit the vapor pressure data and relative concentrations of monomer, dimer and trlmer as described in the table for LlCl(g). This value is in reasonable agreement with the value of 53.5 kcal mol" from a 3rd law analysis of the vapor pressure data of Nesmeyanov and Sazonov (] ) and the relative concentrations of monomer, dimer, and trlmer from the work of Miller and Kusch (2). Also a value of 54.1 kcal mol was found by Milne and Klein (3) from mass spectrometer studies. 

Nitrogen has been the subject of several investigations employing both mass spectrometer ionization chambers and discharges for the production of ions. The ions of greatest interest are N3+ and N4+. The mass spectrometer studies have shown N3+ to be formed by the reaction ... 

A drift-tube mass spectrometer study of reaction (127) with 0 ( S) ions has also been carried out very recently by Johnsen and Biondi [229]. The experiment covers the energy range 0.04 to 1 eV and confirms the existence of the minimum in the cross-section at around 0.12 eV. The general features are in good agreement with those of Kaneko and Kobayashi. 

A number of additional reactions of the parent and fragment ions with methane have also been proposed by several authors [134, 243, 245—252]. These are, however, either not well established or not important. The tandem mass spectrometer studies by Abramson and Futreir [243, 245] seem to provide fairly decisive information on these reaction channels. 

The tandem mass spectrometer study with partially deuterated propanes and butanes by Abramson and Futrell [275] gave finer details of the mechanism of H and H2 transfer reactions. The more important conclusions obtained in the study of the -butane ion + propene reaction are summarized as (a) there is no H2 elimination from one carbon atom, (b) there is no H2 elimination from 1—3 (2—4) and 1—4 positions, (c) the ratio of the probabilities of 1—2 (3—4) elimination and 2—3 elimination is 1/2, (d) H transfer occurs only from secondary carbons and (e) the intermolecular and intramolecular isotope effects are very small. 

Several techniques have been used to investigate the reactivity of the metal carbide cluster ions formed in a laser vaporization source. The earliest investigations performed by Castleman s group relied on a preliminary mass selection of the desired cluster. The ion beam was then injected into a drift tube where the selected cluster encounters the reactant mixed with helium as a buffer gas. The FTICR (Fourier-transform ion cyclotron resonance) mass spectrometer studies reported by Byun, Freiser and co-workers basically rely on the same principle even though the total pressure of the reaction chamber is 10 torr, compared with 0.7 torr in Castleman s experiments. A new method of forming met-car ligand complexes was then reported by Castleman et al. this involved the direct interaction of the vaporized metal with mixtures of methane and selected reactant gases. ... 

It has recently been established, both in flowing afterglow studies and in mass spectrometer studies " (see also the discussion in Chapter 7), that the reaction... 

F. H. Field and M. S. B. Munson, Reactions of gaseous ions XIV. Mass spectrometer studies of methane at pressures to 2 Torr, J. Am. Chem. Soc. 87, 3289-3294 (1965). E. E. Ferguson, F. C. Fehsenfield, and A. L. Schmeltekopf, Laboratory measurements of ionospheric ion-molecule reactions. Space Research VII, 135-140 (1966). 

Portman R, Quin M, Sagert N et al (1989) A Knudsen cell mass-spectrometer study of the vaporization of cesium telluride and cesium tellurite. Thermochim Acta 144 21-31 Piacente V, Scardala P (1994) A study on the vaporization of copper(II) selenide. J Mater Sd Lett 13 1343-1345... 

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