Field desorption spectroscopy

Various ionization methods were used to bombard phenol-formaldehyde oligomers in mass spectroscopic analysis. The molecular weights of resole resins were calculated using field desorption mass spectroscopy of acetyl-derivatized samples.74 Phenol acetylation was used to enable quantitative characterization of all molecular fractions by increasing the molecular weights in increments of 42. 

Bob Ardrey obtained a first degree in Chemistry from the University of Surrey where he went on to obtain his doctorate stndying the chemistry of trans-2,3-dichloro-l,4-dioxan and the stereochemistry of its reaction prodncts using primarily mass spectrometry and nnclear magnetic resonance spectroscopy. He then carried ont post-doctoral research at King s College, London, into the development of emitters for field-desorption mass spectrometry. 

The apparatuses used for the studies of both ammonia synthesis emd hydrodesulfurization were almost identical, consisting of a UHV chamber pumped by both ion and oil diffusion pumps to base pressures of 1 x10 " Torr. Each chamber was equipped with Low Energy Electron Diffraction optics used to determine the orientation of the surfaces and to ascertain that the surfaces were indeed well-ordered. The LEED optics doubled as retarding field analyzers used for Auger Electron Spectroscopy. In addition, each chamber was equipped with a UTI 100C quadrupole mass spectrometer used for analysis of background gases and for Thermal Desorption Spectroscopy studies. 

Field desorption mass spectrometry [1606], C nuclear magnetic resonance, and fourier-transform infrared spectroscopy [1337] have been used to characterize oil field chemicals, among them, scale inhibitors. Ion... 

Hufford et al [57] used proton and 13C NMR spectrometric data to establish the novel sulfur-containing microbial metabolite of primaquine. Microbial metabolic studies of primaquine using Streptomyces roseochromogenus produced an A-acety-lated metabolite and a methylene-linked dimeric product, both of which have been previously reported, and a novel sulfur-containing microbial metabolite. The structure of the metabolite as an S-linked dimer was proposed on the basis of spectral and chemical data. The molecular formula C34H44N604S was established from field-desorption mass spectroscopy and analytical data. The 1H- and 13C NMR spectra data established that the novel metabolite was a symmetrical substituted dimer of primaquine A-acetate with a sulfur atom linking the two units at carbon 5. The metabolite is a mixture of stereoisomers, which can equilibrate in solution. This observation was confirmed by microbial synthesis of the metabolite from optically active primaquine. 

Schulten, H.-R., and Soldati, F. (1981). Identification of ginsenosides from Panax ginseng in fractions obtained by high-performance liquid chromatography by field desorption mass spectrometry, multiple internal reflection infrared spectroscopy and thin layer chromatography. J. Chromatogr. 212, 37-i9. 

Lattimer, R.P. Harmon, D.J. Welch, K.R. Characterization of Low Molecular Weight Polymers hy Liquid Chromatography and Field Desorption Mass Spectroscopy. Anal. Chem. 1979,57,293-296. 

Fibrillin, calcium binding, 46 473, 474, 477 Fibulin-I, calcium binding, 46 473 Field desorption mass spectroscopy, 28 6, 21 Field effects, of astatophenols, 31 66 Fine structure, 13 193-204 Fingerprinting of polymetalates, 19 246-248 Finite perturbation theory, 22 211, 212 First transition series, substitution, transferrins, 41 423 26... 

From the shell of A. crassipina has been isolated a sulfoquinovosylmono-glyceride, and its structure has been established by chemical splitting (alkaline methanolysis and acid hydrolysis), as well as by such physicochemical methods as H- and l3C-n.m.r. spectroscopy, g.l.c.-mass spectrometry, and field-desorption mass spectrometry.214 The major component was shown to be l-0-hexadecanoyl-3-0-(6-C-sulfo-a-D-quinovosyl)glycerol (96% of the mixture), and the minor one was its analog containing tetradecanoic acid. 

Schulton W.D. Lehmman, High-Resolution Field Desorption Mass Spectroscopy. Part VII. Explosives and Explosive Mixtures , AnalChem-Acta 93,19-31 (1977) 153) A. Aim et al,... 

Elemental tellurium and bis[di-t-butylphosphano]sulfur diimide in tetrahydrofuran at — 20° produced a dark-brown compound that quickly deposited tellurium from a solution at room temperature. Data from field-desorption mass spectrometry and 31P-NMR spectroscopy suggest an eight-membered ring with a tritelluro group as the structure for this brown compound2. 

Elemental analysis generally poses no problems because of the limited stability of the compounds and the formation of elemental gold in decomposition and combustion, which does not form carbides, nitrides, or other interstitial phases. Atomic absorption and inductively coupled plasma spectroscopy are presently the methods of choice for An estimation. Many organogold compounds are sufficiently volatile to allow registration of good mass spectra by gas-phase electron impact. Field desorption, fast-atom bombardment, and chemical ionization mass spectrometry have also been successfully applied. 

At the outset of the structure investigation it was hoped that single-crystal X-ray methods might be successful, particularly with the large alkaloids however, as a number of trials were not promising, the approaches to structures have relied on spectroscopic and chemical methods. Spectroscopic examination involved electron impact, chemical ionization, and field desorption mass spectrometry, H- and C-nuclear magnetic resonance study (sometimes NOE and correlation spectroscopy), and this was followed by isolation of the polyhydroxylated core by alcoholysis or hydrolysis. Core 30 was novel and its structure established spectroscopically 48), whereas euonyminol was characterized as its octaacetate and compared with an authentic sample. 

Mass spectroscopy (field desorption technique) reveals an increasing ease of positive charging of these molecules with the extension of their conjugated system. The relative intensities of the molecular ions decrease from 100% (7a, 7b) to 0% (10b), whereas ions of higher charge appear with increasing intensity 8b, 9b = 100%, 10b = 100% and = 4%. The molecular ion... 

Divalent samarocene complexes also show unique reactivity toward a-olefins [55]. Bis-Cp complexes of type 13 display high polymerization activity toward ethylene, but yield rather low molecular weights (M < 25 000) [56]. The polymerization mechanism was investigated using field desorption mass spectroscopy (FD-MS) and proposed as outlined in Scheme 2. A 2 1 complex of 13 with ethyl-... 

Field desorption mass spectrometry Heteronuclear multiple-quantum correlation Heteronuclear multiple-quantum correlation Homonuclear Hartmann-Hash spectroscopy High performance liquid chromatography High resolution electrospray ionization High resolution first atom bombardment massspectrometry... 

The oil shale of the Julia Creek deposit has been shown to contain a very complex mixture of vanadium porphyrin compounds. Several groups of compounds were isolated by column chromatography and high pressure liquid chromatography and examined by ultra-violet-visible spectroscopy, insertion probe, fast atom bombardment and field desorption mass spectrometry. These groups of compounds were found to consist of several homologous series, and included some compounds tentatively identified as phylloerythrin and chlorin derivatives. 

The development by Muller (393) of the field ion microscope gave a considerable thrust to studying surface structures. In a recent modification of this technique, Panitz (394) designed a field desorption spectrometer that promises determination of the crystallographic distribution of species on metal surfaces. Secondary ion mass spectroscopy can also provide some quantitative information of surface species by sputtering atoms with an inert gas ion beam and detecting them by mass spectrometry. Submonolayers of adsorbed gases can be studied by this method (395). 

Fully hindered amines are excellent UV stabilizers, but poor thermal antioxidants, for polyolefins. We have found that partially hindered bicyclic amines, such as 3,3-dialkyldecahydroquinoxalin-2-ones, are excellent UV stabilizers and also excellent thermal antioxidants as well. The oxidation of these bicyclic amines with m-chloroperbenzoic acid was studied by electron spin resonance spectroscopy. They form stable, partially hindered nitroxyl radicals (6-line spectra). However, these primary radicals are easily oxidized to a new, fully hindered nitroxyl radical (3-line spectra) which are also very stable. Field desorption mass spectroscopic studies of the oxidation of these amines show that the primary nitroxyl radicals, which form first, lose two hydrogen atoms and add an oxygen. Thus, these bicyclic partially hindered amines are unique in being both stable and at the same time hydrogen atom donors. 

There are several methods of ionizing organic materials such as particle bombardment, chemical and field ionization, electron impact, field desorption, and laser pulse. For example, in the laser micro-mass analysis method, a laser pulse is used to supply the necessary energy to volatilize a sample from the surface for mass spectroscopy. 1 1 Mass spectrometry is often used in conjunction with gas chromatography to identify the separated components. The working technology of mass spectrometry is quite complex. 

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