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  • Articles  (630)
  • Analytical Chemistry and Spectroscopy  (630)
  • 2010-2014
  • 1990-1994  (630)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 108-113 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A method is described whereby, under software control, the scan function employed to collisionally excite ions in an ion-trap mass spectrometer is regulated so as to obtain parent ion (fixed product) tandem mass spectral data. At the same time, constant neutral-loss information is also provided. Key features are the automatic ‘intelligent’ selection of parent ions from observation of the initial mass spectrum and the scanning of the applied ‘tickle’ frequency in order to locate the precise resonance points for excitation of these ions. Results for the model compounds perfluorotributylamine (‘FC43’) and n-butylbenzene are reported and complicating effects such as the unimolecular decay of the precursor ion species and charge exchange between product ions and the original sample material are discussed.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 415-417 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The aims of the investigation were to use the method of dynamically programmed scans to study in detail some tandem mass spectrometric characteristics of the ion-trap mass spectrometer and then to use the programs to investigate the possibility of performing benchtop gas chromatography/tandem mass spectrometry experiments on the standard instrument. In particular we have examined the effect of applying a DC ramp during the ‘tickle’ period as a means of broadening the range of resonant frequencies, thereby facilitating the tuning required to effect excitation.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin sputtered films of the high-Tc material YBa2Cu3O7-Δ were investigated using 180° back-scattering geometry with Fourier transform (FT) Raman spectroscopy. It is established that the main bands in the spectra of a YBa2Cu3O7-Δ film on strontium titanate substrate exhibit similarity with those obtained for oriented untwinned crystallites of the superconductor having their c-axis perpendicular to the surface of the substrate. No degradation or excessive heating of the film was observed with 1.064 μm excitation for low laser powers. The film on a magnesium oxide substrate gives unique evidence of the isolated strong, featureless, almost flat continuum, producing a broad maximum near the region of the antiphase axial bending O(2)—Cu(2)—O(3) motions of planar oxygens at very low excitation energy. This appears to be the first application of FT-Raman spectroscopy using near-infrared excitation (1.064 μm) to the field of high-temperature superconducting films and their detailed characterization.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectrometric behaviour of pairs of stereoisomeric mono- and di-substituted norbornanes, namely bicyclo[2.2.1]heptane-2-endo- and -exo-carboxylic acid, methyl bicyclo[2.2.1]heptane-2-endo- and -exo-carboxylate, 2-exo-acetamidobicyclo[2.2.1]heptane-2-endo- and 2-endo-acetamidobicyclo[2.2.1]heptane-2-exo-carboxylic acid and methyl 2-exo-acetamidobicyclo[2.2.1]heptane-2-endo- and 2-endo-acetamido-bicyclo[2.2.1]heptane-2-exo-carboxylate was studied in detail with particular emphasis on characterization of the stereoisomers. The fragmentation patterns, studied with the aid of mass-analysed ion kinetic energy spectrometry, were supported by semi-empirical MO-SFC calculations, performed using the AM1 method included in the AMPAC program.
    Additional Material: 5 Ill.
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  • 5
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eight monosulfonated and disulfonated azo dyes were analyzed using liquid secondary ion mass spectrometry/tandem mass spectrometry, in the negative ion mode, under low-energy collision conditions (110-150 eV). Many structurally characteristic fragment ions were obtained, several of which have not been reported previously using other mass spectrometric techniques. Among the structurally important ions observed were those due to loss of SO2, SO3 and various aromatic substituents, such as NO2 and NHCOCH3. Losses of N2 were also proposed. In addition, product ions due to cleavage at the azo linkage were observed, and also SO3- and HSO3- ions. Several of the azo cleavage product ions detected did not contain sulfonate groups. Possible pathways for the formation of product ions are proposed. The structural information obtained should help to better characterize and identify sulfonated azo dyes in the future.
    Additional Material: 9 Ill.
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  • 6
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The structural investigation of the products arising from 28 days incubation of albumin with high glucose concentration and further enzymatic hydrolysis has been carried out by means of high-performance liquid chromatography/mass spectrometry (HPLC/MS) under plasmaspray conditions. By this approach many different compounds have been detected, and for most of them, possible structures have been proposed on the basis of literature data and molecular weight assignments.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 403-406 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Massive-cluster impact is demonstrated to be an effective ionization technique for the mass analysis of proteins as large as 17 kDa. The design of the cluster source permits coupling to both magnetic-sector and quadrupole mass spectrometers. Mass spectra are characterized by the almost total absence of chemical background and a predominance of multiply charged ions formed from 100% glycerol matrix. The number of charge states produced by the technique is observed to range from +3 to +9 for chicken egg lysozyme (14 310 Da). The lower m/z values provided by higher charge states increase the effective mass range of analyses performed with conventional ionization by fast-atom bombardment or liquid secondary ion mass spectrometry.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 996-1000 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Massive-cluster impact (MCI) ionization was found to be capable of producing high secondary-ion yields from biological samples without the use of a liquid matrix. Dry samples of molecules as large as cytochrome c were observed to be efficiently desorbed without significant fragmentation by the MCI beam of glycerol clusters. In addition, signals from protonated molecules retained a significant proportion of their initial intensity even after several minutes exposure to the primary beam. It was determined that these remarkable phenomena are not the result of the build-up of a layer of glycerol caused by the cluster bombardment.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 512-517 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Coincidence techniques have been used to investigate double photoionization and subsequent decay of a series of polycyclic aromatic hydrocarbons (PAHs) from benzene to perylene. At fixed photon energy (40.8eV) the total yield of double ionization relative to single photoionization for both PAHs and for aliphatic compounds increases asthe same function of the excess energy above the double ionization energy. The ratio of double to single ionization for a given compound at different photon energies varies linearly with the excess energy. The fraction of dissociative double photoionization falls with increasing size in the PAH series; the ejection of characteristic neutral species (H·, H2 and C2H2) is the main dissociation pathway in the larger PAHs while charge separation is important for smaller species. Partial hydrogenation or aliphatic substitution results in decreasing stability of the doubly charged ions and increasing dissociation.
    Additional Material: 7 Ill.
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  • 10
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A combined approach using gas chromatographic retention indices and mass spectrometric characteristics has been elaborated for the isomer-specific identification of the 1700 bromo-, chloro- and bromochloro-dioxins which may be found in the environment. Over 100 dioxins were synthesized to develop this approach. This environmental monitoring strategy allows qualitative and quantitative monitoring of the 2,3,7,8-substituted isomers, which are considered to be more toxic, and many of which have assigned toxicity equivalency factors.
    Additional Material: 2 Ill.
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