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  • Analytical Chemistry and Spectroscopy  (14)
  • 1990-1994  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Peptide sequencing by partial acid hydrolysis and high resolution plasma desorption mass spectrometry (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 906-912 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A method of deriving peptide sequence information using partial acid hydrolysis in combination with accurate mass measurements and immonium ion analysis provided by high-resolution plasma desorption mass spectrometry has been developed. The technique is very simple in terms of the chemistry and involves a short-time (3-30 min) incubation of the peptide in 1N-6N HCl at 100-110°C with subsequent mass spectrometric analysis. Partial acid hydrolysis is found to produce sequence-specific segments, often ladder-like, although not always a complete set. Two application examples of the method are given: the linear peptide bradykinin and desmopressin, a peptide with an internal S—S bond and a non-amino-acid constituent. The technique has proved to be particularly useful in cases where some a priori information on the peptide structure was already known or where the automated Edman degradation technique might yield erratic results or not work at all.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290081109
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  • 2
    Electronic Resource
    Electronic Resource
    Formulation of a universal electron probe microanalysis correction method (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 21 (1992), S. 27-35 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new correction method for obtaining quantitative electron probe microanalysis results is described. It utilizes data provided by Monte Carlo simulations and tracer measurements to obtain a detailed picture of the way in which the x-ray emission process is influenced by the relevant experimental parameters. Then empirical equations are derived which model the intensity of x-ray emission for an extremely wide range of experimental conditions, encompassing electron beam energies from 5 to 40 keV, characteristic x-ray wavelengths from 11.4 to 0.08 nm, angles of electron incidence from 90° to 40° and elements ranging from beryllium to uranium in the Periodic Table. The method treats separately, as with the traditional approach, the effects of atomic number difference in specimen and standard, x-ray absorption and x-ray fluorescence. The correction method was tested on an extensive range of microanalysis data and shown to work well under all conditions, providing chemical compositions which are accutate to within a few percent relative. The capability of handling ultra-light element (beryllium to sodium) analysis is particularly impressive and the r.m.s. error of 3.8% for carbon analysis on carbides is very close to the errors incurred in measuring actual x-ray intensities. The correction program is currently being developed for commercial use on IBM-compatible computers and the final stage in the evolution of the universal correction will be to extend it to deal with the analysis of thin surface films.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300210109
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  • 3
    Electronic Resource
    Electronic Resource
    Structure of ions [ZnNCR]+ and [Zn(NCR)2]+ (R = H, CH3) in the gas phase (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 742-745 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structures of [ZnNCR]+ and [Zn(NCR)2]+ ions (R = H, Me), which are abundant in the mass spectra of many types of coordination compounds, were studied by the MNDO method. In all cases the most stable isomers correspond to the zinc ion coordinated with the nitrogen(s) of the nitrile ligand. For [Zn(NCR)2]+, the N-Zn-N angles are ∼108°.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210260905
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  • 4
    Electronic Resource
    Electronic Resource
    Novel aryloxy migrations in substituted diphenyldithiocarbonates under electron impact conditions (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 459-462 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unusual expulsion of ‘SO’ was observed from the molecular ions of substituted diphenyldithiocarbonates under electron impact conditions. An initial aryloxy migration to sulphur followed by further rearrangement is proposed for this process, based on the substituent effects. The diarylthioketone radical-cation structure assigned for the [M - SO] ion was confirmed through the collision-activated dissociation B/E linked-scan spectra.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280433
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  • 5
    Electronic Resource
    Electronic Resource
    Absolute x-ray fluorescence method for the determination of metal thicknesses by intensity ratio measurements (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 19 (1990), S. 93-96 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An absolute method for the determination of the thickness of a metal film deposited on a metallic substrate is described. The method is based on the measurement of fluorescent intensity ratios for two lines from the substrate element. Titanium sheets covered with nickel layers of different thicknesses (between 3 and 22 μm) were employed to test the method. Intensity measurements were performed using different excitation modes and detection systems. Additionally, the proposed method can be employed to determine the density of the deposited material or the incident angle of primary radiation and take-off angle if the deposited metal film thickness is known. The method can be applied by using the intensity ratios of two lines generated through electron vacancies in the same shell.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300190303
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  • 6
    Electronic Resource
    Electronic Resource
    Photon-excited K x-ray fluorescence cross-sections for some light elements in the energy range 20-60 keV (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 406-409 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Kα and Kβ x-ray fluorescence cross-sections were experimentally determined for elements in the range 26 ≤ Z ≤ 40 at various excitation energies using and x-ray tube with a secondary exciter system as the excitation source. The x-ray tube with a secondary target arrangement was used to obtain high intensity with a high degree of monochromatization. Experimental values were compared with the theoretical values calculated using IKβ/IKα ratios based on Hartree - Fock and Hartree - Slater theories. The experimental values for all the elements at various excitation energies were in good agreement with the theoretical values.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220607
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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of L1, Lα, Lβ and Lγ x-ray fluorescence cross-sections in heavy elements excited by 36.62, 43.69, 48.30, 50.20 and 53.50 keV photons (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 401-405 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: L1, Lα, Lβ and Lγ x-ray fluorescence cross-sections were measured in Au and Pb at excitation energies of 36.62, 43.69, 48.30, 50.20 and 53.50 keV. Measurements were made using an x-ray tube with a secondary exciter system as the excitation source. The x-ray tube with a secondary target arrangement was used to obtain high intensity with a high degree of monochromatization. By using an x-ray tube it is possible to measure L x-ray fluorescence cross-sections even for low-intensity x-rays (L1). The experimental results were compared with the theoretically calculated values of L x-ray fluorescence cross-sections and a fairly good correspondence was observed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220606
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  • 8
    Electronic Resource
    Electronic Resource
    Ortho effects in organic molecules on electron impact part 22. Competing oxygen transfers from the nitro group to sulphur and the olefinic double bond in 2-nitrophenyl styryl sulphides (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 25 (1990), S. 161-164 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Double oxygen migration to sulphur from the ortho-nitro group leading to eliminations of SO2 and ·SO2H from the molecular ions and single oxygen transfer to the olefinic double bond in the side-chain giving rise to the most abundant ion at m/z 138 have been observed in 2-nitrophenyl styryl sulphides on electron impact. The proposed fragmentation mechanisms and the product ion structures were confirmed with the aid of high-resolution data, B/E linked scan and CID spectra.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210250308
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  • 9
    Electronic Resource
    Electronic Resource
    Unusual neutral and radical losses in 2′-substituted N-phenylanthranilic acids on electron impact (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 305-310 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unusual expulsions of [H2O + CO2] from the M+· of N-(o-carboxyphenyl)anthranilic acid, [H2O + CH2O] from the M+· of N-(o-methoxyphenyl)anthranilic acid and [H2O + ·NO2] from the M+· of N-(o-nitrophenyl) anthranilic acid were observed under electron impact conditions. These processes are stepwise in the corresponding para-substituted N-phenylanthranilic acids. The proposed fragmentation pathways and their mechanisms are supported by B/E linked-scan spectra, collision-activated decomposition (CAD)-mass-analysed ion kinetic energy (MIKE) spectra, high-resolution data, deuterium labelling and chemical substitution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210260423
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  • 10
    Electronic Resource
    Electronic Resource
    Competing oxygen transfers from nitro group to sulphur and allenic double bonds in allenyl o-nitrophenyl sulphides on electron impactDedicated to Professor Hans-Fr. Grützmacher on the occasion of his 60th birthday. (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 27 (1992), S. 515-518 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interesting oxygen transfers from the o-nitro group to allenic carbons were observed in allenyl o-nitrophenyl sulphides under electron impact conditions giving rise to abundant fragment ions at m/z 151, 138 and 136. However, a similar oxygen transfer to the sulphur leads to another intense ion at m/z 145. The proposed fragmentation pathways and the ion structures were established through high-resolution data, collision-activated dissociation mass-analysed ion kinetic energy and B/E linked-scan spectra.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210270425
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