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  • Analytical Chemistry and Spectroscopy  (630)
  • 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.
    Type of Medium: Electronic Resource
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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.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 217-221 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Nanogram quantities of glucuronic acid conjugates of GR117289 in rat and dog bile have been analysed by semi-microbore high-performance liquid chromatography (HPLC)/ionspray mass spectrometry with on-line UV diode array detection. The determination of drug metabolites in bile has often proved problematical due to the large number of endogenous components in this biological matrix, in particular the bile acids. Semi-microbore HPLC is useful for concentrating small quantities of material and, in combination with an on-line diode array detector, for distinguishing between drug related and endogenous components. A novel angiotensin II receptor antagonist, GR117289, had proved difficult to analyse by thermospray mass spectrometry because of its thermal lability. The use of the less thermally dependent technique of ionspray mass spectrometry allowed the characterization of nanogram quantities of glucuronic acid metabolites of GR117289 in bile.
    Additional Material: 6 Ill.
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 187-191 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An excimer pumped dye laser generating ultra-short (560 fs full width at half maximum, FWHM) pulses in the ultraviolet (UV, 248 nm) and visible (496 nm) spectral ranges is used to desorb protein ions from different matrices. The effects of laser-light energy and power density on secondary-ion yields from insulin are reported. These data are compared to data obtained by employing a nitrogen laser (337 nm, 3 ns FWHM). The existence of a threshold energy density for the matrix-asisted laser desorbtion (MALD) of insulin ions by the ultra-short pulses is established. This threshold energy is of the same order of magnitude for the two laser systems employed and does not depend on the laser pulse length (the energy deposition time). Thus we demonstrate that the amount of laser energy deposited into the sample, rather than the laser power, is the important parameter in the MALD process.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 727-733 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An electrospray interface for liquid chromatography/mass spectrometry (LC/MS) is described that combines the direct heating of High-performance liquid chromatography (HPLC) effluent that is characteristic of thermoooospray-type interfaces. This interface is called the thermally assisted electrospray interface for LC/MS. The device can accept the total effluent from a liquid chromatograph at flow rates ranging up to 500 μL/min. The HPLC effluent is nebulized into charged droplets by a combination of heat and an applied electric field. Ions emitted from charged droplets are mass-analyzed by a triple quadraupole mass spectrometer equipped with an atmospheric pressure ion sampling orifice. Singly or multiply charged ions, indicating the molecular weight of a sample, are observed with minimal fragmentation. The extent of multiple charging observed in electrospray and ion spray mass spectrometry is decreased somewhat in thermally assisted electrospray. Labile compounds which undergo thermal decomposition by conventional thermospray show no decomposition with thermally assisted electrospray.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The detection limits of a number of steroids have been determined by means of loop-injection thermospray (TS) mass spectrometry. The measured limits were found to be in the range 1 pg-1O ng/μL. Combined positive-ion TS/tandem mass spectrometry yielded clear qualitative differences between mass selected protonatcd testosterone and estriol ions, both of which have the same nominal molecular weight. These differences are necessary for the correct identification of either species which may be present within a complex mixture. The heights of the peaks due to the two competing reaction channels, [M + H]+ and [M + NH4]+, were monitored as a function of the repeller voltage in the range 100-350 V, and the implications of the acquired data are discussed.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 475-478 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Multiple-coincidence techniques involving detection of two near-threshold electrons in coincidence with each other and with product ions are proposed to measure spectra of doubly charged ions and the decay of their energy-selected states. The new techniques are demonstrated by laboratory experiments on double photoionization of CO2 and SO2.
    Additional Material: 4 Ill.
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