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  • Analytical Chemistry and Spectroscopy  (11)
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  • Analytical Chemistry and Spectroscopy  (11)
  • Chemistry  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Measurement of unimolecular decay in peptides of masses greater than 1200 units by a reflecting time-of-flight mass spectrometer (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 443-448 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Daughter ions from decomposition of [M + H]+ parent ions have been observed in a time-of-flight mass spectrometer fitted with an ion mirror. Unit mass resolution is obtained for parent ions of masses up to several thousand u when the mirror voltage is set at a value determined by the usual velocity-focusing criterion for parent ions. Under this condition the daughter-ion resolution in the low-mass range suffers. Considerable improvement is obtained when the daughter-ion spectrum is examined in several segments, with the mirror voltage optimized for each segment. The daughter-ion spectrum from decay of metastable [M + H]+ parent ions in Substance P is measured using this technique. Reasons are suggested for differences between the spectrum obtained and a spectrum for the same compound recently obtained using a tandem double-focusing instrument.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290031210
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  • 2
    Electronic Resource
    Electronic Resource
    Recent events (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 361-363 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040915
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Enhanced secondary ion yields with fast incident molecular ionsWork performed under the auspices of the Office of Basic Energy Sciences, US Department of Energy under contract number W-31-109-ENG-38. (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 59-60 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020306
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  • 4
    Electronic Resource
    Electronic Resource
    Properties of matrix-assisted laser desorption. Measurements with a time-to-digital converter (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 117-123 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Some properties of matrix-assisted laser desorptio have been studied using single-ion-counting methods and a time-to-digital converter. The methods allow examination of the process for irradiances near the reported threshold for observation with a transient recorder. All measurements were made using bovine insulin as a test compound. We presernt direct evidence that an irradiance threshold near 106 W cm-2 exists for ion production, and that the process in a collective effect, either involving a large number of molecular ions (∼104)in a successful event or none at all. Above the threshold, the yield is found to scale with a high power (4th to 6th) of the irradiance. Measurements of initial velocity distributions indicate an axial velocity spread corresponding to ∼50 eV and a radial velocity spread corresponding to ∼2.4 eV. Thus the ejection or extraction mechanism appears to be strongly asymmetric.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290050306
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetic energy measurements of molecular ions ejected into an electric field by matrix-assisted laser desorption (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 671-678 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Measurements of kinetic energy distributions of molecular ions ejected into an extraction field by matrix-assisted laser desorpton re reported. The measurements were made in a time-of-flight mass spectrmeter with an electrostatic mirror by measuring the reflected signal as a function of the difference between the accelerating voltage and the voltage applied t the mirror. The molecular ions ere found to have less kinetic energy than the extraction field alone would normally provide, i.e. we observed an nergy deficit. Under conditons typical for a matrix-assisted laser desrptio experiment, the deficit is about 24 eV for oleclar ions of insulin. The size of the deficit increases with the intensity of the molecular ion signal, and the molecular weight of the protein; t is also larger for negative molecular ions than for positive molecular ions.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061109
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  • 6
    Electronic Resource
    Electronic Resource
    Narrowing the gap between keV and fission fragment secondary ion yields with nitrocellulose (1987)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 1 (1987), S. 114-116 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290010707
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  • 7
    Electronic Resource
    Electronic Resource
    Factors affecting the ultraviolet laser desorption of proteins (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 233-237 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The production of high-mass quasimolecular ions from proteins by matrix-assisted ultraviolet laser desorption is described. A simple time-of-fight system using a Q-switched frequency-quadrupled Nd-YAG laser to desorb protein molecules is shown to have a mass range of up to 116 000 u by the observation of intact, singly charged quasimolecular ions from 700 fmol of β-galactosidase subunit (mol.wt = 116 336 Da). Both positive- and negative-ion spectra of proteins are shown. Four new matrix materials, with properties as good as or better than nicotinic acid, are described. A mass resolution of approximately 500 (full width at half maximum definition) is demonstrated for proteins with mol.wt 〈 20 000 Da. Product species, formed by fast photochemical reactions in the matrix, are observed to form adduct ions with protein molecules. These adduct ions are a significant cause of the observed broadness of protein quasimolecular ion peaks. The practical physical considerations in detection of large-mass quasimolecular ions from laser desorption, such as detector overloading, are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030708
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  • 8
    Electronic Resource
    Electronic Resource
    Matrix-assisted laser-desorption mass spectrometry using 355 nm radiation (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 436-439 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Matrix-assisted laser desorption of proteins with the 355 nm frequency-tripled output of a neodymium:yttrium-aluminium-garnet laser has been demonstrated. In order to produce desorption at this wavelength, the cinnamic acid derivatives ferulic, caffeic and sinapinic acids have been employed as matrices. Excellent sensitivity (routinely one pmol of protein) and good mass resolution (m/Δm 400, Full width at half maximum) have been obtained by this new method. Ultraviolet photo-spectrometry of the cinnamic acid derivative matrices suggests strongly that they can be used as protein laser-desorption matrices at any wavelength between 260 nm and 360 nm, allowing the development of laser-desorption mass spectrometers based on nitrogen or excimer lasers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290031208
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular ion emission from superposed langmuir-blodgett films of different molecules in MeV ion induced desorption. Possibility of emission from a conical volume (1987)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 1 (1987), S. 22-24 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290010204
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  • 10
    Electronic Resource
    Electronic Resource
    Secondary-ion and electron production from surfaces bombarded by large polyatomic ions (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 147-157 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Heavy molecular ions with energies in the range 10-20 keV and masses from 276 u to 132 000 u, produced by matrix-assisted laser desorption, were used as primary projectiles to produce secondary-ion spectra from a variety of surfaces ina tandem time-of-fight mass spectrometer. In the negative mode the ratio of electron emission to secondary-ion emission was found to decrease rapidly with increasing projectile mass. Ion emission was found to dominate for primary ions larger than ∼ 10 000 u. Positive or negative molecular ions and cations were observed from several organic targets of masses up to 1140 u (gramicidin S) for incident projectiles up to mass 132 000 u, i. e., for projectile speeds down to ∼7000 m/s. Other ions characteristic of the target were also observed for these projectiles. Thus, large polyatomic ions can cause secondary-ion desorption even at very low velocity. The background ions of both polarities are similar to those found in keV particle bombardment by monatomic projectiles. The same ions are observed for all the projectiles; most can be identified with hydrocarbon background. The relative intensities of the background positive ions are largely independent of projectile, and for both polarities the ratio of the ions characterizing the target to those forming the background is approximately constant for all the projectiles. These results strongly suggest that the background ions come from the usual layer of organic impurities attached to the target surface. No direct evidence for surface-induced dissociation was observed in this mass and energy range.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060215
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