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  • 1
    Electronic Resource
    Electronic Resource
    The extent of internal excitation of the protonated molecules of some liquid martices bombarded by keV Cs+ ion beams (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 224-228 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In an attempt to probe the extent of internal excitation of protonated ions formed by positive fast-ion bombardment, the protonated molecules of four commonly used liquid matrices are formed by means of the above technique and their respective mass-selected collision-induced dissociation (CID) spectra are investigated within the collision energy range, 5-200 eV (in the laboratory frame of references). These measurements are also repeated for the same four precursor ions formed by means of positive-ion chemical ionization in two different reagent gases, NH3 and CH4. The observed dissociation channels and the relative peak heights associated with them imply that the internal excitation of protonated molecules formed by fast-ion bombardment is much higher than that associated with the protonated ions formed in positive-ion ammonia CI(NH3-CI+). On the other hand, close resemblance between the CID spectra of ions formed by the first technique, by CH4-CI+ and by electron ionization is clearly evident.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060315
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  • 2
    Electronic Resource
    Electronic Resource
    Differentiation between isomeric methylated purine derivatives by means of chemical ionization and collision-induced dissociation (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 596-600 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A number of commercially available purine derivatives were investigated by means of chemical ionization in ammonia and methane reagent gases. The protonated molecules of the compounds investigated were mass selected and their collision-induced dissociated (CID) spectra monitored using 100 eV collision energy. Competition between the protonation and addition reaction channels which yield MH+ and [M + NH4]+ ions and the major fragment ions observed in the CID spectra reflect certain stereochemical differences between the isomeric precusors investigated. The present work is an attempt to contribute to the continuous search for first and effective means of distinguishing between the various isomers of biomedically important classes of compounds.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061003
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation of some β-lactam antibiotics by means of 2-35 keV cesium ion bombardment (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 712-716 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A number of commercial β-lactam antibiotics are investigated by means of cesium ion (Cs+) bombardment in the kinetic energy range 2-35 keV. The relative intensities of the protonated molecules, as well as some of the major fragment ions, are monitored as a function of the Cs+ kinetic energy. The dependence of the intact protonated molecule:fragment ion ratios on the primary-ion kinetic energy is evident in some of the spectra investigated. An attempt is made to interpret these results in terms of existing secondary-ion mass spectrometry data which have been obtained in a different kinetic energy range.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061116
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  • 4
    Electronic Resource
    Electronic Resource
    Suitability of fast-ion bombardment mass spectrometry for the investigation of 1,4-dihydropyridine derivatives (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 493-498 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Positive/negative fast-ion bombardment (FIB+/FIB-, negative-ion chemical ionization (CI-) and positive-ion electron ionization (EI+)mass spectrometry are used to investigate a number of 1,4-dihydropyridine derivatives. The FIB+ mass spectra presented, acquired at fixed Cs+ ion-gun voltage as well as at different voltages ranging from 1-16 kV, display a close resemblance to their EI+ mass spectral counterparts. Comparison of the FIB- data with data acquired in ammonia CI- demonstrates that for the type of compound investigated in this work, the latter ionization technique yields a superior molecular anion signal and negligible fragmentation. Some of the FIB+ mass spectra presented display a number of unmistakeable qualitative differences which are tentatively attributed to the isomeric stereo-chemistry of the compounds investigated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290051102
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  • 5
    Electronic Resource
    Electronic Resource
    Structural characterization of isomeric didehydro amino acids using chemical ionization (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 291-298 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The positive-ion mass spectra of a number of didehydro amino acids (DDAA) obtained by electron ionization (EI) and chemical ionization (CI) using different regent gases as well as the collision-induced dissociation (CID) of mass-selected odd-electron ions and/or protonated molecules have been performed on a multiple quadrupole instrument. The positive-ion EI/CI mass spectra presented display a number of differences which are expected from different isomeric structures. Furthermore, differences associated with the proton affinities of the reagent gases are clearly evident in the poisitive-ion chemical ionization mass spectra as well as in some CID spectra of protonated molecules. This investigation demonstrates the suitability of chemical ionization for characterization of isomers of this important class of compounds and underlines the effect of the proton affinity of the reagent gas on the overall character of the positive-ion chemical ionization spectra.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290050609
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  • 6
    Electronic Resource
    Electronic Resource
    Investigation of some steroids by means of thermospray and tandem mass spectrometryPaper delivered at the 11th Informal Meeting on Mass Spectromeetry, Budapest, 1993. (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 673-675 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070725
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  • 7
    Electronic Resource
    Electronic Resource
    Investigation of some thiosulfonate derivatives by means of chemical ionization and tandem mass spectrometryPaper delivered at the 11th Informal Meeting on Mass Spectrometry, Budapest, 1993. (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 670-672 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A number of thiosulfonate derivatives have been investigated by means of ammonia chemical ionization (NH3-CI), electron impact ionization (El) and mass-selected collision induced dissociation (CID). For most of the compounds investigated, the NH3-CI positive-ion mass spectra exhibit the addition ion, [M + NH4]+, as the dominant species, which implies that the proton affinities of the compounds investigated are less than the proton affinity of NH3. Deviation from true chemical ionization conditions resulted in efficient dissociation of the addition ion to yield substantial amounts of the protomated molecule, [M + H]+. The major fragment ions observed in the EI mass spectra and in the CID spectra indicate the cleavage of the sulfur-sulfur bond to be more efficient than other competing cleavages. This and other experimental observations are discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070724
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  • 8
    Electronic Resource
    Electronic Resource
    Probing conformational changes in some proteins by positive-ion electrospray mass spectrometry (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 144-148 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Charge-state distributions in the positive-ion electrospray (ES+) mass spectra of some proteins are monitored at various temperatures of the ion source. The observed shifts in charge-state profiles favouring higher charge-states are linked to heat-induced conformations cited by other research groups. To gain more insight into the origin of the observed shifts, a number of measurements were also performed at different flow rates of the electrospray drying gas, on both aqueous and organic solutions of protein. The flow rate of the drying gas was found to influence the relative intensities of high charge-states induced by heat or organic solvents to a small extent, but it did not produce substantial shifts in the charge-state distributions observed in room temperatures ES+ mass spectra of aqueous solutions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080203
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  • 9
    Electronic Resource
    Electronic Resource
    Newly-identified metastable excited state of Kr3+· (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 53-54 
    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.1290020304
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  • 10
    Electronic Resource
    Electronic Resource
    Seventh informal meeting on mass spectrometry (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 281-281 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030810
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