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  • Analytical Chemistry and Spectroscopy  (210)
  • 1
    Electronic Resource
    Electronic Resource
    Application of 15N spectroscopy and dynamic NMR to the study of ureas, thioureas and their lewis acid adducts (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 13 (1980), S. 396-402 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rotational barriers and 15N chemical shifts have been measured in a number of ureas and thioureas. As anticipated on the basis of the 15N shifts, several previously unobserved rotational barriers could be detected by using lanthanide reagents or a high field spectrometer. Nearly constant effects on both the rotational activation energy and the 15N shift are produced on going from ureas to the corresponding thioureas, and correlations are found between the ΔG
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270130603
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  • 2
    Electronic Resource
    Electronic Resource
    Separation of metal complexes by on-line coupled LC-GC (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 170-172 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; Gas chromatography ; LC/GC ; On-line coupling ; Metal complexes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The on-line coupled LC-GC technique was applied to the analysis of several metal chelates of N,N-diethyldithiocarbamic acid. A 10-port valve interface was used to couple the LC and GC instruments. Conditions during sample transfer into the GC gave fully concurrent solvent evaporation. The chelates investigated were separated with a short apolar fused silica column. LC preseparation was made with cyano or amino phases using a hexane/dichloromethane mixture as eluent. On-line LC-GC combination seems to be very suitable for the separation of the metal chelates studied.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240130306
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  • 3
    Electronic Resource
    Electronic Resource
    Elucidation of some fragmentations of small peptides using sequential mass spectrometry on a hybrid instrument (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 217-221 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Sequential daughter-ion-scanning analyses of small peptides have been performed using a hybrid tandem instrument of BEqQ configuration. Precursor ions are selected by B and allowed or induced (by high-energy collisional activation) to decompose in the region preceding E. Decoupling of E from the accelerating voltage permits the selection of the first-generation daughter ion whilst retaining appropriate float voltages for the quadrupole assemblies. The daughter ion selected by E is further subjected to low-energy collisional-activation dissociation (CAD) in q and the fragment-ion spectrum is obtained by scanning Q. The sequential daughter-ion-scanning technique has been used to establish that ‘internal’ fragments of the types, (AY′) and (BY′), are formed via initial Y-type cleavage. Fragmentation of a protonated peptide (angiotensin III) by loss of the C-terminal amino acid residue, yielding a (Bn′ + OH) ion, is reported for the first time. This process is analogous to that previously described for metal-cationized peptides.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030704
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  • 4
    Electronic Resource
    Electronic Resource
    Abnormal effects in the detection of ions from bioorganic substances by mass spectrometry (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 13-15 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The characteristics of the detection of ions of the alkali metals and of cluster ions of the type (H2O)NMH+ (where M is an amino acid) are markedly different from those for the detection of protonated saccharose ions. The latter are shown to produce a signal from a secondary electron multiplier detector at a lower ion energy than the threshold energy for the former ions. An explanation is proposed in terms of the charge localization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040105
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence for a reaction window in double-electron-capture reactions in collisions involving the molecular target CH3Br (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 125-128 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Double-electron-capture reactions in which singly charged projectile ions A+ convert to negative ions A- in collisions with molecules M are endoergic. Non-zero cross-sections for the reactions occur when the endoergicities fall within a ‘reaction window’. The existence of a window for reactions with CH3Br molecules is demonstrated in this investigation by altering the population of ground and excited states of the resulting CH3Br2+ ions using three projectile ions, S+·, OH+ and F+ which markedly alters the endoergicities of the double-electron-capture reactions. Analysis of the energy-loss spectra indicates that the reaction window for CH3Br is between endoergicities of about 8 and 22 eV. Using F+ as the projectile ion, it is shown that the population of the more highly excited states of CH3Br2+ is enhanced.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040408
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  • 6
    Electronic Resource
    Electronic Resource
    The calibration of the energy-loss scale for charge-stripping reactions of singly-charged positive ions (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 167-169 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Two methods of calibrating the energy-loss scale in charge-stripping experiments are compared. It is shown that the linear-offset method rather than the multiplicative method should be used.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020807
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  • 7
    Electronic Resource
    Electronic Resource
    Discrimination effects in inorganic ion-cluster detection by secondary-electron multiplier in mass spectrometry experiments (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 9-12 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Discrimination effects in secondary electron multipliers due to the differences in kinetic energy with which ions of different masses strike the dynode surface are investigated. The threshold energy at which ions of a particular mass can be detected is discussed. The efficiencies of such multipliers when used with cluster ions such as H+(H2O)N (where Cat+ represents an alkali-metal cation) are investigated and discussed, in terms of both the ‘kinetic’ and ‘potential’ emission coefficients.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040104
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  • 8
    Electronic Resource
    Electronic Resource
    Doubly ionized states of CH4 studied by double-charge-transfer and auger-electron spectroscopies (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 438-448 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: High-resolution double-charge-transfer spectroscopy has been used to measure the double-electron-capture reactions with CH4. Using kilo electron volt OH+, CI+ and F+ projectile ions it is possible in double-electron-capture reactions with CH4 molecules to populate the ground triplet state of CH42+. The energy of this state relative to the gound state of CH4 is found to be 38.2±0.4 eV, while the fiest excited triplet state is found at a double-ionization energy of 46.7±0.8 eV. In double-electron-capture reactions involving H+ projectile ions and CK4 molecules, low-lying singlet states of CH42+ are populated. The energies of the four lowest singlet states in CH42+ were measured to be 39.2±0.4, 40.5±0.4, 42.1±1 and 51.0±1 eV. High-resolution photon-induced Auger-electron spectra of the CH4 molecule have been recorded. The KLL Auger Spectrum shows four distinct structures in the 30-70 eV double-ionization evergy range centred at 40.3±0.1, 47.03, 53.2±0.3 and 6.9±0.3 eV. The previously published data on CH42+ have been reviewed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060708
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  • 9
    Electronic Resource
    Electronic Resource
    Negative electrospray ionization mass spectrometry analysis of gangliosides, sulphatides and cholesterol 3-sulphate (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 491-494 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Negative electrospray ionization mass spectrometry (NESI-MS) of a series of native gangliosides containing one, two or three sialic acid groups, sulphatide-I and cholesterol 3-sulphate was undertaken, using a magnetic sector instrument. The results show that NESI-MS of gangliosides leads to the formation of multiple-charged molecular ions of the type [M — H]-, [M — 2H]2- and [M — 3H]3-. The number of charges appears to be correlated to the number of sialic acid groups present. NESI-MS of sulphatide-I predominantly gave ions of type [M — H]- whilst cholesterol 3-sulphate gave a more complex ionization pattern. The sensitivity of the NESI-MS system was enhanced by using water+methanol, 9:1 (v/v) as solvent, containing 300 pmol/μL of NH4HCO3. The application of NESI-MS to these compounds is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090604
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  • 10
    Electronic Resource
    Electronic Resource
    The components of the venom of a spider Scodra griseipes. 1. Analysis of low molecular weight products using gas chromatography/mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 289-292 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Low molecular weight venom constituents of the spider Scodra griseipes have been derivatized using bis(trimethylsilyl)-trifluoracetamide and pentafluoropropionic anhydride. Examinatio of these derivatives by coupled gas chromatogrtaphy/mass spectrometry using electron ionization or ammonia- or isobutane-chemical ionization allows their structural identification. Comparisons have also made with retention time and mass spectra of the pure compounds. Four acids: phosphoric, lactic, citric, Y-aminobutyric (neurotransmitter0 and four basic biogenic amines: putrescine, cadaverine, spermidine and spermine have been found.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060413
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