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  • Analytical Chemistry and Spectroscopy  (211)
  • 1990-1994  (130)
  • 1970-1974  (81)
  • 1990  (130)
  • 1974  (81)
Collection
Keywords
Publisher
Years
  • 1990-1994  (130)
  • 1970-1974  (81)
Year
  • 1
    Electronic Resource
    Electronic Resource
    The use of dynamically programmed scans to generate parent-ion tandem mass spectra with the ion-trap mass spectrometer (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 108-113 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040404
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  • 2
    Electronic Resource
    Electronic Resource
    A detailed study of the characteristics of the ion-trap mass spectrometer using dynamically programmed scans (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 415-417 
    Details
    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
    URL: http://dx.doi.org/10.1002/rcm.1290041015
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  • 3
    Electronic Resource
    Electronic Resource
    Mass spectrometry of synthetic oligopeptides N, O-permethylated, N-acetylated derivativesAbbreviation: DMF = dimethylformamide. (1974)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 175-189 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of a series of stable isotope derivatives aided a structure elucidation study of an amino acid amide (Tyr-NH2) and the following family of synthetic oligopeptides: Gly-Tyr-NH2, Gly-Gly-Tyr-NH2, Gln-Gly-Gly-Tyr-NH2, Gln-Gln-Gly-Gly-Tyr-NH2, Ala-Gln-Gln-Gly-Gly-Tyr-NH2, Ser-Ala-Gln-Gln-Gly-Gly-Tyr-NH2 and Lys-Ser-Ala-Gln-Gln-Gly-Gly-Tyr-NH2. This series of peptides was synthesized by classical methods. N,O-permethylated, N-acetylated derivatives were synthesized to provide sufficient volatility for mass spectrometry. Various combinations of stable isotope derivatives (CH3CO + CH3, CD3CO + CH3, CH3CO + CD3, CD3CO + CD3) confirmed proposed fragmentation pathways and corroborated hypothetical ion structures. This family of oligopeptides corresponds to the C-terminus of scotophobin.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200010307
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  • 4
    Electronic Resource
    Electronic Resource
    Multiple ion detection by accelerating voltage alternation in conjunction with voltage sweeping (1974)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 418-422 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analog multiple ion detection system has been developed for magnetic sector mass spectrometers based on accelerating voltage alternation in conjunction with the accurate maintenance of focusing by means of voltage sweeping, using a superimposed a.c. sine wave voltage. This multiple ion detector voltage sweep system is easily constructed, inexpensive and produces analytical data of much greater precision than that reported from conventional systems. The application of the multiple ion detector voltage sweep system to biomedical problems is illustrated by the development of a method for the determination of stable isotope enrichment in blood glucose and alanine in children infused with tetradeuterio-L-alanine and dideuterioglucose to study gluconeogenesis and glucose utilization in vivo.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200010610
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  • 5
    Electronic Resource
    Electronic Resource
    Alternative driving functions for a collision quadrupole (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 440-441 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The work presented here introduces a new variable parameter in the design of quadrupole collision cells. A brief summary of the mathematical theory is given to demonstrate how the maximum value of the parameter q may be altered. This is achieved through changing the driving function used for the rod potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290041021
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  • 6
    Electronic Resource
    Electronic Resource
    Theoretical studies of ion trajectories in quadrupole systems (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 442-446 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A brief introduction to the mathematical theory of quadrupole systems is given and the configuration of hyperbolic and circular cross-section rods is considered. Application of the theory of electrostatics to the latter case indicates that multipole contributions to the field occur which influence the ion trajectories. We have considered motion in the x-z plane of a static quadrupole (DC-only) for the simplest case of a 1:1 combination of quadrupole and dodecapole contributions. The quadrupole contribution to ion motion is simple harmonic and may be described as a sine function, whereas the dodecapole contribution may only be obtained by solving the appropriate elliptic integral. This solution gives rise to a sine (amplitude) or sn function. In the case of collision cells (RF-only) we have attempted to solve the Mathieu equation both analytically and numerically. Both stable and unstable trajectories may be calculated from these solutions and are presented in various formats. Some consideration is also given to the problems of collisional interaction and the associated difficulties likely to be encountered when the study is expanded to include this phenomenon.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290041022
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  • 7
    Electronic Resource
    Electronic Resource
    The field ionization spectra of some natural coumarins (1974)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 5-9 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The field ionization and electron impact mass spectra of eleven coumarins have been compared. In the field ion spectra the molecular ions were the base peaks and structurally diagnostic fragment ions formed by direct cleavage were present, whereas the molecular ions were weak in the electron impact spectra and fragment ions formed by rearrangement were dominant. Crude coumarin mixtures obtained from natural sources have been successfully examined using field ionization and gas chromatography + field ionization mass spectrometry.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200010104
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of stable isotopic enrichment of underivatized acetate by gas chromatography/mass spectrometry: Application to in vivo estimation of acetate production (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 554-558 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to assess endogenous and colonic production of acetate, we have developed an assay for determining the isotopic enrichment of plasma acetate using gas chromatography/mass spectrometry (GC/MS). Acidified, deproteinized plasma (200 μl) was extracted into ethyl ether, and the ether phase was then injected into a gas chromatograph/mass spectrometer fitted with a 30 m × 0.252 mm i.d. capillary column (temperature program 50-245°C at 10°C min-1). Using electron impact GC/MS and selected ion monitoring, peak areas of ions with m/z 60 and 61 (M + 1) were determined. Triplicate extractions of enriched plasma samples (mol.% excess 1.38-1.5%) resulted in a coefficient of variation of 1.6-5.9%. Unenriched plasma samples were found to have an enrichment close to theoretical natural abundance, and analysis of our (1-13C)acetate tracer (99 at.% excess) revealed an ion at m/z 61 and no ion at m/z 60. To verify accuracy, we conducted an in vivo isotope dilution study. In a 1-month-old piglet, fasted for 24 h, changing the rate of a 4 h infusion (mmol h-1) of (1-13C)acetate from 0.141 to 0.282 doubled the isotope enrichment (2.08 x) of the second plateau. The rate of appearance of acetate was 26.0 μmol kg-1 min -1, which is comparable to that reported in fasting sheep.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200190906
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  • 9
    Electronic Resource
    Electronic Resource
    NMR studies of sulphur heterocycles. IIFor Part I, see Ref. 1. - substituent effects in the thieno[2,3-b] [1]benzothiophene and thieno[3,2-b] [1]benzothiophene systems (1974)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 293-297 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituent chemical shifts for the title systems have been determined at infinite dilution in CDCl3 from a study of 40 derivatives. An excellent correlation is found between the ortho effect of substituents in the thiophene ring and the corresponding effects in thiophene itself, indicating negligible perturbation by the fused rings. Long range effects of 2- and 3-substituents on the 5- and 6-protons are electronic in origin, but cannot be interpreted in terms of simple resonance theory. These long range effects correlate linearly with σp°. An O, S-cis conformation for the formyl group in 2-formyl-thieno[2,3-6][1]benzothiophene is adduced on the basis of chemical shifts.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270060512
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  • 10
    Electronic Resource
    Electronic Resource
    Stéréochimie en pentacoordination. Apport des réactifs inducteurs de déplacement chimique à l'etude de spirophosphoranes à liaison P—H (1974)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 340-345 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The NMR spectra of eight spirophosphoranes bearing a P—H bond have been recorded in the presence of europium NMR shift reagent. The spectra are simplified by addition of the europium chelate. The observed displacements in the proton NMR lines allow the assignment of the endo and exo signals in some cases. By addition of the NMR shift reagent, one observes a displacement in the phosphite-spirophosphorane equilibrium in some cases.
    Notes: Le spectre de Résonance Magnétique Nucléaire de huit spirophosphoranes à liaison P—H a été enregistré en présence de chélate d'europium. L'addition du complexe d'europium amène la levée partielle ou totale de dégénérescence des spectres. Les modifications observées dans les déplacements chimiques permettent de proposer une attribution de position endo ou exo de certains signaux. L'addition du complexe d'europium entraîne, dans certains cas, une modification de l'équilibre entre les formes phosphites et spirophosphoranes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270060609
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