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  • Analytical Chemistry and Spectroscopy  (4)
  • 2015-2019
  • 1980-1984  (4)
  • 1930-1934
  • 1
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Combined high performance liquid chromatography mass spectrometry using a moving belt interface was used to investigate C-methylation artifacts arising from the permethylation reaction of peptides with methyl sulfinyl carbanion and methyl iodide. C-Methylation was not limited to glycine but, depending on the reaction conditions, other amino acids were also susceptible to it. In the absence of a glycine residue, preference for C-methylation of the C-terminus amino acid was observed. The use of on-line high performance liquid chromatography mass spectrometry allowed the separation of N, O, C-methylated from the N, O, S-permethylated derivatives, thus facilitating interpretation of the mass spectra.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: Thin layer chromatography ; TLC ; Time optimization ; Steroids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Optimized multilayer X-ray spectrometry, using lead myristate and lead stearate analyzers (2d values of 80 and 100 Å) has been applied to the measurement of the O--Kα and the C--Kα spectral bands from CO and CO2 in the gas and solid phases. The LII, III spectra were also measured for argon in the gas and solid states under similar conditions in order to identify and to minimize any non-molecular components in the CO and CO2 spectra. These molecular orbital data have been related to those obtained with X-ray and ultraviolet photoelectron spectroscopy and grating X-ray spectroscopy. The consistency of the results of these complementary measurements is excellent. The ionization energies for the C and O 1s levels have been determined to be 295.4 and 542.0 eV for CO and 296.8 and 540.3 eV for CO2. The MO data have also been compared with that predicted from the symmetry, strength and binding energy of the molecular orbital spectral components as calculated using the currently available computational models, CNDO/2, MINDO/3, MNDO, extended Hückel and ab initio. The molecular orbital calculated results for these organic compounds, CO and CO2, are not in as good agreement with the experimental data as previously demonstrated for molecular orbital spectra measured for C--Kα and the LII, III bands of Cl, S and P for both organic and inorganic compounds.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Preparation of deactivated capillaries for routine analysis ; Easy deactivation and pretreatment steps described in detail ; Comparison of different modes given ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new surface pretreatment for the preparation of wall-coated open tubular (WCOT) glass capillary columns has been evaluated. This technique involves the application of a non-extractable layer of Superox™-4, a 4,000,000 MW polyethylene glycol, to the glass surface as a pretreatment and deactivation agent. Unlike other polyethylene glycols, Superox-4 is stable at high temperatures (〉 300°C) in the absence of oxygen, coats smoothly onto a bare glass surface and resists droplet formation. WCOT columns (SE-54, Carbowax 20M, and SP-2250) prepared using this technique are compared to columns prepared using a modified Grob [2,3] BaCO3 procedure. The Superox-4 pretreated columns were equal or superior in quality to the BaCO3 pretreated columns, based on the appearance of an activity standard and the effective theoretical plates (Neff) per meter. Chromatograms showing practical application of the WCOT columns prepared using both methods is given.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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