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  • Analytical Chemistry and Spectroscopy  (5)
  • 1995-1999  (3)
  • 1990-1994  (2)
  • 1920-1924
  • 1
    ISSN: 0935-6304
    Keywords: Epoxytriacylglycerols ; high temperature gas chromatography ; hydroxytriacylglycerols ; ketotriacylglycerols ; lipids ; negative chemical ionization mass spectrometry ; SOP-50 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Five seed oils consisting of unusual triacylglycerols have been examined by high temperature gas chromatography using glass capillary columns coated with the stationary phase SOP-50 (50%-diphenyl-50%-dimethylpolysiloxane, methoxy-terminated). The investigated hydroxy, epoxy, and ketokonjuene triacylglycerols were first derivatized in order to permit analysis by high temperature gas chromatography. Structural elucidation of the intact triacylglycerols was performed with high temperature gas chromatography/negative chemical ionization-mass spectrometry using NH3 as a reagent gas. Individual derivatized lipid species with a molecular weight up to 1176 g/mol could be identified.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: cis-13-Eicosenoic Acid (Paullinic Acid) ; Cyanolipids ; Fatty acids ; GLC-MS ; NMR spectroscopy ; Oxazoline derivatives ; Paullinia elegans Sapindaceae ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fatty acids of the total lipids, triglycerides, and the cyanolipid of Paullinia elegans (Sapindaceae) have been analyzed as their methyl esters and 4,4-dimethyloxazoline derivatives by gas chromatography-mass spectrometry. It was shown that the gas chromatographic separation of the oxazoline derivatives was sufficient to ensure the correct identification of the monoenic fatty acid positional isomers. Stereochemistry of the double bonds has been confirmed by infrared and 13C-nuclear magnetic resonance (NMR) spectroscopy. cis-13-Eicosenoic Acid (Paullinic acid) (44.4%) and cis-11-octadecenoic acid (cis-vaccenic acid) (19.8%) were found to be the main components beside other monoenoic acid positional isomers. The cyanolipid of P. elegans was identified as 2,4-dihydroxy-3-methylenebutyronitrile derivative by IR, 1H-NMR, 13C-NMR spectroscopy and was quantified by 1H-NMR spectroscopy (71.4%).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0935-6304
    Keywords: α-Monoacetotriacylglycerides ; Celastraceae ; Fatty acids ; GLC ; GLC-(NCI)MS ; Maytenus seed oils ; OV-225-OH, OH-terminated ; SOP-50, methoxy-terminated ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The seed oils of three Maytenus species have been examined by high temperature GLC using SOP-50 (methoxy-terminated) and OV-225-OH (OH-terminated) glasscapillary columns. The main compounds (71-76%) could be identified as α-mono-acetotriacylglycerols by a combination of high temperature GLC-MS in negative chemical ionization mode with a CH4/N2O mixture as reactant gas and other spectroscopical methods (infrared, 1H- and 13C-nuclear magnetic resonance spectroscopy). The OV-225-OH phase demonstrated better separation properties that the SOP-50 phase for this substance class and up to eight species of α-monoacetotriacylglycerols could be separated. The content of usual triacyclglycerols was below 1%. The results of the analysis of the individual fatty acids as their methyl esters by GC and GC-MS are also presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0749-1581
    Keywords: Phase-editing ; Relayed responses ; 2D HMQC-TOCSY ; NMR Spectra ; Digoxin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An NMR technique for the determination of proton vicinal couplings relayed at the carbon chemical shift is presented. With this technique, which is an extension of DEPT-HMQC-TOCSY, it is possible to generate phaseedited 2D NMR data in which the 1H—13C relayed responses differ in phase as a function of the proton multiplicity of the carbon from whose proton(s) the response originates. A simple pulse scheme is presented to allow further simplification of the spectrum by eliminating the direct 1H—13C correlations. Thus, responses arising from methines or methyls will be of opposite phase from responses originating from methylenes; direct correlations are eliminated to minimize congestion. An example is presented with the cardiac drug digoxin.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0749-1581
    Keywords: NMR ; Region-selective inverse detected long-range heteronuclear chemical shift correlation ; Shaped pulses ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: F1 region-selected variants of the HMBC experiment were compared and evaluated. In particular, a significant advantage was demonstrated for an E-BURP-2 pulse over a Gaussian 270° pulse for region-selected applications. The Gaussian 270° pulse would still, however, be the preferred pulse for use in single-resonance, on-resonance selective excitation. Data are presented from NMR spectrometers both equipped and not equipped with programmable pulse modulators (waveform generators). Pulse evaluations were performed using the simple heteroaromatic alkaloid quindoline; application of the technique to the important immunosuppressive cyclic peptide cyclosporin-A is also presented and discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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