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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 8 (1981), S. 5-9 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotope dilution mass spectrometry is one of the best candidates for reference and definitive methods for the quantitative measurement of organic compounds. In this study sources of error were investigated. Where possible they were removed, and commercially available equipment had to be modified. The method was applied to the measurement of serum cholesterol. The precision is optimized and in the order of 0.5%. The mean of the recoveries of three measurements is 99.8%. The accuracy of the mean of three measurements is 0.2% if no interference are present in the gas chromatographic mass spectrometric measurements.
    Additional Material: 6 Ill.
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  • 2
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A confirmation method which can be used in regulatory screening programs for diethylstilbestrol in the urine of cattle is presented. trans- Diethylstilbestrol is purified from urine by Sep-Pak extraction and high-performance liquid chromatography and converted into its trimethylsilyl derivative. Identification is based on both accurate mass measurement of the molecular ion of trans-diethylstilbestrol trimethylsilyl by gas chromatography high resolution mass spectrometry and determination of the [M + 1]+/[M]+ peak height ratio by selected ion monitoring in low resolution. Specificity is such that on the basis of mass spectrometric data alone, all molecular formulae except those of diethylstilbestrol trimethylsilyl and only one other compound can be excluded. Additional specificity is provided by chromatographic data. The quantification is based on the standard addition method. The average recovery of trans-diethylstilbestrol is 76% with a standard deviation of 18% (n = 23).
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 18 (1982), S. 92-97 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vicinal proton coupling constants were obtained for some 6-membered ring unsaturated heterocyclic compounds. The R values and ring dihedral angles were determined and found to be consistent with half-chair conformations. Relative to saturated heterocyclic compounds, the effect of the sulfur atom on ring puckering was attenuated. However, an increase in ring puckering resulted from the sulfone group and was attributed to torsional energy.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 544-547 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The routine use of the INEPT pulse sequence is shown to be the method of choice for the assignment of multiplicity from 13C NMR spectra where no prior information about the 1J(CH) coupling constants is available, or where these are expected to vary over a large range. This technique is illustrated using spectra obtained from polyhalogenated monoterpenes isolated from the red alga Plocamium angustum, which have 1J(CH) values varying from 127 to 203 Hz.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 34-36 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotope labelling experiments and also consecutive fragmentation investigations of metastable ions, a novel technique in mechanistic studies, have been carried out to elucidate structure and genesis of the m/z 45 ions from dimethyl oxalate as well as dimethyl carbonate. It is shown that the formation of the m/z 45 ions, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{O}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document}, in the mass spectra of these compounds arises via single step processes. Mechanisms involving hydrogen transfer and subsequent formation of cyclic intermediates which then collapse to give \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{O}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document} directly from molecular ions are suggested. No evidence was found for a two-step fragmentation route to m/z 45 from the molecular ions of either dimethyl oxalate or dimethyl carbonate.
    Additional Material: 2 Ill.
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  • 6
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 481-482 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Phosphoglycerides ; Molecular species ; Phosphatidic acid dimethyl esters, PAME ; Phosphatidic acid dibenzyl esters, PABE ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 506-507 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Detector cell, backpressure ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 400-404 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Thin-layer chromatography, TLC ; Amniotic fluid ; Fetal lung maturity ; Phospholipids ; Lecithin/Sphingomyelin ratio, L/S ; Shake test ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the HPLC separation of phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylcholine (PC), and sphingomyelin (SPH) was achieved using five in-series columns packed with LiChrosorb, Partisil, and μ-Porasil adsorbents, a solvent mixture of chloroform/methanol/ammonium hydroxide (50 : 36 : 6.7, by volume), and a Pye LCM2 Moving Wire (FID) detector. The same phospholipid mixture was also separated using four μ-Porasil columns with the same eluent and detector. The latter conditions were found to be suitable for the analysis of phospholipids obtained after centrifuging, extraction, and precipitation of surface-active lipid components of patient amniotic fluid collected at amniocentesis section. The lecithin/sphingomyelin (L/S) ratios, determined by the HPLC method, correlated well with those determined by the TLC technique in four normal pregnancies, whereas results of shake tests did not correlate too well with L/S ratios determined by the above two chromatographic methods. Besides the lecithin/sphingomyelin ratio, the present method was able to supply additional information: the concentrations of phosphatidylglycerol and phosphatidylinositol, for prediction of fetal lung maturity, and the palmitic acid content of amniotic fluid phosphatidylcholine.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 595-604 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; GC/MS ; Pyrolysis GC ; Pyrolysis MS ; Headspace sampling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrolysis gas chromatography (P/GC) has been successful in differentiating coal tar pitches which are used in the manufacture of high temperature graphite materials [1,2]. In the present study, coal tar and petroleum pitches received from five suppliers were readily differentiated using three distinct methods of polymer analysis: dynamic headspace and pyrolysis gas chromatography mass spectrometry (DH/GC/MS and P/GC/MS, [3]), and pyrolysis mass spectrometry (P/MS, [4,5]). All of these methods are appropriate for the analysis and pattern recognition study of coal and petroleum products; however, methods which incorporate GC usually necessitate long analysis times and are subject to problems associated with gas chromatographic reproducibility (e.g. active sites [6], and nonconstant retention times). As a fingerprint analysis method, P/MS is rapid and ideally suited to computerized pattern recognition study of pitches due to the simple format of P/MS data (computer tabulation of normalized intensities versus masses); whereas, in the present study, the normalized peak area versus retention time date from DH/GC/MS and P/GC/MS analyses were not suitable for direct input to a computerized pattern recognition analysis program, (due to non-constant retention times and improper data format). One limitation is that P/MS does not provide positive identification of thermally evolved products (as can DH/GC/MS and P/GC/MS) due to the complexity of the spectra of a mixture of compounds produced by P/MS. Within the limits of the commercial instrumentation and computer programs used in this study, a combination of all three techniques provided the greatest capability for the differentiation of the five coal tar and petroleum based pitches studied.
    Additional Material: 16 Ill.
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