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  • Analytical Chemistry and Spectroscopy  (509)
  • ENERGY PRODUCTION AND CONVERSION  (476)
  • 1980-1984  (985)
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Year
  • 11
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the quantitative determination of 1,2,3-propanetrioltrinitrate (nitroglycerin) in human plasma by gas chromatography mass spectrometry has been developed. After addition of 1,2,3-propanetriol(15N)trinitrate as internal standard, plasma (1 ml) is extracted by a mixture of pentane and methyl acetate (90:10). The extracts are purified by partition between, first, the extraction solvent and a mixture of acetonitrile and water (60:40) and, secondly, the resultant aqueous phase and benzene. The solvent is evaporated to a small volume before injection. The fragment ions at m/z 46 and 47 are monitored for the measurement of the [NO2]+ and [15NO2]+ ions using electron impact ionization. The mean recovery (%) ±SD in blind plasma samples spiked with amounts in the concentration range 0.35-3.52 nmol I-1, was 97.4 ± 9.0 (n = 58). Within a day, recovery experiments gave rise to coefficients of variation of 9.6, 6.4 and 2.7% at the levels 0.44,0.88 and 11 nmol I-1, respectively. Concentrations in plasma down to about 0.2 nmol I-1 (50 pg mI-1) could be estimated. Percent recovery of duplicate determinations in the range 0.5-1.96 nmol I-1± SD was 99.4 ± 6.0 (n = 80).
    Additional Material: 1 Ill.
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  • 12
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods are described to extract and measure 2,3-bis(3-hydroxybenzyl)-γ-butyrolactone (enterolactone) and 2,3-bis(3-hydroxybenzyl)butane-1,4-diol (enterodiol) from physiological fluids. They are based on the use of stable labelled analogues of each compound as internal standards with end point assay being by gas chromatography mass spectrometry. The methods were developed to quantify enterolactone and enterodiol in experiments designed to investigate the significance and source of these compounds in man and animals. Examples of studies on human ovarian blood and investigations of their excretion in urine following dietary manipulation are described.
    Additional Material: 9 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 10 (1983), S. 369-376 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simultaneous acquisition of both positive ion and negative ion data under chemical ionization mass spectrometric conditions can aid in the confirmation of assignments made by electron impact gas chromatography mass spectrometry or electron capture gas chromatography. Pulsed positive ion negative ion chemical ionization mass spectrometry coupled with fused-silica capillary column gas chromatographic methods is shown to be useful in environmental and hazardous waste sample analysis. The chemical ionization conditions which maximize sensitivity and the amount of molecular ion information for the priority pollutants are presented. Replicates of response factors for these compounds show good precision. Saturation is observed about 10 ng for those pesticides which give linear responses from 50 pg to 1-10 ng.
    Additional Material: 10 Ill.
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  • 14
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analysis of antimalarials by high-performance liquid chromatography (HPLC)/mass spectrometry demonstrates a new dimension in specificity along with increased sensitivity compared to conventional HPLC detection methods. Both direct liquid introduction and thermospray HPLC/mass spectrometry interfaces provided molecular weight information as well as characteristic fragment ions for antimalarials not normally amenable to direct probe or gas chromatographic/mass spectrometric techniques. The direct liquid introduction interface, which incorporated a 1/100 split, showed a detection limit of 30 ng using selected ion monitoring. The thermospray technique showed less than 1 ng detection limits using selected ion monitoring.
    Additional Material: 8 Ill.
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  • 15
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Negative ionization resulted in the simplification of a previously published method. The new method permits the determination of 0.25 nmol l-1 nitroglycerol in plasma with a coefficient of variation of 9.1%.
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  • 16
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 13 (1980), S. 143-147 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two resonance lines were observed in 2,6-dichlorobenzamide, both in liquid nitrogen and at room temperatures, using a self quenched super-regenerative NQR spectrometer. Analysis of the Zeeman effect on the two lines using an uncut crystal grown from solution reveals: (1) the crystal belongs to the orthorhombic system; (2) there are two crystallographically equivalent but physically non-equivalent directions for the principal field gradient making an angle of 71° for the low frequency line, and four such directions for the high frequency line; (3) the directions of the crystalline axes a, b and c are tentatively fixed as (90°, 90°), (90°, 90°) and (0°, - ); (4) from morphological studies a: b: c are estimated as 0.959 ± 0.005: 1:1,402 ± 0.005 and, from the estimated density (1.440 gms/cc) of the crystal, the absolute values a, b, c are calculated, on the basis of four molecules per unit cell, as a = 8.33 Å, b = 8.68 Å and c = 12.18 Å; (5) there are a mininium of four molecules per unit cell; the four molecules lie in four different planes which are, however, connected by symmetry operations. There is an inplane bending by 6.5° between the two C—Cl bonds away from one another and (6) the ionic, single bond and double bond characters for both chlorines are almost equal and are in the ratio 25:72:3.
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  • 17
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 192-197 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton spectra of exo- and endo-3-thiatricyclo[4.2.1.02,5]non-7-ene 3,3-dioxide have been analysed and completely assigned. Considerations of coupling constants indicate that the thietane ring is nonplanar and that the norbornene residue is significantly distorted from the geometry of norbornene itself. The sulfone group induces significant changes in the shielding of the proximate olefinic proton in the endo isomer and the bridge protons in the exo isomer. These shifts appear to be the result of the electrostatic effects and effects associated with the diagmagnetic anisotropy of the sulfone group.
    Additional Material: 3 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 15 (1981), S. 280-284 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 13C NMR spectra of 8-hydroxyquinoline (oxine) and its 5-Me, 5-F, 5-Cl, 5-Br and 5-NO2 derivatives have been studied in DMSO-d6 solution. The 1H and 13C chemical shifts and proton-proton, proton-fluorine, carbon-proton and carbon-fluorine coupling constants have been determined. The 1H and 13C chemical shifts have been correlated with the charge densities on the hydrogen and carbon atoms calculated by the CNDO/2 method. The correlation of the 1H and 13C chemical shifts with the total charge densities on the carbon atoms is approximately linear (rH2 = 0.85, rC2 = 0.84). The proton in peri position to the nitro group in 5-NO2-oxine is an exception.
    Additional Material: 2 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 15 (1981), S. 311-316 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The assignment of all ring carbons of p-benzoquinones derived from perezone and from thymoquinone was completed using gated decoupled spectra. The long range proton-carbon couplings are discussed in terms of the degree of substitution of the quinone ring. The tautomeric interconversion of the two energetically equivalent forms of 2,5-dihydroxy-1,4-benzoquinones has been studied in various solvents and at several temperatures.
    Additional Material: 2 Ill.
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  • 20
    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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