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  • Analytical Chemistry and Spectroscopy  (180)
  • 2020-2020
  • 1995-1999  (180)
  • 1
    Electronic Resource
    Electronic Resource
    GC-MS determination of catechin and epicatechin levels in human plasma (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 621-623 
    Details
    ISSN: 0935-6304
    Keywords: GC-MS ; Catechin ; Epicatechin ; Flavonoids ; Plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240201111
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational and configurational study of 1,3-dioxolanes by proton and carbon NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 167-173 
    Details
    ISSN: 0749-1581
    Keywords: 1,3-dioxolanes ; NOE ; vicinal proton-proton coupling ; configurational analysis ; conformational analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configurational and conformational properties of six 4-trimethylammoniummethyl 2,2-disubstituted 1,3-dioxolanes were studied using NOE experiments and vicinal coupling constants. Selective 1D NOE experiments proved to be effective tools in the configurational assignment of C-2 relative to C-4. The preferred conformation of the dioxolane ring and the exocyclic group at C-4 was obtained by employing vicinal coupling constants and NOE results. The 1H and 13C NMR chemical shifts show stereochemically dependent trends. Quantitative analysis of conformer populations was performed using Haasnoot et al's equation. The —N+(CH3)3 group was found to be synclinal with respect to the heterocyclic O-3 atom and points outside the ring. When a phenyl group is present at C-2, the 4-CH2N+ -  group in a trans relationship to the 2-phenyl ring was found to occur prevalently in a pseudo-axial orientation, whereas it was established to be prevalently pseudo-equatorial when cis with respect to the phenyl ring.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330303
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  • 3
    Electronic Resource
    Electronic Resource
    Detection of high molecular weight starburst dendrimers by electrospray ionization mass spectometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1552-1555 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An entire series of Starburst polyamidoamine (PAMAM) dendrimers consisting of generations 1 through 10 (G1-10) have been studied by positive-ion electrospray ionization mass spectrometry (ESI-MS) using an extended m/z range quadrupole mass spectrometer. Charge-state distributions were detected as high as m/z 12 000 for the generation 10 dendrimer, having a theoretical molecular weight of 1 megadalton and containing approximately 93 maximum positive charges on the molecule. Accurate molecular weight determinations of the smaller generation dendrimers (G1-3, Mr ∼ 1.4kDa to 6.9kDa) were obtained using a commercial triple quadrupole instrument. The unit resolution ESI mass spectra provide information on the number of incomplete reactions which may occur during polymer synthesis. The extent of gas-phase charging observed by ESI-MS on the entire series of macromolecules was found to exhibit a linear relationship to Mr2/3, consistent with theoretical models prediciting a spherical ion structure with maximum charging controlled by Coulombic effects.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091516
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  • 4
    Electronic Resource
    Electronic Resource
    Accuracy and precision of gas chromatography/combustion isotope ratio mass spectrometry for stable carbon isotope ratio measurements (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1007-1011 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: We evaluated the precision, accuracy and linearity of three commercial gas chromatography/combustion isotope ratio mass spectrometry (GC/C-IRMS) instruments in regard to stable carbon isotope ratio measurements of fatty acids with 13C enrichment levels ranging from natural abundance to 924‰, in comparison to measurements by conventional gas isotope ratio mass spectrometry (GIRMS). Memory effect was also evaluated with a fatty acid mixture containing methyl myristate and methyl stearate at natural abundance levels of 13C but methyl palmitate at 13C enrichment levels of 460 or 924‰. At natural abundance, the δ13C values of fatty acids measured by the GC/C-IRMS instruments were reproducible to within 0.34‰ (range: 0.11‰ to 0.32‰) and accurate to -0.38±0.40‰ (mean difference ± standard deviation; range: -0.03±0.25‰ to -0.84±0.39‰). At enrichment levels of 13C (23 to 924‰), the δ13C values were reproducible to within 1.48‰ (range 0.20‰ to 1.00‰) and accurate to -1.11±3.16‰ (range: -1.02±3.23‰ to +4.56±13.42‰). Stable carbon isotope ratio measurements by all three GC/C-IRMS instruments were found to be linear from -30 to 924‰ (r2 〉 0.9999; p ≤ 0.004) in comparison to those measured by GIRMS. Significant memory effect was found in only one system. Based on our data, the GC/C-IRMS instruments can provide linear, precise and accurate stable carbon isotope ratio measurements and require only pico-and nanogram quantities of samples.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091107
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  • 5
    Electronic Resource
    Electronic Resource
    Revisit of MALDI for small proteins (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1315-1320 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Matrix-assisted laser desorption/ionization (MALDI) was used for several small proteins (such as insulin) and for peptides. It was found that the detection efficiencies of MALDI for the insulin B chain and the insulin A chain are drastically different. Similar phenomena were also observed for various types of peptides. The positive-ion signal of MALDI in detecting proteins or peptides was found to be greatly enhanced by the presence of a basic amino acid in their chains. The experimental results indicate that this enhancement may arise from proton transfer in solution by an acid-base reaction between the protein/peptide and matrix molecule. This pre-protonated mechanism provides a low energy barrier for the ionization of peptides in a MALDI process, and greatly reduces the energy threshold of MALDI. Matrix effects on the ionization mechanism are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091318
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  • 6
    Electronic Resource
    Electronic Resource
    Detection of ΔF508 mutation of the cystic fibrosis gene by matrix-assisted laser desorption/ionization mass spectrometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 772-774 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The most common mutation of the cystic fibrosis gene is characterized by the deletion of three nucleotides that code phenylalanine in the 508 position of the cystic fibrosis transmembrane conductance regulator. We report the first measurements by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry for the ΔLF508 mutation in cystic fibrosis carriers and patients. Furthermore, in a blind test, results from the normal and ΔLF508 mutant alleles in 30 clinical samples based on MALDI mass spectrometry and on conventional gel analysis of the DNA were in total agreement. These results demonstrate the utility of MALDI mass spectrometry in the molecular diagnosis of mutant alleles and point to its potential use for ultra-fast detection in large-scale screening of DNA mutations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090910
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  • 7
    Electronic Resource
    Electronic Resource
    High temperature mass spectrometric study of the B2O3—Al2O3 system at 1248-1850 K (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1244-1251 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The high-temperature mass spectrometric Knudsen effusion method has been used to study the vaporization processes and thermodynamic properties of the B2O3—Al2O3 system in the temperature range 1248-1850 K. Data on the B2O3 partial vapour pressures and the B2O3 activities in the system under consideration were obtained. The enthalpies of formation of Al4B2O9 and Al18B4O33 have been evaluated from the values of the enthalpies of B2O3 sublimation from boron oxide and from these compounds. Comparison is made between the available phase diagram of the B2O3—Al2O3 system and the results obtained in the present study, using the complete isothermal vaporization method.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091306
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  • 8
    Electronic Resource
    Electronic Resource
    Anharmonic force constants of helical molecules (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 297-304 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Central to our anharmonic potential-effective charge method of computing relative Raman intensities of large helical molecules, such as DNA, are the anharmonic force constants of such molecules. We have thus been led to derive explicit expressions of them and to study their properties. These properties prove to be indispensable in carrying out the computational steps leading to the final Raman intensity expressions for helical molecules. A general expression of cubic force constants of a helical molecule is presented and its properties discussed. Explicit expressions are listed for the cases of stretch and anglebend contributions. Other uses of the anharmonic force constants are also discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bspy.350010408
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  • 9
    Electronic Resource
    Electronic Resource
    Column liquid chromatography coupled on-line with mass spectrometry using post-column phosphate suppression (1995)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 45-48 
    Details
    ISSN: 0935-6304
    Keywords: Column liquid chromatography ; On-line phosphate suppression ; On-line mass spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coupling of column liquid chromatography on-line with mass spectrometry using post-column phosphate suppression is described. A membrane suppressor is used to remove the non-volatile phosphate ions from the mobile phase after the chromatographic separation prior to introduction into the mass spectrometer. Using post-column phosphate suppression by a membrane device phosphate concentrations up to 10 mM phosphate, at a mobile phase flow rate of 0.1 ml/min, could be removed for more than 99% without any decay of the sensitivity of the MS detection.Using a new antidepressant tetracyclic basic compound, ORG 4428, and some structure related compounds as model compounds electron impact as well as chemical ionisation spectra of all compounds could be obtained. The set-up could be used for several weeks running, using a phosphate containing mobile phase, without any loss of performance.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240180110
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  • 10
    Electronic Resource
    Electronic Resource
    Cyanobiphenyl-substituted polymethylsiloxane encapsulated particles for packed capillary column supercritical fluid chromatography (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 411-419 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; stationary phases ; packing materials ; packed capillary columns ; cyanobiphenyl-substituted polymethylhydrosiloxane ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nine isomeric cyanobiphenyl-substituted (25%) polymethylsiloxane (CBP) stationary phases were coated and immobilized by free-radical crosslinking on silica packing materials for use in supercritical fluid chromatography (SFC). The selectivities of these packing materials to benzene derivatives, polycyclic aromatic hydrocarbons (PAHs), and double bonds in fatty acid methylesters (FAMEs) were determined. Among the nine isomeric CBP-coated packing materials, the o, p-CBP phase was found to be the most selective to both double bonds and aromatic isomers under SFC conditions. The durability of the packing materials was evaluated by measuring the changes in selectivity with SFC use. The loss in selectivity was less than 0.20% after being continuously washed by supercritical carbon dioxide at 100°C and 300 atm for more than 100 h.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220070414
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