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  • 1
    Digitale Medien
    Digitale Medien
    In Situ Characterization of Polymorphic Forms: The Potential of Raman Techniques (1999)
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 23-43 
    Details
    ISSN: 1572-8943
    Schlagwort(e): hot-stage Raman microscopy ; lufenuron CAS RN [103055-07-8] ; paracetamol CAS RN [103-90-2] ; polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The use of hot-stage Raman microscopy — the direct coupling of Raman spectroscopy and thermomicroscopy — is demonstrated for the drug substances paracetamol and lufenuron. Paracetamol is a well-known analgesic and antipyretic drug, for which three polymorphic forms are currently known. Lufenuron is a benzoylphenyl urea derivative that has been classified as a chitin synthesis inhibitor. It is indicated for the use in pets for the prevention and control of flea population and used in crop protection for the control of Lepidoptera, Western Flower thrips and rust mites. It is the first time that the polymorphism of lufenuron is addressed. All known modifications of paracetamol and lufenuron were produced and identified by hot-stage Raman microscopy. A close correlation of thermal and spectroscopic information was achieved by this combination of techniques. For lufenuron a series of new polymorphic forms were found and characterized. Raman spectroscopy allowed to identify the thermodynamic stable form A as the one which is marketed in tablets.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010184805966
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  • 2
    Digitale Medien
    Digitale Medien
    Vapor Pressure and Heat of Sublimation of Crystal Polymorphs (1999)
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 45-60 
    Details
    ISSN: 1572-8943
    Schlagwort(e): caffeine ; carbamazepine ; crystal forms ; heat of sublimation ; polymorphism ; theophylline ; transition temperature ; vapor pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In order to determine the applicability of vapor pressure studies on polymorphic modifications, pairs of enantiotropically related modifications of caffeine, theophylline and carbamazepine were investigated. The studies were performed over a wide temperature range (71 to 191°C) and accordingly over a wide vapor pressure range (0.02 to 400 Pa) using an automatic instrument constructed on the basis of the gas saturation principle. This instrument enables an analytical determination of the main component and the impurities present by the chromatographic separation of the substances transported in the gas flow. Therefore, the real partial pressure of the main component can be measured. Due to the high precision of the applied method it was possible to determine partial pressure curves and the thermodynamic transition temperature — the point at which the vapor pressure of two crystal polymorphs is equal. The thermodynamic transition temperatures of caffeine and theophylline were determined to be 136 and 232°C, respectively. These values are in agreement with experimental or calculated values derived from DSC investigations but are more reliable. Vapor pressure measurements of carbamazepine are only meaningful in the low temperature range due to its decomposition at high temperatures. The thermodynamics, advantages and limits of vapor pressure determinations of polymorphic modifications are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010188923713
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  • 3
    Digitale Medien
    Digitale Medien
    Fast-cycle trace analysis of dioxin in flue gas. Monitoring of the incineration of dioxin-containing waste from sevesoAn extended version of this paper giving experimental details will be published in a special issue of Chimia [42 (1988)]. (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 480-486 
    Details
    ISSN: 0935-6304
    Schlagwort(e): GC/MS ; 2,3,7,8-TCDD ; Stack gases ; Seveso waste incineration ; Fast cycle trace analysis ; Adsorptive charcoal filter ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The fast trace analysis method used to monitor 2,3,7,8-TCDD in stack gas during the incineration of the waste from Seveso is described. The sampling of volatile organic compounds from flue gases, distributed between all three aggregation states, is based on a micromethod developed for the trace analysis of water using a specially dimensioned adsorptive charcoal filter (1.5 mg charcoal). In conjunction with subsequent GC/MS measurements the rapid “fast cycle trace analysis” ensured specific 2,3,7,8-TCDD detection down to 100 pg per m3 flue gas in cycle times of about 1-2 hours.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240110609
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