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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 47 (1998), S. 189-196 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Experimental design ; Mosapride ; Reversal of retention order ; Effect of pH and column temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enantiomeric separation of mosapride and a structurally related compound was performed using chiral chromatography and experimental design. Unique effects of mobile phase pH and column temperature made it possible to control the elution order of the enantiomers when using Chiral-AGP as the solid phase. At a low mobile phase pH (〈6) the (R)-enantiomer of mosapride elutes before the (S)-form whereas the (S)-enantiomer elutes first at a high mobile phase pH (〉6). By using a mobile phase pH around 6, the column temperature could also be used to control the elution order of the enantiomers of mosapride. Similar effects of mobile phase pH and column temperature were obtained for the enantiomers of a structurally related compound, a metabolite (M1). Isocratic chromatographic systems made it possible to determine enantiomeric impurities less than 0.1% in the respective enantiomer of mosapride. The enantiomers of mosapride as well as the enantiomers of M1 could easily be separated simultaneously using Chiral-AGP and a simple gradient elution.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. 327-332 
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Semi-preparative chromatography ; Peak compression effect ; Dihydropyridine drug
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Peak compression of a dihydropyridine drug, clevidipine, is obtained in both analytical and semi-preparative scale supercritical fluid chromatography, resulting in extremely high apparent efficiencies. The observed effect, when utilising a carbon dioxide/2-propanol mobile phase with a bare silica stationary phase, is achieved when the retention of the clevidipine peak is controlled to coalesce with a system peak, generated as a result of having water in the sample. Apparent efficiencies of 350,000 and 170,000 plates meter−1 were obtained when 0.25 and 0.5 mg, respectively, are directly injected to a 200×4.6 mm ID 5 μm Hypersil silica packed column. The effect was extended to a semi-preparative system where apparent efficiencies in the region of 2,000,000 plates meter−1 were observed when 0.3 mg of a clevidipine sample containing 80% water was injected to a 250×10 mm I.D. column containing 5-μm Hypersil silica particles.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 2 (1973), S. 75-83 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Demands of more rapid and accurate answers for the steel plant made it necessary to develop a computerized system for calculation and control of the analysis performed on X-ray fluorescence and optical emission spectrometers. The interelement effects which occur in X-ray fluorescence analysis are briefly described and the evolution of a model for these corrections is examined. This model includes corrections for absorption and secondary fluorescence as well as overlapping, dead time effects, etc. which are based on simplified theoretical formulae and can be used for a broad field of applications. The parameters in the model have been determined empirically by measuring a wide range of binary alloys. The interelement effects in optical emission analysis are calculated according to a simple emprical formula. The mathematical models have been fitted to a computer (Datasystem Trask P100) which also controls the two separate spectrometers. Examples are given of routine analysis performed by this model on bulk solids of steels and fused glassy borates of sinters, slags and hard metals. Its chief advantage is that the usual requirement for a great number of standards is eliminated.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
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