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  • 1
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbohydrates ; Anomer separations ; Post-column derivatization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A sensitive post-column fluoresence method based on the reaction of reducing sugars with a fluorigenic reagent (benzamidine) under alkaline conditions and elevated temperature is described. Optimum reaction conditions suitable for the detection of fluorescent reaction products have been investigated. A porous graphitized carbon column (shandon Hypercarb) was employed as the chromatographic solid phase and elution was isocratic by an aqueous acetonitrile mixture. A special problem in sugar analysis is the tendendy of anomer formation giving doublet peaks. This tendency varies largely among the different sugars, and systematic studies on conditions that eliminate this problem were performed. Efficient and selective separations of a series of disaccharides were obtained using high temperatures and a low concentration of acetonitrile in the mobile phase. The detection limits (S/N=3) with an injection volume of 20 μL ranged from 10–60 picomoles. Linear calibration graphs were obtained in the 2–20 μM concentration range (r 2〉0.99). A relative standard deviation between 1–3% (n=6) demonstrated good precision of the developed system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1612-1112
    Schlagwort(e): Micellar electrokinetic capillary chromatography ; Enkephalin related peptides ; Response surface modelling ; Central composite designs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A simultaneous optimization of resolution, efficiency and migration times of enkephalin-related peptides in micellar electrokinetic capillary chromatography (MEKC) was performed. Six experimental variables; the surfactant concentration, the percentage of organic modifier, the ionic strength of the buffer, the injected plug length, the applied temperature and the sample solution composition were studied via central composite design (CCD). Large differences in separation performance were observed at a commonly used level of organic modifier in the background electrolyte. Partial least squares regression of the responses revealed that the experimental domain was too large and complicated to be explained by the model. A new CCD model was obtained with improved prediction ability at narrower ranges of the experimental factors, especially of the organic modifier. A conflict between maximum resolution and efficiency within the shortest analysis time was observed. Therefore, constraints were set on maximal resolution and analysis time, while solving for maximum efficiency. Optimal operating conditions were found at 35 mM sodium dodecyl sulfate (SDS), 5% v/v of acetonitrile, 1.9 mm injected plug length, 35°C and sample solution with no added micelles, giving high efficiency and resolution at short analysis time. The value predicted by the model was found to agree very well to the observed values, at the optimal experimental conditions, even on a new capillary.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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