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  • 1
    Digitale Medien
    Digitale Medien
    Response patterns with indirect UV detection in capillary zone electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 1683-1690 
    Details
    ISSN: 0173-0835
    Schlagwort(e): Capillary electrophoresis ; Indirect UV detection ; Response pattern ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Capillary zone electrophoresis with indirect UV-detection was used to separate mixtures containing both positively and negatively charged species. In order to understand the dependence of detector response patterns on the changes in compositions of the background electrolytes and the charge of marker ions (UV-absorbing ions), the separations were performed in two different systems. In a three-ion system (analyte ion, coion and counterion) a marker ion was the major ionic component of a buffer solution and in a two-coion or counterion system the marker ion was used as an additive. In the three-ion system the response profile of an analyte was in good agreement with the mathematical treatment based on the Kohlrausch regulation function. In the two-coion or counterion system the response patterns were more complicated; however, the experimental results agree well with data obtained from a computer simulation program. Peak directions of the analytes were not only determined by their relative charge to the marker ion, but were also associated with their relative mobilities to the buffer coion and the marker ion. The analytes with higher effective mobilities compared to the marker ion were detected as positive peaks and the ones with lower effectice mobilities as negative peaks. Similarly to the three-ion system, the detector response of an analyte was stronger by applying a marker coion compared to a counterion. An interesting result was obtained in the separation of a mixture of quaternary ammonium ions and sugars by using a cationic marker ion. The highest and most symmetrical peak was not a cation, but raffinose anion, which appeared most closely to the system peak. The observation suggests that the electromigration dispersion in its zone was eliminated by migrating close to the electroosmosis. A system peak with the mobility corresponding to the electroosmotic flow was obtained in both systems, and an additional system peak with a mobility close to that the marker ion was present in the systems using marker ions as additives.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elps.1150191027
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Capillary electroseparations of enkephalin-related peptides and protein kinase A peptide substrates (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 564-573 
    Details
    ISSN: 0173-0835
    Schlagwort(e): Capillary electrophoresis ; Micellar electrokinetic chromatography ; Mixed micelles ; Dynamic modification ; Reversed electroosmosis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The separations of enkephalin-related peptides and protein kinase A peptide substrates, with the common structural feature -Arg-Arg-X-Ser-Val-, were studied in micellar electrokinetic chromatography (MEKC) systems and compared with the capillary zone electrophoresis (CZE) mode. The influence of the magnitude and the direction of the electroosmotic flow on the selectivity was studied. Reversed electroosmosis was obtained by adding a hydrophobic amine, dimethyldodecylamine, to the background electrolyte; the amine forms cationic micelles with a low critical micelle concentration (0.3 mM). The neutral micellar agent, Brij 35, competes with the amine for adsorption sites on the capillary surface decreasing the reversed electroosmosis. In such a system, mixed cationic micelles are formed to which the peptides were not distributed at low pH, but an improved resolution was obtained due to the effects on electroosmosis. In systems containing the less hydrophobic amine dimethyloctylamine, in which probably no mixed micelles are formed, an improved separation of protein kinase A peptide substrates was obtained due to distribution to Brij 35 micelles. In separations of enkephalins, a high pH gave very low efficiencies due to surface-analyte interactions, and the best CZE separations were obtained at low pH. Changes in migration order were observed in the pH range 2-3, possibly due to differences in peptide pKa values or conformation changes of the peptides. The enkephalins were only to a small extent distributed to the Brij 35 micelles, but this improved the separation at pH 2 compared to the CZE mode.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elps.1150160192
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Indirect UV detection of carbohydrates in capillary zone electrophoresis by using tryptophan as a marker (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 325-332 
    Details
    ISSN: 0173-0835
    Schlagwort(e): Capillary zone electrophoresis ; Indirect UV detection ; Highly alkaline buffer ; Sugars ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: A rapid and sensitive method for the analysis of sugars was developed by capillary zone electrophoresis (CZE) with indirect UV detection. A mixture of nine mono- and oligosaccharides was separated in about 20 minutes on a fused silica capillary in a highly alkaline (pH 〉 12) background electrolyte (BGE). With tryptophan as the marker detected at 280 nm the femtomole level detection of sugars was possible. The system was optimized by studies on the buffer pH, the marker concentration, as well as the inner diameter of the capillary. The indirect detection of sugars was also performed with a cationic marker, N-benzylcinchonidium chloride (BCDC). However, the detection sensitivity was much lower in comparison to the tryptophan marker system.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elps.1150170207
    Standort Signatur Erwartet Verfügbarkeit
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