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  • Chiral separation  (2)
  • Association constants  (1)
  • Column-coupling system  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Separation of tryptophan-derivative enantiomers with iron-free human serum transferrin by capillary zone electrophoresis (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 1510-1518 
    Details
    ISSN: 0173-0835
    Keywords: Chiral separation ; Enantiomers ; Human serum transferrin Stereoselective interactions ; Capillary zone electrophoresis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Enantiomers can be separated by using human serum transferrin as a chiral phase. With the help of the native protein we were able to separate enantiomers with high efficiency, using a low ionic strength 2-(N-morpholino)ethanesulfonic acid (MES) buffer, pH 6, in capillary zone electrophoresis. Tryptophan methyl, ethyl and butyl ester enantiomers - moving towards the cathode at pH 6 - were resolved by passing through an iron-free transferrin zone in coated capillaries. Since the isoelectric point of the iron-free transferrin is a little higher than 6, the protein zone is either not moving in the experiment or is slowly moving towards the anode. Under the simplest experimental conditions the highest resolution was obtained for the butyl ester enantiomers and the lowest for the methyl ester ones. By changing the experimental conditions, however, this order could be reversed. The results indicate that the lengths of the alkyl chains in the enantiomers have a significant effect on the resolution, i.e., on the interaction between the protein and the separands.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501601250
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A practical procedure for the determination of association constants of the analyte-chiral selector equilibria by capilllary zone electrophoresis (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 1921-1924 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Chiral separations ; Association constants ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A practical procedure is proposed for the determination of association constants and mobility of the associate of a solute with a chiral selector in chiral separations by capillary zone electrophoresis. The procedure is based on the measurement of the effective mobility of a solute at zero and two different nonzero concentrations of the chiral selector. Simple explicit formulas have been derived in order to calculate the required data. The essence of the procedure is that all mobility data are adjusted to the background electrolyte (BGE) without chiral selector, serving as the viscosity reference. A simple procedure is described for measuring the viscosity of the operational electrolytes directly with the commercial capillary electrophoresis instrumentation, and Walden's rule has been utilized for adjusting the experimental mobility data to constant reference viscosity. The use of the procedure is exemplified by a separation of D,L-tryptophan in BGE containing α-cyclodextrin as chiral selector.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150171219
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Cyclodextrin modified micellar electrokinetic chromatography for the chiral direct resolution of (+), (-)-trans-1,2-dihydrodiol metabolite of chrysene in vitro activated by rat liver microsome S9 fraction (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 784-788 
    Details
    ISSN: 0173-0835
    Keywords: Cyclodextrin modified - micellar electrokinetic chromatography ; Chiral separation ; Chrysene metabolism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A γ-cyclodextrin (γ-CD) modified electrokinetic micellar capillary chromatography (MEKC) method was used for the enantiomer separation of a racemic trans-1,2-dihydro-1,2-dihydroxy-chrysene (chry-trans-1,2-diOH) mixture. The chiral resolution was strongly influenced by several important parameters: surfactant concentration and addition of organic modifier to the background electrolyte (BGE). An optimized electrophoretic system was used, consisting of the following conditions: 25 mM phosphate buffer, pH 7.8, 50 mM sodium dodecyl sulfate, 20 mM γ-CD, 7.4% V/V 2-propanol as BGE; the applied voltage, 18 kV, corresponded to 37 μA at a constant temperature of 25°C. This electrophoretic method was applied for monitoring the chry-trans-1,2-diOH enantiomer formation in a real sample, obtained from in vitro metabolic activation of chrysene by phenobarbital-ß-naphthoflavone-induced rat microsomes. The (+) and (-) enantiomers were identified by the racemate and the single enantiomer standard addition method and by spectra comparison with the synthetic compound. Under the experimental conditions used for chrysene activation, the (+) optical isomer was the prevailing form. The CD-MEKC system showed high reproducibility and selectivity, allowing a fast and interference-free analysis even of the in vitro metabolic sample extract, without any pretreatment.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501601128
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Highly sensitive chiral analysis in on-line combined chiral and achiral media by capillary zone electrophoresis (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 968-973 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Chiral separations ; Column-coupling system ; α-Hydroxycarboxylic acids ; Sensitivity of optical detection ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A new approach is described for highly sensitive chiral analyses by capillary zone electrophoresis, based on using an on-line combination of two capillaries filled with either chiral selective or achiral background electrolytes (BGE). Thus, the BGEs are selected in such a way that the first capillary provides optimum chiral selectivity and the second one optimum detection sensitivity. Direct chiral separations of enantiomers of mandelic, m-methoxymandelic, 3-phenyllactic and 3-indolelactic acids served as a model example for testing the approach proposed. The analyses were performed in a BGE containing acetate as a coion and L-OH-proline or aspartame as a chiral selector. For high sensitive analyses, an arrangement containing on-line combined chiral and achiral media were tested in one or two capillaries coupled via a bifurcation block. A detection limit as low as 10-18 moles was reached in the column-coupling system when the direct chiral separation was performed in the first capillary, filled with 20 mM acetate buffer, pH 4.4, containing 8 mM Cu (II) and 16 mM aspartame (L-aspartyl-L-phenylalanine methylester) and separated enantiomers were detected in the second capillary, filled with 20 mM acetate buffer, pH 3.1. The principle described is of general use in cases where the separation and detection of analytes in question require mutually different BGEs to reach the optimum selectivity and sensitivity, respectively.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501601162
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    Paper (German National Licenses)
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