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  • 1
    Digitale Medien
    Digitale Medien
    Separation of Diastereomers by Capillary Zone Electrophoresis with Polymer Additives: Effect of Polymer Type and Chain Length (1995)
    s.l. : American Chemical Society
    Analytical chemistry 67 (1995), S. 3866-3870 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac00117a008
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  • 2
    Digitale Medien
    Digitale Medien
    Use of cyclodextrins in capillary zone electrophoresis for the separation of optical isomers: Resolution of racemic tryptophan derivatives (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 56-61 
    Details
    ISSN: 0899-0042
    Schlagwort(e): capillary zone electrophoresis ; enantiomers ; cyclodextrins ; tryptophan derivatives ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this study capillary zone electrophoresis has been used for the separation of racemic tryptophan derivatives in their enantiomers. The effect of cyclodextrins with different shape, added to the background electrolyte, on the migration time of 10 compounds, including methyl tryptophan, hydroxy tryptophan, and tryptophan ester derivatives, has been studied. Furthermore, the effect of cyclodextrins with different shape and that of the composition of the background electrolyte on the enantiomer resolution are discussed. Among different cyclodextrins used α-cyclodextrin and heptakis(2,6-di-O-methyl)-β-cyclodextrin were found to possess the best complexing capacity and thus the resolution power toward analysed compounds.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530040112
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  • 3
    Digitale Medien
    Digitale Medien
    A further study on the chiral separation power of a soluble neutral β-cyclodextrin polymer (1995)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 348-352 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; Enantiomers ; Cyclodextrin polymer ; Organic modifiers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Enantiomeric separation of some basic compounds, namely selegiline, amphetamine, and clenbuterol, was studied by capillary electrophoresis using an uncharged β-cyclodextrin polymer added to the background electrolyte at pH 2.5. Both complexation and resolution were influenced by the concentration of the chiral polymer confirming our previous results obtained in our earlier work for a wide number of pharmaceutical compounds. In this further study, we examined the influence of different organic additives to the background electrolyte on the enantioselectivity of the chiral selector, also using an extended number of analytes. In most cases, the use of an organic additive resulted in a decrease of resolution. However opposite to that, in some cases, e.g. ephedrine, the organic solvent proved to be essential to achieve enantiomeric resolution. Furthermore the influence of the capillary temperature on the resolution of the analytes was evaluated. Increase of temperature had a deleterious effect on the resolution of the enantiomers. For ephedrine, however, relatively high temperature (50 °C) proved to be advantageous, for the resolution of the optical isomers.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240180605
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  • 4
    Digitale Medien
    Digitale Medien
    Separation of Enantiomers by On-Line Capillary Isotachophoresis-Capillary Zone Electrophoresis (2000)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 531-538 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary isotachophoresis ; capillary electrophoresis ; column-coupling electrophoresis ; enantiomers ; chiral ; amino acids ; tryptophan ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The ability of capillary zone electrophoresis (CZE) coupled on-line with capillary isotachophoresis (ITP) sample pretreatment in the column-coupling capillary electrophoresis equipment to separate trace enantiomers present in samples of complex ionic matrices and enantiomers present in their mixtures at significantly differing concentrations has been studied. Enantiomers of 2,4-dinitrophenyl labeled norleucine (DNP-Nleu) and tryptophan enantiomers were employed as model analytes in this work while urine and mixtures of tryptophan enantiomers of differing concentrations served as model samples. Experiments performed with urine samples spiked with the DNP-Nleu racemate at sub-μmol/L concentrations demonstrated excellent sample pretreatment capabilities of ITP (concentration of the analytes, in-column and post-column sample clean up) when coupled on-line with chiral CZE separations. In the CZE separations of enantiomers present in the samples at trace concentrations the sample pretreatment could be performed in both achiral and chiral ITP electrolyte systems. The use of a chiral electrolyte system was found to be essential in the ITP pretreatment of the samples containing the enantiomers at very differing concentrations. For example, a 2×10-7 mol/L concentration of L-tryptophan could be detected in the CZE separation stage of the ITP-CZE combination in samples containing about a 104 excess of D-tryptophan only when the ITP pretreatment was carried out in the electrolyte system providing the resolution of enantiomers (α-cyclodextrin served for this purpose in the present work). A post-column ITP sample clean up was found effective in enhancing the destacking rate of the trace enantiomer in the CZE stage when the migration configuration of the enantiomers was less favorable (the trace constituent migrating behind the major enantiomer).
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Teicoplanin-Based Enantiomeric Separations in CZE Using a Partial Filling Technique (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 315-321 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Glycopeptide antibiotics ; chiral selectors ; Teicoplanin ; enantioseparations ; CZE ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Baseline separation of the enantiomers of a number of negatively charged amino and mandelic acid derivatives was achieved in less than 10 min by capillary electrophoresis in a polyacrylamide coated capillary, using the “partial filling method” (PFM) with submillimolar concentration of Teicoplanin (TE) as the chiral selector. The influence of the charge and concentration of TE, electrolyte solution composition and pH, on the enantioresolution was examined. Further proofs were brought to corroborate the hypothesis that the enantiorecognition takes place at the D-Ala-D-Ala binding site, whose blockade is responsible for the antibacterial activity of glycopeptide antibiotics. While the dependence of the chiral recognition capabilities of TE on electrolyte solution composition and pH could limit its applicability, improved sensitivity, reduction of TE wall adsorption, resulting in a good efficiency, and high cost reduction, due to the very small amount of chiral selector required, were shown as advantages of the PFM adopted in this study.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Indirect UV photometric detection in capillary zone electrophoresis for the determination of phytate in soybeans (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 4 (1992), S. 9-11 
    Details
    ISSN: 1040-7685
    Schlagwort(e): phytate ; capillary zone electrophoresis ; indirect UV detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A rapid and simple analytical method was developed to determine phytate anion in soybeans. The analysis was performed by capillary zone electrophoresis with indirect UV photometric detection. The determination of phytate was carried out with a background electrolyte in which benzoate was the absorbing ion at 254 nm.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mcs.1220040103
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  • 7
    Digitale Medien
    Digitale Medien
    Use of vancomycin as chiral selector in capillary electrophoresis. Optimization and quantitation of loxiglumide enantiomers in pharmaceuticals (1996)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 322-326 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; Enantiomer separation ; Drugs ; Loxiglumide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vancomycin has been used as chiral selector for the enantiomers separation of D, L-loxiglumide, a new drug proposed for the treatment of gastrointestinal pathology. The chiral selector, dissolved at very low concentration in the running buffer, filled only part of the capillary (polyacrylamide coated) and allowed chiral resolution in less than 12 min using a 50 mM phosphate buffer at pH 6. The partial separation technique allowed to obtain a detection limit of 0.5 μg/ml for each enantiomer avoiding the drop in sensitivity due to the strong UV absorption of vancomycin when present in the detector path. The effects of vancomycin concentration and buffer pH on enantiomers resolution have been studied in order to find the optimum experimental conditions for the chiral purity control of drug. The optimized method, using the internal standard, showed good reproducibility for both migration times and normalized peak area ratio and for linearity. Under the studied operating conditions it was possible to detect 0.2 % (w/w) of L-loxiglumide as a chiral impurity. Analysis of pharmaceutical preparations of D-loxiglumide did not reveal the presence of the impurity (L-isomer).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240190604
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  • 8
    Digitale Medien
    Digitale Medien
    Capillary zone electrophoretic separation of cyclodextrins with indirect UV photometric detection (1990)
    Weinheim : Wiley-Blackwell
    Electrophoresis 11 (1990), S. 774-776 
    Details
    ISSN: 0173-0835
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: A method for the separation of cyclodextrins by capillary zone electrophoresis with indirect detection is described. It is based on the formation of inclusion complexes with benzoate which simultaneously forms a UV absorbing constituent of the background electrolyte used for the separation.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elps.1150110917
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  • 9
    Digitale Medien
    Digitale Medien
    Enantiomer resolution by using capillary zone electrophoresis: Resolution of racemic tryptophan and determination of the enantiomer composition of commercial pharmaceutical epinephrine (1990)
    Weinheim : Wiley-Blackwell
    Electrophoresis 11 (1990), S. 757-760 
    Details
    ISSN: 0173-0835
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The enantiomers of D- and L-tryptophan were separated by capillary electrophoresis, using α-cyclodextrin as a chiral active component in the background electrolyte. The separation of (-) and (+) epinephrine was achieved by supplementing the background electrolyte with Heptakis (2,6-di-O-methyl-β-cyclodextrin). As a practical application of the method, the quantitative analysis of (-)and(+)enantiomers in commercial pharmaceutical solutions of adrenaline is shown.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elps.1150110913
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  • 10
    Digitale Medien
    Digitale Medien
    Capillary zone electrophoresis of rare earth metals with indirect UV absorbance detection (1990)
    Weinheim : Wiley-Blackwell
    Electrophoresis 11 (1990), S. 780-783 
    Details
    ISSN: 0173-0835
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The separation of 14 lanthanides by capillary zone electrophoresis was studied in the background electrolyte containing hydroxyisobutyric acid as complexing counterion and creatinine as a UV absorbing coion for indirect detection of lanthanide zones. A complete separation was achieved in less than 5 min and the applicability of the method for the analysis of real samples was demonstrated.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elps.1150110919
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