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  • 1
    Electronic Resource
    Electronic Resource
    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
    Keywords: Capillary isotachophoresis ; capillary electrophoresis ; column-coupling electrophoresis ; enantiomers ; chiral ; amino acids ; tryptophan ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---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).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    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
    Keywords: phytate ; capillary zone electrophoresis ; indirect UV detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220040103
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  • 3
    Electronic Resource
    Electronic Resource
    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
    Keywords: Capillary electrophoresis ; Enantiomer separation ; Drugs ; Loxiglumide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240190604
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  • 4
    Electronic Resource
    Electronic Resource
    Separation of α-hydroxy acid enantiomers by high performance capillary electrophoresis using copper(II)-L-amino acid and copper(II)-aspartame complexes as chiral selectors in the background electrolyte (1994)
    Weinheim : Wiley-Blackwell
    Electrophoresis 15 (1994), S. 864-869 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Optical isomers of some α-hydroxy acids, namely 2-, 3-phenyllactic acid, mandelic, p-hydroxy-, m-hydroxy and 3,4-di-hydroxymandelic acid, were separated by means of capillary zone electrophoresis in free solution, using copper (II) complexes with L-amino acid or aspartame ligands in the background electrolyte. The concentration and the pH dependence of the enantiomer separations have been studied in the cases of different chiral ligands and/or analytes. With the use of L-proline as ligand only the optical isomers of 3-phenyllactic acid were resolvable, whereas using L-hydroxyproline the D and L forms of all compounds, except for 2-phenyllactic acid, were separated. Better results were obtained with aspartame as chiral ligand.Part of this work was presented at the 5th International Symposium on High Performance Capillary Electrophoresis, January 25-28, 1993, Orlando, FL, USA.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501501122
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  • 5
    Electronic Resource
    Electronic Resource
    Capillary electrophoresis quantitation of l-L-folinic acid in the presence of its inactive d-L-form (1993)
    Weinheim : Wiley-Blackwell
    Electrophoresis 14 (1993), S. 823-825 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The diastereomers d-L and l-L-folinic acid were separated by capillary electrophoresis, using heptakis (2,3-di-O-methyl)-β-cyclodextrin as a chiral active component in the background electrolyte. The method proved suitable for the quantitation of these compounds in one commercial pharmaceutical preparation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501401129
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  • 6
    Electronic Resource
    Electronic Resource
    Use of a Hepta-tyr glycopeptide antibiotic as chiral selector in capillary electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 1742-1751 
    Details
    ISSN: 0173-0835
    Keywords: Antibiotics ; Chiral separations ; Enantiomers ; Drugs ; Herbicides ; Capillary electrophoresis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A new glycopeptide antibiotic, MDL 63,246 (Hepta-tyr), of the teicoplanin family, has been evaluated in capillary electrophoresis for the resolution of chiral compounds of pharmaceutical and environmental interest. Electrophoretic separations were carried out in a polyacrylamide-coated capillary using the partial filling-counter current mode with aqueous-organic buffers in the pH range 4-6. Experimental parameters affecting resolution, such as antibiotic concentration, buffer pH, organic modifier type and capillary temperature, were studied. The Hepta-tyr antibiotic exhibited a high enantiorecognition capability towards the studied compounds at very low concentrations (1-2 mg/mL). The optimum experimental conditions were achieved by using a buffer at pH 5 containing acetonitrile at 25°C.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191036
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  • 7
    Electronic Resource
    Electronic Resource
    Quantitative analysis of synthetic dyes in lipstick by micellar electrokinetic capillary chromatography (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 1478-1483 
    Details
    ISSN: 0173-0835
    Keywords: Micellar electrokinetic capillary chromatography ; Dyes ; Cosmetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The separation of synthetic dyes, used as color additives in cosmetics, by micellar electrokinetic capillary chromatography (MEKC) is described in this study. The separation of seven dyes, namely eosine, erythrosine, cyanosine, rhodamine B, orange II, chromotrope FB and tartrazine has been achieved in about 3 min in an untreated fused silica capillary containing as background electrolyte a 25 mM tetraborate/phosphate buffer, pH 8.0, and 30 mM sodium dodecyl sulfate. The electrophoretic method exhibits precision and relatively high sensitivity. A detection limit (LOD, signal/noise = 3) in the range of 5-7.5 × 10-7 M of standard compounds was recorded. Intra-day repeatability of all the studied dye determinations (8 runs) gave the following results (limit values), % standard deviation: 0.24-1.54% for migration time, 0.99-1.24% for corrected peak areas, 0.99-1.24% for corrected peak area ratio (analyte/internal standard) and 1.56-2.74% for peak areas. The optimized method was successfully applied to the analysis of a lipstick sample where eosine and cyanosine were present.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150190844
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  • 8
    Electronic Resource
    Electronic Resource
    Atrazine and simazine determination in river water samples by micellar electrokinetic capillary chromatography (1992)
    Weinheim : Wiley-Blackwell
    Electrophoresis 13 (1992), S. 698-700 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A rapid and sensitive micellar electrokinetic capillary chromatography analytical method was used for the determination of chlorotriazine herbicides in river water samples. Several electrolyte systems in the pH range 7-10 were tested in order to optimize the separation. The two compounds were separated in less than 10 min and the determination limit was about 0.4 ppb for each herbicide. Recovery values of the method were in the range 80%-117%.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501301148
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  • 9
    Electronic Resource
    Electronic Resource
    Stereoselective analysis of herbicides by capillary electrophoresis using sulfobutyl ether β-cyclodextrin as chiral selector (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 227-234 
    Details
    ISSN: 0173-0835
    Keywords: Herbicides ; Enantiomers ; Cyclodextrin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary zone electrophoresis has been used for the enantiomeric separation of several herbicides. Different β-cyclodextrin (CD) derivatives have been investigated for chiral separations and among them the negatively charged sulfobutyl ether β-cyclodextrin (SBE-β-CD) proved to be effective for the stereoselective resolutions of the investigated herbicides. The effect of CD concentration, buffer pH and organic modifier on effective mobilities, resolution and selectivity of the analytes have been studied. Addition of SBE-β-CD (5-50 mg/mL) to the buffer at pH 9 resulted in a general increase of migration times as well as resolution. A CD concentration as low as 5 mg/mL was effective to completely resolve napropamide and ethofumesate enantiomers. Buffer solutions containing 40 mg/mL of SBE-β-CD were chosen to study the effect of buffer pH (7, 8, and 9) on chiral separation of the herbicides. No great differences in resolution and effective mobilities have been found in the pH 7-9 range. The addition of different organic modifiers to the background electrolyte at pH 9, containing 20 mg/mL of SBE-β-CD, showed different effects. Methanol was the most effective in improving resolution but in some cases total loss in enantiomeric separation was observed. The qualitative analysis of an enantiomerically pure herbicide (flamprop isopropyl) commercial preparation is also shown.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180209
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  • 10
    Electronic Resource
    Electronic Resource
    Use of cyclodextrins in capillary electrophoresis: Resolution of tramadol enantiomers (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2883-2889 
    Details
    ISSN: 0173-0835
    Keywords: Tramadol ; Enantiomers ; Cyclodextrins ; Capillary zone electrophoresis ; Validation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary zone electrophoresis was successfully applied to the enantiomeric resolution of racemic tramadol. Both uncoated and polyacrylamide-coated capillaries were tested for method optimization using either negatively charged or native cyclodextrins (CD) added to the background electrolyte (BGE). The resolution was strongly influenced by the CD type and concentration as well as by the pH and the concentration of the BGE. Among the CDs tested, carboxymethylated-β-cyclodextrin allowed the baseline separation of tramadol enantiomers. After the method was optimized, it was validated in a coated capillary for enantiomeric analysis of tramadol enantiomers in pharmaceutical formulation, including specificity and elution order, linearity, accuracy and precision, determination of limit of detection (LOD) and quantification (LOQ), enantiomeric purity linearity, freedom from interference, and stability of sample solutions. Precision at the target concentration was less than 2%, with an accuracy higher than 99%. Furthermore, the method was able to detect 0.3% and to quantify 1% of the minor enantiomer in the presence of the major one at the target value.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191614
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