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  • 1
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0899-0042
    Keywords: human serum albumin ; electrokinetic chromatography ; chiral drugs ; ligand-ligand interactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When a protein such as human serum albumin is added to the separation buffer in capillary electrophoresis, the mobility of solutes which bind to that protein may be altered. The change in mobility of the solute is a function both of the strength of the binding interaction, and the difference in mobility between the free solute and protein additive. By adding other ligands which themselves bind to the protein, the strength of the solute-protein binding may be modified, leading to a measurable change in the mobility of the solute. These effects are particularly striking for chiral compounds, where enantioselectivity may be completely lost on addition of a competitive ligand. Capillary electrophoresis with human serum ablumin as a buffer additive was used to separate the enantiomers of benzoin and three phenothiazine derivatives. A comparison of the binding of (S)-benzoin to human serum albumin as determined by capillary electrophoresis and by ultrafiltration was made. A variety of other ligands were then added to the buffer along with the protein, and the effects on mobility and enantioselectivity were studied. The displacers included (R)- and (S)-oxazepam hemisuccinate, (R)- and (S)-warfarin, nitrazepam, phenylbutazone, and octanoic acid. From the results obtained, it seems that capillary electrophoresis may be a useful, rapid method to screen for drug-drug interactions. There are some advantages of using this technique to study protein-ligand interactions: Only very small amounts of ligand are needed (useful when dealing with metabolites); for chiral compounds, if protein binding is stereoselective, then the method is also stereoselective, so single enantiomers are not needed; finally, measurements are obtained in solution, without the need for immobilization of the protein. A disadvantage is that the ligand and protein must have significantly different electrophoretic mobilities. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; optimization ; mixture design ; DUP 654 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary Electrochromatography (CEC) offers a rapid, economical, and efficient means for resolving nonionic compounds in the reversed phase mode on octadecylsilane (ODS) columns. A CEC optimization on a Hypersil ODS capillary column was employed to identify a suitable mobile phase for the pressure-driven (reversed phase ODS) separation of the anti-inflammatory 2-phenylmethyl-1-naphthol (DUP 654), and its related substances. The proportions of mobile phase modifiers methanol, acetonitrile, and water as well as pH were employed as variables in a stacked mixture design. Comparable response surface profiles were obtained for the CEC separations at pH 4 and pH 8. However, subtle differences were evident in the quality of separations obtained in the liquid chromatographic (LC) mode when using a specially-prepared column packed with exactly the same stationary phase as used in the CEC experiments. A mapping of the response surface for separations on a commercially available Hypersil ODS LC column revealed obvious differences. The differences indicate that the transfer of ODS based separation methods between CEC and LC involves more than simply transferring the conditions from one mode to the other.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 251-264 
    ISSN: 0899-0042
    Keywords: optical activity ; optical rotation ; chiroptical detection ; enantiomeric purity ; chiral separation ; enantioselective reactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiroptical detection for HPLC is particularly useful as a selective detection method for chiral molecules, and in enantiomeric purity determination with partial chiral separation or without chiral separation. The recent development of laser-based polarimeters with microdegree sensitivity has increased the applicability of optical rotation detection in HPLC. The detection limit of these instruments is submicrogram on-column for many chiral compounds in analytical HPLC. A variety of applications of the selective detection of optically active molecules are reviewed. The use of polarimetric detection with partial chiral separation is considered, both as an aid to method development and for enantiomeric purity determination. Finally applications to enantiomeric purity determination without chiral separation are reviewed, with the dual use of nonchirally selective and chiroptical detectors to determine the total amount and optical purity of the analyte. Determinations of chiral purity for samples of high enantiomeric excess are described, which with laser-based instrumentation may give accuracies of better than ± 1% with sample loadings of 50 μg on an achiral column. Applications to the study of enantioselective reactions are also considered, with determination of enantiomeric excess in near-racemates to better than ± 0.1%.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0173-0835
    Keywords: Micellar electrokinetic chromatography ; Capillary electrophoresis ; Bioanalysis ; Toxicology ; Plasma ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Plasma samples can be analyzed with direct injection onto a capillary electrophoresis system if interactions between the plasma proteins and capillary walls are minimized. This can be achieved using micellar electrokinetic capillary chromatography with a surfactant such as sodium dodecyl sulfate. The surfactant complexes with the proteins, giving them a net negative charge, and thus causes them to be repelled from the negatively-charged fused-silica capillary walls. Migrating as anions, the complexed proteins appear late in the electropherogram. In such analyses, it is important to manipulate the mobility of the analyte(s) of interest such that they migrate in the useful analytical time window before the plasma proteins. In this article, a study of the effect of buffer pH and surfactant concentration on the width of the migration time window is reported. It is shown that at pH 6 the migration time window is wide, but reduced electroosmosis can result in inordinately long run times; pH 7 gives an acceptable analytical window with acceptable run times over a wide range of sodium dodecyl sulfate (SDS) concentrations; pH 8 and higher are most useful when higher concentrations of surfactant (〉 50 mM SDS) are employed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0173-0835
    Keywords: Chromatographic retention ; Retention factory ; Electrokinetic chromatography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Many selectors are used both in pressure-driven liquid chromatography (LC) and in electrokinetic chromatography (EKC), particularly chiral species such as cyclodextrins and proteins. It should be possible to readily apply information gleaned using one technique to the other, since in both techniques the underlying molecular interactions which lead to separations are expected to be the same. Superficially this may be the case, but an exact transfer of operating conditions, i.e., background electrolyte (BGE) composition/mobile phase composition, assuming that these meet certain minimum requirements for each technique, is not often possible. To investigate the reason for this we have measured retention (K′) of a neutral solute (racemic benzoin) in HPLC and EKC using an identical range of BGE/mobile phase conditions in both techniques. The selector used was human serum albumin. The K′ measurements obtained for each benzoin enantiomer were consistently higher in HPLC than in EKC. This can be explained very simply if one considers that retention in both systems is related to the selector concentration [S], by the expression K′=K[S], where K is the affinity constant. In EKC, [S] is simply the concentration of free selector in the BGE, while in LC, [S] = mp/Vo, where mp is the number of moles of accessible selector, and Vo is the column void volume. In LC, [S] is generally considerably higher than in EKC, leading to larger values of K′.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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