Enantiomer chromatographic separation

Enantiomers -chromatographic separation of [BIOPOLYMERS - ANALYTICAL TECHNIQUES] (Vol 4) -as sweeteners [SWEETENERS] (Vol 23)... 

Interactions even weaker than ionic bonds can be used to separate enantiomers. Chromatographic separation relies on a difference in affinity between a stationary phase (often silica) and a mobile phase (the solvent travelling through the stationary phase, known as the eluent) mediated by, for example, hydrogen bonds or van der Waals interactions. If the stationary phase is made chiral by bonding it with an enantiomerically pure compound (often a derivative of an amino acid), chromatography can be used to separate enantiomers. 

Figure 8-12. Examples of las eluted enantiomers In a chromatographic separation on chiral HPLC with teicoplanin stationary-phase.

Most chiral chromatographic separations are accompHshed using chromatographic stationary phases that incorporate a chiral selector. The chiral separation mechanisms are generally thought to involve the formation of transient diastereomeric complexes between the enantiomers and the stationary phase chiral ligand. Differences in the stabiHties of these complexes account for the differences in the retention observed for the two enantiomers. Often, the use of a... 

Polysaccharide derivatives for chromatographic separation of heterocyclic enantiomers 98AG(E)1021. 

Calculated on chromatographic separation, affording the pure enantiomers in 49% and 37% yield, respectively. 

The gas chromatographic separation of some sulphoxide enantiomers was observed on quartz fused silica capillaries coated with the chiral silicon phase chirasil-val280. 

TYPICAL HOMOCHIRAL DERIVATIZING REAGENTS FOR GAS CHROMATOGRAPHIC SEPARATION OF ENANTIOMERS... 

Francotte, E. and Junker-Buchheit, A., Preparative chromatographic separation of enantiomers, /. Chromatogr., 576, 1, 1992. 

Pais L. S., Loureiro J. M., Rodrigues A. E. (1997b) Modeling, Simulation and Operation of a Simulated Moving Bed for Continuous Chromatographic Separation of l,l -bi-2-naphthol Enantiomers, J. Chromatogr. A 769 25-35. 

Masurel, D., Wainer, I.W. (1989). Analytical and preparative high-performance liquid chromatographic separation of the enantiomers of isofamide, cyclophoshamide, and trofosfa-mide and their determination in plasma. J. Chromatogr 490, 133-143. 

The chiral recognition ability of a CSP is quantitatively evaluated from the results of chromatographic separation of enantiomers. Figure 3.4 shows a chromatogram of the resolution of benzoin (19) on cellulose tris(3,5-dimethylphenylcarbamate). The (+)-isomer elutes first followed by the (—)-isomer complete baseline separation is achieved. The results of the separation can be expressed by three parameters—capacity factors (k1), separation factor (a), and resolution factor (Rs)—defined as follows ... 

For initial work on cyclodextrin-mediated chromatographic separation of enantiomers, see Hinze, W. L. Armstrong, D. W. ed. Ordered Media in Chemical Separations, ACS Symposium Series 342, 1986. 

Cyclodextrin-mediated chromatographic separation of enantiomers is also discussed in Braithwaite, A. Smith, F. J. Chromatographic Methods, 5th Edition, Blackie Academic Professional, London, New York, 1996. 

Recent advances in gas chromatographic separations of enantiomers allow precise determination of the enantiomeric purity of the algal pheromones. The czs-disubstituted cyclopentenes, such as multifidene, viridiene, and caudoxirene, are of high optical purity [ 95% enantiomeric excess (e.e.)] whenever they have been found (32,33). The situation is different with the cyclopropanes and the cycloheptadienes, as shown in Table 2 and Figure 1. Hormosirene from female gametes or thalli of... 

A simple and efficient alternative to the traditional UV detection of amino acids and related compounds is nowadays represented by the evaporative light scattering (ELS) detector, which allows the direct chromatographic separation, with no need for preliminary derivatization. In the field of glycopeptides-based CSPs, it was applied for the first time in the chromatographic resolution of carnitine and 0-acylcarnitine enantiomers on a TE CSP [61]. The considered compounds are nonvolatile solids and gave optimal ELS response under a variety of experimental conditions (buffered and unbuffered mobile phases, flow-rates from 0.5 to 1.5 mL/min, different kind and... 

Elargitai, T., Kaida, Y., and Okamoto, Y., Preparation and chromatographic evaluation of 3,5-dimethylphenyl carbamoylated beta-cyclodextrin stationary phases for normal-phase high-performance liquid-chromatographic separation of enantiomers, J. Chromatogr., 628, 11, 1993. 

Peter, A., Torok, G., and Armstrong, D.W., High-performance liquid chromatographic separation of enantiomers of unusual amino acids on a teicoplanin chiral stationary phase, J. Chromatogr. A, 793, 283, 1998. 

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