Chiral separation principles

G Gubitz, MG Schmid. Recent progress in chiral separation principles in capillary electrophoresis. Electrophoresis 21 4112-4135, 2000. 

Gtibitz, G. Schmid, M.G. Review chiral separation principles in capillary electrophoresis. J. Chromatogr. A 1997, 792, 179-225. 

Gubitz G, Schmid M.G, Chiral separation principles in chromatographic and electromigration... 

Chankvetadze, B. Capillary Electrophoresis inChiral Analysis. (John Wiley Sons, New York, 1997). Gubitz G, Schmid M.G, Recent advances in chiral separation principles in capillary electrophoresis and capillary electrochromatography. Electrophoresis, 25,3981-3996 (2004). 

Standardized commercial TLC plates are essential for routine handling of large sample volumes. Homemade layers usually do not meet the quality requirements of modem analysis. However, they often contribute substantially to the understanding of chiral separation principles (119-142). It is not the purpose of this chapter to present a detailed description of layer preparations we refer to the separation examples listed in Table 6. In this context the published works of Lepri et al (133-139) and Armstrong et al. (142) are worth mentioning. 

Chip-based enantioseparations using an electrophoresis principle were presented by Gao et al. [59]. They used mono-, two-, and four-channel chips to develop chiral separations of fluorescein isothiocyanate (FlTC)-labeled basic compounds. To obtain the chiral separations, seven neutral CD were screened (i.e., a-CD, fi-CD, y-CD, HP-a-CD, HP-y-CD, and DM-fi-CD). Using the monochannel chip, the seven selectors were screened sequentially. Using the two-channel chip, between-channel repeatability could be demonstrated using the same separation conditions. Using two different selectors in the channels, the analysis time for the screening of the seven CD can be reduced to half, compared to the time needed in the monochannel... 

A. Principles of Chiral Separation in LC Direct and Indirect Approaches... 

An overview of the principles of chiral separations in CE and HPLC is given in the first part of this chapter. The second part is dedicated to an overview of chiral separation with CE. The popularity of electrophoretic techniques has grown spectacularly in recent years, mainly due to their exceptional performances in the chiral field. Various selectors can easily... 

In most cases, the chiral selector is simply added to the BGE. " Interactions between the analytes and the chiral selector will determine the stability of the diastereomeric complexes formed. The interactions involved in the chiral recognition process in CE are hydrophobic, electrostatic, Van der Waals and hydrogen bond-type interactions. Several reviews discuss the principles of electrophoretic chiral separations. 

One of the main principles for chiral separation used in modern capillary GC is the bonding of the optically active compounds via hydrogen bridges to a stationary-phase material. Feibush and Gil-Av [8] suggested a rapid and reversible formation of association complexes between carbonyl and amide functions of selector and selectand. The formation of diastereomeric associates yields complexes of different stability, depending on the relative configuration. The introduction of dipeptide and diamide phases leads... 

Investigation with the two optical transduction principles mentioned before confirmed the preferential enrichment of the S-enantiomer resulting in more than ninefold higher signals, which is the highest separation factor found for chiral separation on cyclodextrins up to now. The good agree-... 

Large-scale Sorbex processes have been developed for a variety of different bulk separations a brief summary is given in Table IV. In recent years, the same principle has been applied also to a wide range of chiral separations and other difficult separations that are important in the pharmaceutical industry. Several novel system configurations have been developed. In one system, a carousel of 12 small columns rotates between two stationary circular headers, which act as the switch valve, thus effectively incorporating the adsorption and the flow switching functions within a single unit. 

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