Capillary electrochromatography enantioseparation

This review provides an overview of the literature published to date on macrocyclic antibiotics exploited for enantioselective separations in high-performance liquid chromatography (HPLC). It was not intended as a comprehensive issue on the applications of such antibiotics in sub- and supercritical fluid chromatography (SFC), thin layer chromatography (TLC), capillary electrophoresis (CE), and capillary electrochromatography (CEC). A number of structural properties of the most important macrocyclic antibiotics applied in HPLC enantioseparations are listed in Table 2.1. 

Schmid, M.G, et al., Enantioseparation of dipeptides by capillary electrochromatography on a teicoplanin aglycone chiral stationary phase, J. Chromatogr. A., 990, 83, 2003. 

Mangelings, D., Hardies, N., Maftouh, M., Suteu, C., Massart, D.L., Vander Heyden, Y. Enantioseparations of basic and bifunctional compounds by capillary electrochromatography using polysaccharide stationary phases. Electrophoresis 2003, 24, 2567-2576. 

Zheng, J., and Shamsi, S. A. (2006). Simultaneous enantioseparation and sensitive detection of eight p-blockers using capillary electrochromatography-electrospray ionization-mass spectrometry. Electrophoresis 27, 2139—2151. 

Olsson and Blomberg [141] enantioseparated omeprazole and its metabolite 5-hydroxyomeprazole using open tubular capillary electrochromatography with immobilized avidin as chiral selector. The separation was performed with open tubular capillary electrochromatography. The protein avidin was used as the chiral selector. Avidin was immobilized by a Schiffs base type of reaction where the protein was via glutral-dehyde covalently bonded to the amino-modified wall of a fused-silica capillary, 50 /an i.d. Both racemates were baseline resolved. Resolution... 

Girod, M., Chankvetadze, B., and Blaschke, G. (2000) Enantioseparations in non-aqueous capillary electrochromatography using polysaccharide type chiral stationary phases, J. Chromatogr. A 887, 439-455. 

More recently, capillary electrochromatography (CEC) has been adapted for enantioseparation concepts. In this separation method, the driving force for solute transport through the capillary columns is the electroosmotic flow (EOF) in addition, for charged SAs, an electrophoretic transport increment has also to be considered. The enantioseparation occurs due to differential distribution of the SA-enantiomers to the immobilized chiral SO moieties, or in the additive mode due to differential migration of diastere-omeric SO-SA a.ssociates and/or their differential distribution onto an achiral stationary phase. Thus, the following strategies have been adopted for CEC enantioseparations,... 

Capillary electrophoresis and its most popular hybrid technique - capillary electrochromatography - are complementary to HPLC, offering rapid analysis, low consumption of sample and solvents, and usually a higher efficiency of separation (due to a larger number of theoretical plates). Similar to HPLC, enantioseparation with the use of electrophoretic methods can be conducted by direct (chiral phase... 

Figure 10. Enantioseparation of (a) benzoin, (b) methylbenzoin, and (c) trans-stilbene oxide in capillary electrochromatography using a capillary column (100 pm x 25 cm) packed with chiral poly-pyridylmethylmethacrylate on silica (Chiralpak OP) [174],...

Andre, C., Berthelot, A., Thomassin, M., Guillaume, Y. C. (2006). Enantioselective aptameric molecular recognition material design of a novel chiral stationary phase for enantioseparation of a series of chiral herbicides by capillary electrochromatography. Electrophoresis 27, 3254-3262. 

Krause, K. Girod, M. Chankvetadze, B. Blaschke, G. Enantioseparations in normal- and reversed-phase nano-high-performance liquid chromatography and capillary electrochromatography using polyacrylamide and polysaccharide derivatives as chiral stationary phases. J. Chromatography A 1999, 837 (1-2), 51-63. 

Lin, J.M. Nakagama, T. Uchiyama, K. Hobo, T. Enantioseparation of D,L-phenylala-nine by molecularly imprinted polymer particles filled capillary electrochromatography. J. Liq. Chrom. Rel. Technol. 1997, 20, 1489 1506. 

Deng, Y. Zhang, J. Tsuda, T. Yu, P.H. Boulton, A.A. Cassidy, R.M. Modeling and optimization of enantioseparation by capillary electrochromatography. Anal. Chem. 

Fanali S, Orazio GD, Lomsadze K, Samakashvili BS, Chankvetadze B. Enantioseparations with amylose(5-chloro-2-methlphenylcarbamate) in nano liquid chromatography and capillary electrochromatography. J Chromatogr A 2010 1217 1166-74. 

Schmid, M. G. 2012. Chiral metal-ion complexes for enantioseparation by capillary electrophoresis and capillary electrochromatography A selective review. ]. Chromatogr. A 1267 10-16. 

The majority of enantioseparations are performed by pressure-driven liquid chromatography. However, in the last decade other liquid-phase separation techniques have evolved and demonstrated their usefulness for enantioseparations, including supercritical fluid chromatography (SFC), capillary electrophoresis (CE), micellar electrokinetic chromatography (MEKC), and open-tubular and packed-bed electrochromatography (OT-EC and CEC). 

Another approach is electrochromatography with capillary columns packed with an achiral stationary phase, preferentially a reversed-phase type material. The chiral SO is added to the background electrolyte, and may be adsorbed onto the stationary phase by a secondary equilibration process. Enantioseparations in this additive mode have been reported with cyclodextrin type SOs )504-507) and with a chiral ion-pair agent derived from quinine 1508) as mobile phase additives. 

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