Capillary electrochromatography chiral separations

In a different approach, Lin et al. have used particles derived from a ground MI-bulk polymer and mixed with a polyacryl amide gel for chiral separation. Using a polymer imprinted with L-phenylalanine, D-phenylalanine could be separated from the template with a separation factor of 1.45 [35]. Although the combination of MIP with capillary electrochromatography is still not widely used, the ability to separate enantiomers in nanoliter samples promises interesting developments for the future. 

Mangelings, D., Tanret, I., Matthijs, N., Maftouh, M., Massart, D.L., Vander Heyden, Y. Separation strategy for acidic chiral pharmaceuticals with capillary electrochromatography on polysaccharide stationary phases. Electrophoresis 2005, 26, 818-832. 

Kamande, M. W., Zhu, X., Kapnissi-Christodoulou, C., and Warner, 1. M. (2004). Chiral separations using a polypeptide and polymeric dipeptide surfactant polyelectrolyte multilayer coating in open-tubular capillary electrochromatography. Anal. Chem. 76, 6681—6692. 

Y. Gong and H. K. Lee, Application of Cyclam-Capped (5-Cyclodextrin-Bonded Silica Particles as a Chiral Stationary Phase in Capillary Electrochromatography for Enantiomeric Separations, Anal. Chem. 2003, 75,... 

M. W. Kamande, X. Zhu, C. Kapnissi-Christodoulou, and 1. M. Warner, Chiral Separations Using a Polypeptide and Polymeric Dipeptide Surfactant Polyelectrolyte Multilayer Coating in Open-Tubular Capillary Electrochromatography, Anal. Chem. 2004, 76, 6681. 

The use of antibiotic-based CSPs has been reported in capillary electrochromatography (CEC) for chiral resolution [60]. Teicoplanin CSP covalently bonded to silica gel was used to resolve the enantiomers of tryptophan and dinitrobenzoyl leucine by CEC [61]. Good levels of enantioselectivity were obtained with optimized separations. Vancomycin covalently bonded to silica gel was also evaluated in CEC for the chiral resolution of thalidomide and jS-adrenergic blocking agents under all the three mobile phase modes. The... 

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... 

The first and most often encountered separation mechanism in CE is based on mobility differences of the analytes in an electric field these differences are dependent on the size and charge-to-mass ratio of the analyte ion. Analyte ions are separated into distinct zones when the mobility of one analyte differs sufficiently from the mobility of the next. This mechanism is exemplified by capillary zone electrophoresis (CZE) which is the simplest CE mode. A number of other recognized CE modes are variations of CZE. These are micellar electrokinetic capillary chromatography (MECC), capillary gel electrophoresis (CGE), capillary electrochromatography (CEC), and chiral CE. In MECC the separation is similar to CZE, but an additional mechanism is in effect that is based on differences in the partition coefficients of the solutes between the buffer and micelles present in the buffer. In CGE the additional mechanism is based on solute size, as the capillary is filled with a gel or a polymer network that inhibits the passage of larger molecules. In chiral CE the additional separation mechanism is based on chiral selectivity. Finally, in CEC the capillary is packed with a stationary phase that can retain solutes on basis of the same distribution equilibria found in chromatography. 

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,... 

Koide T and Ueno K. Enantiomeric separations of primary amino compounds by capillary electrochromatography with monolithic chiral stationary phases of chiral crown ether-bonded negatively charged polyacrylamide gels. J. Chromatogr. A 2001 909 305. 

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... 

The most frequently applied CE techniques for chiral separations are capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC) and chiral capillary electrochromatography (CEC). Two strategies are generally adopted for the enantiomer resolution in these electrophoretic techniques ... 

CD). The partial-filling technique (PFT) proved to be a suitable and efficient approach to avoid MS source contamination, as well as signal suppression due to nonvolatile additives. Therefore, fhe PFT technique is particularly adapted with chiral selectors added into fhe electrolyte solution. Because of fhe counter-current contribution, charged chiral selectors were found to be more suitable for the online MS detection of separated enantiomers. Capillary electrochromatography with chiral stationary phases has also been developed, but to a lesser extent. 

TD Hatajik, PR Brown. Chiral separations of pharmaceuticals using capillary electrochromatography (CEC). J Capillary Electroph 5 143-151, 1998. 

D Wistuba, V Schurig. Enantiomer separation of chiral pharmaceuticals by capillary electrochromatography. J Chromatogr A 14 255-276, 2000. 

G Gubitz, MG Schmid. Chiral separation by capillary electrochromatography. Enantiomer 5 5-11, 2000. 

Chiral separation by capillary electrochromatography Gubitz, G. Schmid, M. G. Enantiomer 2000, 5, 5-11. 

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