Separation enantiomers

W. A. Kirnig, The Practice of Enantiomer Separation by Capillay Gas Chromatography, Hbthig Vedag, Heidelberg, Germany, 1987. 

C. Bicchi and A. Pisciotta, Use of two-dimensional gas cliromatography in the dkect enantiomer separation of chkal essential oil components , J. Chromatogr. 508 341-348(1990). 

A. Mosandl, U. Hener, U. Hagenauer-Hener and A. Kuster mann, Stereoisomeric flavor compounds. 33. Multidimensional gas chromatography dkect enantiomer separation of -y-lactones from fr uits, foods and beverages , 7. Agric. Food Chem. 38 767-771 (1990). 

B. Sellergren, Enantiomer separation using tailor-made phases prepared by molecular imprinting in A practical approach to chiral separations by liquid chromatography, G. Subramanian, VCH, Weinheim (1994) Chapter 4. 

Despite the difficulties caused by the rapidly expanding literature, the use of chiral stationary phases (CSPs) as the method of choice for analysis or preparation of enantiomers is today well established and has become almost routine. It results from the development of chiral chromatographic methods that more than 1000 chiral stationary phases exemplified by several thousands of enantiomer separations have been described for high-performance liquid chromatography (HPLC). 

Fig. 5-13. Schematic representation of the Akzo Nobel enantiomer separation process. Two liquids containing the opposing enantiomers of the chiral selector (FI and K) are flowing countercurrently through the column (4) and are kept separated by the liquid membrane (3). The racemic mixture to be separated is added to the middle of the system (1), and the separated enantiomers are recovered from the outflows of the column (2a and 2b) [64],...

Fig. 5-20. Enantiomer separation in a easeaded ultrafil-tration (UF) system of 60 stages [77]...

Enantiomer Separations using Designed Imprinted Chiral Phases... 

For preparative or semipreparative-scale enantiomer separations, the enantiose-lectivity and column saturation capacity are the critical factors determining the throughput of pure enantiomer that can be achieved. The above-described MICSPs are stable, they can be reproducibly synthesized, and they exhibit high selectivities - all of which are attractive features for such applications. However, most MICSPs have only moderate saturation capacities, and isocratic elution leads to excessive peak tailing which precludes many preparative applications. Nevertheless, with the L-PA MICSP described above, mobile phases can be chosen leading to acceptable resolution, saturation capacities and relatively short elution times also in the isocratic mode (Fig. 6-6). 

The procedure used to accomplish enantiomer separation is shown in Fig. 8-2. It is assumed that the a value is large enough to permit essentially complete separation... 

Enantiomer separation factors (a values) for valine and phenylalanine as well as their esters of 5-10 for phenylalanine and 4-10 for valine have been shown at the 0.1-1 g ChiraLig scale. These a values vary as a function of solvent and other loading matrix factors (pH, salts, etc.). However, all of these cases show a values high enough to obtain reasonable enantiometric purity in less than or equal to three stages. The system with a value of = 6 for the valine methyl ester enantiomers has the ability to load the valine onto the resin in H,0 containing LiClO and also to... 

Pais L. S., Loureiro J. M., Rodrigues A. E. (1998a) Modeling Strategies for Enantiomers Separation by SMB Chromatography, AIChEJ 44 561-569. 

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