Capillary electrophoresis using chiral selectors

Capillary electrophoresis employing chiral selectors has been shown to be a useful analytical method to separate enantiomers. Conventionally, instrumental chiral separations have been achieved by gas chromatography and by high performance liquid chromatography.127 In recent years, there has been considerable activity in the separation and characterization of racemic pharmaceuticals by high performance capillary electrophoresis, with particular interest paid to using this technique in modem pharmaceutical analytical laboratories.128 130 The most frequently used chiral selectors in CE are cyclodextrins, crown ethers, chiral surfactants, bile acids, and protein-filled... 

It is clear that this type of system could be also used with some slight modification for the separation of enantiomers. This type of separation has been termed miceller electrokinetic chromatography [1]. Watarai [2] carried the concept further and used a micro emulsion to the same purpose and termed the technique micro emulsion electrokinetic chromatography. In chiral, capillary electrophoresis, the chiral selector can also be an additive to the electrolyte, or take the form of an emulsion or be immobilized on the capillary tube surface as a traditional type of stationary phase. 

Tanaka, Y., and Terabe, S. (1997). Separation of the enantiomers of basic drugs by affinity capillary electrophoresis using a partial filling technique and ai-acid glycoprotein as chiral selector. 

Y Tanaka, S Terabe. Enantiomer separation of acidic racemates by capillary electrophoresis using cationic and amphoteric f -cyclodextrins as chiral selectors. J Chromatogr A 781 151-160, 1997. 

A Shibukawa, DK Lloyd, IW Wainer. Simultaneous chiral separation of leu-covorin and its major metabolite 5-methyltetrahydrofolate by capillary electrophoresis using cyclodextrins as chiral selectors. Estimation of the formation constant and mobility of the solute—cyclodextrin complex. Chromatographia 35 419-429, 1993. 

Fig. 5 Separation of ( )-epinastine by capillary electrophoresis using the partial-separation-zone technique and bovine serum albumin as chiral selector. (Reprinted with permission from Ref. 62. Copyright 1995 Elsevier Science.)...

H Matsunaga, J Haginaka. Separation of basic drug enantiomers by capillary electrophoresis using ovoglycoprotein as a chiral selector comparison of chi-... 

R Gotti, V Cavrini, V Anchisano, G Mascellani. Dermatan sulfate as useful chiral selector in capillary electrophoresis. J Chromatogr A 814 205-211, 1998. 

The chiral recognition mechanisms in NLC and NCE devices are similar to conventional liquid chromatography and capillary electrophoresis with chiral mobile phase additives. It is important to note here that, to date, no chiral stationary phase has been developed in microfluidic devices. As discussed above polysaccharides, cyclodextrins, macrocyclic glycopeptide antibiotics, proteins, crown ethers, ligand exchangers, and Pirkle s type molecules are the most commonly used chiral selectors. These compounds... 

The resolution of 3,4-dihydro-2/f-l-benzothiopyran-4-one 1-oxide has been achieved by capillary electrophoresis using heptakis-6-sulfato-/3-cyclodextrin or, better, its 2,3-diacetyl derivative as the chiral selector the i -sulfoxide migrated before the A-enantiomer <2001JSS766>. It has also been noted that (R)-thiochroman 1-oxide is eluted before the (d )-enantiomer from a Chiralcel cellulose tribenzoate column <2001TA1551> and a Daicel Chiralpak AD-H column using hexane/APrOH 90 10 has been used to resolve the (3.y,l. R) 249 and (3/ ,l A) 250 enantiomers of the substituted tetrahydrothiopyran-4-one <20050BC84>. 

Haginaka, J. Enantiomer separation of drugs by capillary electrophoresis using proteins as chiral selectors. J. Chromatogr., A 2000, 875, 235-254. 

Desiderio, C. Polcaro, C.M. Padiglioni, P. Fanali, S. Enantiomeric separation of acidic herbicides by capillary electrophoresis using vancomycin as chiral selector. J. Chromatogr., A 1997, 781, 503-513. 

To date, the use of chemometrics for method development and robustness testing has been published for all areas of CE, including capillary zone electrophoresis (CZE), capillary electrokinetic chromatography (EKC) using chiral selectors for enantioseparations, micellar electrokinetic chromatography (MEKC), and microemulsion electrokinetic chromatography (MEEKC). A comprehensive description can be found in Chapters 5 and 13 as well as in recent reviews (6-11). Several monographs on chemometrics in analytical chemistry have been published such as References 12-14. This chapter will... 

Fig. 5 A typical application of capillary electrophoresis for chiral separations of small peptides. Chiral separation of the isomeric dipeptides (A) of Asp-PheOMe and P-Asp-PheOMe and (B) of Asp-PheNH2 and P-Asp-PheNH2. The separation was carried out at pH 3.3 using 15 mg/mL of carboxymethyl-P-cyclodextrin as the chiral selector. (For details of experimental conditions, see Ref. 171.)...

M Blanco, J Coello, H Iturriaga, S Maspoch, C Perez-Maseda. Separation of profen enantiomers by capillary electrophoresis using cyclodextrins as chiral selectors. J Chromatogr A 793 165-175, 1998. 

C Desiderio, S Fanali. Chiral analysis by capillary electrophoresis using antibiotics as chiral selector. J Chromatogr A 807 37-56, 1998. 

Tang W, Muderawan IW, Ng S-C, Chan HSO. 2006. Enantioselective separation in capillary electrophoresis using a novel mono-6 -propylammonium-P-cyclodextrin as chiral selector. Analytica Chimica Acta 555(1 ) 63-67. 

Methaqualone enantiomers were separated by capillary electrophoresis using ( )-N-dodecyl-]V-methylephedrinium bromide as chiral selector and surfactant (97PHA762). 

Fanah S., Cartoni C., Desiderio C., Chiral separation of newly synthesized arylpropionic acids by capillary electrophoresis using cyclodextrins or a glycopeptide antibiotic as chiral selectors. Chromatographia, 54, 87-92 (2001). 

Kodama, S., Yamamoto, A., Matsunaga, A., and Hayakawa, K., Direct chiral resolution of tartaric acid in food products by ligand exchange capillary electrophoresis using copper (II)-D-quinic acid as a chiral selector, J. Chromatogr. A, 932, 139, 2001. 

In chromatographic separations, CDs and mainly specific derivatives are used widely. In the years 1990-2000, about 25 papers monthly were published on successful application of some CD in gas or liquid chromatography. In gas chromatography, CDs are used only in the stationary phase, while in HPLC, the CD is used either dissolved in the mobile phase, or bound to a surface in the stationary phase. In capillary zone electrophoresis, the most used chiral selectors are CDs. as their anionic cationic. or alkylated derivatives (Fig. 4). 

This entry summarizes the application of cyclodextrins (CDs) for separation of enantiomers by using capillary electrophoresis (CE) [capillary electrokinetic chromatography (CEKC) and micellar electrokinetic chromatography (MEKC)]. Together with major properties of cyclodextrins as very useful chiral selectors, some mechanistic aspects of enantioseperations by using CE techniques are also emphasized. 

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