Cyclodextrins in capillary electrophoresis

Stathakis, C., and Cassidy, R. M. (1998). Control of relative migration of small inorganic and organic anions with cyclodextrins in capillary electrophoresis (CE). Can.. Chem. 76, 194—198. 

S Fanali, E Camera. Use of methylamino-/3-cyclodextrin in capillary electrophoresis. Resolution of acidic and basic enantiomers. Chromatographia 43 247-253, 1996. 

B Chankvetadze, M Fillet, N Burjanadze, D Bergenthal, C Bergander, H Luft-mann, J Crommen, G Blaschke. Enantioseparation of aminoglutethimide with cyclodextrins in capillary electrophoresis and studies of selector-selectand interactions using NMR spectroscopy and electrospray ionization mass spectrometry. Enantiomer 5 313-322, 2000. 

PK Owens, AF Fell, MW Coleman, M Kinns, JC Berridge. Use of H -NMR spectroscopy to determine the enantioselective mechanism of neutral and anionic cyclodextrins in capillary electrophoresis. J Pharm Biomed Anal 15 1603-1619, 1997. 

Evans C.E., Stalcup A.M., Comprehensive strategy for chiral separations using sulfated cyclodextrins in capillary electrophoresis. Chirality, 15, 709-723 (2003). 

Kodama, S., Yamamoto, A., and Matsunaga, A., Direct chiral resolution of pantothenic acid using 2-hydroxypropyl-fi-cyclodextrin in capillary electrophoresis, J. Chmmatogr. A, 811, 269, 1998. 

Chankvetadze B, Buijanadze N, Maynard DM, Beigander K, Bergentheil D, Blaschke G (2002) Comparative enantioseparations with native p-cyclodextrin and heptakis-(2-0-methyl-3,6-di-0-sulfo)-P-cyclodextrin in capillary electrophoresis. Electrophoresis 23 3027-3034... 

Bergholdt BA, Lehmann SV (1998) High-speed separation of ormeloxifene enantiomers using sulfated P-cyclodextrin in capillary electrophoresis. Chirality 10 699-704... 

Scriba GKE. Cyclodextrins in capillary electrophoresis enantioseparations ecent developments and applications. J. Sep. Sci. 2008 31 1991 2011. 

Enantioresolution in capillary electrophoresis (CE) is typically achieved with the help of chiral additives dissolved in the background electrolyte. A number of low as well as high molecular weight compounds such as proteins, antibiotics, crown ethers, and cyclodextrins have already been tested and optimized. Since the mechanism of retention and resolution remains ambiguous, the selection of an additive best suited for the specific separation relies on the one-at-a-time testing of each individual compound, a tedious process at best. Obviously, the use of a mixed library of chiral additives combined with an efficient deconvolution strategy has the potential to accelerate this selection. 

Bergholdt, A.B., Jprgensen, K.W., Wendel, L., Lehmaim, S.V. Fast chiral separations using sulfated fS-cyclodextrin and short-end injection in capillary electrophoresis. 

Rudaz, S., Calleri, E., Geiser, L., Gherkaoui, S., Prat, J., and Veuthey, J. L. (2003). Infinite enantiomeric resolution of basic compounds using highly sulfated cyclodextrin as chiral selector in capillary electrophoresis. Electrophoresis 24, 2633—2641. 

B Chankvetadze, G Endresz, G Blaschke. Charged cyclodextrin derivatives as chiral selectors in capillary electrophoresis. Chem Soc Rev 25 141-146,... 

T Schmitt, H Engelhardt. Charged and uncharged cyclodextrins as chiral selectors in capillary electrophoresis. Chromatographia 37 475-481, 1993. 

F Lelievre, P Gareil, A Jardy. Selectivity in capillary electrophoresis application to chiral separations with cyclodextrins. Anal Chem 69 385—392, 1997. 

F Lelievre, P Gareil, Y Bahaddi, H Galons. Intrinsic selectivity in capillary electrophoresis for chiral separations with dual cyclodextrin systems. Anal Chem 69 393-401, 1997. 

G Galavema, R Corradini, A Dossena, R Marchelli, G Vecchio. Histamine-modified f -cyclodextrins for the enantiomeric separation of dansyl-amino acids in capillary electrophoresis. Electrophoresis 18 905—911, 1997. 

TH Seals, C Sheng, JM Davis. Influence of neutral cyclodextrin concentration on plate numbers in capillary electrophoresis. Electrophoresis 22 1957-1973, 2001. 

S Sabbah, GKE Scriba. Separation of dipeptide and tripeptide enantiomers in capillary electrophoresis using carboxymethyl-beta-cyclodextrin and succinyl-beta-cyclodextrin. Influence of the amino acid sequence, nature of the cyclodextrin and pH. Electrophoresis 22 1385-1393, 2001. 

JC Reijenga, BA Ingelse, FM Everaerts. Thermodydnamics of chiral selectivity in capillary electrophoresis separation of ibuprofen enantiomers with (3-cyclodextrin. J Chromatogr A 792 371-378, 1997. 

E Szoko, J Gyimesi, L Barcza, K Magyar. Determination of binding constants and the influence of methanol on the separation of drug enantiomers in cyclodextrin-modified capillary electrophoresis. J Chromatogr A 745 181-187,... 

S Hamai, H Sakurai. 2H20 effects on the inclusional complexation of cyclodextrin with sodium 2-naphthalenesulfonate in capillary electrophoresis and UV spectrometry. J Chromatogr A 800 327-332, 1998. 

S Sabah, GKE Scriba. Influence of the structure of cyclodextrins and amino acid sequence of dipeptides and tripeptides on the pH-dependent reversal of the migration order in capillary electrophoresis. J Chromatogr A 894 267-272, 2000. 

T Schmitt, H Engelhardt. Derivatized cyclodextrins for the separation of enantiomers in capillary electrophoresis. HRC—J High Resol Chromatogr 16 525-529, 1993. 

B Chankvetadze, K Lomsadze, D Bergenthal, J Breitkreutz, K Bergander, G Blaschke. Mechanistic study on the opposite migration order of clenbuterol enantiomers in capillary electrophoresis with /3-cyclodextrin and single-isomer heptakis(2,3-diacetyl-6-sulfo-)-/3-cyclodextrin. Electrophoresis 22 3178-3184. 

In contrast, CSPs have achieved great repute in the chiral separation of enantiomers by chromatography and, today, are the tools of the choice of almost all analytical, biochemical, pharmaceutical, and pharmacological institutions and industries. The most important and useful CSPs are available in the form of open and tubular columns. However, some chiral capillaries and thin layer plates are also available for use in capillary electrophoresis and thin-layer chromatography. The chiral columns and capillaries are packed with several chiral selectors such as polysaccharides, cyclodextrins, antibiotics, Pirkle type, ligand exchangers, and crown ethers. 

Contrary to conventional HPLC, almost 98% of chiral resolution in CE is carried out using the chiral selector as a mobile phase additive. Again all the common chiral selectors used in NLC can also be used in NCE. But, unfortunately, few chiral molecules have been tested in NCE for enantiomeric resolution of some racemates. To the best of our knowledge only cyclodextrins and protein-based chiral mobile phase additives have been used for this purpose. Manz and coworkers discussed chiral separations by NCE in their reviews in 2004 [21] and 2006 [22], Later on, Pumera [16] reviewed the use of microfluidic devices for enantiomeric resolutions in capillary electrophoresis. Not much work has been carried out on chiral resolution in NCE but the papers that are available are discussed here. 

Since micellar electrokinetic chromatography (MEKC) was hrst introduced in 1984, it has become one of major separation modes in capillary electrophoresis (CE), especially owing to its applicability to the separation of neutral compounds as well as charged ones. Chiral separation is one of the major objectives of CE, as well as MEKC, and a number of successful reports on enantiomer separations by CE and MEKC has been published. In chiral separations by MEKC, the following two modes are normally employed (a) MEKC using chiral micelles and (b) cyclodextrin (CD)-modilied MEKC (CD-MEKC ... 

Flurer CL, Lin LA, et al. Determination of ephedrine compounds in nutritional supplements by cyclodextrin-modified capillary electrophoresis. J Chromatogr B Biomed Appl 1995 669 133-9. 

J Wang, IM Warner. Combined polymerized chiral micelle and gamma-cyclodextrin for chiral separation in capillary electrophoresis. J Chromatogr A 711 297— 304, 1995. 

T de Boer, R Bijma, K Ensing. Tuning of the selectivity in capillary electrophoresis by cyclodextrins illustrated by the separation of some structurally related phenothi-azines. J Capillary Electrophor 5 65-71, 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. 

Brown, R. S., Luong, J. H. T., Szolar, O. H. J., Halasz, A., and Hawaii, J., Cyclodextrin-modified capillary electrophoresis determination of polycyclic aromatic hydrocarbons in contaminated soils. Anal. Chem., 68, 287-292, 1996. 

The computational studies described above are representative examples meant to illustrate the diversity of computational techniques used to assess chiral recognition by cyclodextrins in chiral chromatography. Other published examples include the use of molecular mechanics to describe shapes of aminoalkylphosphonic acids binding to a covalently linked acetylated cyclodextrin [72], the computation of free energies of atenolol binding to a perphenylcarbamate-p-cyclodextrin likewise covalently bound to silica gel [73], and studies of cyclodextrins used as chiral mobile phase additives in reverse-phase HPLC [74] and in capillary electrophoresis [75]. 

Kuo C.Y., Wu H.L., Wu S.M., Enantiomeric analysis of methotrexate in pharmaceuticals by cyclodextrin-modified capillary electrophoresis. Anal. Chim. Acta, 471, 211-217 (2002). 

R 570 U. Schmitt, S. K. Branch and U. Holzgrabe, Chiral Separations by Cyclodextrin - Modified Capillary Electrophoresis - Determination of the Enantiomeric Excess , J. Sep. Sci.,2002,25,959 R 571 D. Schneider and A. Prodoehl, Hydrophiles in Hydrophobic Studies The Role of Polar Amino Acids in Membrane Proteins , BlOspectrum, 2003,9, 366... 

The final compound is a mixture of two enantiomers (C2 is chiral) (Scheme 17.5). The use of lipases in 1991 to separate racemic mixture of a key synthon represents the cornerstone of the synthetic scheme leading to each enantiomer [40]. The two enantiomers of tetraconazole were separated using p cyclodextrin-mediated capillary electrophoresis in 2001 [42]. 

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