Cyclodextrins chromatography

R.D. Armstrong, T. J. Ward, N. Pattabiraman, C. Benz and D.W.Armstrong, Separation of Tamoxifen Geometric Isomers and Metabolites by Bonded Phase P-Cyclodextrin Chromatography, J. Chromatogr., 414(1987)192. 

Fig. 7. A tethered cyclodextrin and the structure of P-cyclodextrin, the most common cyclodextrin used as a bonded ligand in Hquid chromatography.

Analytically, the inclusion phenomenon has been used in chromatography both for the separation of ions and molecules, in Hquid and gas phase (1,79,170,171). Peralkylated cyclodextrins enjoy high popularity as the active component of hplc and gc stationary phases efficient in the optical separation of chiral compounds (57,172). Chromatographic isotope separations have also been shown to occur with the help of Werner clathrates and crown complexes (79,173). 

Immobilization. The abiUty of cyclodextrins to form inclusion complexes selectively with a wide variety of guest molecules or ions is well known (1,2) (see INCLUSION COMPOUNDS). Cyclodextrins immobilized on appropriate supports are used in high performance Hquid chromatography (hplc) to separate optical isomers. Immobilization of cyclodextrin on a soHd support offers several advantages over use as a mobile-phase modifier. For example, as a mobile-phase additive, P-cyclodextrin has a relatively low solubiUty. The cost of y- or a-cyclodextrin is high. Furthermore, when employed in thin-layer chromatography (tic) and hplc, cyclodextrin mobile phases usually produce relatively poor efficiencies. 

GC using chiral columns coated with derivatized cyclodextrin is the analytical technique most frequently employed for the determination of the enantiomeric ratio of volatile compounds. Food products, as well as flavours and fragrances, are usually very complex matrices, so direct GC analysis of the enantiomeric ratio of certain components is usually difficult. Often, the components of interest are present in trace amounts and problems of peak overlap may occur. The literature reports many examples of the use of multidimensional gas chromatography with a combination of a non-chiral pre-column and a chiral analytical column for this type of analysis. 

Figure 10.1 Analysis of racemic 2,5-dimethyl-4-hydroxy-3[2H]-furanone (1) obtained from a strawbeny tea, flavoured with the synthetic racemate of 1 (natural component), using an MDGC procedure (a) dichloromethane extract of the flavoured strawbeny tea, analysed on a Carbowax 20M pre-column (60 m, 0.32 mm i.d., 0.25 p.m film thickness earner gas H2, 1.95 bar 170 °C isothermal) (b) chirospecific analysis of (1) from the sti awbeny tea exti act, ti ansfened foi stereoanalysis by using a pemiethylated /3-cyclodextrin column (47 m X 0.23 mm i.d. canier gas H2, 1.70 bar 110 °C isothemial). Reprinted from Journal of High Resolution Chromatography, 13, A. Mosandl et al., Stereoisomeric flavor compounds. XLIV enantioselective analysis of some important flavor molecules , pp. 660-662, 1990, with permission from Wiley-VCH.

Figure 10.2 MDGC-MS differentiation between the enantiomers of theaspiranes in an aglycone fraction from puiple passion fruit DB5 pre-column (25 m X 0.25 mm i.d., 0.25 p.m film thickness canier gas He, 0.66 ml/min oven temperature, 60-300 °C at 10 °C/min with a final hold of 25 min) permethylated /3-cyclodextrin column (25 m X 0.25 mm i.d., 0.25 p.m film thickness canier gas He, 1.96 ml/min 80 °C isothermal for 20 min and then programmed to 220 °C at 2 °C/min). Reprinted from Journal of High Resolution Chromatography, 16, G. Full et al., MDGC- MS a powerful tool for enantioselective flavor analysis , pp. 642-644, 1993, with permission from Wiley-VCH.

In relation to separation of nucleotides, Hoffman61 found that adenine nucleotides interacted most strongly with cycloheptaamylose, presumably by inclusion of the base within the cavity of cyclodextrin. When epichlorohydrin-cross-linked cycloheptaamylose gel was used as a stationary phase for nucleic acid chromatography, adenine-containing compounds were retarded most strongly. 

N. A. Konig, "Enantioselective Gas Chromatography With Modified Cyclodextrins , Huethig, Heidelberg, 1991. 

Early attempts to use cyclodextrins and their simple derivatives as chira stationary phases in gas chromatography met... 

Rizzi, A. M. and Plank, C., Coupled column chromatography in chiral separations systems employing P-cyclodextrin phases for chiral separation, /. Chromatogr., 557, 199, 1991. 

Makino, Y., Suzuki, A., Ogawa, T., and Shirota, O., Direct determination of methamphetamine enantiomers in urine by liquid chromatography with a strong cation-exchange precolumn and phenyl-p-cyclodextrin-bonded semimicrocolumn, ]. Chromatogr. B, 729, 97, 1999. 

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... 

Terabe, S., Ozaki, H., Otsuka, K., and Ando, T., Electrokinetic chromatography with 2-O-carboxymethyl-P-cyclodextrin as a moving "stationary" phase, /. Ckromatogr., 332, 211, 1985. 

Nishi, H. and Matsuo, M., Separation of corticosteroids and aromatic hydrocarbons by cyclodextrin-modified micellar electrokinetic chromatography, J. Liq. Chromatogr., 14, 973, 1991. 

Gas chromatography (GC) has also been used for preparative purposes, but is restricted to relatively volatile racemates such as anesthetics, pheromones or monoterpenes and, therefore, very few applications are reported. Nevertheless, in the cases to which GC may be applied, it could be considered as an economical alternative to HPLC. Most of the resolutions of enantiomers were performed on cyclodextrin-derived CSPs [109, 144-153], and only on very few occasions were other chiral selectors used [153]. 

A. M. Stalcup, Cyclodextrin bonded chiral stationary phases in enantiomer separations in A practical approach to chiral separations by liquid chromatography, G. Subramanian, VCH, Weinheim (1994) Chapter 5. 

The reaction mixtures of isophorone were analysed with a gas chromatograph. The GC analyses were carried out with gas chromatograph equipped with a p-cyclodextrine capillary column (analysis temperature dihydroisophorone at 110 °C) and FID. The chromatograms were recorded and peak areas were calculated with Chromatography Station for Windows CSW32 v. 1.2 (DataApex Ltd. 2001, Prague). 

The mobile phases used with cyclodextrin CSPs are similar to those used in reverse phase chromatography, ie water or buffer solutions modified with methanol or acetonitrile. 

Bordajandi, L.R., Korytar, P., De Boer, J., Gonzalez, M.J. (2005). Enantiomeric separation of chiral polychlorinated biphenyls on P-cyclodextrin capillary columns by means of heart-cut multidimensional gas chromatography and comprehensive two-dimensional gas chromatography applications to food samples. J. Sep. Sci. 28, 163-171. 

Lopez-Nicolas JM, Nunez-Delicado E, Perez-Lopez AJ, Carbonell A and Cuadra-Crespo P. 2006. Determination of stoichiometric coefficients and apparent formation constants for (3-cyclodextrin complexes of trans-resveratrol using reversed-phase liquid chromatography. J Chromatogr A 1135 158—165. 

Organolead and organoselenium compounds were separated satisfactorily by high-performance capillary electrophoresis, using /1-cyclodextrin-modified micellar electroki-netic chromatography with on-column UVV detector set at 210 nm130. 

FEURLE, J., JOMAA, H., WILHELM, M GUTSCHE, W.B., HERDRICH, M., Analysis of phosphorylated carbohydrates by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry utilising p-cyclodextrin bonded stationary phase, J. Chromatogr., 1998,803,111-119. 

An understanding of the recognition of chirality at a molecular level has become of interest in many fields of chemistry and biology. In the past decade, many attempts to clarify the mechanism of chiral recognition on CSPs for liquid chromatography have been made by means of chromatography, NMR spectroscopy,199 202 X-ray analysis, and computational methods.203 - 206 The successful studies have been mostly carried out for the small-molecule CSPs, especially cyclodextrin-based CSPs and Pirkle-type (brush-type) CSPs. In contrast, only a few mechanistic studies on chiral discrimination at the molecular... 

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