Solvent systems, hydrophilic

Table II. Hydrophilic Solvent Systems Compared with Octanola...

Procyanidin Separation by CCC with Hydrophilic Solvent Systems... 

The values of the capillary wavelengths are smaller for hydrophilic solvent systems than those for hydrophobic ones The first family of solvent systems tends to form small droplets of one phase in the other one, hence leading to a more stable emulsion. Their stationary phase is consequently less retained in the CCC column than the one of hydrophobic solvent systems this phenomenon is well known in CCC [1]. 

For the sample mixmre with an unknown composition, the search for the suitable two-phase solvent system may be initiated with the partition coefficient measurement with n-hexane/ethyl acetate/n-butanol/methanol/water (5 5 0 5 5) (Table 1), chloroform/methanol/water (10 3 7) (Table 2) or ferf-butyl methyl ether/butanol/ acetonitorile/water (6 0 3 8) (Table 3). If the Ai(org/aq) value is too large, the search should be directed toward the more hydrophobic solvent systems and, if the K value is too small, the search should be directed toward the more hydrophilic solvent systems until the proper K values are obtained. 

If the above solvent search reaches the solvent system of n-hexane/methanol/water (2 1 1), which is suitable for the most hydrophobic compounds, and a more hydro-phobic solvent system is required, one may reduce the amount of water from the above solvent system and/or replace methanol with ethanol. Some useful solvent systems for the extremely hydrophobic compounds are M-hexane/ethanol/water (6 5 2) and w-hexane/methanol (2 1). On the other hand, if the solvent search reaches the solvent systems of w-butanol/water or ferf-butyl methyl ether/butanol/acetonitorile/water (2 2 1 5), which are suitable for the most hydrophilic compounds, and a still more hydrophilic solvent system is required, the above solvent system may be modified by the addition of acid or salt trifluoroacetic acid (TFA) or ammonium acetate has been successfully used. 

The chromatogram shown in Fig. 3 was the first separation profile of oligomeric procyanidins by HSCCC using a two-phase solvent system. In recent times, other hydrophilic solvent systems, such as hexane/methyl acetate/acetonitrile/ water three-phase system,methyl terf-butyl ether/l-buta-noFacetonitrile/water two-phase systems,and ethyl acet-ate/1-butanol (or 2-propanol)/water two-phase systems, were also applied to HSCCC separations of other proantho-cyanidins and/or related polyphenolic oligomers. 

For separation of lipophilic substances, such as fatty acids and steroids, a reversed phase system of P.c. can be used. In this technique, the chromatography paper is made hydrophobic by impregnation with silicone or paraffin oil, or by acetylation. The phases are therefore reversed, i.e. the hydrophilic solvent system is repelled by the cellulose fibers, so that it forms the mobile phase the more strongly hydrophobic organic solvent becomes the stationary phase. ZafEaroni systems are important for the separation of steroids these are usually water-free, and the paper is impregnated with formamide or propylene glycol, which acts as the stationary phase. 

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