Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1996-02-20
1997-06-24
Therkorn, Ernest G.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210656, 2101982, B01D 1508
Patent
active
056414048
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The instant invention is in the field of liquid chromatography. In general, liquid chromatography is a method of chemical separation. Most often, liquid chromatographic separations involve components of different molecular formulas. However, in some circumstances, such as the separation of enantiomers, the components to be separated have the same molecular formula.
BACKGROUND
An important goal of chromatography is a complete separation of components in a mixture. Therefore, the field of chromatography is continually striving to increase the efficiency of separating components in order to improve resolution and to permit better isolation of different components.
In particular, there is an increasing demand for the better isolation of enantiomerically pure forms of biologically active chiral compounds in order to investigate relationships between the stereochemistry of these compounds and their biological activity. Therefore, the individual enantiomers should be isolated efficiently, with high optical purity, and in sufficient quantity to perform biological, clinical, or other tests and then, perhaps, to produce commercial amounts of the enantiomer if the test is successful. Chromatography on chiral stationary phases has been recognized as a useful tool in achieving these goals and is now established as an acceptable method for this purpose.
Among the myriad of chiral stationary phases developed and studied since the 1980's, derivatized cellulose-based and amylose-based stationary phases are known to be efficient and versatile chiral sorbents for the chromatographic resolution of enantiomers. Such cellulose-based and amylose-based sorbents show very different selectivities depending on the devitalizing groups on the cellulose and amylose. (Francotte & Wolf, Journal of Chromatography, 595 (1992) 63-75).
The effort to achieve greater separation of enantiomeric mixtures has focused on the stationary phase used, which, as mentioned, is often a cellulose or amylose derivative. However, the mobile phase used for the separation generally is not discussed at length. Typically, the mobile phase used is hexane-isopropanol (9:1). Hexane/ethanol eluents are also known. (Chiral Technologies, Inc.)
With current methods, separation and resolution of enantiomeric mixtures is difficult. Therefore, the art of liquid chromatography would be advanced if greater separation and resolution between enantiomers could be obtained.
SUMMARY OF THE INVENTION
The instant invention is a process for separating enantiomeric mixtures comprising two steps. The first step is to contact a liquid phase with a chiral phase; the liquid phase comprising methanol and pentane such that the concentration of methanol is greater than one tenth percent on a volume basis, and less than or equal to the saturation concentration of methanol in the liquid phase. The second step is to contact an enantiomeric mixture with the chiral phase and with the liquid phase, the concentration of pentane in the liquid phase being at least that necessary to resolve the enantiomeric mixture into its enantiomers with a resolution at least one and one half times greater than when the pentane of the liquid phase is replaced with hexane.
The instant invention is also a process for separating enantiomeric mixtures by column liquid chromatography comprising two steps. The first step is to flow a mobile phase through a column means containing a chiral stationary phase, the mobile phase comprising methanol and pentane such that the concentration of methanol is greater than one tenth percent on a volume basis and less than or equal to the saturation concentration of methanol in the mobile phase. The second step is to introduce an enantiomeric mixture into the column so the enantiomeric mixture flows from the column resolved into its enantiomers, the concentration of pentane in the mobile phase being at least that necessary to resolve the enantiomeric mixture into its enantiomers with a resolution at least one and one half times greater than when the pen
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Synder, Introduction to Modern Liquid Chromatography, John Wiley & Sons, Inc., 1979, New York, pp. 248 and 261-263.
Goralski Christian T.
Nicholson Lawrence W.
Pfeiffer Curtis D.
Stevens Timothy S.
The Dow Chemical Company
Therkorn Ernest G.
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