SEPARATION OF HYDROXYLATED POLYENOIC FATTY-ACID ENANTIOMERS ON PIRKLE-TYPE CHIRAL PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC COLUMNS

Enantiomers of monohydroxy polyenoic fatty acids containing a conjugated diene system can be separated on an (R)-(-)-N-(3,5-dinitrobenzoyl)-α-phenylglycine (DNBPG) column. For all hydroxy fatty acids tested the S-isomer is earlier eluted than the R-isomer. Columns with ionically linked chiral phases show a better enantiomer resolution than those with covalently linked phases. Derivatization of the hydroxy polyenoic fatty acids to their corresponding benzoyl or naphthoyl derivatives strongly improved the enantiomer resolution, but reversed the elution order. Various Pirkle-type chiral stationary phases and several derivatization procedures were tested to optimize the enantiomer resolution. The best resolutions were achieved for the separation of the naphthoyl esters on a DNBPG column. There are considerable differences in the enantiomer resolution between columns obtained from different manufacturers. Some racemic diastereomers of dihydroxy polyenoic fatty acids which cannot be separated by reversed- and normal-phase high-performance liquid chromatography were separated on (R)-DNBPG columns. © 1990.