HPLC separation of linezolid enantiomers using polysaccharide-based chiral stationary phases

Separation of the enantiomers of linezolid has been compared on derivatized cellulose and amylose chiral stationary phases (Chiracel OD and Chiralpak AD) with mixtures of hexane with I-propanol, 2-propanol, or ethanol as mobile phases. It was found that use of a small amount of water as mobile phase additive can improve or prevent enantioseparation, depending on the column. The order of elution of the linezolid enantiomers was different on the Chiracel OD and Chiralpak AD columns, and baseline resolution was achieved on the Chiralpak AD column only. Reversal of the order of elution of the enantiomers on changing from the propanols to ethanol was observed on both columns. The effect of temperature (in the narrow range 15-35 degrees C) on retention and enantioselectivity was studied for both columns and a variety of mobile phases. The standard enthalpy (Delta H degrees) and entropy (Delta S degrees) changes for solute transfer between the mobile and stationary phases, were also estimated.