OPTIMIZATION OF THE MOBILE PHASE FOR THE LIQUID-CHROMATOGRAPHIC SEPARATION OF MODAFINIL OPTICAL ISOMERS ON A CHIRAL-AGP COLUMN

Optical isomers of modafinil were separated by chiral liquid chromatography on a Chiral-AGP column. Optimization of the mobile phase was undertaken in order to obtain a complete resolution of the two isomers. Two buffers, sodium dihydrogenphosphate and ammonium acetate, were studied and the influence of ionic strength and pH was investigated. The results showed that ionic strength was not a major parameter for optimization but that pH was. Ammonium acetate was a considerably better buffer than sodium dihydrogenphosphate phosphate. Different organic modifiers, ethanol, 1-propanol, 2-propanol, 1-butanol and 1-pentanol were studied with the two buffers. The best separations were obtained with 1-butanol and 1-pentanol.