COMPARISON OF DERIVATIZED POLYSACCHARIDE PHASES FOR SEPARATION OF WARFARIN AND RELATED DRUGS

In this study, amylose and cellulose derivatized with 3,5-dimethylphenylcarbamate (DMPC) are compared using polar-organic eluents. Investigation of different mobile phase modifiers and acid/base additives showed that these stationary phases vary greatly in their retention and chiral selectivity for coumarin-based solutes. The DMPC-cellulose phase was found to have excellent resolution for coumatetralyl and adequate resolution for coumachlor enantiomers. However, no selectivity was shown for warfarin and coumafuryl enantiomers. In contrast, the DMPC-amylose phase was found to be the most promising for the separation of these solutes. The enantiomers of warfarin, coumachlor, and coumatetralyl have high resolution in this stationary phase. The type and concentration of organic modifiers affect the thermodynamic and kinetic aspects of the separation in these phases. Methanol and acetone decrease the selectivity in both phases, but tetrahydrofuran increases the selectivity of coumafuryl and coumatetralyl enantiomers on the DMPC-amylose phase. Interesting behavior was observed when the kinetic aspects of the separation were compared by using coumatetralyl as a probe and tetrahydrofuran as a modifier. As the concentration of tetrahydrofuran increased, the rate constants of sorption and desorption for the first-eluted enantiomer increased in both stationary phases. In contrast, the rate constants for the second-eluted enantiomer decreased on DMPC-amylose, but increased on DMPC-cellulose. Ultimately, when 10% THF was used on DMPC-amylose, the first-eluted enantiomer underwent rapid kinetics with a desorption rate constant of 63 s−1, whereas the second-eluted enantiomer showed sluggish kinetics with a desorption rate constant of 0.08 s−1.