OPTIMIZATION OF CHIRAL SELECTIVITY ON CELLULOSE-BASED HIGHPERFORMANCELIQUID-CHROMATOGRAPHIC COLUMNS USING APROTIC MOBILE-PHASE MODIFIERS

Tris-3,5-dimethyl phenyl carbamate-derivatized cellulose HPLC columns and other cellulose-based columns are popular for the direct separatio n of many racemic drugs and agrichemicals. These columns exhibit good efficiency and stability under well-controlled chromatographic conditi ons. Cellulose-based chiral columns also exhibit high sample-load capa city with normal-phase solvents, which is particularly advantageous fo r isolating purified solutes. Several investigators have reported that the stereoselectivity of these columns can be varied by changing the type and composition of alcohol modifiers in the mobile phase, and by altering temperature. We now find that separation selectivity and reso lution can be significantly increased, and often optimized, by modifyi ng the nonpolar mobile phase with certain aprotic solvents. The potent ial of this new separation dimension greatly increases the general app licability of cellulose-based columns for analytical and preparative s eparations of racemates. A simple, systematic scheme is proposed for o ptimizing the separation of enantiomeric drugs with the Chiralcel OD c olumn.