Retention model for the resolved enantiomers of felodipine on chiral‐AGP using micellar mobile phases

Abstract

Abstract A retention model for the chiral separation of an uncharged solute, felodipine, on CHIRAL‐AGP, using a micellar mobile phase is proposed. The model assumes the presence of two stereoselective sites and each enantiomer was found to interact with different sites. Addition of a chiral aliphatic alcohol, (+)‐(S)‐2‐octanol, preferentially interacted with the binding site for (−)‐(S)‐felodipine. The monomeric form of the micellar agent (Tween® 20) competed with the enantiomers for the adsorption sites, and the formation of a 1:1 complex between the enantiomers and the micelles was assumed. The retention of the solutes was effectively controlled by adding small quantities (<1.63 × 10 −3 M ) of the nonionic detergent Tween 20 to the mobile phase. Baseline separation was achieved by addition of 1.0 m M n ‐octylamine to the mobile phase; 8.14 × 10 −4 M Tween 20 in phosphate buffer pH 7.0. The separation factor (α = 1.74) was unaffected by the detergent concentration in the presence of 1.0 m M n ‐octylamine. © 1995 Wiley‐Liss, Inc.