Studies Of Separation Of Chiral Ion-pair Chromatography For Separation Of Chiral Drugs

This paper mainly deals with the separation of enantiomers through the ion-pair chromatographic system. Separations based on formation of diastereomeric ion-pairs were fulfilled in systems with an organic mobile phase using achiral and chiral stationary phases. In this study, cinchona alkaloids and D- camphorsulfonic acid(CSA) were chosen to serve as chiral ion complex for the separation of enantiomers.Quinine and other related cinchona alkaloids were chosen for the separation of some tart enantiomers of phenylalanine, aromatic acids and other acids. The experimental results indicated that Phenylalanine derivatives, Mandelic Acid, Naproxen,Ramatroban and Isoquinolinic Acid formed complexes with this kind complexing reagents. These conclusions were in fair agreement with the results obtained from chromatographic experiments. Polar functions in the vicinity of the chiral centre seem to be necessary for stereoselective separation. Enantiomeric derivatives of phenylalanine was separated, and mandelic acid, naproxen,ramatroban and isoquinolinic acid were separated with low efficiency, but no resolution was obtained for Ibuprofen. The influence of the mobile phase composition on the retention and stereoselectivity has been studied in detail. Different solid phases have been investigated with respect to retention and stereoselectivity.CSA was used for the chiral separation of amines.With a mobile phase consisting of hexane,isopropanol,dichlormethane, diethylamine, and CSA used as the complexing reagent, Ephedrine and thalidomide were separated but not baseline resolved using Inertsil CN column. The enantioseparation of fenfluramine using the chiral stationary phase(CSP) of β-CD, Chiradex, was also investigated with and without an addition CSA in the reverse mode. Fenfluramine was partially separated using the mobile phase system .In the presence of CSA, separation factor( α ) was improved .Using CSP of amylase tris(3,5-dimethylphenyl-carbamate), Chirapak AD, was also investigated with and without an addition CSA in the normal mode.In the presence of CSA, the separation time of metoprolol reduced obviously.Ephedrine was basline resoved only in the presence of CSA.This study demonstrated interest and advantage in using a chiral stationary phase in combination of a chiral additive in the mobile phase to enhance the chiral separation.