Chiral Mobile-Phase Additives in HPLC Enantioseparations

High-performance liquid chromatography (HPLC) is one of the main separation techniques for chiral drugs. Among the chiral HPLC techniques available, the chiral mobile-phase additive (CMPA) technique is a valuable method for the direct enantioseparation of chiral chemical entities. In the CMPA method, the chiral selector is dissolved in the mobile phase while the stationary phase is achiral. Interaction with the analyte enantiomers results in the formation of transient diastereomeric complexes. These complexes differ in their formation constants and/or distribution between the (achiral) stationary phase and the mobile phase resulting in an enantioseparation. This chapter describes the HPLC separation applying CMPA methods by several most useful types of chiral selectors including chiral ligand exchangers, macrocyclic antibiotics, and cyclodextrins.