Chiral ligand-exchange chromatography with Cinchona alkaloids. Exploring experimental conditions for enantioseparation of α-amino acids

Revisiting ligand-exchange chromatography for valsartan chiral analysis using a conventional non-chiral column

As the chiral drug market grows, developing efficient separation methods while ensuring quality has become a key focus for the pharmaceutical industries. Chiral column chromatography is effective but often impractical due to its expense. In our research, we established a cost-effective chiral analysis method for valsartan using ligand-exchange chromatography (LEC), an underutilized yet promising analytical technique with significant potential for further development in pharmaceutical research. This approach allows separation on a non-chiral column by forming complexes with metal ions in the mobile phase. Valsartan, a widely used antihypertensive drug, and its enantiomeric impurity were analyzed through LEC on a C18 column. We optimized the conditions for chiral selectors, copper ions, and pH, achieving a resolution exceeding 2.7. The method, validated per ICH Q2(R1) guidelines for assay and impurity determination, exhibited outstanding linearity (r² > 0.999) and recovery (97.8 %-101.7 %), ensuring a complete separation of the target peak, even after forced degradation. LEC presents a cost-effective alternative for in-house chiral drug analysis, addressing the challenges posed by limited access to chiral columns in countries focused on local generic drug production, and offering a practical solution to the increasing global demand for efficient chiral separation.

Recognition Mechanisms of Chiral Selectors: An Overview

Stereospecific recognition of chiral molecules plays an important role in nature as the basis of the interaction of chiral bioactive compounds with the chiral target structures. In separation sciences such as chromatographic and capillary electromigration techniques, interactions between chiral analytes and chiral selectors, i.e., the formation of transient diastereomeric complexes in thermodynamic equilibria, are the basis for chiral separations. Due to the large structural variety of chiral selectors, different structural features contribute to the overall chiral recognition process. This introductory chapter briefly summarizes the present understanding of the structural enantioselective recognition processes for various types of chiral selectors.