Capillary Electrophoretic Chiral Separation of Antihistamines: Enantiomers Recognition Mechanism by Isothermal Titration Calorimetry and Simulation Studies

The chiral separation of chlorpheniramine, brompheniramine, and dimetindene antihistamines was achieved by capillary electrophoresis using β-CD, DM-β-CD, and TM-β-CD in 50 mM phosphate buffer (pH 3.0), with an applied voltage of 20 kV, a temperature of 20°C, and UV detection at 220 nm. The migration times of the enantiomers were in the ranges 7.31-28.10, 14.10-17.02, and 7.30-16.19 min for the three cyclodextrins, respectively. The number of theoretical plates varied between 6588-14,038, 9744-45,780, and 41,983-107,846. The separation factors (α) were 1.01-1.02, 1.03-1.04, and 1.02-1.03, while the resolution factors (Rₛ) ranged from 1.16-1.20, 2.06-2.19, and 2.25-2.60, indicating partial to complete enantioseparation. The isothermal titration calorimetry and molecular docking revealed that hydrogen bondings and π-alkyl interactions played key roles in chiral recognition. The developed method is suitable for assessing enantiomeric purity in antihistamine formulations.