Chiral Recognition Mechanism of Amlodipine by Capillary Electrophoresis Using Carboxymethyl-β-cyclodextrin: An...

Chiral capillary electrophoresis (CCE) represents an effective technique for enantioselective separations. However, additional techniques may be necessary to determine the enantiomers migration order (EMO) and elucidate the chiral recognition mechanism. This study details the development and optimization of a CCE method for the enantioseparation of amlodipine (AML). Furthermore, it contributes computationally to determining the EMO and the mechanisms responsible for chiral discrimination. The study proposed the optimization of several key parameters in CCE, including the type, concentration and pH of the background electrolyte, as well as the concentration of the chiral selector. In line with previous research, only one anionic cyclodextrin, carboxymethyl-β-cyclodextrin (CM-β-CD), was evaluated as the chiral selector. Following optimization, the most favorable results were achieved using 50 mM phosphate background electrolyte pH 4.0 with 2.5 mg mL^-1 CM-β-CD. These conditions enabled baseline separation of AML enantiomers, reduced analysis time, and minimized consumption of the chiral selector. Calculations were conducted using a sequential methodology, beginning with the PM3 semiempirical followed by density functional theory (DFT) calculations. The theoretical analysis indicated that differences in ΔE and ΔG values are reliable indicators for predicting the EMO. Specifically, the (-)-(S)-AML/CM-β-CD complex exhibited superior energetic characteristics compared to the (+)-(R)-AML/CM-β-CD complex, likely due to differences in their intermolecular interactions, including hydrogen bonds and electrostatic interactions, consequently, this finding can be related to elongation migration time within the electrophoretic system. These results underscore the synergistic benefits of computational and experimental approaches in elucidating chiral discrimination mechanisms and identifying EMO in CCE.