Study of the enantiomeric separation of the anticholinergic drugs on two immobilized polysaccharide‐based chiral stationary phases by HPLC and the possible chiral recognition mechanisms

Abstract

In this work, the enantiomeric separation of ten anticholinergic drugs was first examined on two derivative polysaccharide chiral stationary phases (CSPs), i.e., Chiralpak ID and Chiralpak IA in the normal phase mode. Except for scopolamine hydrobromide, the remaining nine analytes could be completely separated with good resolutions using both columns under the optimized mobile phase conditions. And the enantiomeric discrimination ability of the studied CSPs towards nine analytes was in the order of Chiralpak ID > Chiralpak IA. The influences of organic modifier types, alcohol content, and base/acid additives on the enantiomeric separation were evaluated and optimized. According to the experimental results, the effect of the structures of analytes on enantiomeric separation was discussed. Additionally, the chiral recognition mechanisms were proposed based on the thermodynamic analysis of the experimental data.

Enantioselective separation of twelve pairs of enantiomers on polysaccharide‐based chiral stationary phases and thermodynamic analysis of separation mechanism

“…As a consequence of the negative values for Δ H °, Δ S *, Δ G °, the solute transfer from the mobile to stationary phase was enthalpically favorable but entropically unfavorable in this temperature range. Additionally, the Van't Hoff plots for the retention (ln k versus 1/ T ) of all racemates were linear with coefficient of determination ( r 2 ) ranging from 0.9810 to 0.9990, suggesting that the retention mechanism was independent of temperature in the studied range .…”

“…The related thermodynamic parameters were calculated by Van't Hoff equations : where ΔG°, ΔH°, and ΔS° represent the standard Gibbs free energy, enthalpy, and entropy of solute transfer from the mobile phase to the CSP, T is the absolute temperature, and R is the gas constant (8.314 J/mol/K). Since the value of Φ is unknown, the Δ S * value [Δ S * = Δ S °+ R ln Φ] is generally used.…”

“…Derivatization of the native polysaccharide with multifunctional groups could improve its chiral recognition ability by introducing various intermolecular interactions, such as hydrogen bonding, dipole‐dipole, π‐π interactions, etc. Until now, a wide variety of chiral racemates have been resolved on these CSPs , and a series of reviews on these CSPs are available .…”

Enantioseparation and determination of flumequine enantiomers in multiple food matrices with chiral liquid chromatography coupled with tandem mass spectrometry

“…Column temperature is regarded as a significant parameter with reference to chiral separations . The thermodynamic parameters could be calculated according to the capacity factor (k), separation factor (α), and resolution (Rs) by classical Van't Hoff equations, which assumes that analyte retention is only due to enantioselective interactions with the stationary phase and does not distinguish between chiral and nonchiral interactions . The classical Van't Hoff equations are exhibited as follows: …”

“…The negative Δ H ° values revealed that the distribution of the two enantiomers between the mobile phase and the stationary phase was exothermic. Moreover, both ΔΔ H ° and ΔΔ S ° were negative showing that separation of flumequine was enthalpy‐driven …”