Discriminating quinine stereoisomers through collision cross-section differences enhanced by cyclodextrin complexation

Quinine (QN) and its derivatives, such as quinidine, hydroquinine (HQN), and hydroquinidine (HQD), are important therapeutic agents with significant biological and pharmacological properties. However, their stereoisomeric nature poses challenges for separation and identification due to their similar mass-to-charge ( m/z ) ratios. In this work, a simple and quick method based on trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) and theoretical calculations was developed to effectively separate and identify QN stereoisomers and their derivatives by forming diastereomeric complexes with cyclodextrins (α, β, and γ-CD). The separation efficiency improved with the enlargement of the CD cavity, achieving an R p-p value of 1.23. density functional theory (DFT) calculations and independent gradient model (IGMH) analysis provided insights into the molecular interactions and conformational variations among the complexes, revealing how differences in interaction sites and types lead to distinct conformations. The reliability of these calculations was supported by the good agreement with experimental collision cross-section values, which showed deviations ranging from only 4.12% to 8.84%. Additionally, tandem mass spectrometry (MS/MS) was employed to analyze the structural stability of the complexes, revealing differences in dissociation energies. Quantitative analysis demonstrated excellent linearity (R 2 > 0.99) and precision (RSD ≤ 2.32%), with recovery rates in serum and urine samples exceeding 84.0%. This method offers a rapid, accurate, and efficient approach for the separation and quantification of QN stereoisomers, with potential applications in pharmaceutical research and quality control.