Pipette-tip micro solid-phase extraction coupled with HPLC-UV using a zwitterionic cyclodextrin-based copolymer for the determination of fluoroquinolones in food.

The trace determination of fluoroquinolone antibiotics (FQs) in animal-derived foods requires effective sample pretreatment to minimize matrix interference and improve analytical sensitivity. Herein, a pipette-tip micro solid-phase extraction method coupled with high-performance liquid chromatography and ultraviolet detection (PT-μSPE-HPLC-UV) was developed for the determination of FQs in food samples. A porous zwitterionic cyclodextrin-based copolymer was synthesized as the PT-μSPE sorbent. The copolymer integrates hydroxypropyl-γ-cyclodextrin (HP-γ-CD) cavities with zwitterionic phosphorylcholine groups, combining host-guest recognition, hydrogen bonding, electrostatic interactions, and antifouling hydration to improve analyte enrichment and matrix tolerance. Density functional theory (DFT) calculations suggested complementary recognition in the hybrid system, which exhibited generally shorter hydrogen-bond distances than those calculated for the zwitterionic monomer-only models and electrostatic potential extrema of greater magnitude than those of γ-CD alone. Under the optimized conditions, the method exhibited good linearity over the range of 1.0 to 500 μg L⁻¹, limits of detection of 0.07 and 0.24 μg L⁻¹, and limits of quantification of 0.23 and 0.72 μg L⁻¹ for lomefloxacin and gatifloxacin, respectively. Recoveries in spiked milk and honey ranged from 74.8% to 110.3%, and norfloxacin and enrofloxacin were also effectively enriched. The proposed miniaturized method provides a simple, economical, and practical approach for FQs enrichment and screening in complex food matrices.