Zwitterionic-based hybrid monoliths for capillary microextraction of polypeptides in dairy products

The pretreatment of complex food matrices is challenging due to matrix interferences and non-specific adsorption of macromolecules. This study proposes a biocompatible solid-phase microextraction method to effectively enrich polypeptide antibiotics in dairy products using various zwitterionic-based capillary microextraction (CME) techniques. The proposed method demonstrated a broad linear range of 20–800 μg L⁻¹, with a detection limit (LOD) of 10 μg L⁻¹ when employing the phosphorylcholine-based column for polypeptide antibiotics extraction. Additionally, a linear range of 8.0–1000 μg L⁻¹ was achieved, with a lower detection limit of 5.4 μg L⁻¹ on the sulfobetaine-based column. Density functional theory (DFT) calculations indicated that zwitterionic CME columns containing typical phosphorylcholine and sulfobetaine groups facilitate target capture primarily through hydrophilic, electrostatic, and hydrogen bonding interactions. This advanced method was applied to detect peptide residues in a variety of dairy products, yielding results that significantly improved detection accuracy and demonstrated potential practical application value.