Aptamer-functionalized magnetic covalent organic frameworks for rapid extraction and LC-MS/MS quantification of gentamicin in milk

Gentamicin (GEN) residues in food products, arising from its extensive use in veterinary medicine, have prompted stringent regulations and a demand for simple, rapid detection methods. In this study, aptamer-modified magnetic covalent organic frameworks (COFs), denoted as TpDBD@Fe₃O₄@apt, were synthesized and employed as adsorbents in magnetic solid-phase extraction (MSPE) for the highly specific capture and enrichment of GEN residues in milk. Several factors influencing MSPE efficiency were systematically evaluated and optimized. Coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS), the developed method exhibited good linearity within the linear range (R² ≥ 0.999), low detection limits (0.48-0.54 ng/mL), satisfactory recoveries (92.7 %-108.8 %), and high precision (RSDs ≤10.8 %). The proposed method was successfully applied to real milk samples, providing an efficient solution for the detection of GEN residues.