Polyethyleneimine-based magnetic molecularly imprinted polymer for selective enrichment and highly sensitive...

A polyethyleneimine-functionalized magnetic molecularly imprinted polymer (MHNT-PEI@MIP) was developed for selective enrichment and detection of gallic acid (GA) in complex tea matrices. Halloysite nanotubes provided a low-cost, high-surface-area substrate with abundant hydroxyl groups for polyethyleneimine (PEI) grafting, creating amine-rich active sites. Surface molecular imprinting with 4-vinylpyridine produced GA-specific recognition cavities. Comprehensive characterization confirmed a uniform core-shell structure, mesoporous features, and superparamagnetic behavior. Coupled with magnetic solid-phase extraction (MSPE) and HPLC, the method enabledpreconcentration of GA, achieving a limit of detection of 0.21 μg mL^-1, a limit of quantification of 0.65 μg mL^-1, recoveries of 95-103%, and high reproducibility. MHNT-PEI@MIP exhibited high adsorption capacity (139.7 mg g^-1), pseudo-second-order kinetics, Langmuir-type isotherm behavior, and an imprinting factor of 4.12, demonstrating selectivity over structural analogues. This work provides a durable, low-cost technique integrating strong molecular recognition, high adsorption, and magnetic separability for efficient polyphenol analysis in complex food systems.