Magnetic solid-phase extraction of tetracyclines from milk using metal-organic framework MIL-101(Cr)-NH₂...

Novel metal-organic framework MIL-101(Cr)-NH₂ functionalised hydrophilic polydopamine-modified Fe₃O₄ magnetic nanoparticles (Fe₃O₄@PDA@MIL-101(Cr)-NH₂) were synthesised and used as magnetic solid-phase extraction (MSPE) adsorbents for extracting tetracyclines (TCs) from milk samples. The integrated Fe₃O₄@PDA@MIL-101(Cr)-NH₂ exhibited convenient magnetic separation and exceptional multi-target binding capabilities. Furthermore, the PDA coating significantly enhanced the hydrophilicity and extraction efficiency of the material, thereby facilitating the extraction of trace TCs. Various factors affecting MSPE, such as adsorbent dosage, extraction time, pH value, and desorption conditions, were optimised. The developed MSPE method coupled with high-performance liquid chromatography demonstrated good linearity (R² ≥ 0.9989), acceptable accuracy (82.2%-106.1%), good repeatability (intra-day precision of 0.8%-4.7% and inter-day precision of 1.1%-4.5%), low limits of detection (2.18-6.25 μg L^-1), and low limits of quantification (6.54-18.75 μg L^-1) in TCs detection. The approach was successfully used for the quantification of trace TCs in real milk samples.