Amino-Functionalized MIL-101(Cr)-Based Syringe Filter for Selective Solid-Phase Extraction and Trace Determination of Naproxen in Environmental Waters

A miniaturized solid-phase extraction (SPE) method was developed using a disposable syringe filter packed with amino-functionalized metal-organic framework (MOFs) NH₂-MIL-101-(Cr) for the selective extraction of naproxen from environmental water samples. The NH₂-MIL-101-(Cr) material was synthesized hydrothermally and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, Fourier infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) to confirm its structure and surface functionality. To construct the solid-phase extraction (SPE) tip, only 5 mg of MOF was immobilized within a 0.22 μm nylon syringe filter, enabling rapid and solvent-efficient sample pretreatment. Coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), the method achieved a detection limit of 0.038 μg/L and a recovery rate of 96.84% at pH 3. The extraction performance was strongly influenced by solution pH, with ζ-potential analysis revealing electrostatic attraction as the primary mechanism for naproxen adsorption under acidic conditions. The method exhibited excellent selectivity over structurally related interferents such as ibuprofen and was successfully applied to spiked lake and drinking water samples, demonstrating its practical utility. This work introduces a cost-effective, portable, and sensitive platform for trace-level detection of pharmaceutical contaminants in environmental monitoring.