MIL-125@ZIF-8 based solid phase microextraction coating for sensitive determination of organophosphate esters in aqueous environments

A novel MOF-on-MOF heterostructure (MIL-125@ZIF-8) was synthesized and utilized as a coating material for solid-phase microextraction (SPME), which was subsequently coupled with gas chromatography (GC) for the sensitive determination of organophosphate esters (OPEs) in water samples. Compared to commercial fiber, the MIL-125@ZIF-8 coated fiber (MIL-125@ZIF-8-F) demonstrated superior extraction performance for medium-polar or non-polar compounds due to multiple interactions such as hydrophobic interaction, π-π stacking, and hydrogen bonding. The synergistic effect of MIL-125 and ZIF-8 endowed the MIL-125@ZIF-8-F with high efficiency and excellent stability under extreme conditions. Specifically, the developed MIL-125@ZIF-8-F could withstand 80 conditioning cycles without significant loss of extraction capacity. Moreover, the established method exhibited a wide linear range (10–1000 μg L⁻¹), low detection limits (0.03–0.20 μg L⁻¹), and excellent reproducibility under optimized condition. Finally, this proposed method provided a promising approach for the efficient enrichment of trace OPEs in actual environmental water samples.