Metal-organic framework-based molecularly imprinted polymers for solid-phase extraction of fluoroquinolones in coastal-zone water samples

Antibiotics have received wide concerns especially in coastal-zone waters, necessitating their sensitive determination. Metal-organic frameworks (MOFs) based molecularly imprinted polymers (MIPs) composites have demonstrated excellent versatility, recognition properties, and practical applicability in the sample preparation. Herein, zeolitic imidazolate frameworks (ZIFs)-8 (ZIF-8) as a kind of typical MOF material, was employed as the support of MIPs and the resultant ZIF-8-MIPs were used for solid-phase extraction (SPE) of fluoroquinolones (FQs) in coastal-zone environmental water samples followed by high-performance liquid chromatography (HPLC) determination. The composites were facilely prepared via precipitation polymerization combined with surface imprinting, using enrofloxacin (ENR) as template molecule. The composition, structure and morphology of ZIF-8@MIPs were well characterized, and the adsorption followed pseudo-second-order kinetic and Langmuir isotherm models. Rapid adsorption equilibrium can be reached within 30 min, with a maximum adsorption capacity of 79.97 mg/g. Then, key parameters of SPE packed with ZIF-8@MIPs were systematically investigated. Under the optimal conditions, a sensitive SPE-HPLC method was developed towards four FQs, offering high enrichment factors of 82–153. Excellent linearity was attained in the wide range of 0.1–200 μg/L, and the limits of detection were as low as 0.024–0.034 μg/L together with limits of quantitation within 0.081–0.113 μg/L. The matrix effect values in the tested coastal waters including seawater, aquaculture wastewater, lake water, and river water, were from –6.69% to 5.47%, indicating the ZIF-8@MIPs-SPE efficiently eliminated matrix interference and ensured accurate reliable quantification. Consequently, in all the four water samples, high recoveries ranged from 91.4 to 105.2%, with low relative standard deviations of 1.8–8.7%. This study can enrich the research connotation of MOF@MIPs composites based sample preparation and provide an alternative detection scheme for the monitoring of trace antibiotics in complicated matrices.