Experimental and molecular docking investigation on metal-organic framework MIL-101(Cr) as a sorbent for vortex assisted dispersive micro-solid-phase extraction of trace 5-nitroimidazole residues in environmental water samples prior to UPLC-MS/MS analysis.

In the presented work, metal-organic framework (MOF) material MIL-101(Cr) (MIL, Matérial Institute Lavoisier) was used as a sorbent for vortex assisted dispersive micro-solid-phase extraction (VA-D-μ-SPE) of trace amount of metronidazole (MNZ), ronidazole (RNZ), secnidazole (SNZ), dimetridazole (DMZ), tinidazole (TNZ), and ornidazole (ONZ) in different environmental water samples. Ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) was used to quantify the target analytes. The extraction conditions, including type of sorbents, amount of MIL-101(Cr), solution pH, extraction method, extraction time, effect of salt, and elution conditions were investigated. Upon the optimal conditions, the developed method showed an excellent extraction performance with the average recovery ranging from 75.2 to 98.8 %. Good sensitivity levels were achieved with the detection limits of 0.03∼0.06 μg/L and the quantitation limits of 0.09∼0.20 μg/L. The linear ranges were varied from 0.1 to 20 for SNZ and ONZ and from 0.2 to 40 μg/L for MNZ, RNZ, DMZ, and TNZ (r 2  > 0.992), and repeatability of the method was satisfactory with the relative standard deviations (RSD) <8 %. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of 5-nitroimidazoles (5-NDZs) in 12 real water samples, showing the positive findings of MNZ and TNZ ranging from 0.3 to 1.0 μg/L. Furthermore, molecular docking was applied to explain the molecular interactions and free binding energies between MIL-101(Cr) and 5-NDZs, providing a deep insight into the adsorption mechanism. The proposed method exhibited the advantages of simplicity, rapidly, less solvent consumption, ease of operation, higher sensitivity, and lower matrix effect. Graphical abstract Schematic diagram of the extraction process and molecular docking investigation.