Synthesis and characterization of a new ZIF-67@MgAl₂O₄ nanocomposite and its adsorption behaviour

Fabricating suitable adsorbents with low-cost and high efficiency extraction for measurement of very small amounts of agricultural pesticides in food and water is playing a vital key role in personal and environmental health. Here, a new composite of zeolitic imidazolate framework-67@magnesium aluminate spinel (ZIF-67@MgAl₂O₄) has been fabricated by a simple method at room temperature with different weight ratios. Several techniques such as FE-SEM, BET, XRD, and TGA have been used to confirm the structural characterization of the obtained materials. The obtained ZIF-67@MgAl₂O₄ was utilized as an adsorbent in the solid phase microextraction technique to extract and preconcentrate the herbicide molinate (as an analyte) in aqueous solution. Corona discharge ionization-ion mobility spectrometry (CD-IMS) was applied for quantification of the analyte molecules. Extraction temperature, extraction time, stirring rate, and sample pH as the main parameters that affected the extraction proficiency were chosen and considered. Under optimal conditions, the linear dynamic range (LDR) of the various concentrations of the molinate and correlation coefficient were 10.0-100.0 μg L^-1 and 0.9961, respectively. The limit of quantification (LOQ) and method detection limit (MDL) were 10.0 μg L^-1 and 3.0 μg L^-1, respectively. The relative standard deviation (RSD) of the ZIF-67@MgAl₂O₄ for extracting the molinate molecules (molinate concentration; 50 μg L^-1) was calculated to be 4% and the enrichment factor (EF) was ∼5.