Evaluation of metal–organic framework-based adsorbents for preconcentration of pesticides from water samples

Water quality monitoring is important for protecting the environment and human health. Pesticides are widely used to improve crop yields and quality, but can have serious impacts on ecosystems and human health if they remain in the environment. It is therefore extremely important to accurately determine the concentration of pesticides in water.

Because pesticide concentrations in environmental water are extremely low, sample pretreatment for the purpose of concentration is essential for pesticide analysis. Adsorbents such as activated carbon and zeolites have traditionally been used for this purpose. However, these adsorbents have problems such as low selectivity and degradation of adsorption performance, so there is a need to develop new adsorbents. Recently, metal–organic frameworks (MOFs) have attracted attention as new adsorbents: they are porous crystalline materials constructed by a three-dimensional coordination of metal ions and organic ligands and have a high specific surface area, controllable pore structure, and excellent thermal and chemical stability. In particular, MIL-53(Fe) (Fe-based), ZIF-8 (Zn-based), and MIL-53(Al) (Al-based) have been reported as MOFs that exhibit relatively high structural stability even in aquatic environments. In this study, the adsorption performance of these MOFs as adsorbents was compared and evaluated for the preconcentration of pesticides such as diuron, probenazol, and bensulfuron-methyl in aqueous samples.

Batch-mode solid phase extraction was employed for the preconcentration of the pesticides. The pretreated samples were determined by high performance liquid chromatography (HPLC).

Among the tested MOFs, MIL-53(Al) exhibited the highest recovery. To improve analytical performance, the preconcentration conditions will be optimized in future studies.