Metal organic frameworks (MOFs) for magnetic solid-phase extraction of pyrazole/pyrrole pesticides in environmental water samples followed by HPLC-DAD determination

Magnetic metal-organic frameworks (MOFs, [MIL-101]) were prepared and used as magnetic solid-phase extraction (MSPE) adsorbents for preconcentration of four kinds of pyrazole/pyrrole pesticides (flusilazole, fipronil , chlorfenapyr , and fenpyroximate) in environmental water samples, followed by high-performance liquid chromatography-diode-array detector (HPLC-DAD) determination. Several variables affecting MSPE efficiency were systematically investigated, including amount of MIL-101, extraction time, sample pH, salt concentration, type of desorption solvent and desorption number of times. Under optimized conditions, excellent linearity was achieved in the range of 5.0–200.0   μg/L for flusilazole and fipronil, and 2.0–200.0   μg/L for chlorfenapyr and fenpyroximate, with correlation coefficients r >0.9911. Limits of detection and quantification were 0.3–1.5   μg/L and 1.0–5.0   μg/L, respectively. The intra-day and inter-day precision (relative standard deviation, n =6, %) at three spiked levels were 1.1–5.4% and 3.9–7.8% in terms of peak area, respectively. The method recoveries at three fortified concentration levels ranged from 81.8% to 107.5% for reservoir water samples, 81.0–99.5% for river water samples, and 80.2–106.5% for seawater samples. The developed MOFs based MSPE coupled with HPLC method proved to be a convenient, rapid and eco-friendly alternative to the sensitive determination of pyrazole/pyrrole pesticides with high repeatability and excellent practical applicability.