High-throughput multipesticides residue analysis in earthworms by the improvement of purification method: Development and application of magnetic Fe₃ O₄ -SiO₂ nanoparticles based dispersive solid-phase extraction

As a key representative organism, earthworms can directly illustrate the influence of pesticides on environmental organisms in soil ecosystems. The present work aimed to develop a high-throughput multipesticides residue analytical method for earthworms using solid-liquid extraction with acetonitrile as the solvent and magnetic material-based dispersive solid-phase extraction for purification. Magnetic Fe₃ O₄ nanoparticles were modified with a thin silica layer to form Fe₃ O₄ -SiO₂ nanoparticles, which were fully characterized by field-emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry, and vibrating sample magnetometry. The Fe₃ O₄ -SiO₂ nanoparticles were used as the separation media in dispersive solid-phase extraction with primary secondary amine and ZrO₂ as the cleanup adsorbents to eliminate matrix interferences. The amounts of nanoparticles and adsorbents were optimized for the simultaneous determination of 44 pesticides and six metabolites in earthworms by liquid chromatography with tandem mass spectrometry. The method performance was systematically validated with satisfactory results. The limits of quantification were 20 μg/kg for all analytes studied, while the recoveries of the target analytes ranged from 65.1 to 127% with relative standard deviation values lower than 15.0%. The developed method was subsequently utilized to explore the bioaccumulation of bitertanol in earthworms exposed to contaminated soil, verifying its feasibility for real sample analysis.