Efficiency and mechanism of C18-functionalized magnetic nanoparticles for extracting weakly polar pesticides from human serum determined by UHPLC-QTOF-MS and molecular dynamics simulations.

Detecting pesticide residues in human serum is a challenging process due to trace-level chronic exposure. Several methods using magnetic adsorbents have been developed for analyzing pesticide residue levels in human serum, but it is still difficult to achieve lower quantitative levels, and the adsorption mechanism for extracting pesticides is unclear. Herein, we propose a feasibility concept of using C18-functionalized magnetic nanoparticles for the adsorption of target pesticides, focusing on the extensively used weakly polar pesticides based on molecular dynamics (MD) simulations. To support this, the facilitated target nanoparticles of Fe3O4@SiO2-C18 were synthesized at a size of 12-13 nm with a magnetic saturation of 40 emu/g. After optimizing and establishing the extraction conditions (1.8 mL C18 modifier, 10 mg sorbents, 3 min adsorption time, 1000 μL ACN for desorption eluent at pH 3.8 and 5 min desorption time), which exhibited recovery = 72.3%-118.3% with RSDs = 0.03-6.57, linearity at 0.01-10 ng/mL with R2 = 0.9561-0.9993, and LODs = 0.01-0.30 ng/mL for the 11 weakly polar pesticides in human serum. Furthermore, the mechanism by which the C18 group selectively extracts weakly polar pesticides was confirmed by binding van der Waals and electrostatic interactions under stable and strong binding energy. The extraction process of efficient adsorption and desorption with C18 functional magnetite nanoparticles suggests a simple method for detecting weakly polar pesticides. The concept may lead to a general approach to analyzing multiple pesticide residues in human serum at trace levels.