Abstract: Iprodione, procymidone, and propiconazole are pesticides widely used in fruit and vegetable cultivation, and their residues may pose risks to human health. In this study, imine-linked covalent organic frameworks (COFs) were synthesized by reacting three alkoxy-modified terephthalaldehyde derivatives (2,5-dimethoxy, 2,5-dihexyloxy, and 2,5-dioctyloxy) with 1,3,5-tris(4-aminophenyl) benzene and they were named as COF-a, COF-b, and COF-c, respectively. These materials were physically coated onto iron-cored rods to prepare stir bars for the enrichment of the three pesticide residues in fruit samples. Among them, COF-a exhibited the highest extraction efficiency for the polar target pesticides due to its shortest alkoxy chain, minimal steric hindrance, and strong π-π interactions, along with good stability. Based on this, a stir bar sorptive extraction-high performance liquid chromatography (SBSE-HPLC) method was established for the simultaneous detection of iprodione, procymidone, and propiconazole. The method showed good linearity over the concentration range of 1–1 000 μg/L (determination coefficient R2 ≥ 0.991 8), with limits of detection (LOD) ranging from 0.21 to 0.52 μg/L. The prepared stir bars demonstrated good reproducibility, with inter- and intra-batch relative standard deviations (RSD) not exceeding 5.6% and 8.5%, respectively. Analysis of strawberry and Cyclocodon lancifolius fruit samples revealed no detectable target pesticide residues. Spiked recoveries ranged from 81.4% to 119% for strawberry and 86.2% to 99.2% for C. lancifolius fruit, indicating that the method is accurate and reliable for pesticide residue analysis in fruits and vegetables, offering technical support for food safety monitoring.

Key words: covalent organic frameworks; pesticide residues; stir bar sorptive extraction; high performance liquid chromatography; fruit and vegetable detection