Etched stainless steel wire modified with conjugated microporous polymers-F6 for jacket-free stir bar sorptive extraction of benzoylureas in juice sample†

Benzoylurea (BU) insecticides have been widely used for pest control as third-generation insecticides. Considering that their residues in food may cause adverse effects on human health, the upper limits of BUs remaining in food have been set by the administration. Therefore, it is essential to develop a sensitive and efficient analytical method to determine the residues of BUs in food. Stir bar sorptive extraction (SBSE) is a novel sample preparation technique, and stainless steel wire (SSW) is an ideal substrate for an SBSE device. In this work, a novel SBSE device of SSW jacket-free stir bar with a dumbbell shape was designed and prepared. The conjugated microporous polymer CMP-F6, which possesses a porous structure, high hydrophobicity and rich fluorine-containing functional groups, was immobilized on the surface of SSW by the method of polyacrylonitrile glue adhesion. Compared with previous studies, which used SSW as a substrate, the method of etching partial SSW with hydrochloric acid, on the one hand, made the surface of SSW rough and easy to modify the extraction coating, and on the other hand, converted itself into a dumbbell-shaped structure, which is conducive to improving the extraction efficiency and stability of the SBSE device. The method of SBSE-HPLC-UV was established for determining five BUs. Owing to the hydrophobic interaction and F–F interaction between CMP-F6 and analytes, this method showed good extraction efficiency and had good linearity (R² ≥ 0.9945) and high sensitivity (LODs in the range of 0.1–0.2 ng mL⁻¹). It was used for the analysis of benzoylurea in an apple juice sample, and the recoveries were 74.3–117.9%.