Magnetic Nanocomposite-Based TpPa-NO2 Covalent Organic Framework for the Extraction of Pyrethroid Insecticides in Water, Vegetable, and Fruit Samples

In this work, a magnetic covalent organic framework (COF) named Fe 3 O 4 @TpPa-NO 2 was designed and synthesized by a solvothermal method employing 1,3,5-triformylphloroglucinol (Tp) and 2-nitro-p-phenylenediamine (Pa-NO 2 ) as the organic units. Fe 3 O 4 @TpPa-NO 2 was explored as an adsorbent for magnetic solid-phase extraction (MSPE) of four pyrethroid insecticides. Fe 3 O 4 @TpPa-NO 2 displayed excellent adsorption capacity in the adsorption test of pyrethroid insecticides. Taking bifenthrin as an example, the adsorption capacity reached 885 mg·g −1 . A sensitive method for the determination of pyrethroid pesticide residues was developed using high-performance liquid chromatography (HPLC) coupled with MSPE. The linearity of the proposed method has a correlation coefficient ( R 2 ) of 0.9992–0.9999 in the range of 15–1000 ng·mL −1 . Under optimal conditions, the limits of detection (LODs) and limits of quantification (LOQs) were 3.98–6.21 and 13.28–22.05 ng·mL −1 , respectively. Furthermore, satisfactory precision and accuracy were obtained with relative standard deviations (RSDs) of 2.58–3.42% and recoveries of 85.7–109.8%. The adsorption mechanism inferred that π-π interactions, hydrophobic interactions, and hydrogen bonding could promote the adsorption of pyrethroids. The developed MSPE-HPLC method has the advantages of rapidity, accuracy, sensitivity, recyclability, and good practical applicability.