Synthesis of composite materials combining magnetic metal-organic frameworks and conjugated organic frameworks for selective extraction of carbendazim and thiabendazole residues from Chinese herbal medicine samples

Abstract

A magnetic metal-organic framework MIL-68(Al) and a covalent organic framework were used as magnetic solid-phase extraction (MSPE) adsorbents in combination with high-performance liquid chromatography ultraviolet detection (HPLC-UV) to detect carbendazim (CBZ) and thiabendazole (TBZ). The main parameters affecting the extraction in the MSPE process were studied and optimized. Fe₃O₄@MIL-68(Al) coated with 1,3,5-tris(4-aminophenyl)benzene and terephthaldehyde (Fe₃O₄@MIL-68(Al)@TAPB-PDA-COF) was analyzed and verified. The material was proven to be suitable for adsorbing CBZ and TBZ. Various adsorption models were used to study its adsorption mechanism. The adsorption results were in good agreement with the pseudo-second-order kinetic model and Langmuir isotherm model. The maximum adsorption capacities of Fe₃O₄@MIL-68(Al)@TAPB-PDA-COF over CBZ and TBZ were 54.24 and 67.87 mg g^-1, respectively, and the equilibrium adsorption time was 200 min. Fe₃O₄@MIL-68(Al)@TAPB-PDA-COF with excellent recyclability showed higher adsorption capacity and selectivity. A method based on Fe₃O₄@MIL-68(Al)@TAPB-PDA-COF combined with HPLC-UV was established under the optimal extraction conditions and used to separate and detect trace imidazole drugs in Chinese herbal samples, achieving a low limit of detection (0.65-1.30 μg L^-1) with excellent linear correlation (r > 0.999). The recovery rate and relative standard deviation were 86.05-99.78 % and 0.15-4.90 %, respectively. Therefore, the Fe₃O₄@MIL-68@TAPB-PDA-COF can be regarded as an effective adsorbent for the pretreatment of CBZ and TBZ drugs in Chinese herbal samples.

Keywords: High-performance liquid chromatography; Imidazole drugs; Magnetic solid-phase extraction adsorbent.