Evaluation of a porous imine-based covalent organic framework for solid-phase extraction of nitroimidazoles

Exploration of porous imine-based covalent organic framework for solid-phase extraction of five trace sulfonamides in food samples

In this article, a highly crystalline porous imine-based covalent organic framework was synthesized at room temperature and used as solid-phase extraction (SPE) adsorbent for the purification and enrichment of trace sulfonamides (SAs) from food samples. The structure of the obtained material was characterized and studied in detail. The extraction process was optimized and the final elution was determined by the ultra-high-performance liquid chromatography-quadrupole time of flight mass spectrometry method. Low limits of detection (0.02-0.19 μg/kg) were obtained under optimal conditions, with the recoveries ranging from 70.5% to 105.3% when spiked at different levels. The adsorption process of the material for SAs was fitted by the Langmuir and Freundlich adsorption isotherm model, and the extraction capacity for Nitrofuran metabolites from food samples was also investigated for comparison. The results demonstrated that the framework was a good candidate SPE adsorbent that can be used for the enrichment of drug residues in complex matrix, and the work may provide a systematic study method for the development of porous adsorbents.

Exploration of an imine-based covalent organic framework for the solid phase extraction of nitroimidazoles in milk and meat samples

TAPT-AN-COF, an imine-based covalent organic framework, was synthesized by a solvothermal method of 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (TP) and 4,4',4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (TAPT). The structure was characterized and tested by several techniques, revealing that the material had good stability and high specific surface area. The adsorption experiment demonstrates that the adsorption isotherm of TAPT-AN-COF followed the Freundlich isothermal equation, while its adsorption kinetics conformed to the pseudo second-order kinetic model. After characterization, the prepared TAPT-AN-COF was used to separate and enrich nitroimidazoles (NDZs) in milk and meat as the solid-phase extraction (SPE) adsorbent. The effects of adsorbent dosage, pH value, washing solvent, elution solvent type and volume on recoveries were studied. Under the optimal conditions, a method for the determination of NDZs in milk and meat samples was established based on high performance liquid chromatography-ultraviolet detection(HPLC-UVD).The result showed that NDZs had good linearity in the concentration range of 25-500 µg·kg^-1, and the determination coefficients (r²) were all above 0.99. When spiked at 25, 50 and 125 µg·kg^-1, the recoveries of three kinds of food samples ranged from 64.5% to 85.3%, the limits of detection (LODs) were between 2 and 10 µg·kg^-1, and the relative standard deviations were all below 15.9%. In addition, the recoveries of NDZs didn't decrease significantly after being reused for 6 times, showing that TAPT-AN-COF has excellent reusability. Compared with HLB and MCX sorbents, TAPT-AN-COF had better extraction efficiency and qualified purification efficiency. The established method had a satisfying performance on the determination of NDZs in food samples.