Preparation Of Three-Dimensional Covalent Organic Framework Incorporated Monolithic Column For High Performance Liquid Chromatography Application In Food Analysis

High performance liquid chromatography(HPLC)is widely used for the determination of nutrients,additives and contaminants in foods because of its high selectivity and simultaneous determination of multiple analytes.The separation performance of liquid chromatography mainly depends on the non-covalent interactions between stationary phase and the analytes.As the core of HPLC,stationary phase has an important effect on separation efficiency.However,existing stationary phases are still difficult to satisfy the analysis of a wide variety of food samples with complex compositions.Hence,the discovery of new versatile materials as the stationary phase with distinctive interactions is great of significance in the improvement of chromatographic separation.The ordered structure,low density and good stability of three-dimensional covalent organic frameworks(3D COFs)with rich interactions including hydrophobic interaction,?-? interaction and the electron donor-acceptor interaction make them ideal as stationary phases for chromatography.But the direct application of bulky 3D COFs as stationary phase suffers from high column pressure and low column efficiency owing to their irregular morphology and wide size distribution.The integrating of 3D COFs and porous monolith is an efficient way to solve the above-mentioned limitations.In this thesis,3D COF incorporated monolithic column for HPLC was first designed and prepared,and the chromatographic separation performance and potential application in the analysis of food additives and contaminants were further explored.The main research results are as follows:(1)A novel 3D-IL-COF-1 monolithic column was prepared for liquid chromatography.The conditions(temperature,porogen and 3D COF)for the preparation of 3D-IL-COF-1monolithic column were optimized by single-factor experiments and orthogonal experiment in terms of permeability and column efficiency.The optimal condition for the preparation of3D-IL-COF-1 monolithic column was obtained: 15 mg 3D-IL-COF-1,35 ?L monomer,450 mg porogen,400 mg crosslinker,10 mg initiator at 65? for 24 h.Powder X-ray diffraction and the Fourier transform infrared spectroscopy confirmed the successful synthesis of3D-IL-COF-1 and its monolithic column.3D-IL-COF-1 monolithic column had uniform structure,good permeability and high mechanical stability,being promising for HPLC separation.(2)The chromatography separation performance of 3D-IL-COF-1 monolithic column and its potential for the application of food analysis was evaluated.The 3D-IL-COF-1monolithic column showed a reversed-phase chromatographic mechanism,and possessed hydrophobic,?-?,hydrogen bonding and shape selectivity for the separation of four groups of probe analytes.The separation performance of 3D-IL-COF-1 monolithic column for acid and basic compounds as well as isomers was investigated by four groups of food contaminants including acid phenols,basic anilines,aminophenols and PAHs isomers.The results showed that 3D-IL-COF-1 monolithic column gave better separation performance than commercial C18 column.Furthermore,food additives(preservatives,antioxidants)and endocrine disruptors(estrogens)were used to investigate the application potential of 3D-IL-COF-1monolithic column in food analysis.Rapid separation of the above analytes was achieved in 8mins on 3D-IL-COF-1 monolithic column.The relative standard deviations(RSDs)of relative retention time,selectivity factor and peak area in the repeatability tests of run-to-run(n=10),day-to-day(n=5)and column-to-column(n=3)were 0.1%-0.6%,0.1%-0.9% and 0.8%-2.9%,respectively.The results proved great HPLC separation repeatability and stability of the prepared 3D-IL-COF-1 monolithic column.Finally,the method for the analysis of parabens preservatives in real samples(milk and milk powder)based on 3D-IL-COF-1 monolithic column was established.The limit of detection(S/N=3)and limit of quantification(S/N=10)of four preservatives were 0.5 mg/kg and 0.5-2 mg/kg,respectively.Compared with the national standard and industry standard method,3D-IL-COF-1 monolithic column with isocratic elution method gave faster analysis,showing great application prospect of3D-IL-COF-1 monolithic column for the analysis of real samples.