关键词: 介孔, 共价有机骨架, 固定相, 黄芪甲苷

Abstract:

Quality control of traditional Chinese medicine （TCM） has always been a key and challenging issue in the field of its modernization research. This has posed a high demand for advanced separation materials due to the complex compositions. Covalent organic framework materials （COFs） are a new class of porous crystalline materials composed of multidentate organic units connected by covalent bonds. They have demonstrated significant application value in areas such as catalysis and chromatographic analysis. This study focused on developing a novel core-shell-type chromatographic stationary phase using 2，4，6-tris（4-aminophenyl）-1，3，5-triazine （TAPT） and 1，4-benzenedicarboxaldehyde （TA） as building units. The TAPT-TA-COF@SiO₂ core-shell composite materials were successfully prepared on the surface of silica microspheres using a multi-step polymerization strategy， in which the SiO₂ cores were fabricated using the polymerization-induced colloidal aggregation （PICA） method. The imine-linked TAPT-TA-COF@SiO₂ core-shell stationary phase was subjected to comprehensive physicochemical characterization and chromatographic evaluation experiments. The analytical techniques employed included scanning electron microscopy （SEM）， transmission electron microscopy （TEM）， energy dispersive spectroscopy analysis （EDS）， nitrogen adsorption-desorption isotherms， Fourier transform infrared spectroscopy （FT-IR）， and powder X-ray diffraction （PXRD）. The systematic characterization results clearly indicate that the prepared stationary phase exhibits excellent monodispersity， and the COF layer is uniformly coated on the surface of the SiO₂ core. TEM characterization demonstrated that the thickness of the COF materials on the surface of SiO₂ is approximately 110 nm. Furthermore， FT-IR spectra were collected and the results demonstrated that the characteristic stretching vibrations at 3 209， 2 927， and 1 515 cm^-1， attributed to N-H， C-H， and C=N stretching， confirm the condensation reaction between TAPT and TA. In the XRD pattern， the peaks observed at 16.6°， 18.9°， 25.2° and 27.5° were attributed to the COF material and were consistent with previous reports， thereby confirming the successful synthesis of this derivative. The N₂ adsorption-desorption isotherm analysis confirmed that the material possesses a typical mesoporous structure. Its specific surface area and pore size distribution are similar to those of the original porous SiO₂ microspheres， subsequently providing a structural basis for efficient chromatographic mass transfer kinetics. In addition， the chromatographic performance was investigated. And it was confirmed that the stationary phase was effectively used for the separation of representative neutral polar or non-polar compounds such as benzenes， alkylbenzenes， phthalate esters， formamides， and aniline mixtures. These compounds are separated due to hydrophobic interactions， π-π interactions， and the unique mesoporous structure in the reversed-phase chromatography mode. ACN-water （30∶80 or 40∶60， volume ratio） was selected as the mobile phase at a flow rate of 1 mL/min. The results of the methodological validation indicate that the intra-batch relative standard deviations （RSDs） of one TAPT-TA-COF@SiO₂ packed chromatographic column were less than 1.6%， demonstrating excellent preparation reproducibility. Furthermore， this stationary phase was applied to the quality control of traditional Chinese medicine. Specifically， it was used to determine the content of astragaloside Ⅳ in Astragalus according to pharmacopoeial records. The measured result met the pharmacopoeia standard of ≥0.08%. This research work not only provides new opportunities for advancing fundamental and applied research on novel COF stationary phases， but also helps to further promote in-depth research on the application of COF materials at the intersection of separation science and pharmaceutical sciences.

Key words: mesoporous, covalent organic framework （COF）, stationary phase, astragaloside Ⅳ