Layer-by-layer assembled quinone-amine network on silica as a robust mixed-mode stationary phase for liquid...

To overcome the limited retention of hydrophobic analytes on commercial amino columns, a PBQ-PEI network coating was constructed on silica via quinone-amine coupling between polyethyleneimine and p-benzoquinone, and core-shell PBQ-PEI@SiO₂ particles were prepared by layer-by-layer assembly as a new LC stationary phase. The resulting material enabled efficient separations of both hydrophilic compounds (nucleobases, nucleosides, imidazoles, and xanthines) and hydrophobic compounds (alkylbenzenes, polycyclic aromatic hydrocarbons, and halogenated benzenes), exhibiting a characteristic RP-HILIC mixed-mode retention behavior. Column performance evaluation demonstrated good repeatability and long-term stability (RSD < 0.59% for nine consecutive injections and <1.87% deviation over four months). For caffeine determination, the developed method showed acceptable analytical performance, including good linearity in the range of 20-260 mg·L^-1, an LOD of 0.20 mg·L^-1, an LOQ of 0.61 mg·L^-1, and satisfactory recovery values of 89.30%-103.15%, and was successfully applied to the analysis of commercial tea beverage samples. This work expands the application of quinone-amine chemistry in stationary-phase fabrication and provides a new material option for mixed-mode liquid chromatography.