Graphene quantum dots-functionalized C18 hydrophobic/hydrophilic stationary phase for high performance liquid chromatography

Graphene quantum dots (GQDs) were chosen as functional material to improve the separation performance of C-18 column since GQDs could provide multiple interactions such as hydrophilic, pi-pi stacking and hydrogen bonding interactions. In this study, a novel octadecyl modified GQDs-bonded silica (C-18/GQDs/SiO2) stationary phase was prepared and applied in reversed-phase and hydrophilic interaction liquid chromatography. This column showed satisfactory separation performance for both hydrophobic, polar and hydrophilic compounds including polycyclic aromatic hydrocarbons, alkylbenzenes, anilines, phenols, aromatic acids, alkaloids, nucleosides and nucleobases. Through investigating the impact of organic solvent content on retention, it was found this new stationary phase had typical characteristics of hydrophobic/hydrophilic chromatography. Compared with commercial C-18 column, this column showed better separation performance for polar aromatic compounds because the introduction of GQDs provided more interactions such as pi-pi stacking, hydrophilic and hydrogen bonding interaction with analytes. To get an in-depth understanding of the retention mechanism, linear solvation energy relationship model was established for both C-18/GQDs/SiO2 and C-18 columns, theoretically calculated data indicated that C-18/GQDs/SiO2 column had higher pi-pi stacking and hydrogen-bonding acceptance ability. C-18/GQDs composite stationary phase equipped with hydrophobic/hydrophilic properties has great prospect in separation science.