Preparation of quinine and poly (ionic liquid)s co-modified silica gel and its application in mixed mode chromatographic separation.

A novel mixed-mode stationary phase (Sil-PQn-IL) was developed by co-modifying silica with quinine and poly (ionic liquid)s for mixed mode chromatographic separations. The combined modification of quinine with ionic liquid has achieved a combination of multiple mechanisms between the stationary phase and the analyte, making Sil-PQn-IL a truly high-performance mixed-mode stationary phase. Successful functionalization was confirmed by EA, FT-IR, and XPS characterization. The exploration of chromatographic conditions has proved that the chromatographic separation mode can be switched by changing the mobile phase. Moreover, through the LSER and Van't Hoff equations, it has been demonstrated that there are hydrogen bonds, π-π, hydrophobic, and electrostatic interactions between the stationary phase and the analytes. Meanwhile, the Sil-PQn-IL chromatographic column demonstrates excellent separation reproducibility (RSD < 0.87%) and column efficiency (N = 92520 plates/m). In addition, Sil-PQn-IL successfully separated PAHs, phenols, and sulfonamide substances under the RPLC mode, successfully separated 7 types of nucleosides and nucleobases under the HILIC mode, and could achieve baseline separation of 7 types of organic acids under the IEC mode. Compared with commercial mixed-mode chromatographic columns, Sil-PQn-IL demonstrates superior separation ability and efficiency, especially in the HILIC and RPLC modes. Finally, Sil-PQn-IL enabled simultaneous analysis of polyphenols (rutin, chlorogenic acid, scopolamine) and inorganic anions (nitrate, nitrite) in tobacco samples by switching between RPLC and HILIC modes on a single column. This work presents a promising stationary phase for comprehensive analysis of complex matrices, offering significant advantages in flexibility, efficiency, and cost-effectiveness for routine analytical applications.