Pyrene trisulfonic acid-functionalized silica-based multi-mode stationary phase for separation of hydrophilic, hydrophobic compounds and rare earth ions

Background To address the limitations of traditional single-mode stationary phases in separating complex samples, mixed-mode or multi-mode chromatographic stationary phases, which can provide two or more interaction mechanisms, have attracted extensive research interest. Among them, sulfonated pyrene derivatives present a promising candidate ligand, as they synergistically retain the hydrophobicity and π-π interaction capability of the pyrene moiety along with the hydrophilicity and strong cation-exchange capacity provided by the sulfonic acid groups. This synergistic multi-mechanism design significantly enhances separation selectivity for diverse and complex components. Results A pyrene trisulfonic acid-functionalized silica stationary phase (Sil-PyTSa) was successfully prepared and evaluated. In hydrophilic interaction liquid chromatography (HILIC) mode, Sil-PyTSa could efficiently separate nucleobases and nucleosides, ginsenosides, and alkaloids. For nucleobases and nucleosides, it utilized hydrophilic, electrostatic, and π-π interactions, showing superior retention and selectivity over a control HILIC column. In reversed-phase liquid chromatography (RPLC) mode, favorable separation of PAHs was achieved via hydrophobic and π-π interactions, enabling faster analysis and lower solvent consumption than a C18 column. In ion-exchange chromatography (IEC) mode, baseline separation of 14 rare earth elements (REEs) and removal of Fe/U impurities were accomplished. The column efficiency reached 95,920 N/m for naphthalene. Additionally, Sil-PyTSa achieved effective separation for REEs and iron (Fe) in a simulated NdFeB leaching solution and detected nucleobases and nucleosides in Angelica, indicting promising potential for analyzing complex matrices. Significance and novelty This work developed a novel multi-mode chromatographic stationary phase with multiple interactions mechanisms to enable high-performance separations in HILIC, RPLC, and IEC modes. It demonstrates good separation efficiency and selectivity, low solvent consumption, and high stability. This offers a versatile and green solution for the separation of complex samples with diverse analytes.