Constructing promising amino acid hydrogel functionalized silica for mixed-mode chromatographic separation through...

In the field of chromatographic separation, the exploration of high-performance stationary phase materials has never ceased. Amino acid hydrogels, due to their unique structure and chemical properties, exhibit excellent biocompatibility, selectivity, and tunability, providing new opportunities for the development of chromatographic stationary phases. Polyionic liquids, with their rich ionic characteristics, diverse structures, excellent thermal stability and solubility, have attracted much attention in separation science. The combination of amino acid hydrogels and polyionic liquids is expected to integrate the advantages of both, opening up new avenues for enhancing the performance of chromatographic stationary phases to meet the demands of complex sample separation and analysis.

In this study, we synthesized two types of amino acid hydrogels, each crosslinked with different agents, on the surface of silica gel via click chemistry for using in chromatographic separation. Among the four chromatographic separation modes - RPLC, HILIC, IEC, and PALC - the separation of various substances such as nucleotides, bases, alkylbenzenes, polycyclic aromatic hydrocarbons, phenols, sulfonamides, anilines, cations, and organic acids has been achieved. Furthermore, the amino acid/polyionic-liquid composite hydrogel exhibited superior separation performance for positional isomers. Concurrently, the modification of amino acid hydrogel ensures stationary phases separation stability when pure water is employed as the mobile phase, thereby guiding the advancement of green chemistry. Furthermore, both Sil-Ph-Cys-IL and Sil-Ph-Cys-MBA columns exhibited excellent separation reproducibility and column efficiency. The Van't Hoff equation and the linear solvation energy relationship (LSER) model were utilized to elucidate the retention mechanism.

This study has confirmed that the amino acid/polyionic liquid composite hydrogel effectively combines the advantages of amino acids and ionic liquids. It has demonstrated that the performance of the stationary phase can be improved by adjusting the crosslinking agent, significantly broadening the application scope of the gel stationary phase. This research provides ideas for the future development of hydrogel stationary phase materials in chromatographic separation.