Flexible ether chain-bridged dicationic ionic liquid stationary phase for multifunctional separation and interaction mechanism elucidation.

Dicationic ionic liquids (DILs) possess higher thermal stability and more abundant interaction sites than monocationic ionic liquids. A novel ether chain-bridged dicationic ionic liquid (EDIL) was synthesized and immobilized onto silica via crosslinking polymerization to prepare a mixed-mode stationary phase (Sil-PEDIL). The stationary phase efficiently separated diverse analytes, including nucleosides, phthalates, and fluorobenzoic acid isomers, achieving a maximum column efficiency of 85,950 plates m-1. Sil-PEDIL also exhibited stable retention and improved peak shapes under pure aqueous mobile phase conditions compared with HILIC. Chromatographic studies revealed a mixed-mode retention mechanism involving HILIC, RPLC, and IEC. Quantum chemical calculations demonstrated the conformational flexibility of EDIL and its adaptive interactions with different analytes, while wave function analysis elucidated the underlying intermolecular interactions. This work provides insights into the design of advanced mixed-mode stationary phases and the understanding of analyte-stationary phase interactions.