Preparation and evaluation of versatile zwitterionic mixed-mode chromatographic stationary phases

The limitations of traditional single-mode stationary phases in complex chromatographic separations underscore the critical need for versatile mixed-mode stationary phases. Zwitterions, characterized by tunable ionic structures, have attracted considerable attention in the development of stationary phases. This study presents the innovative design of a bidentate phenyl-embedded zwitterionic stationary phase (SIL–BA–BMPPA), synthesized through the strategic integration of tertiary amine groups and carboxyl groups onto silica spheres. The retention mechanism of SIL–BA–BMPPA was comprehensively evaluated with analytes of diverse structures under various separation conditions. Its chromatographic performance was then compared with that of an alkyl-embedded counterpart (SIL–BA–BDA), as well as traditional C18 and bare silica stationary phases. As expected, SIL–BA–BMPPA exhibited satisfactory separation performance in both reversed-phase and hydrophilic interaction modes. Moreover, amphipathic analytes, including acidic, basic, and zwitterionic compounds, were efficiently separated on SIL–BA–BMPPA through the selective synergistic effects of multiple interactions. SIL–BA–BMPPA demonstrates versatile mixed-mode separation capabilities, endowing it with substantial potential for complex chromatographic separations.