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.