Triphenyl-Modified Mixed-Mode Stationary Phases With and Without Embedded Ion-Exchange Sites for High-Performance Liquid Chromatography

The present work reports on the preparation, characterization, and evaluation of a set of novel triphenyl-modified silica-based stationary phases without and with embedded ion-exchange sites for mixed-mode liquid chromatography. The three synthesized triphenyl phases differed in additionally incorporated ion-exchange sites. In one embodiment, allyltriphenylsilane was bonded to thiol-modified silica by thiol-ene click reaction, leading to particles with no ion-exchange sites. A second stationary phase was obtained by thiol-yne click reaction of thiol silica with 2-propinyl-triphenylphosphonium bromide, yielding a strong anion-exchanger (SAX). A third stationary phase was obtained from this SAX phase by the oxidation of residual thiols to sulfonic acid moieties, leading to a zwitterionic surface. All synthesized materials were subjected to elemental analysis, ¹³C and ²⁹Si solid-state cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy analysis, and pH-dependent ζ-potential determinations via electrophoretic light scattering. The prepared stationary phases were chromatographically evaluated under classical reversed-phase, ion-exchange, and hydrophilic interaction chromatography conditions and classified within a set of commercially available columns by principal component analysis of retention factors. Finally, the obtained stationary phases were applied for biomolecule separations (e.g., teicoplanin and siRNA patisiran). These LC tests proved the orthogonality of the three prepared stationary phases and indicated possible fields of application.