Silica-based, hyper-crosslinked acid stable stationary phases for high performance liquid chromatography

A new family of hyper-crosslinked (HC) phases for use under very aggressive acid conditions including those encountered in ultra-fast, high temperature two-dimensional liquid chromatography (2DLC) has been recently introduced. This type of stationary phase shows significantly enhanced acid and thermal stability compared to the most acid stable, commercial RPLC phases. In addition, the use of "orthogonal" chemistry to make surface-confined polymer networks ensures good reproducibility and high efficiency. One of the most interesting features of the HC phases is the ability to derivatize the surface aromatic groups with various functional groups. This has led to the development of a family of hyper-crosslinked phases possessing a wide variety of chromatographic selectivities by attaching hydrophobic (e.g. -C ₈), ionizable (e.g. -COOH, -SO ₃H), aromatic (e.g. -toluene) or polar (e.g. -OH) species to the aromatic polymer network. HC reversed phases with various degrees of hydrophobicity and mixed-mode HC phases with added strong and weak cation exchange sites have been synthesized, characterized and applied. These silica-based acid-stable HC phases, with their attractive chromatographic properties, should be very useful in the separation of bases or biological analytes in acidic media, especially at elevated temperatures. This work reviews prior research on HC phases and introduces a novel HC phase made by alternative chemistry.