The effect of particle and ligand types on retention and peak shape in liquid chromatography

A well performed, detailed characterization of stationary phase properties can serve as a useful tool for choice of suitable separation environment for a given purpose. This work shows effects of particle type/technology and ligand chemistry on retention and peak shape of neutral, acidic, basic and zwitterionic compounds. Eight columns differing in endcapping technology, particle type and ligand bonded were evaluated, namely XSelect CSH C18, XSelect CSH Phenyl-Hexyl, XSelect CSH Fluoro-Phenyl, XSelect HSS C18, XSelect HSS C18 SB, XSelect HSS PFP, XBridge C18 and XBridge Shield RP18. A simple Walters test for evaluation of hydrophobicity and silanol activity was performed. Mobile phases composed of acetonitrile and aqueous part (pH 2.1; pH 4.7 and pH 8.0) were used. More detailed description of interactions participating in the retention mechanism was provided by the linear free energy relationship model. For a more detailed characterization of possible electrostatic interactions, compounds with permanent charge across selected pH range were used. A good agreement between the Walters test results, the expanded linear free energy relationship model, and the test of ionic-interactions was observed, suggesting that each testing method provides value for characterization of the solute-stationary phase interactions.