Update of the Wayne State University system constant database for reversed-phase liquid chromatography columns for...

The solvation parameter model is used to characterize the retention properties of silica-based, reversed-phase liquid chromatography (RPLC) columns. System constants are obtained for the range 10-70 % (v/v) organic solvent at 10 % (v/v) increments for methanol-water (27 columns), acetonitrile-water (25 columns), acetone-water (7 columns), tetrahydrofuran-water (3 columns), and 2-propanol-water (1 column). The Wayne State University 2025 (WSU-2025) compound descriptor database is used as the sole source for compound descriptors to unify the system constants with a verified descriptor database. Column properties are described by system maps, a general feature of which is the dominant role of water in the retention mechanism. Water is more cohesive, hydrogen-bond acidic, and dipolar than common water-miscible organic solvents. The organic solvent moderates the controlling hand of water in the mobile phase while its selective absorption by the stationary phase is responsible for variation in the column phase ratio and contributes to the solvation properties of the stationary phase. A generic ligand designation is employed for the classification of octadecylsiloxane-type and phenylalkylsiloxane-type stationary phases for which the within the group variation of the system constants (selectivity) are comparatively small compared with those associated with changes of mobile phase composition. Changes in retention cannot simply be explained by differences in selectivity without also considering changes in the phase ratio with mobile phase type and composition. Hierarchical cluster analysis with the system constants as variables for a range of mobile phase compositions affords a useful classification tool to organize columns into groups with similar selectivity and to identify columns of different selectivity for method development. Octadecylsiloxane-type stationary phases with embedded polar functional groups, octylsiloxane-bonded, pentafluorophenylpropylsiloxane-bonded, and a perfluorohexylpropylsiloxane-bonded silica stationary phase are shown to have complimentary retention properties to octadecylsiloxane- and phenylalkylsiloxane-type stationary phases for both methanol- and acetonitrile-water binary mobile phase compositions. System constant correlation plots provide a useful tool for the identification of columns of equivalent selectivity. Ternary solvent systems are shown to provide a useful approach for method development.