Comparison of the separation characteristics of the organic-inorganic hybrid stationary phases XBridge C8 and phenyl and XTerra phenyl in RP-LC

Differences in the system constants of the solvation parameter model and retention factor correlation plots for varied solutes are used to study the retention mechanism on XBridge C-8, XBridge Phenyl and XTerra Phenyl stationary phases with acetonitrile-water and methanol-water mobile phases containing from 10 to 70% (v/v) organic solvent. These stationary phases are compared with XBridge C-18 and XBridge Shield RP18 characterized in an earlier report using the same protocol. The XBridge stationary phases are all quite similar in their retention properties with larger difference in absolute retention explained by differences in cohesion and the phase ratio, mainly, and smaller changes in relative retention (selectivity) by the differences in individual system constants and their variation with mobile phase type and composition. None of the XBridge stationary phases are selectivity equivalent but XBridge C-18 and XBridge Shield RP18 have similar separation properties, likewise so do XBridge C-8 and XBridge Phenyl, while the differences between the two groups of two stationary phases is greater than the difference within either group. The limited range of changes in selectivity is demonstrated by the high coefficient of determination (> 0.98) for plots of the retention factors for varied compounds on the different XBridge phases with the same mobile phase composition.