Solute–solvent interactions in chemistry and biology. Part 7. An analysis of mobile phase effects on high pressure liquid chromatography capacity factors and relationships of the latter with octanol–water partition coefficients

log k′ values on a C18 stationary phase with 90/10, 75/25, 60/40, 45/55 and 30/70 methanol–water mobile phases are correlated in terms of the generalized linear solvation energy relationship, log k′= XYZo+mVI/100 +sπ*+bβm+aαm where VI is the intrinsic (van der Waals) molar volume, and π*, βm, and αm are the solvatochromic parameters that measure solute dipolarity–polarizability, hydrogen-bond acceptor basicity, and hydrogen-bond donor acidity. The correlation equations are combined with the corresponding equation for octanol–water partition coefficients to generate new equations that demonstrate the exact relationships between the various log k's and log Kow.