Stationary phases
As mentioned above, the most commonly-used silica-based C18 columns have defects caused by free silanol sites. The interference of silanophilic interaction between investigated compounds and residual silanol groups might lead to inferior linearity between logP and logkw, especially for basic compounds. In response to this problem, columns with different packing materials have been extensively assessed for applicability to lipophilicity measurement by RP-HPLC. Basically, these newly-developed stationary phases are based on either silica or polymer.