A new method for assessing the effect of residual silanol groups on total retention in reversed-phase HPLC

A new approach is proposed to assess the effect of residual silanol groups (hydrophilicity) on the retention of polar substances in reversed-phase high-performance liquid chromatography (HPLC). It is shown that the numerical characteristic of the relative position of trend lines in the coordinates logk(B) vs. logk(A) of the relative retention parameters (at different mobile phase compositions) for any stationary phase relative to the stationary phase selected as a standard is preferable to the separation selectivity of the same pair of substances. Full information can be obtained by determining the retention of corresponding adsorbates with two different mobile phase compositions for each column under study. It was shown that the pair of adsorbates p-toluidine-p-cresol exhibits higher sensitivity to a change in the hydrophilicity of stationary phases as compared to the pair aniline-phenol. However, the use of a nonpolar substance as a reference compound is more informative.