Method for estimating the residual silanol activity of reversed-phase chromatographic adsorbents

The retention of some organic bases on reversed-phase adsorbents was studied as a function of the concentration of KH₂PO₄ in the mobile phase. It was shown that, for some adsorbents, retention decreases with an increase in the salt concentration, while an opposite dependence was observed for the other adsorbents. Such behavior of adsorbates can be explained by the prevailing silanophilic interactions in the former case and hydrophobic interactions in the latter case. The observed dependence can be used to change the chromatographic selectivity in the analysis of complex mixtures containing organic bases and to assess the properties of reversed-phase columns. Diphenhydramine hydrochloride was proposed as a test substance to assess the properties of the columns in the analysis of multicomponent pharmaceutical preparations. It was used in the comparative study of the properties of some adsorbents.