Applicability of hybrid micelle liquid chromatography for practical determination of acid dissociation constant

Abstract

Hybrid micellar liquid chromatography was used for practical determination of acid dissociation constant (pKa) of three analytes, namely, ibuprofen (IBU), naproxen (NPX) and benzoic acid (BZA). The proposed method was established based on the principle adopting the dependence of the retention time of ionizable analytes on the mobile phase pH. Simple data manipulation was carried out without the need of specialized software, allowing estimation of practically determined pKa values, which were found to be in accordance with calculated and experimentally determined values, emphasizing on the versatility and applicability of the proposed method. The present methodology carries unique features which support its utility over traditional techniques adopted for pKa determination, like its solubilizing ability, overcoming long retention times experienced in reversed phase chromatography, non-limitation to a specified chemical class and possible justification of the determined pKa values using linear regression equations.