Retention prediction and hydrophobicity estimation of weak acidic compounds by reversed-phase liquid chromatography using acetic and perchloric acids as ion suppressors

Simple acids are usually applied to suppress the ionization of weakly ionizable acidic analytes in reversed-phase liquid chromatography. The purpose of this study is to investigate the retention behavior of various weak acidic compounds (monoprotic, diprotic, triprotic, and tetraprotic acids) using acetic or perchloric acid as ion suppressor in a binary hydroorganic mobile phase. The apparent n-octanol–water partition coefficient (K _ow ″) was proposed to calibrate the n-octanol–water partition coefficient (K _ow) of weak acidic compound. LogK _ow ″ was found to have a better linear correlation with logk _w, the logarithm of the retention factor obtained by extrapolating to neat aqueous fraction of the mobile phase, for all weakly ionizable acidic compounds. This straightforward relationship offers a potential medium for direct measurement of K _ow data of weak acidic analytes and can be used to predict retention behavior of these compounds in the ion suppression reversed-phase liquid chromatographic mode.