Potential of High-Performance Liquid Chromatography for Distribution Coefficient Determination of 3-Hydroxyquinolin-4(1H)-one Derivatives

The potential of reversed-phase HPLC for the determination of distribution coefficient D _7.4 of selected 3-hydroxyquinolin-4(1H)-ones (3HQs) as compounds with significant biological activity was studied. Various stationary phases with C18 as well as hexyl-phenyl modification reflect current trends in RP-HPLC development such as higher sorbent silanophilicity, core–shell technology, hybrid and/or charged surface particles. Because of significant peak tailing of 3HQs at physiological pH on reversed-phase sorbents the separations at pH 3 were performed as well. Surprisingly, the pH change did not affect significantly the partition coefficients of 3HQs. Very affordable and common standards such as anisole, acetophenone, benzyl alcohol, brombenzene, ethylbenzoate and trichlorethylene were applied in the described methodology. The best linearity (R ² 0.9895) of the correlation between log P and log k _w for standards was obtained for hexyl-phenyl sorbent, but this stationary phase was shown to be unsuitable for HPLC separation of 3HQs. The highest linearity (R ² 0.9499) of the relationship between log D _7.4 determined by the classic shake-flask method and log D determined by means of HPLC for 3HQs was attained with Cortecs C18+ column at pH 7.4. The described methodology with Cortecs C18+ as stationary phase offers fast and accurate estimation of log D _7.4 of the tested 3HQs. In an effort to increase the throughput of the HPLC method for log D _7.4 determination, we evaluated almost aqueous mobile phase that contained only 3 % of acetonitrile. Although a worse correlation between log D _7.4 determined by shake-flask method and HPLC with almost aqueous mobile phase was observed, the described procedure offers a very simple and high-throughput alternative for the estimation of log D _7.4.