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pKa Determination of a Non-hydro-soluble Chemical Substance, Issued from Chiral Chromatographic Solubility Profiles and Mat-pKa Calculations

Lionel Vidaud, Antoine Pradines, Jérôme Marini, Elodie Lajous and Patrick Clavières

After development and implementation of Mat-pKa software, since 3 years, pKa(s) determinations for approximately 70 compounds were successfully conducted. But a remaining objective was to enlarge the capabilities of this software to resolve cases for non-soluble compounds in aqueous phases. Until now, pKa(s) calculations were based on solubility profiles obtained in aqueous buffered solutions. A new application of this software was successful for solubility profiles obtained in pure water, in which, various concentrations of the substance led to different pH of solutions. A new approach, based on solubility profile elaborated from the Yasuda-Shedlovsky experiment, is presented in this paper, for a non-hydro-soluble chemical substance. More challenging in this case, the pKa value was determined for a chiral compound and, outside of the range 0 to 14. In this third new application, Mat-pKa software confirmed its ability to define pKa values in extended ranges and its independence to diverse techniques (generally the chromatography) delivering solubility profiles, even in very specific and delicate conditions.