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Potentiometric Titration Method for the Determination of Solubility Limits and pKa Values of Weak Organic Acids in Water

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journal contribution
posted on 08.07.2020, 14:04 by Eduard Wiedenbeck, Denis Gebauer, Helmut Cölfen
The determination of solubility limits of compounds in water is unprecise and relies on certain prerequisites such as UV–vis absorption activity. In this study, we designed an experimental approach based on potentiometric titrations to determine solubility limits of various organic compounds by exploiting their pH-active carboxylic acid groups. By applying the law of mass action, utilizing a double-dosing method ensuring a constant compound concentration, it is possible to determine the intrinsic solubility limits, which are independent of the pH value. The derived equations enable the precise and fast determination of intrinsic solubility limits of organic compounds in aqueous solutions within 2–4 h. Moreover, it is shown how the pKa value can be determined based on titrations carried out at two different compound concentrations.