Aqueous Solubility, Complex Formation, and Induction Time of Calcium Oxalate Monohydrate in the Presence of Natural Organic Small Molecules

The solubility of calcium oxalate monohydrate (COM) has been measured in aqueous solutions of various naturally sourced organic small molecules such as carboxylic acids, amino acids, and polyphenols. All of these compounds enhanced its solubility, with carboxylic acids such as citric and malic acid exerting the most pronounced impact, within the addition concentration range of up to 100 μM. The observed solubilities were well correlated at all concentrations using a theoretical model that incorporates the specific interaction theory (SIT) specifically developed for this system. The complexation of these molecules with calcium ions was found to play a major role, which is subject to the material and charge balance. The induction time was also measured and found to increase with all of the compounds studied, suggesting their capability to bind with calcium.