Solubilities of Amino Acids in Aqueous Solutions of Chloride or Nitrate Salts of Divalent (Mg(2+) or Ca(2+)) Cations

[Image: see text] The solubilities of glycine, l-leucine, l-phenylalanine, and l-aspartic acid were measured in aqueous MgCl(2), Mg(NO(3))(2), CaCl(2,), and Ca(NO(3))(2) solutions with concentrations ranging from 0 to 2 mol/kg at 298.2 K. The isothermal analytical method was used combined with the refractive index measurements for composition analysis guaranteeing good accuracy. All salts induced a salting-in effect with a higher magnitude for those containing the Ca(2+) cation. The nitrate anions also showed stronger binding with the amino acids, thus increasing their relative solubility more than the chloride anions. In particular, calcium nitrate induces an increase in the amino acid solubility from 2.4 (glycine) to 4.6 fold (l-aspartic acid) compared to the corresponding value in water. Amino acid solubility data in aqueous MgCl(2) and CaCl(2) solutions collected from the open literature were combined with that from this work, allowing us to analyze the relations between the amino acid structure and the salting-in magnitude.