Solubilities of L-cystine, L-tyrosine, L-leucine, and glycine in sodium chloride solutions at various pH values

The solubilities of four amino acids (L-cystine, L-tyrosine, L-leucine, and glycine) at T = 298 K and at the pH values of 0.00, 1.00, 2.00, 11.00, 12.00, and 13.00 in water solutions of sodium chloride, have been measured. The concentration of NaCl was varied from (0.0 to 3.0) mol.dm(-3). The solubility of L-cystine increased as the concentration of salt was raised from (0.0 to 3.0) mol.dm(-3). For the same variation of sodium chloride concentration the solubilities of L-tyrosine and L-leucine decreased. The solubility of glycine was not influenced significantly by the presence of NaCl. A simple relation between the ratio of the solubilities of the amino acids with, and without, salt and NaCl concentration is presented. The relation predicts well the solubilities of L-cystine, L-tyrosine, L-leucine, and glycine in aqueous solutions of NaCl starting from known values of the solubilities in pure water, (C) 1998 Academic Press Limited.