Phase Diagrams, Molal Volumes and Polarizabilities of (Lysine, Methionine Amino Acids-Alcohol-Water) Tri-Component Systems

The molal solubility, density and refractive index of DL-Methionine (as a nonpolar neutral amino acid) and L-Lysine (as polar basic amino acid) in water–methanol and water–ethanol mixed solvents with alcohol mole fractions (0.0, 0.10, 0.30, 0.50, 0.70, 0.90, and 1.0, by volume) at 298.15 K were determined experimentally. From the values of the measured refractive indices, molal solubilities and densities, the apparent molal volumes, the excess refractive indices, the molar refractions and the polarizabilities, of the amino acids under study were calculated and discussed. The solvation of the amino acids under study was discussed in terms of their molal solubility, apparent molar volume and refractive index. The molal solubility data were modeled according to Setchenow equation.

The phase diagram of the tri-component systems under study (amino acid-alcohol-water) were also determined and discussed. The effect of the solvent on the solubility of neutral amino acids (DL-Methionine), basic amino acid (L-Lysine) was discussed. The results indicate that the molal solubility of L-Lysine is higher than that of DL-Methionine in the solvents under study.