Ternary phase diagram and the formation mechanism of two distinct solid solutions of amino acid systems: l -Valine/ l -norvaline and l -valine/ l -alanine

Abstract

Abstract The ternary phase diagram of l -valine ( l -Val)/ l -norvaline ( l -Nva)/water system was determined at 293.15 K, in which the tie lines clearly indicate the formation of complete solid solution and X-ray powder diffraction (XRPD) analysis of the solid phases further confirms complete miscibility of l -Val and l -Nva molecules in the solid state. Further, homogeneous solid solution can be obtained via mechano-chemical method of non-solution system and via anti-solvent method. Similar composition analysis of solid and liquid phase suggests that l -Val and l -alanine ( l -Ala) is partially miscible with only a narrow scope of component substitution. The similarity degree of the three amino acids in cell dimensions and supramolecular organization determines the miscibility of l -Val and l -Nva or l -Val and l -Ala, and the investigation in molecular incorporation of l -Val/ l -Nva system was developed. Applying the experimental solid-liquid equilibrium data, fractional crystallization is verified as an effective purification method.