The peculiarities of the interphase distribution of amino acids in the cloud point extraction systems

Abstract

This study presents the particularities of interphase distribution of amino acids between water and non-ionic surfactant-rich phase at cloud point temperature. The influence of a number of hydrophobic/structural parameters of amino acids, such as total hydrophobicity (logP), hydropathy index (Hi), which characterized the nature of amino acid fragment, total molecular surface of amino acids (Sa), their polarity (F), electronegativity of the molecule (X), the maximum possible number of hydrogen bonds, which may form a molecule (Hb), the molecular refraction (Mr), the value of organic (O) and the value of inorganic (I) properties on effectiveness of their cloud point extraction have been studied. Based on obtained data, the equation logD=1.05–0.005Mr+0.004Sa–0.030Hb–0.008F has been suggested to describe the interphase transfer of amino acids into surfactant-rich phase. The values of solvation free Gibbs energy for the interphase transfer of amino acids into the surfactant-rich phase were also calculated. The obtained values of free Gibbs energy of amino acids in cloud point extraction system were in the range from −4.4 to −8.0kJmol−1. A significant difference between thermodynamic parameters of the cloud point extraction and traditional liquid-liquid extraction with organic solvents is reflected in the ability of surfactant-rich phase extract both hydrophobic and hydrophilic compounds as a consequence of “high organization” and supramolecular nature of this type of phase.