Amino acid extraction with AOT reverse micelle

The extraction of amino acid with AOT reverse micelle is elucidated from the association reactions between AOT and amino acid in both the zwitterionic form of A± and the cationic form of A+ for the system of AOT-n-heptane/phenylalanine-NaCl (0.1 mol l−1)-H2O. The equilibrium constants of these reactions at 298 K, 308 K and 318 K are obtained respectively. The water contents in the microemulsion phase are strongly affected by the form of associated amino acid at the interface. W0 increases with the increase of the amounts of A±, but decreases with the increase of the amount of A+. The effect of the aqueous pH on the extraction ratio of various amino acids is also measured. It is found that the extraction ratios of more hydrophobic phenylalanine and lysine change sharply at about aqueous pH of pKa+1, but that for hydrophilic aspartic acid, the extraction ratio does so at about its acidic ionization constant, pH=pKa.