Liquid–liquid extraction and transport through membrane of amino acid methylesters by calix[n]arene derivatives

The extractability together with the transport through liquid membrane of some amino acid methylesters by using p-tert-butylcalix[4]arene as extractant or carrier was studied. In this context, p-tert-butylcalix[n]arenes (n = 6, 8) were found to act as useful carriers or extractant reagents for l-tryptophan methylester and l-tyrosine methylester. The calix[n]arene derivatives used in experiments extracted amino acids methylesters from the aqueous phase into chloroformic phase in the presence of tropaeolin 00 ([4(4′-anilinophenylazo)benzenesulphonic acid]) as counterion at \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{pH}} \cong 5.0 $$\end{document}. The extraction and the transport depend on the structure of calixarenes, the structure of amino acids, the pH, and the nature of anion used as ion pair for cation-receptor complexes. The properties of solvent involved in liquid membrane play an important role in membrane stability and also in selecting membrane systems. The results demonstrated that the inclusion properties of the investigated hosts are correlated with their structural properties and also they suggest further possibilities for optimal separation of amino acids derivatives.