POTENTIOMETRIC AND LASER-ACOUSTIC STUDY OF AMINECARBOXYLATE INTERACTION OF AMINO-ACID MOLECULES

This paper reports the results of studying aminocarboxylate interactio n of amino acid molecules in suspensions of solvent-impregnated sulfon ate ion exchangers (SISIEs) with widely variable capacities obtained b y modification of the macroporous PS-DVB polymers Amberlite XAD-2 and XAD-4 with toluene solutions of dinonylnaphthalenesulfonic acid. Varia tion of SISIE capacities leads to modulation of their surface electroc hemical properties, such as surface charge density, surface potential, and so forth, which can be easily evaluated by measuring suspension e ffects (Delta pH) in, for example, SISIE-HCl systems and interpretatio n of the results obtained within the Gouy-Chapman model of the electri c double layer (EDL). The results of measuring Delta pH in SISIE-zwitt erlyte systems including solutions of beta-alanine and epsilon-aminohe xanoic acid in a wide range of amino acid concentrations have shown th at the behavior of SISIE suspensions in amino acid solutions differs d ramatically from that of simple electrolyte (HCl) systems. Unlike SISI E-HCl systems, SISIE-zwitterlyte suspensions are characterized by the absence of the concentration compression of the diffuse part of the ED L, which can be interpreted within the framework of the aminecarboxyla te interaction of amino acid molecules mechanism as the structuring of the diffuse part of EDL due to formation of amino acid chains surroun ding SISIE beads. The results obtained by determination of the sound a bsorption coefficient in SISIE-electrolyte and SISIE-zwitterlyte syste ms by wide-band laser-acoustic spectroscopy are in good agreement with those obtained by a potentiometric technique.