Chiral and electrokinetic separation of amino acids using polypyrrole-coated adsorbents

An optically active and electroconductive polymeric adsorbent has been developed for the use in chromatographic resolution of nonderivatized amino acids. The chiral selectivity of the adsorbent is based upon ligand exchange of coordinated copper(II) complexes of d or l-amino acids and a molecular imprinting technique by modifying the resin surface with polypyrrole coating. Applying a potential difference of ±1.5 V to the chiral and conductive column, racemic amino acids are separated according to their charge characteristics, and simultaneously resolved with respect to their optical isomerisms. A pH-controlled mixture of d,l-lysine and d,l-aspartic acid is resolved displaying enantioselectivity values of 1.19 and 2.08, respectively, and a baseline separation of the two amino acids is accomplished by alternating the polarity of the electric field. The synthesized adsorbent also exhibits size exclusion factor discriminating amino acids with larger side chains.