ELECTROFILTRATION OF SOLUTIONS OF AMINO-ACIDS OR PEPTIDES

Enhanced transfer according to the isoelectric point (pi) of amino acids and peptides (molecular mass 130-6000 g mol(-1)) was achieved using laboratory filtration in the presence of an electric field. The permeate was enriched with arginine and lysine of negative electrophoretic mobility, while the retentate was enriched with the amino acid characterized by the lowest pi value, aspartic acid. A model which assumes no retention of amino acids by ultrafiltration (UF) membranes describes reasonably well their transmission to the permeate. The peptide mixture permeate was enriched with peptides which were either positively or negatively charged according to the electric field direction. The effect was significant even under low electric field. The model did not quantify satisfactorily the experimental transmission probably because of significant retention of some peptides by the ultrafiltration membranes. The present study shows that electrofiltration (EF) may be a useful and efficient process for achieving selective separation of charged biological molecules provided that further work is aimed at a better understanding of which mechanisms rule the retention in EF and of the effect of process variables (flux, electric field, conductivity, charge of the molecules).