Separation of peptide derivatives by pH-zone-refining counter-current chromatography.

pH-Zone-refining counter-current chromatography was applied to the preparative separation of oligopeptide derivatives containing up to three amino acids. Both acidic benzyloxycarbonyl peptides and basic peptides-beta-naphthylamide were successfully separated with two-phase solvent systems composed of methyl tert.-butyl ether, 1-butanol, acetonitrile and water using a set of suitable retainer and eluent reagents for each group. The preparative ability of the method was demonstrated in the separation of multigram quantities of analyte with a standard separation column with a total capacity of 325 ml. The effects of important factors such as polarity of the two-phase solvent system, concentrations of the eluent base and the retainer acid were discussed.