Development of a capillary electrophoretic separation of an N-(substituted)-glycine-peptoid combinatorial mixture

Capillary electrophoresis was used for the separation of a combinatorially synthesized N-(substituted)-glycine (NSG) peptoid mixture. This mixture consisted of 24 trimeric compounds sharing a common backbone structure but differing in the side chain attached at the N-terminal residue. Standards of the individual components were unavailable so that development of the separation was based on the mixture. A variety of buffer additives were investigated to enhance the CE resolution of this diverse mixture. Ion-pairing agents, cyclodextrins and organic modifiers were all evaluated as buffer additives. The best separations were achieved using a combination of buffer additives, each serving a different purpose in the separation. Heptane sulphonic acid (HSA) was used to reduce hydrophobic intramolecular interactions. Methyl-beta-cyclodextrin was used to provide host-guest interactions in order to resolve the very hydrophobic components of the NSG-peptoid mixture. The optimized run buffer consisted of 250 mM sodium phosphate buffer, pH 2.0, with 25 mM HSA and 40 mg/ml BCD and resulted in the resolution of 21 peaks for the 24 peptoids in the combinatorial mixture.