Pairing Ion Effects in the Reversed Phase High Performance Liquid Chromatography of Peptides in the Presence of Alkylsulphonates

Abstract

The influence of pH and the concentration of the two lipophilic pairing ions, hexylsulphonate and camphor-10-sulphonate, on the retention of a group of small peptides to chemically bonded hydrocarbonaceous, microparticulate silicas has been further investigated. With low pH aqueous methanol mobile phases containing various concentrations of these surface active anions, the capacity factors of unprotected and C-protected peptides show similar dependencies on the concentration of the pairing ion. Column selectivity becomes essentially independent of pairing ion concentration above ca 25mM. At higher pH values, the influences of pairing ion interactions on peptide retention appear to diminish due to competing protic equilibria.