COMPARATIVE-STUDY OF THE RETENTION BEHAVIOR OF LIPIDIC PEPTIDES ON RP-118 AND SUPELCOSIL(TM) LC-ABZ STATIONARY PHASES

A series of lipidic amino acids and peptides were investigated by syst ematic change of the mobile phase composition using traditional octade cylsilica stationary phase and the newly developed Supelcosil(TM) LC-A BZ column. The mobile phases contained various concentrations of metha nol and acetonitrile combined with 0.1% trifluoroacetic acid (TFA). Th e log k' values were plotted as a function of organic phase concentrat ion in the mobile phase. In some cases parabolic curves were obtained on the traditional octadecyl silica stationary phase due to the presen ce of the free silanol groups, while on the Supelcosil(TM) LC-ABZ colu mn straight lines were obtained. Much lower concentration of organic p hase was needed for getting similar retention times on the Supelcosil( TM) LC-ABZ column, so no retention was observed at higher organic phas e concentrations where the silanol effect could have been observed. Th e slope and the intercept values of the linear section of the log k' v s organic phase concentration lines were calculated and the chromatogr aphic hydrophobicity index (rho(0)) was also expressed for each compou nd. By the help of the log k' vs organic phase concentration plots the optimum conditions for the separation of diastereomeric isomers were predicted.