HIGH-PERFORMANCE MICELLAR LIQUID-CHROMATOGRAPHY WITH SILICA MICROPARTICLES HAVING SURFACE-BOUND CATIONIC SURFACTANT MOIETIES .1. COMPARISON WITH OCTADECYLSILICA AND APPLICATIONS TO THE SEPARATION OF DANSYL AMINO-ACIDS, HERBICIDES, AND CATECHOLAMINES

The usefulness of silica microparticles having surface-bound cationic surfactant ligands in reversed phase chromatography (RPC) and micellar liquid chromatography (MLC) was examined, and the influence of surfactant type on retention and separation selectivity was studied. Different selectivities were observed by using silica microparticles having surface-bound cationic surfactant ligands, such as n-octadecyldimethyl(propylsilyl)ammonium groups (C18N+(Me)(2)Pr) when compared to a C-18-silica column in the separation of dansyl amino acids (Dns-AA), herbicides and catecholamines by RPC and MLC. The presence of surface-bound charged moieties affected the amount of surfactant adsorbed onto the surface of the stationary phase from a given micellar mobile phase, which in turn influenced the retention behavior of neutral and charged species, thus leading to a unique chromatographic selectivity.