Investigation of dynamically coated alumina stationary phases for reversed-phase high-performance liquid chromatography

Dynamically coated alumina (DCA) was prepared by pumping mobile phase containing methanol and concentration of 10mM Sodium Lauryl Sulphate (SLS), an anionic surfactant prepared in water, through a bare alumina column. The mechanism of separation of a test mixture were characteristic of reversed phase chromatography as evident in the decreased retention time as the percentage of methanol increased. However, the effects of changing the pH of the mobile phase on retention of solutes were different than that expected in reversed phase separations, indicating the presence of another retention mechanism. Excellent resolutions, peak shapes and peak symmetries were obtained using the DCA conditions and were comparable to similar separations performed on an ODA (octadecylalumina) column. Comparisons of retentions of a variety of organic compounds on DCA with those of commercial ODS (octadecylsilica) and ODA phases were also performed.