Capillary electrochromatography with a silica column with a dynamically modified cationic surfactant

A novel mode of capillary electrochromatography (CEC), called dynamically m odified silica-capillary electrochromatography, is described in this paper. The column packed with bare silica was dynamically modified with long chai n quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), which wa s added into the mobile phase. CTAB ions were adsorbed onto the surface of bare silica, and the resulted hydrophobic layer on the silica gel was used as the stationary phase; Using the dynamically modified silica column, neut ral solutes were separated by CEC. The highest number of theoretical plates obtained was about 71 500/m and the relative standard deviations for t(0) and capacity factor of toluene were 4.7% and 4.9% for 20 consecutive runs, respectively. The separation mechanism of neutral solutes and the influence of mobile phase composition on the separation was investigated. The separa tion of nitrogen-containing solutes was carried out with this mode and the peak tailing of basic solute was effectively eliminated because the adsorpt ion of basic solute on silica was blocked by the preferred adsorption of CT AB. (C) 1999 Elsevier Science B.V. All rights reserved.