High efficiency separation in capillary electrochromatography and capillary liquid chromatography using monolithic stationary phase

Abstract

C18 monolithic silica capillary columns modified with octadecyl moieties (ODS) and poly(octadecyl methacrylate) (ODM) were prepared for reversed-phase capillary liquid chromatography (CLC). A high column performance was obtained with plate height (H) nearly or less than 10 m and permeability in a range of 7.3×10-14-9.4×10-14 m2. In comparison of ODM and ODS stationary phase selectivities for halogenated compounds, such as halogenated benzenes and chlorophenols, the ODM columns have greater preference and greater selectivity for these compounds due to the greater dispersive interaction by more densely packed C18 groups on ODM polymer coated column together with the contribution of carbonyl groups in ODM side chain. In addition, the reversed-phase ODS and mixed-mode ODS/AP1 or ODS/AP2 monolithic silica capillary columns were prepared for capillary electrochromatography (CEC) with H in the range of 3.7-4.0 µm, where AP1 and AP2 refer to aminopropyl and 3-(2-aminoethylamino)propyl moieties, respectively. These mixed-mode columns have the preference for phenolic compounds. Moreover, the separation selectivity was compared in capillary electrophoresis with different modes. Capillary zone electrophoresis with the addition of cyclodextrin (CD-CZE) showed the better separation selectivity for chloro- and methylbenzoates than CZE without cyclodextrin and micellar electrokinetic chromatography. The separation selectivity patterns were also developed for the separation of fully charged achiral compounds using a neutral cyclodextrin.