Mixed-mode monolithic silica as a chromatographic separation medium

Abstract

Capillary electro chromatography (CEC) is a separation technique that combines the dual properties of capillary zone electrophoresis (CZE) and micro-liquid chromatography (µ-LC). A hybrid-type silica monolith capillary column was prepared from a mixture of tetramethoxysilanes (TMOS) and methyltrimethoxysilanes (MTMS). Surface modification with octadecyldimethyl-(N- N-diethylamino)silane (ODS-DEA) and N-3[-(dimethylamino)propyl]acrylamide methyl] chloride-quaternary salt, (DMAPAA-Q) was carried out to form a mixed-mode of C 18 and a strong anion exchange stationary phase. The synthesized mixed-mode silica monolithic column was then characterized physically with a scanning electron microscope (SEM) and shown to have an average through-pore size and skeleton size of 2.2 µm and 2.0 µm, respectively. This new column with mixed-mode characteristic of reversed-phase (RP) and strong anion exchange (SAX) functionalities was then applied as the stationary phase in CEC for the separation of inorganic and organic ions using a 50mM phosphate electrolyte of pH 6.9. The inorganic and organic anions were base-line separated within 10min with column efficiency up to 114 900 plates/min.