Preparation of various silica-based columns for capillary electrochromatography by in-column derivatization

Chemically bonded silica gels were prepared in a capillary by pumping an ethanolic solution of a silylating reagent, such as octadecyltrimethoxysilane, 3-aminopropyltrimethoxysilane and dimethyloctadecyltrimethoxysilylpropylammonium chloride into a heated capillary packed with bare silica particles. The silylation reactions were completed in a short time and thus-prepared columns showed high column efficiency and high reproducibility. Examples are shown for the separation of 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives of aldopentoses on a 3-aminopropylated silica column and benzoate homologues as well as PMP derivatives of the component monosaccharides of glycoproteins on an octadecylammonium column. Since the presence of frit filters hampers high efficiency separation, an attempt was made to fix the bed of modified silica gel particles to the capillary inner wall by a cross-linking technique. The results indicated that this technique is promising.