A new type of open-tubular C-18 ester-bonded electrochromatographic column was prepared with sol-gel technology, followed by an on-column octadecyl silylation reaction, Glycidoxypropyltrimethoxysilane, a widely used and important silane agent, was used as the sol-gel precursor to form a thin coating layer on the wall of the fused-silica capillary. The C-18 groups were introduced into the coating layer by on-column esterification reaction with stearic acid. The electrochromatography behavior of the column was evaluated in terms of the separation of peptides. A high efficiency of 4.8 x 10(5) plates/m was achieved for a basic pentapeptide using the C-18 ester-bonded column. In comparison with bare capillaries and glycidoxypropyltrimethoxysilane sol-gel-coated capillaries, the C-18 ester-bonded column showed the best separation of a mixture of seven pentapeptides under identical conditions of buffer, pH, and applied voltage.