Open tubular capillary electrochromatography migration behavior of enkephalins in etched chemically modified fused silica capillaries

Fused silica capillaries for use in electrophoretic analyses are etched with ammonium bifluoride in the presence of a second inorganic salt (CuCl2, CrCl3, NaNO3, or (NH4)2CO3). The effects of the presence of these inorganic components in the surface matrix on the electromigration behavior of enkephalins are evaluated. Resolution, efficiency and peak shape are used to compare the various columns. In some cases the etched surface is then modified by the addition of an octadecyl moiety using a silanization/hydrosilation procedure. The surface properties of the etched capillaries can also be evaluated by electroosmotic flow measurements. RSDs of migration times under identical experimental conditions were <1%.