Dynamically coated capillaries for enantioselective separations by capillary electrophoresis

The level of variability in migration times and peak areas often encountered in capillary electrophoresis (CE) has restricted its use for routine analysis. Cationic analytes also tend to interact with the capillary wall, resulting in skewed peak shapes and reduced efficiency. We investigated a dynamic coating procedure that involves a two-step process to modify the capillary and that results in a higher but stable electro-osmotic flow (EOF) at low pH. We compared enantioselective separations of several basic compounds on unmodified and dynamically coated capillaries. A derivatized cyclodextrin was used as the chiral additive. When the dynamic coating was used, peak symmetry improved, and migration times were significantly shorter. The dynamic coating procedure also resulted in improved migration time and peak area precision.