Fritless capillary electrochromatography

The preparation of packed capillaries with stable frits of good quality can be a hurdle to obtain efficient separations in capillary electrochromatography (CEC). Especially with particles smaller than 3 μm, frit preparation is cumbersome. Highly efficient separations using packed capillaries without frits are presented. Under appropriate CEC conditions the particles were retained by electrophoretic attraction towards the anode by a tapered capillary inlet, without the need of a frit at the outlet end. Such fritless capillaries, packed with 1.5 μm nonporous reversed‐phase particles, allowed separations with efficiencies of more than 500 000 plates/m. Once the capillaries were conditioned properly, more than 100 separations could be performed with good repeatability. With respect to separation efficiency, fritless capillaries packed with 3 μm particles were comparable with standard CEC capillaries with frits. Examples of separations of steroids, a pesticide and its by‐products, and cardiac glycosides under various CEC conditions are shown.