Ethylbenzene-modified fused-silica columns for capillary electrophoresis

Summary Coated capillaries modified with a hydrocarbon layer have been developed. Modification of the surface with ethylbenzene greatly improved the electrophoretic performance of the capillaries. The column efficiency for basic organic compounds was as high as 378000 theoretical plates per meter on a 50 μm i.d. ethylbenzene-surface-treated fused-silica capillary column. This value did not change during 25 replicate analyses and the capillary columns were very stable against continuous treatment for 30 h with buffer of pH 10 and treatment for 3 h with HCl of pH 1 and NaOH of pH 12. The relative standard deviation of run-to-run, day-to-day, and capillary-to-capillary for coating with the ethylbenzene layer was<2.6%, and reproducibility was good. The separation of four aromatic amines and six pharmacological amines at pH 2.5 is reported.