The analysis of five antibiotics (ampicillin, tetracycline, oxytetracycline, chlorotetracyline, and erythromycin) in milk by open tubular capillary electrochromatography is evaluated. The separation medium is an etched capillary chemically modified with the liquid crystal 4‐cyano‐4′‐n‐pentoxy‐1‐1′‐biphenyl. A simple sample preparation method is used to produce a milk serum with a relatively small number of components and then the antibiotics are analyzed electrophoretically in this matrix. The effects of pH and addition of organic modifier to the mobile phase are also evaluated.