the sodium deoxycholate (dcna) source is the surfactant used in the biopharmaceutical industry for the solubilization of outer membrane vesicles. it is well known the importance of control of this metabolite in biological materials due to its high toxicity for humans. to demonstrate significant small variations of this metabolite in vaccine formulations it is necessary to use a methodology highly selective, sensitive, specific and reproducible. in this report we used the micellar electrokinetic chromatography (mekc) in a capillary ion analyzer (water corp. milford ma) detection at 185 nm mercury lamp. it employed a fused silica capillary uncoated (waters corp. milford ma). we assessed the purity of 2 lots of sodium deoxycholate and analyzed 15 samples of purified vesicles active pharmaceutical ingredient vaccine formulations. data were recorded and processed with software millennium tm (waters corp. milford ma). it was found that lots of sodium deoxycholate containing 1.19 and 0.44% cholic acid and contaminate that 93% of the purified vesicles samples were from 0 to 2.44 mg protein dcna/100 μg. meck's results were compared with a kinetic test used to determine bile acids in blood (merckotest). meck system showed better results regarding the merkotest.