Analysis of bile acids and their conjugates by capillary electrochromatography/electrospray ion trap mass spectrometry

Different macroporous, monolithic capillary columns were prepared to separate various bile acid mixtures through capillary electrochromatography (CEC) at high efficiency. These columns are shown to be ideally suitable for coupling to an electrospray ionization/ion trap mass spectrometer. Detection and structural identification of different bile acid derivatives in either the positive- or negative-ion mode necessitated column technologies with different polarities and the capabilities of a reversed electroosmotic now. High column efficiencies (610 000 theoretical plates/meter for glycocholic acid in normal-phase separation) were preserved in the coupling to mass spectrometry (MS), with the detection limits of similar to 40 femtomole (for cholic acid) and identification through CEC/MS/MS.