Method for the quantitative assay of fatty acid–bile acid conjugates by tandem mass spectrometry

Fatty acid–bile acid conjugates and especially arachidyl amido cholic acid are synthetic molecules that were shown to prevent cholesterol gallstone formation in mice and hamsters as well as to dissolve pre-existing gallstones in mice. To measure these novel compounds we developed a liquid chromatography electrospray tandem mass spectrometry method based on the analysis of 100 μl of plasma with stearyl amido cholic acid (stamchol, 1.5 μmol/l) added as internal standard. Repeatable calibrations between 0 and 50 μmol/l exhibited consistent linearity and reproducibility. Inter- and intraassay C.V.s were 5.3–11.4% and 2.6–6.4%, respectively, at targeted concentrations of 0.1, 2.3 and 50 μmol/l.