“…Therefore, the measurement of bile acids in various compartments and systemic delineation of the changes of bile acids in whole gastrointestinal tracts, tissue, and circulation are very important for the full understanding of biological functions of bile acids. To date, numerous reports have been analyzed bile acids in various biological matrices , such as chemical , thin layer chromatography , HPLC , radioimmunoassay , enzyme linked colorometric and radioimmunoassay , MS and direct infusion ESI‐MS , MS/MS , GC using high resolution glass capillary columns and MS , GC , GC‐MS , enzymatic colorimetric method and enzymatic fluorimetric method , NMR spectroscopy , LC coupled with ultraviolet (UV) or MS , HPLC‐MS/MS , HPLC‐ELSD , and ultra‐performance LC‐MS detection . NMR methods are relatively insensitive and only applicable in specific areas where the concentration of bile acids is very high, such as the analysis of bile composition .…”