Determination of bile acids in human faecal samples using supercritical fluid extraction and high-performance liquid chromatography.

A supercritical fluid extraction (SFE) method for the extraction of bile acids from faeces is described. HPLC with pulsed amperometric detection was used to examine and confirm the recovery of bile acids. The analytes were extracted within a period of 75 min using supercritical carbon dioxide at a pressure of 34.5 MPa and a temperature of 90 degrees C. In developing this method the following parameters were investigated: temperature, pressure, and extraction time. Two alternative methods of sample preparation were also investigated with a view to reducing the overall analysis time. The method was validated for the major primary and secondary bile acids found in faeces. It was found that the overall mean +/- SD recoveries were 102.1+/-7.92%, 111.6+/-9.91%, 112.1+/-9.92% and 113.7+/-9.92% for dry samples and 108.5+/-15.77%, 110.0+/-7.22%, 115.9+/-11.11% and 106.6+/-9.16% for wet samples with respect to cholic, deoxycholic, chenodeoxycholic and lithocholic acid. The SFE is an alternative to the traditional methods available. The extraction is relatively easy to conduct and does not utilise as much glassware, solvents or time.