Extraction and fractionation of bile acids and their conjugates using pre-packed microparticulate silica cartridges (Sep-Pak Sil and Bond-Elut C18).

A new method for the extraction of bile acids from human plasma using acetonitrile precipitation of plasma protein and subsequent use of Bond-Elut C18 cartridges is described. After extraction the bile acids can be separated into three fractions: unconjugated, glycine-, and taurine-conjugated, using Sep-Pak SIL cartridges at 4 degrees C, eluting with ethanol--chloroform--water--glacial acetic acid mixtures. These extraction and fractionation procedures were evaluated in terms of recovery, reproducibility and resolution between the fractions. All these parameters were found to be satisfactory. Although the reproducibility of fractionation on Sep-Pak SIL cartridges was found to vary between batches, this did not give rise to significant difficulties. Plasmas from normals and patients with hepatobiliary disease were analysed by capillary gas-liquid chromatography after extraction and fractionation using the procedure described.