A rapid method for the quantitative extraction of bile acids and their conjugates from serum using commercially available reverse-phase octadecylsilane bonded silica cartridges.

Described is a rapid semi-automated technique for the quantitative extraction of bile acids and their conjugates from serum samples using commercially available reverse-phase octadecylsilane bonded silica cartridges. Serum is diluted with 4 volumes of 0.1 mol/l sodium hydroxide and the sample heated to 64 degrees C before application to the cartridge. Bile acids and their conjugates are adsorbed to the octadecylsilane bonded silica particles and reproducibly recovered by elution with a small volume of methanol. The technique is superior to extraction procedures using either Amberlite XAD resins or liquid-liquid partitioning, and gives a quantitative recovery of polar bile acid sulphates. The method is convenient and rapid and by using a specially designed apparatus it is possible to extract up to 60 samples/hour.