Liquid-phase separation of structurally similar steroids using phenyl stationary phases

The selectivity of different phenyl HPLC stationary phases has been evaluated with respect to structurally similar steroids, including sapogenins of plant origin. A column packing containing a biphenyl ligand was best at separating species that differed with respect to their degree of unsaturation. A diphenyl phase performed better than the biphenyl column in separating steroid epimers, but the best phase for epimer separation was octadecasilyl-bonded silica. The various mechanisms responsible for these results are discussed.