Separation by capillary zone electrophoresis of the active anthraquinone components of the Chinese herbPolygonum multiflorum Thunb

Summary An optimization strategy was applied to explore the capability of hybrid micellar eluents of sodium dodecyl sulphate (SDS), using acetonitrile or pentanol as modifiers, to resolve mixtures of eleven steroids showing a wide range of hydrophobicity (clostebol acetate, dehydrotestosterone, dydrogesterone, medroxyprogesterone, medroxyprogesterone acetate, methandienone, methyltestosterone, progesterone, testosterone, testosterone enanthate and testosterone propionate). The accurate prediction of the retention behaviour of the steroids, with relative errors in the 0.8–1.7% and 0.4–2.9% ranges for SDS-acetonitrile and SDS-pentanol eluents, respectively, demonstrated the reliability of the methodology. Acetonitrile and pentanol had a complementary effect in these analyses. The elution strength of acetonitrile was weaker, but allowed higher efficiencies. A 0.094 M SDS-16% acetonitrile eluent separated seven steroids (dehydrotestosterone, dydrogesterone, medroxyprogesterone, medroxyprogesterone acetate, methandienone, methyltestosterone and testosterone) in 27 min, while the most hydrophobic steroids were strongly retained. In contrast, a 0.125 M SDS-5.8% pentanol eluent permitted the elution of a mixture of eight steroids (dehydrotestosterone, dydrogesterone, medroxyprogesterone acetate, methandienone, methyltestosterone, progesterone, testosterone enanthate and testosterone propionate) of diverse hydrophobicity in 14 min. With this eluent, however, the peaks of dehydrotestosterone-medroxyprogesterone and methandienone-testosterone were highly overlapping.