Solid Extraction of Steroid Conjugates from Plasma and Milk

Extraction of steroids and steroid conjugates with Amberlite XAD-2 and Sep-Pak C18 has been studied. Amberlite XAD-2 has ionic sites with high affinity for conjugated steroids, particularly steroid disulphates. Nearly quantitative recoveries of steroid conjugates are obtained when the resin is washed with an aqueous solution of a sulphate prior to elution with methanol. Such treatment is not required using Sep-Pak C18 cartridges. The adsorbents were used for extraction of steroids and their conjugates from plasma and milk. Steroid-protein and steroid-lipid interactions were minimized by diluting the fluid twice with 0.5 M aqueous triethylamine sulphate and passing the solution through the adsorbent a t 64°C. Steroids were eluted with methanol and methanol/chloroform at room temperature. Essentially quantitative recoveries were obtained with both adsorbents.