A method and apparatus for concentrating and stabilizing conjugated estrogens from pregnant mare urine on solid adsorbent supports to obtain a starting material for pharmaceuticals that contain a natural mixture of conjugated estrogens as active ingredient. The apparatus is suitable for decentralized concentration and stabilization of conjugated estrogen mixtures on cartridges in the vicinity of the horses. The adsorber cartridges can be loaded at the site of urine collection so it is unnecessary to transport large volumes of urine to a central processing point. The loading process can take continuously over a period of weeks until the column is saturated. The effluent urine remains at the site where facilities for its disposal are available. Only the loaded cartridge is transported, and transport can occur at longer intervals of up to several weeks. The stability of the conjugated estrogens on the adsorber assures there is no risk of decomposition.