Liquid chromatographic determination of the plant estrogens coumestrol and isoflavones in animal feed.

A simplified procedure is described for the cleanup and determination of the 5 main plant estrogens in animal feed: coumestrol, genistein, biochanin A, daidzein, and formononetin. The estrogens are extracted with ethanol and purified on a Sep-Pak C18 cartridge. All 5 plant estrogens are separated in an isocratic liquid chromatographic system and quantitated by UV and fluorescence responses. The method is sensitive to about 2.5 ppm coumestrol and 10 ppm of the isoflavones.