High-performance liquid chromatographic analysis of phytoestrogens in soy protein preparations with ultraviolet, electrochemical and thermospray mass spectrometric detection.

The phytoestrogens daidzein, genistein, coumestrol, formononetin, and Biochanin A are separated on a C18 reversed-phase column (Hypersil ODS) with methanol-0.1 M ammonium acetate buffer, pH 4.6 (60:40, v/v) as eluent. The retention and resolution are affected by buffer concentrations, pH type, and proportion of organic solvent in the mobile phase. Detection in the (low pg range) is achieved with an electrochemical detector, and the compounds are positively identified by high-performance liquid chromatography-thermospray mass spectrometry. Daidzein and genistein were found in high concentrations in all soy protein preparations analyzed.