Abstract: A method for the determination of soybean isoflavones extracted from soybean whey by HPLC was established. Nova-Pak C₁₈ column (3.9×150 mm, 4 μm) was used. Genistin and daidzin were separated by mobile phase: methanol-0.4% phosphoric acid solution = 30:70 (v/v). The flow rate was 0.7 mL·min^-1. The column temperature was 30℃. The UV detection wavelength was 260 nm. The results showed that the content of soybean isoflavones in the soybean whey extract was 72.5%. Genistin and daidzin were the major components in the soybean isoflavones, and the ratio of the two components was nearly 1∶1. The isoflavone aglycons were not found by HPLC. The average recoveries of genistin and daidzin were 98.1% and 98.4% respectively, and the relative standard deviations of genistin and daidzin were 0.7% (n=5) and 0.8% (n=5) respectively. The method was rapid, accurate and with good reproducibility.

Key words: soybean isoflavones, high performance liquid chromatography, soybean whey