Abstract: The total soysaponins were extracted from defatted soybean meal with alcohol and purified by the n-butanol resolution saturated with water, then stained by HClO4-vanilin staining method. The saponin absorbency was determined by high performanc microplate spectrophotometer and revised by three-wavelength method. The aim of this experiment was to build a method of determining the total soysaponins of soybean samples. The result showed that one time extracting rate was 95.985%, the total extraction rate of two times was 99.510%, and the purification rate was 90%. Markedly significant linear regressive relationship was found between the absorbency and concentration of total saponins. The lowest detection limit was 19.667μg/ml. The coefficient of variation (cv) of the accuracy experiment was 2.7%. The average recovery rate was 95.519% with cv being 5.719%. The new determining method is reliable, which could efficiently overcome the staining reaction instability and the declination of absorbency with the time, and avoid or eliminate, to a degree, the influence of the interfering components and the peak floating.

Key words: soysaponins, high performance microplate spectrophotometer, three-wavelength colorimetry, ration de-termination