Determination of soybean phytosterols by reversed phase chromatography and gas chromatography-mass spectrometry

The reversed phase chromatographic column Waters symmetry C ₁₈(4.6 mm x 250 mm) and mobile phase consist of acetonitrile- isopropanol (95:5, V/V), suitable to separate soybean phytosterols, was screened out. Effects of solvent ratio of mobile phase and column temperature on the retention behaviors and resolutions of soybean phytosterols were investigated. Four predominant phytosterols in soyasterol products extracted from soybean deodorizer distillate including sitosterol and stigmasterol, campesterol and brassicasterol were baseline resolved, and other unknown components were purified by high performance liquid chromatography and then initially identified by gas chromatography-mass spectrometry as γ-sitosterol, epibrassicasterol, dihydrobrassicasterol (24β-epimer of campesterol) and isomer of stigmasterol. The sterol contents of soybean oil, deodorizer distillate and extracted soyasterol products were determined under optimum chromatographic condition. The detection limits for stigmasterol and β-sitosterol were 14.4 ng and 10.6 ng, and the average quantitative recoveries of the two phytosterols for soybean oil sample were 97. 3% and 96.9%, respectively.