Liquid chromatography-UV determination and liquid chromatography-atmospheric pressure chemical ionization mass spectrometric characterization of sitosterol and stigmasterol in soybean oil

A narrow-bore HPLC-UV method was developed for the analysis of two of the m ore abundant naturally occurring phytosterols in vegetable oils: sitosterol and stigmasterol. The method enabled detection of the compounds at a conce ntration of 0.42 mug/ml and quantitation at concentrations of 0.52 and 0.54 mug/ml for sitosterol and stigmasterol, respectively. An excellent lineari ty was determined over two orders of concentration magnitude (r(2) 0.999-1. 000) and verified by applying the Mandel fitting test (p >0.099) and the la ck-of-fit test (p >0.057) performed at the 95% confidence level. A good int ra-day precision ranging from 0.15 to 1.16% was calculated at two concentra tion levels (2 and 100 mug/ml). The inter-day reproducibility was verified on 3 different days by performing an homoscedasticity test and analysis of variance. A solid-phase extraction method was developed on silica cartridge s for the isolation of phytosterols from soybean oil providing recovery val ues of 101 +/-9 and 106 +/-7% for sitosterol and stigmasterol, respectively . Good accuracy of the method was statistically demonstrated since no matri x effect was found for both the analytes. The developed method was applied to the quantitative assay of phytosterols in a soybean oil sample (61 +/-5 mg/100 g of stigmasterol and 118 +/-4 mg/100 g sitosterol). The HPLC-atmosp heric pressure chemical ionization MS technique enabled the identification of stigmasterol, sitosterol and campesterol in the oil sample. (C) 2001 Els evier Science B.V. All rights reserved.