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A Method for Determination of Free Phytosterols Derived from Vegetable Oils by SPE-GC-GC-TOFMS and Its Application for Discrimination of Refined Waste Oils

XU Baocheng1,2,3, ZHANG Liangxiao2,4, ,*, YANG Qingqing2,6, LUO Denglin3, LI Peiwu2,4,6,7,8,*   

  1. 1. College of Food Science and Engineering, Northwest A&F University, Yangling 712100, China;
    2. Oil Crops Research Institute of the Chinese Academy of Agricultural Sciences, Wuhan 430062, China;
    3. College of Food and Bioengineering, Henan University of Science and Technology, Luoyang 471003, China;
    4. Quality Inspection and Test Center for Oilseeds Products, Ministry of Agriculture, Wuhan 430062, China;
    5. Shanxi Engineering Research Center for Viti-Viniculture, College of Enology, Northwest A&F University, Yangling 712100, China;
    6. Laboratory of Risk Assessment for Oilseeds Products, Ministry of Agriculture, Wuhan 430062, China;
    7. Key Laboratory of Biology and Genetic Improvement of Oil Crops, Minstry of Agriculture, Wuhan 430062, China;
    8. Key Laboratory of Detection for Mycotoxins, Ministry of Agriculture, Wuhan 430062, China
  • Online:2015-01-25 Published:2015-01-16
  • Contact: WANG Hua,LI Peiwu

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Abstract:

In this study, a multidimensional gas chromatography coupled to time-of-flight mass spectrometry (GCGC-
TOFMS) method was established to determine free sterols in edible oils extracted by rapid solid-phase extraction.
Compared with conventional one-dimensional gas chromatography, a better separation and a higher detection sensitivity
for trimethylsilyl derivatives of free sterols and β-amyrin were obtained by GC-GC. Meanwhile, the validation results of
the established method indicated that the limits of detection for cholesterol, brassicasterol, campesterol and β -sitosterol
were 0.03, 0.04, 0.04 and 0.05 mg/100 g of oil, respectively; and the limits of quantification for the four sterols were
0.06, 0.08, 0.08 and 0.08 mg/100 g of oil, respectively. In addition, the recovery rates of the selected four sterols spiked at
three different levels were higher than 93% with a relative standard deviation ranging from 1.4% to 10.0%. Based on the
established method, six types of edible oils and 25 refined waste oils were analyzed by GC-GC-TOFMS, and the distribution
mode of free sterols in normal vegetable oils and waste oils were also analyzed. Moreover, a method based on discrimination
index (DI) was proposed to identify refined waste oils, and the results indicated that the refined waste oils could be
discriminated from the normal six edible oils completely.

Key words: multidimensional gas chromatography-time-of-flight-mass spectrometry (GC-GC-TOFMS), solid phase extraction (SPE), free phytosterols, refined wasted oils, discrimination

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