SPE-GC-GC-TOFMS检测油脂中游离甾醇及精炼废弃油脂的判别

研究开发一种基于固相萃取的植物油中游离甾醇的快速分离及多维气相色谱串联飞行时间质谱检测方法。与普通一维气相色谱相比，14 种游离甾醇及β-香树脂醇的三甲基硅烷化衍生物在多维气相色谱上得到了更好地分离，并且检测灵敏度更高。方法学验证结果表明：胆固醇、菜籽甾醇、芸薹甾醇和β-谷甾醇的检出限分别为0.03、0.04、0.04 mg/100 g油和0.05 mg/100 g油，定量限分别为0.06、0.08、0.08 mg/100 g油和0.08 mg/100 g油，在不同添加水平条件下的加标回收率皆高于93%，相对标准偏差在1.4%～10.0%之间。同时，利用本方法对6 种商品植物油及25 份精炼废弃油脂中的游离甾醇进行检测，并分析其在植物油和废弃油脂中的分布模式，提出了以判别指数对废弃油脂进行鉴别的方法，结果显示25 份精炼废弃油脂被完全正确识别。

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

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.