Abstract:

A method was established for the determination of eight vitamins E (α-, β-, γ-, δ-tocopherol and α-, β-, γ-, δ-tocotrienol) in vegetable oils using gas chromatography-mass spectrometry (GC-MS). The targets were extracted with methanol, and analyzed by GC-MS in the selected ion monitoring (SIM) mode after concentration to a constant volume, and quantified using the external standard method. Baseline separation were achieved for all the target compounds. The linearities of all the compounds were between 0.01 and 1 mg/L. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.03-0.25 mg/kg and 0.10-0.83 mg/kg, respectively. The average recoveries of all the targets in sesame oil samples were between 87.5% and 107.4% at three spiked levels (10, 50, and 250 mg/kg), and the RSDs were all less than 7.5%. The tocopherols and tocotrienols contents in sesame oil samples and in six lower-price vegetable oils (soybean, rapeseed, sunflower, peanut, corn and palm oils) were determined by the above mentioned method. The results showed that the vitamin E profiles of sesame oil were significantly different from those of the other six vegetable oils. Therefore, vitamin E can be used as a discriminating parameter for detecting the adulteration of sesame.

Key words: gas chromatography-mass spectrometry (GC-MS), tocopherol, tocotrienol, vitamin E, sesame oil, authentication