Vitamin E is synthesized and stored in leaves and plant seeds. It consists of four forms of tocopherols (α-, β-, γ-, δ-tocopherol) and four forms of tocotrienols (α-, β-, γ-, δ-tocotrienol).The main source of vitamin E are vegetable oils. As part of the diploma thesis we have validated the analytical method for the determination of tocopherols in vegetable oils. The sample of the oil was dissolved in hexane, then diluted in methanol, placed on a tube mixer, centrifuged and filtered through a 0.45 m filter. For the analysis, RP-HPLC and the C18 column were used, which did not enable the separation of all four tocopherols. Alpha and delta tocopherol were determined individually, beta and gamma tocopherol as the sum of both. Through validation we determined the limit of detection, the limit of determination, the linearity of the method, the working range of the method, the accuracy of the method, the repeatability of the method, the method's reproducibility and the robustness of the method. We determined the measurement uncertainty by analyzing the certified reference material. We analyzed the contents of tocopherols in sixteen different vegetable oils. We also analyzed several samples of sunflower oils, olive oils and pumpkin oils, and compared the levels of tocopherols in the same matrices.
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