2.2 Methods
2.2.1 Analysis of mixed tocopherols
Thin-layer chromatography (TLC) was employed to perform a qualitative analysis of the composition of mixed tocopherols samples. A mixed tocopherols sample was loaded on a TLC plate of silica gel for fractionation. A mixture of chloroform-ethyl acetate (94:6, v/v) was chosen to be the developing solvent, and the iodine vapor was used as the coloring reagent. These three tocopherols and impurities were identified using α-, β-, γ-, δ-tocopherol and fatty acid methyl ester standards. Quantitative analysis of mixed tocopherols and their monomers were determined by high performance liquid chromatography (HPLC) using the AOCS method specified in Chapter Ce 8-89.