The vitamin E complex is easily quantified provided some precautions are observed during the extraction of the biological tissues. When samples are too fatty, a saponification step is needed to remove the excess of fatty acids before the HPLC analysis. When samples contain only few amounts of triacylglycerols, an extraction with apolar solvants is suitable and the saponification step is not necessary.
Several methods are reliable.
Vitamin A, carotenoids, and all apolar lipids may be also determined in this type of extract. After vortexing 15-20 min in amber tubes, lipids are extracted after the addition of 3 ml hexane and vortexing 5 min. After a brief centrifugation, the upper hexane phase is evaporated and the residue is stored in a small amount of methanol before HPLC analysis. After centrifugation, the lower phase is washed if necessary with 2 ml of 1M NaCl and evaporated under nitrogen. Tocopherols, cholesterol and individual phospholipids are separated by one-dimensional TLC on Whatman LK5 silica gel plates.