It has been shown that the determination of small amounts of tocopherol in tissue lipids by methods that use, in sequence, saponification, extraction, TLC and colorimetric assay, is greatly influenced by the concentration of soap in the saponification mixture. Soaps appear to interfere with the recovery of tocopherols during the subsequent extraction step.
Based on this knowledge a method is described that was used to measure as little as 15 to 20ng of tocopherol in 3 to 4mg of lipid obtained from rat retinas. Presumably the method would be applicable to other tissues as well.
The results show that the rat retina is readily depleted of tocopherol if none is included in the diet.