Spectrophotometric assay of α‐tocopherol

The benzene washing procedure for the isolation of unsaponifiable residues has been applied to vitamin E preparations containing α‐tocopheryl esters only. The isolation procedure is carried out once (after saponification) or twice (before and after saponification). In the solution thus obtained, β‐tocopherol is determined spectrophotometrically; the absorbance at the maximum is corrected for by‐absorption. By avoiding quantitative extractions and transfers, contact with air is reduced to a minimum; ascorbic acid is used as an antioxidant.