Highly specific and sensitive, the proposed fluorometric method for determining α-tocopherol is robust and fairly fast. It has been tested in parallel with a conventional thin layer chromatographic method on foods and feeds. The only necessary cleanup is the usual saponification. The unsaponificable fraction can be extracted with ethyl e
...ther or, preferably, with Extrelut columns. Reagents and their solvents are added to the isooctane solution before each successive reaction and are then eliminated by partition with water. The α-tocopherol (α-T) derivative always remains in isooctane. The first step is nitrosation and elimination of tocopherols and tocotrienols other than α-isomers. α-T is then oxidized to α-tocored (α-TR) with a mixture of sulfuric acid, ferric chloride, and iodine bromide. Α-TR is then condensed to a new reagent: 4,5-dimethylo- phenylenediamine. The phenazine formed is strongly fluorescent. Iodine and bromine add to the double bonds of α- tocotrienol present and quench the fluorescence of its phenazine.