Micromethod for tocopherol determination in blood serum.

An improved microprocedure for the determination of tocopherol in blood serum is reported. Tocopherol is oxidized by ferric chloride and the pink complex of ferrous ions with 4,7-diphenyl10,10-phenanthroline (bathophenanthroline) is determined spectrophotometrically. The test is more sensitive than colorimetric methods using 2,2’,2” -tripyridine,2,2’-bipyridine (bipyridyl) or 2,4,6tripyridyl-s-triazine. The use of phosphoric acid prevents the photochemical reduction of ferric chloride and also reduces interference of carotene to a minimum. The amount of carotene oxidized by ferric chloride in the first 5 mm. is negligible in the presence of bathophenanthroline. As its further oxidation is stopped by phosphoricacid, the contribution of carotene to the ferrous-bathophenanonthroline complex is insignificant.