RAPID COULOMETRY OF TOCOPHEROLS IN ETHANOL AND CHLOROFORM USING FERRICYANIDE ION MEDIATOR

In order to estimate the absolute determination method of tocopherols, rapid coulometry has been carried out by using a vapor grown carbon f iber electrode impregnated with ethanol-water solution containing ferr icyanide ion as a mediator. The electrolysis time of 1 x 10(-3) M alph a-tocopherol in ethanol was below 30 seconds, and its current efficien cy was attained to be 100.1% when an ethanol content in pH 4.0 electro lyte is 20%. Four isomers of vitamin E in chloroform were also determi ned by indirect coulometry in which ferricyanide solution was mixed wi th sample solution for 10 minutes prior to electrolysis and the curren t efficiencies of alpha-, beta-, gamma-, and delta-tocopherols were ob tained to be 97.6, 100.5, 89.7, and 83.7%, respectively, and the relat ive standard deviations were below 1%.