Polaraphic Studies on Fat-soluble Vitamins in Nonaqueous Media

Part II. Polarography of Vitamin A and its Related Compounds in Acetonitrile-Benzene Micture as Solvent

Abstract

Each of reduction-polarograms of vitamin A-alcohol, -palmitate and β-carotene showed three steps in 60 vol% benzene-acetonitrile mixture containing 0.1M-tetrabutylammonium iodide. The first half-wave potentials were determined at-1.41V vs. Hg-pool for the alcohol, -1.23V for the palmitate and-1.02V for β-carotene. The second half-wave poten-tials were determined at -1.65V identically for first two vitamins and-1.67V for β-caro-tene. The third waves were raised at ca.-2.0V but were quite ill-defined. All of the first and the second waves were controlled by diffusion and those wave-heights were proportional to concentrations of the vitamins and β-carotene in the range from 5×10^-5M (ca. 50 IUA·ml^-1) to 10^-3M (ca. 1000 IUA·ml^-1).
Calculations with Ilkovic Eqn. and Perrin Eqn. gave n≈4 for the first and the second waves of β-carotene, and n≈2 for those of vitamin A and its palmitate.
A preliminary study on vitamin A-acetate was also made under the same experimental conditions. The first and the second half-wave potentials of vitamin A-acetate were -1.26V and -1.66V vs. Hg, respectively, and the proportionalities between wave-heights and concentration were held in the same concentration range as above.