Comparative Studies on the Adsorption Be- Havior of Crude Vitamin A, Carotene, and Cholesterol

Work in this laboratory on the adsorption behavior of vitamin A and related substances was initiated in 1929-30 when two of us (H. N. H., V. G. L.) attempted the concentration of this vitamin from the non-saponifiable portion of cod liver oil. Almost from the first we directed our efforts to adsorption methods of separating vitamin A in order to minimize oxidation or other undesired chemical reactions. Little has been published on the adsorption of vitamin A. Kobayashi and Yamamoto (1) observed a color reaction with Japanese acid clays, Florida clays, and fullers’ earth in contact with cod liver oil or solutions of vitamin A in volatile solvents. Lachat, Dutcher, and Honeywell (2) stated that vitamin A in cod liver oil may be adsorbed on highly activated silica gel so tenaciously that it cannot be rendered available when the silica gel is fed to rats. Toluene, they observed, removes the adsorbed vitamin A from the silica gel, while acetone extracts are inactive. Still more recently von Euler and Karrer (3) made reference to the use of fibrous alumina as an adsorbent in concentration studies on this vitamin. It should be thoroughly understood that mere removal of vitamin A from a solvent is not necessarily due to adsorption, but may result from chemical destruction or from both. Effective adsorption implies the possibility of later liberating or recovering the vitamin from the porous solid used. Willstatter has made most effective use of various forms of alumina in concentrating enzymes from water systems, and various