Process for the production of membrane films of cellulose acetate for electrophoretic separations

摘要

For the production of cellulose acetate films for the electrophoretic separation of mixtures of substances, use is made of a solution of two cellulose acetates having acetyl contents corresponding approximately to a triacetate and a diacetate respectively, the ratio of the concentration of the less acetylated acetate to the concentration of the more acetylated acetate being at least one, and the solvent in which the acetates are dissolved comprising a mixture of a volatile organic liquid which is a solvent for both acetates and another volatile organic liquid capable of causing the acetates to swell, but not to dissolve. The solvent liquid may be methylene chloride or a mixture thereof with a small proportion of butanol. The other organic liquid may be isobutanol. Films may be formed from the solution in the usual manner by casting a layer of the solution on to a glass or metal casting surface and allowing the solvent to evaporate spontaneously, preferably in an atmosphere of RH about 60% at 20 DEG C. After the major portion of the solvent has evaporated, the film may be allowed to remain for several hours on the casting surface before it is stripped therefrom. In an example, films are cast from a solution of 18 grams of a cellulose acetate of acetyl content 53,2%-53,5% and 10 grams of a cellulose acetate of acetyl content 60,5%-60,9% in a mixture of 360 ml. of methylene chloride, 40 ml. of normal butanol, 200 ml. of isobutanol, 7 ml. of glycerine (as plasticizer) and 0,2 gram of a wetting agent. The films may be rendered transparent by treating them with a mixture of glacial acetic acid and methanol until they are swollen, and thereafter drying them. They may be used for the electrophoretic separation of protein-containing liquids.