Аннотация:One of the most important phenomena that can take place in membrane extraction is the formation of a microemulsion. The authors studied membrane extraction of lysine from aqueous solutions of cholesterol (CS), and an emulsion of liposomes prepared from lecithin and CS in phosphate buffer. The emulsions were studied photomicrographically with an electron microscope to determine the drop size distribution. It was determined that the structural-mechanical barrier of the microemulsion drops on the surface of the drops of the internal phase worsens stratification of the emulsion. However, in extraction of surface active substances, the formation of microemulsions can sharply increase the capacity of the extracting emulsion and sometimes also the rate of membrane extraction, which can be useful in extraction from biological fluids.