1. SOLUBILIZATION KINETICS OF LIQUID LINOLEIC ACID USING A ROTATING LIQUID DISC. 2. SOLUBILIZATION KINETICS OF CHOLESTEROL MONOHYDRATE USING A ROTATING SOLID DISC

摘要

A new method for studying liquid-liquid mass transfer was developed, employing a rotating liquid disc. This disc is made from a hydrophobic polymer film which supports the liquid solubilizate. From the dissolution kinetics of heptanoic acid in water it was established that the liquid disc behaved like a solid disc. Consequently, the classical rotating disc technique can be extended to the study of complex liquid-liquid mass transfer problems. The rotating liquid disc method has a number of advantages over the commonly used liquid drop techniques since high flow rates can be obtained and smaller amounts of material can be used.;The rotating liquid disc was used to study the solubilization of linoleic acid, an unsaturated lipid with a melting point of -5(DEGREES)C, by the bile salt, sodium taurodeoxycholate. The dissolution rate was found to be first order in the solubility of lipid in the bile salt solution and to be consistent with a mechanism involving a heterogeneous reaction. Use of sodium chloride increased the solubilization rate; the reciprocal of the flux is linear with the reciprocal of the concentration of added electrolyte. The results are discussed in terms of the kinetics of fat digestion in the intestine.;The classical rotating disc method was used to determine the dissolution kinetics of solid cholesterol monohydrate in bile salt-lecithin-sodium chloride solutions. The dissolution rate is controlled mainly by a heterogeneous surface reaction and shows a first order dependence on solubility of cholesterol monohydrate in either dihydroxy or trihydroxy bile salts. The solubility is independent of the type of bile salt when lecithin is present. The dissolution rate in solutions of bile salt alone shows a second order dependence on solubility or on bile salt concentration above 0.038 gm/ml (2 wt%), but the rate is strongly dependent upon the particular bile salt used. Addition of sodium chloride increases the dissolution rate markedly, but changes the solubility only slightly, a result that is discussed in terms of a Langmuir-Hinshelwood adsorption of bile salt on the cholesterol surface. The dissolution kinetics in the bile salt-lecithin-sodium chloride solutions are discussed in terms of the dissolution of cholesterol gallstones.