A NEW APPROACH FOR DETERMINING THE REACTION RATIO BETWEEN CALCIUM AND SURFACTANT HAVING LOW CALCIUM TOLERANCE: APPLICATION TO BILE SALT

ABSTRACT

Calcium-bile salt interaction plays an important role in gallstone formation and lipid solubilization in human digestive system. This paper presents a method of studying the calcium-bile salt interaction for several bile salts having low electrolyte tolerance. Sodium cholate, sodium glycodeoxycholate, sodium glyco-chenodeoxycholate and sodium deoxycholate were used in this study. Potentiometric titration was performed with calcium ion electrode to determine the calcium-bile salt reaction ratio and the equilibrium constant. Flocculation values by calcium or sodium ions were measured as a function of the bile salt concentration. The flocculation-concentration curves appear to be quite complicated. Precipitation of the bile salt was carefully avoided by adjusting the concentration of the reactants and taking the flocculation-concentration curve as a guidance. For sodium deoxycholate which has extremely low calcium tolerance, the precipitation was postponed by adding nonionic surfactant. Complete titration curves and stoichiometric reaction ratios between calcium and bile salts were obtained.