Interaction between gelatine and sodium dehydrocholate in water

MESSINA, P. V.; MORINI, M.A.; SCHULZ, P.C.

Barcelona

Simposio; 14th SIS Surfactant in Solution Symposium; 2002

Universidad de Barcelona

ConduCtimetry. pH-measurements, surfaCe tension measuremenTS, ion-selective electrodes and dye solubílisatíon methods were used to determine the interaction between gelatine and sodium dehydrocholate in water-Both sodium and dehydrocholate (DHC·) ions react with gelatine. At very low concentratíon. DHC" ions seemed rect with some cationic sites on gelatine molecules, which attained saturation at 0.266 Na+ millimol per gram of gelatine. Then, there was no reaction between gelatine and DHC- ions in an interval of concentrations, followed by a new reaction, which seemed a "condensation" or "precipitation" of DHC"ions on gelatine. The mechanism seemed to be associated with the fonnation of a complex NaH(DHC)2 similar to the "acid soaps" which form in common soap solutions at some determined concentration. The amount of dehydrocholate added by this mechanism was 0.386 mmol/g of gelatine. At higher eoncentrations NaDHC micelles formed by means of a stepwise mechanism. Different structural modifications of NaDHC aggregates, DHC- -gelaline and Na+- gelatine complexes gave a very complex behaviour wilh up to 13 concentrations of NaDHC at which some alteration in the physicochemical properties were detected.