EVALUATION OF 2 FLUORESCENT-PROBES FOR THE CHARACTERIZATION OF W O/W EMULSIONS/

The aims of this work were to select the most convenient fluorescent p robe for the characterization of the W/O/W emulsion and to propose a n ew technique in order to study the release mechanism from the W/O/W em ulsion. For this purpose fluorescence was compared with the well estab lished conductimetric measurements using MgSO4.7H(2)O as electrolyte. Two fluorescent molecules were evaluated: 5,(6)-carboxyfluorescein (5, (6)-CF) and 1,3,6,8, pyrene tetrasulfonic acid, tetrasodium salt (PTSA ). After their introduction in the inner aqueous phase of the W/O/W em ulsions; their stability (in aqueous solutions) to temperature and to light, their sensitivity at different pH conditions and to the presenc e of the constituents of the inner aqueous phase, their partition betw een the different phases of the emulsions and their influence on rheol ogical properties of the emulsions were analysed. PTSA was finally sel ected as the most convenient probe due to its high stability at differ ent conditions and its excellent yield of encapsulation. After the rel ease studies, a satisfying correlation between HPLC fluorescence and c onductimetry was obtained. Both techniques confirm that the release me chanism of the multiple emulsion is swelling-breakdown.