Liquid solubilization dynamics: II. Flux enhancement by interface gel formation

Dynamic solubilization studies were conducted to determine the mechanism of incorporation of oleic acid into aqueous sodium taurodeoxycholate solutions at 37°C in which the apparent diffusion limit of mixed micelles was exceeded. The effects of pH, added NaCl, and surfactant type on the flux of oleic acid were determined by means of a membrane-modified liquid/liquid stirred cell for this model fatty acid digestion system. The apparent enhanced mass transfer of oleic acid into sodium taurodeoxycholate solutions at sufficiently high pH and surfactant concentration can be satisfactorily explained by the formation of an oil/aqueous surfactant liquid crystalline phase at the interface. Under flow conditions this phase may be sheared from the interface and subsequently solubilized in the bulk aqueous phase as a mixed micelle or microemulsion. Experiments conducted under non-flow conditions support the proposed mechanism.