ZERO-ORDER OR 1ST-ORDER RELEASE KINETICS OF WATER-IN-OIL-IN-WATER (W/O/W) MULTIPLE EMULSIONS OF LIPIODOL DEPENDENT ON THE TYPES OF SURFACTANTS

The mechanism of dye release from the water-in-oil-in-water (W/O/W) multiple emulsions of lipiodol was investigated through dialysis. The oily phase containing hydrophilic HCO-60 exhibited bi-phasic zero-order release kinetics, but the oily phase containing both HCO-60 and lecithin indicated one-phasic zero-order release kinetics. Moreover, the higher the concentration of HCO-60, the slower the release rate of dye. When the oily phase contained other hydrophilic surfactants (Tween 80, Brij 35 and Pluronic F-88) or hydrophobic surfactants (Span 80 and lecithin), these multiple emulsions showed a first-order release kinetic. We also found that the release rate of multiple emulsions with hydrophobic surfactants was slower than that of the multiple emulsions with hydrophilic surfactants. The release kinetic of multiple emulsion was a complicated system.