Distribution and chemical kinetics of prostaglandin E sub(1) in lipid emulsions

It has been shown that the partitioning of PGE sub(1) in a lipid emulsion is consistent with a three-phase model that assumes that solute may reside in the bulk aqueous and oil phases and at the oil-water interfaces. Ultrafiltration and dialysis techniques enabled to estimate the relative percentages of PGE sub(1) in each phase at various pHs. The amount of PGE sub(1) present in the bulk oil phase of the emulsion was concluded to be insignificant. A model which assumes that both the non-ionized and ionized PGE sub(1), species may be present at the interface, depending on pH, was shown to be consistent with the data. Estimates were made of the distribution coefficients of the ionized and non-ionized PGE sub(1) between the interface and the aqueous phase and their concentration dependence.