Measurement of the ‘spontaneity’ of self-emulsifiable oils

Abstract

Self‐emulsifiable oils are solutions of surfactants in non‐polar solvents which spontaneously form emulsions when added to water. Measurement of the degree of spontaneity has remained subjective. Accordingly, a method has been devised in which a small volume of the oil solution is injected into a flowing stream of water and carried across an intense beam of parallel light from a helium‐neon laser. Light scattered from the beam by the dispersed oil droplets is collected by means of fibre optics onto an array of silicon photodiodes and the amplified output is integrated as a function of time. By varying the flow rate of the water stream it is possible to estimate the time required for an emulsifying system to come to its equilibrium state of dispersion under the conditions of the experiment, the ‘spontaneity’ of emulsion formation. Under the experimental conditions employed, systems comprising solutions of phosphated nonylphenolethoxylate (PNE) and phosphated fatty alcohol ethoxylate (PFE) in n‐hexane came to equilibrium between 5 and 12 s, depending on the constitution. These times could be approximately correlated with the values for spontaneity estimated by the CPAC dilution test, although this latter test is somewhat subjective. The spontaneity appears to depend on the nature of the material existing within the phase diagram and the anomalous results obtained may be accounted for by the likely presence of a complex formed at the emulsion interface between the PNE, PFE and water during the dispersion process.

Increasing the Proportional Content of Surfactant (Cremophor EL) Relative to Lipid in Self-emulsifying Lipid-based Formulations of Danazol Reduces Oral Bioavailability in Beagle Dogs

“…The ease of emulsification of self-emulsifying formulations has been suggested to be associated with the formation of liquid crystals at the interface of the oil/surfactant mixture and water, resulting from water penetration into the oil/surfactant blend (35,42,43). Self-emulsification is subsequently thought to occur via fracture of the liquid crystals leading to droplet formation under gentle agitation (41,42,44). Inclusion of cosolvents and/or co-surfactants in the formulations may therefore facilitate improved self-emulsification by enhancing the ability of the aqueous phase to penetrate into the liquid crystals formed (45,46).…”

Self Micro-Emulsifying Drug Delivery System: Formulation Development and Biopharmaceutical Evaluation of Lipophilic Drugs

“…In order to understand the mechanism by which subsequent drug absorption occurs from emulsion system, it is necessary to consider the in vivo behavior of constituent components. There are several reports indicating enhanced drug absorption from emulsified dosage form and SMEDDS [26,27]. Various modes of enhanced drug absorption can be hypothesized as follows:…”

Diffusion-Controlled Spontaneous Emulsification of Water-Soluble Oils via Micelle Swelling

“…Spontaneity is typically assessed in industry according to the Collaborative Pesticide Analytical Committee of Europe (CPAC) and the United Nations Food and Agriculture Organization (FAO) where emulsification is visually evaluated as "good", "moderate", or "bad" based on the rate of emulsification. 38 This technique is highly subjective and has low reproducibility between laboratories. 1 Spontaneity has also been measured as the time required for a spontaneous emulsion to reach an equilibrium state by measuring droplet size over time via light scattering.…”