Non-aqueous emulsions: hydrocarbon-formamide systems

There are few reports in the literature on formulation of non-aqueous emuls ions. This study was designed to evaluate some design criteria For such sys tems. Formamide is the closest polar solvent that has the ability to replac e water in emulsification when employing established non-ionic surfactants as stabilisers. For the majority of studies. linear alkanes (C6-C16) were d ispersed in Formamide as the continuous phase were stabilised with polysorb ate 20. Initial studies involved gentle emulsification and observing mean g lobule size. The mean globule size: varied in a non-linear fashion with alk yl chain length, the minimum being between C10 and C12. Sonication for 30 s led to smaller differences in the mean globule size. The effect of various parameters such as surfactant concentration and solvophilicity of the surf actant was observed. The surface activities of polysorbate 20, 40, 60 and 8 0 in formamide and critical micellar concentrations were determined. The la tter were several orders of magnitude higher in formamide than in water. an d the areas per molecule larger. The addition of water to the dodecane form amide systems did not destabilise the emulsion. Release of the model drug d ehydroepiandrosterone from dodecane in formamide emulsions was studied in d istilled water. the rate of release being dependent on the volume fraction of dodecane. (C) 2001 Elsevier Science B.V. All rights reserved.