Investigation in W/O developed microemulsions with DMSO as a cosurfactant.

In this study the effect of dimethylsulfoxide (DMSO) radii on the droplets and on the required non-ionic surfactant volume for preparing water-in-oil microemulsions (MEs) was investigated. Five series of MEs were prepared either with the aid of isopropylpalmitate or medium chain triglycerides (MCTG) as continuous phases. The MEs were stabilized via either Tween80 or Span20 or a mixture of both. A mixture of water:DMSO (W:DMSO) with different ratios formed the colloidal phase of the first four MEs series. Only DMSO was used as colloidal phase of the fifth series. Dynamic light scattering (DLS) was used for measuring the radii of the droplets of MEs. The results showed that the consumed volumes of the surfactants were related to the W:DMSO ratio and the surfactant type. Moreover, the consumed surfactant volumes increased with decreasing radii of the droplets of the MEs. The MEs stabilized with Span20 had lower radii of the droplets (4-15 nm) than MEs stabilized by Tween80 (25-65 nm). It was evident that DMSO changed the interfacial tension which is reflected by changing the the volume of the surfactant consumed and by altering the droplets sizes. Consequently, DMSO acted as co-surfactant in stabilizing the MEs by reducing the required volumes of the surfactant which is important for reducing their toxicity.