Effect of Electrolytes on Formulation and Stability of Water/di-Ethyl Oxalate/Tween Microemulsions

Abstract

The formulated microemulsion (ME) was mainly composed of distilled water as the aqueous phase, diethyl oxalate as the oil phase, and Tween-80 as the surface-active agent (surfactant). Iso-propylene glycol was exploited as the cosurfactant, thus both (water/diethyl-oxalate/Tween-80) and (water/diethyl-oxalate/Tween-80/iso-propylene glycol) microemulsions were formulated, all of which are of the type oil in water (O/W) microemulsion. The effect of different electrolytes on the microemulsification of the oil phase were studied, these electrolytes were classified as strong and weak ones. Phase diagrams that represent the formulated microemulsions were constructed. Properties of the microemulsions such as conductivity and viscosity were examined before and after the addition of the electrolytes. The effect of these electrolytes on the stability of the microemulsions was studied, thus, properties were measured at different time intervals, and after the microemulsions were stored in household freezers and at 50°C. The area within the phase diagram, where the microemulsion is stable can be broadened using a set of strong or weak electrolytes, as additives or cosurfactants, which will result in thin, Newtonian behaving fluids. Using weak electrolytes, like acetic or propanoic acid, generally gives better characteristics in terms of a broader marginal stability and longer shelf-life under high-temperature, ambient, and cold conditions.

Keywords:

• Acetic acid
• diethyl oxalate/iso-propylene glycol
• glycol
• microemulsion
• propanoic acid
• surfactants
• Tween

Notes

^a The percent relative change was calculated with respect to the corresponding control sample for each type of addition.

^a The percent relative change was calculated with respect to the corresponding one-day old sample for each type of addition.