Conductivity, viscosity, NMR and diclofenac solubilization capacity studies of mixed nonionic surfactants microemulsions

The systems studied were water/sucrose laurate/ethoxylated mono-di-glyceride/oleic phase. The oleic phase was isopropylmyristate or (isopropylmyristate + ethanol) at a weight ratio equal to unity. The weight ratio of ethoxylated mono-di-glyceride in the mixed surfactants was varied from 0 to 100 wt.% by steps of 25 wt.%. The pseudoternary phase behavior at 25 °C was explored to determine the amount of solubilized water in the one phase microemulsion regions. For each system the total area of the one phase microemulsion region (AT) was calculated and found that it increases as the weight ratio of ethoxylated mono-di-glyceride in the mixed surfactants increases from 25 to 75 wt.%. It was found that adding ethanol to the system increases the AT compared to the systems free of alcohol. The system water/sucrose laurate/ethoxylated mono-di-glyceride/(isopropylmyristate + ethanol) was investigated using electrical conductivity, dynamic viscosity and nuclear magnetic resonance (NMR). It was found that the electrical conductivity increases as the water content increases. Viscosity increases slightly for water contents smaller than 20 wt.% then a slow decrease is observed for water contents between 20 and 60 wt.%. A slight increase in the viscosity is also observed for water contents between 65 and 75 wt.%, then a sharp decrease is observed. NMR measurements confirm that a progressive transformation of the water-in-oil to bicontinuous and inversion to oil-in-water microemulsions occurs upon dilution with water. The solubilization capacity of diclofenac sodium, a pharmaceutical active ingredient in the formulated microemulsions was studied. A correlation between the microstructure of microemulsions and the quantity of solubilized material was found.