China Science

This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water,; 2?1 Brij 97; 1-butanol by different experimental techniques. A pseudoternary phase diagram was constructed using water titration method. At 45% wt/wt surfactant system, microemulsions containing various ratios of water; IPP were prepared; identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM); nuclear magnetic resonance (NMR). The results from conductivity; viscosity suggested a percolation transition from water-in-oil (water/oil) to oil-in-water (oil/water) microemulsions at 30% wt/wt water. From DSC results, the exothermic peak of water; the endothermic peak of IPP indicated that the transition of water/oil to oil/water microemulsions occurred at 30% wt/wt water. Cryo-FESEM photomicrographs revealed globular structures of microemulsions at higher than 15% wt/wt water. In addition, self-diffusion coefficients determined by NMR reflected that the diffusability of water increased at higher than 35% wt/wt water, while that of IPP was in reverse. Therefore, the results from all techniques are in good agreement; indicate that the water/oil; oil/water transition point occurred in the range of 30% to 35% wt/wt water.

Prapaporn Boonme1?Karen Krauel3?Anja Graf3?Thomas Rades3?Varaporn Buraphacheep Junyaprasert1Email:pyvbp@mahidol.ac.th
[1] Department of Pharmacy, Faculty of Pharmacy, Mahidol University, 10400 Bangkok, Thailand ;[2] Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Prince of Songkla University, 90112 Songkhla, Thailand ;[3] School of Pharmacy, University of Otago, PO Box 913, 9001 Dunedin, New Zealand