title: Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol.
abstract: This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water, and 2:1 Brij 97 and 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 and IPP were prepared and identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM) and nuclear magnetic resonance (NMR). The results from conductivity and 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 and 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 and indicate that the water/oil and oil/water transition point occurred in the range of 30% to 35% wt/wt water.
authors.affiliation: Department of Pharmacy, Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand.
authors.forename: Prapaporn
authors.initials: P
authors.lastname: Boonme
authors.forename: Karen
authors.initials: K
authors.lastname: Krauel
authors.forename: Anja
authors.initials: A
authors.lastname: Graf
authors.forename: Thomas
authors.initials: T
authors.lastname: Rades
authors.forename: Varaporn Buraphacheep
authors.initials: VB
authors.lastname: Junyaprasert
mesh_terms: D020001:1-Butanol / Q000032:analysis / Q000737:chemistry*; D004337:Drug Carriers / Q000032:analysis / Q000737:chemistry*; D004655:Emulsions / Q000032:analysis / Q000737:chemistry*; D005079:Excipients / Q000032:analysis / Q000737:chemistry; D008968:Molecular Conformation; D010168:Palmitates / Q000032:analysis / Q000737:chemistry*; D014677:Pharmaceutical Vehicles / Q000032:analysis / Q000737:chemistry*; D044367:Phase Transition; D010938:Plant Oils / Q000032:analysis / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000032:analysis / Q000737:chemistry*; D014867:Water / Q000032:analysis / Q000737:chemistry*
chemical_list: D004337:Drug Carriers; D004655:Emulsions; D005079:Excipients; D010168:Palmitates; D014677:Pharmaceutical Vehicles; D010938:Plant Oils; D014867:Water; D011092:Polyethylene Glycols; C005060:isopropyl palmitate; D020001:1-Butanol; C033084:polyethylene glycol oleyl ether