Effect of sodium chloride on the formation and stability of n-dodecane nanoemulsions by the PIT method

This paper provides a fundamental study of the effect of sodium chloride on the formation and stability of n-dodecane/nonionic surfactant (Brij30)/NaCl nanoemulsions produced by the phase inversion temperature (PIT) method. Nanoemulsions are an emulsion system containing droplets from 20 to 200 nm and widely used in cosmetics and pharmaceutical industries. The PIT method was chosen due to its low energy and surfactant usage to produce the nanoemulsions by heating and quenching an emulsion system. The changes of conductivity with temperatures were continuously monitored to determine phase inversion, and are found to be the same in low surfactant concentrations. PIT point was found to decrease with NaCl concentration especially from 5 to 7 wt% Brij30. At the storage temperature (20 degrees C), the initial droplet size decreases with NaCl concentration; however, the decrement only occurs from 4 to 7 wt% Brij30 while no nanoemulsions can be produced at 8 wt%. By adding salt, the surfactant concentration needed for the most stable nanoemulsions is reduced to 6 wt% from 7 wt%. Therefore, similar stable nanoemulsions can be produced with less surfactant in a brine system. Furthermore, most of the ageing brine-continuous nanoemulsions could be reproduced to their freshly prepared state by heating process but not for the most stable nanoemulsions. (C) 2010 Curtin University of Technology and John Wiley & Sons, Ltd.