The effect of Na2SO4 concentration in aqueous phase on the phase inversion temperature of lemon oil in water nano-emulsions

Abstract

Lemon oil in water (LO/W) nano-emulsions were synthesized using the phase inversion temperature emulsification technique (PIT), which is used as a low-energy method to produce the samples which are stable in the long term. Tween 40 was used as a surfactant and the effect of Na2SO4 concentration on the synthesizing method i.e. PIT and the particle size was well investigated and elucidated. The particle size and distribution index of LO/W emulsion measurement were carried out using zeta potential analyzer. To compare the size and stability of nano-emulsions by variations in temperature and time, the transmittance percentage of prepared nano-emulsions with different concentrations of Na2SO4 was determined by spectrophotometer UV–Vis at a wavelength of 600nm. According to the results, with increase in Na2SO4 solution concentration from 0.05 to 1M, a gradual reduction was observed in the PIT from 66 to 49°C. The optimum temperature was also reduced with increase of Na2SO4 concentration in the aqueous phase and the optimum temperature was found to be 9 to 16°C below the PIT to have the nano-emulsion with more stability. The average drop sizes for nano-emulsions with 0.25 and 0.8mol/L of Na2SO4 in aqueous phase at 25°C were 9.6 and 11.1nm, respectively, and the dispersion index were 0.380 and 0.311, respectively.