Phase behaviour and physicochemical properties of a microemulsion obtained from an edible oil (saffola)

Abstract

A microemulsion obtained from edible oil saffola, Triton x 100, <i>n</i>-butanol and water (or brine) has been prepared and its phase behaviour and physicochemical properties have been studied. The ternary phase diagram shows an unusually large three-phase region. The single phase (1φ) microemulsion zone increases with increase in temperature and decreases in presence of brine, urea and cholesterol. The effect of the additives on the 1φ microemulsion zone varies in the order: urea ~ cholesterol < brine, upto 50% (w/w) oil as per phase diagram; thereafter, the order is cholesterol < brine < urea. The viscosity of the microemulsion (S + CoS 85%, oil 7.5% and brine 7.5% w/w) at different temperatures in presence of additives, viz.,cholesterol, esters of cholesterol (acetate, benzoate and stearate), a crown ether (18 crown 6) and urea exhibits a systematic decrease, whereas the conductance varies non-systematically. Three distinct trends in conductance are witnessed in the range 10°-60°C at higher ratios of brine/oil. At lower ratios as well as in presence of additives two distinct zones are exhibited. A mild percolation phenomenon is observed at temperatures above 20°C which turns into a moderate phenomenon at 50°C. While increase in temperature imparts fluidity to the microemulsions, the conductance behaviour advocates stage wise changes in their internal (microscopic) structure.