Micellar characterisation of saponin from Sapindus mukorossi

The micellar characteristics of a non-ionic, natural surfactant, saponin obtained from the soapnut tree, Sapindus mukorossi, were studied in aqueous solution. Critical micelle concentration of Sapindus saponin determined using conductivity measurements and UV absorption studies was 0.045 wt%. Increase in temperature and salt concentration led to decrease in the critical micelle concentration of Sapindus saponin. The critical micelle concentration was found to increase with increase in hardness of water and increase in pH. The micellar aggregation number was determined using cyclic voltammetry and was found to be between 13 and 21. The size of the Sapindus saponin micelles was determined using intrinsic viscosity measurements and was found to be independent of saponin concentration for concentrations above the CIVIC. Solubilisation of two types of crude oils and a vegetable oil was studied using micellar solubilisation technique. At lower concentrations of the surfactant, the micellar solubilisation of crude oils in saponin was better than synthetic surfactants like Triton X100 (R) and SDS where as, the solubilisation of vegetable oil was better in synthetic surfactants.