Influence of surfactant structure on physical stability and physicochemical properties of insecticide emulsions

Abstract

A stable oil-in-water (o/w) emulsion to combat mosquitoes has been successfully formulated using palm methyl ester (PME) as carrier solvent, xanthan gum (XG) as thickener and plant-based non-ionic surfactants. The performance of castor oil-based surfactant, polyethylene glycol (20) glyceryl oleoricinoleate (PEG 20G), coupled with palm-based polyoxyethylene (20) sorbitan monooleate (POE 20S) was compared with conventional palm-based surfactant, C12-C14 fatty alcohol ethoxylate (FAE), coupled with POE 20S. The effects of surfactant mixing ratios and total thickener concentrations on stability, droplet size, microstructure and viscosity of the resulting emulsions were investigated. Emulsions obtained with a mixture of the two palm-based surfactants exhibited superior emulsification efficiency and stability in comparison to emulsions obtained with a mixture of castor oil and palm-based surfactant. The results indicated that the molecular structure of palm-based surfactants positively affect surfactant packing conformation at the oil/aqueous phase interface. The present study opens the possibility of using palm-based surfactants in insecticide emulsions in an effort to curb the spread of mosquito-borne diseases around the world.