OPTIMIZATION OF LIQUIDSOAP FORMULATION

The quality of liquid soap for washing hands depends on its chemical composition, and it is evaluated by the physicochemical and functional characteristics of that product. The aim of the work is to prepare different series of liquid soap formulations by varying the concentrations of anionic and amphoteric surfactantsand sodium chloride, and to optimize the formulation. The effects of the optimization were evaluated based on the results of the analysis of the physico-chemical parameters of the prepared formulations, such as density, viscosity, surface tension and critical concentration of micelles. As amphoteric and anionic surfactant concentrations in liquid soap increase, density and viscosity values increase. The value of the surface tension decreases with the increase in the concentration of the surfactants present, with the amphoteric surfactant making a greater contribution to the decrease. Regardless of certain advantages that the anionic surfactant shows in relation to the amphoteric one, the best characteristics of the liquid soap are shown by the formulation thatcontains a combination of both used surfactants. The addition of NaCl to the liquid soap formulation has multiple significance, but also a different effect on the physical and chemical characteristics at lower and higher concentrations. Functional and some physico-chemical characteristics of liquid hand washing soap depend on the pH value of the formulation. As the pH value increases, the surface tension and CMC increase to certain values, so pH=5.5 is taken as the optimal pH value of liquid soap, as a compromise between the values of the measured characteristics and the pH value of human skin. This research showed that the formulation containing 5.4w/w%anionic surfactant, 1w/w%amphoteric surfactant and 4w/w% NaCl represents the optimal liquid soap formulation. KEYWORDS:liquid soap; content of liquid soap; surfactants; electrolyte in liquid soap; characteristics of liquid soap; optimization of formulation