Evaluation of emulsion preparation processes by quartz crystal microbalance

Abstract

The aim of this study is the in situ monitoring of phase change under emulsion preparation process by using QCM method. Water in oil type (W/O) emulsion was prepared by mixing water phase (sodium chloride aqueous solution), oil phase (mixture oil, liquid paraffin : kerosene=9 : 1) and emulsifier (sorbitan sesquioleate, monoester : diester=1 : 1) at a rotating speed of 800 rpm. Oil in water type (O/W) emulsion was prepared from water phase (distilled water), oil phase (liquid paraffin) and emulsifier (tetraoleic acid poly (oxyethylene) sorbitol). The platinum coated crystal and the propeller of a mixer were immersed in oil or water and emulsifier, and water or oil was dropped in above liquid with burette. The resonant frequency was monitored by frequency counter. In the case of W/O type emulsion, at first resonant frequency increased, but after that it decreased below the initial value until the end of water phase dropping. After the end of water phase dropping, the resonant frequency decreased. In the case of O/W type emulsion, at first resonant frequency increased until the end of oil phase dropping and after that it slightly decreased. In general, resonant frequency decreased by the increase of density and viscosity of liquid that contact with QCM electrode. Consequently, in this study, resonant frequency was dominated by the change of density and viscosity. Hence, this method could be an effective tool for monitoring the preparation process of emulsion.