[Preparation and optimization of zhitong micro-emulsion formula]

To prepare Zhitong micro-emulsion in this study, with the empirical formula of Zhitong preparation as the model medicine, the essential oil in the formula as the oil phase, and the water decoction as the water phase. The types of surfactant and co-surfactant were investigated. The changes in micro-emulsion conductivity and construction, the water percentage in the micro-emulsion system, the changing curve of conductivity and the fine pseudo-ternary phase diagram of micro-emulsion were drawn to determine the surfactant-co-surfactant mass ratio (K(m)). Subsequently, the D-mixture design was used to optimize Zhitong Micro-emulsion formula, with particle size and surface tension of micro-emulsion as the indexes. Finally, efforts were made to determine part of physical parameters of Zhitong micro-emulsion and preliminarily detect its stability. The results showed that the micro-emulsion was optimal with the EL-35-tween 20 ratio of 4:1 in surfactant, whereas the absolute ethyl alcohol was recommended as the co-surfactant. The ratio between surfactant and co-surfactant (K(m)) was 1.5. The finalized micro-emulsion formula contains 12% surfactant, 8% co-surfactant, 70% 1 g x mL(-1) water decoction and 8% oil. The results of the preliminary stability experiment showed a better stability of Zhitong micro-emulsion.