The Preparation Of Abamectin EW And Evaluation Of Its Three Liquid-based Formulations

At present the traditional formulation emulsifiable concentrate （EC） contains a lot of organicsolvent which is evaporable, inflammable, explosive and not safe to the environment. Emulsion in water（EW） and microemulsion （ME） are two environment friendly formulations developed on the basis of EC,and there are a lot of water replace the organic solvents which increases the safety in production, storageand transportation. The evaluation of EW, EC and ME is mostly concentrated on bioassay, and therescarcely be systematic study. By taking abamectin as the research object, the prescription of abamectin20EW was prepared which it is within quality specifications. With the prescription of abamectin20EW,20EC and20ME, three liquid-based formulations were evaluated by physical and chemical properties,deposition on cabbage, photodegradation and bioassay. All the results are in order to provide certainsurport to the application of abamectin EW, EC and ME.First the solubility of several solvents was determined to choose appropriate solvent system. Thenthe emulsifier, co-emulsifier, water were determined by means of the stability of being in（54±2）℃，（0±2）℃and room temperature. At the same time, with the freeze-thaw stability the appropriateantifreeze agent was choosed. When the agents were preliminary determined, the orthogonal experimentwas used to optimize the prescription. Finally the prescription was determined as follows: Emulsifer:Termul5030; Co-emulsifer:1-Pentanol and Propane-1,2-diol; The rest is distilled water.The surface tension of the preparation influence the abilities of wetting, spreading and permeatingof the pesticide on the surface of target, also it influences the deposition of the pesticide. Finally itaffects the efficiency of the pesticide. So the chemical and physical properties and deposition oncabbage were determined. The results show that: When diluted at same times, the surface tension of MEis the lowest, and the contact angle and expansion diameter on cabbage leaves are superior to that of ECand EW, while the results of EC and EW are almost the same. Critical micelle concentration（CMC） inME is12.5mg/L while it is not observed significantly neither in EC nor in EW. Maintained quantity ofthe liquid by leaf of the three formulations is ME>EW>EC when the three formulations diluted at2000times. The deposition of the three formulation on cabbage when diluted at2000times is the ME as thehighest which there was significant difference with the deposition of EC and EW, while there is nosignificant difference between EC and EW.Photodegradation affect the efficiency and the transformation in environment of the pesticide, alsoit is one of the most important index of ecological environment safety. Abamectin is sensitive to uv lightand it is the effective component of the photodegradation. The petri dishes were used to simulate plantleaves and prepared pesticide liquid films to study photolysis under sunlight. The results showed that:Photodegradation of the three abamectin liquid formulations increased with solar irradiation time. In theexperimental range of initial concentration, the photodegradation of abamectin followed the first orderreaction kinetic and was negatively correlated with the initial concentration. The photodegradation ratewas EC＞EW＞ME in different concentration, pH or coexistent ions and pH had a great influence onphotodegradation while there almost being no influence of coexistent ions. There is a different effect of the ions of Ca²⁺and Mg²⁺in water that with the concentration of Ca²⁺and Mg²⁺increased, the half timeperiod of ME was decreased while the half time period of EC and EW was slightly increased. The half-life was ME＞EW＞EC in distilled water while it was EW＞ME≈EC in684mg/L of Ca²⁺and Mg²⁺inwater. It was visible that the photodegradation rate of ME and EW was slower than that of EC, and theformulation of ME and EW can prolong the validity of abamectin and can promote the application ofabamectin in field.The bioassay in lab and field were utilized to evaluate this three abamectin formulations. Theresults show that: ME has the highest activity against Plutella xylostella L larvae and the LC50in48hours is0.998mg/L which is higher than that of EC, and the synergistic ratio related to EC is1.68,meanwhile there is no difference between EW and EC. The result in72hours is similar to that of48hours. When the surface tension is lower, it easily cause the loss of the pesticide on the plants which areeasy to wetting, and finally it can reduce the efficiency of the pesticide. The results of field bioassay ongreen vegetables show: The effency of EC is better than that of EW and ME over1d and10d, but thereis no difference over3d and5d.