Study On The Preparation Of Lambda-cyhatothrin Nanosuspension

Pesticide nanosuspension is nano-colloidal dispersion with particle size of blow1um of pesticide active compound particles in crystal or amorphous state stability bysurfactants. Pesticide nanosuspension with small particle size not only can solve theproblem of poor solubility, but also improve water solubility, permeability andbioactivity. Pesticide nanosuspension does not contain organic solvents, isenvironmentally friendly pesticide formulation.Like with lambda-cyhalothrin, this article studied preparing pesticidenanosuspension with the combination of melt emulsification method and highpressure homogenization (HPH), it offers a new direction for preparingnanosuspension of various pesticides with melting points below boling point of water.The dispersant, thickening agent, antifreeze and deformation agent were optimized. Italso evaluated the physicochemical property and stability of lambda-cyhalothrinnanosuspension.The main research work is as follows:1. The article investigated the feasibility of precipitation, media milling, HPHand melt emulsification-HPH method for preparing lambda-cyhalothrinnanosuspension, and chose the melt emulsification-HPH method based on theappearance, particle size and polydispersity index (PDI) of samples. The methodavoids the use of organic solvents and the particle size of samples is small anduniform, the preparation technology is simple, ease of handling and suitable forindustrial production.2. The dispersant is crucial to the preparation of pesticide nanosuspension, couldprevent particles aggregation and keep nanosuspension stability. This article chose4dispersants (SDS, PEGNPE, MRES and tween80) from12dispersants (SL, SDS, F68,SLES, MRES, HPMC, PEGNPE, tween80, span80, PVP K30, PVP K90andpolycarboxylate) based on based on the appearance, particle size and PDI of samples. Then the complex effect of SDS and the other three dispersants (PEGNPE, MRES andtween80) was investigated on the particle size and PDI of the nanosuspension. Bytesting,0.2%SDS and MRES were suitable dispersants. Polyving akohol was chosefor the thickening agent from7thickening agents (polyving akohol, arabic gum,sucrose, diatomite, soluble starch, sodium alga acid and PEG-400) based on theappearance, particle size and PDI of samples after storage at0℃for7days and54℃for14days. Mannitol was chose for the antifreeze from3antifreezes(mannitol, propylene glycol and glycerol) based on the drainage rate of samples afterstorage at0℃for14days. Antifoam204was chose for the deformation agent from2deformation agents (antifoam204and normal octane) based on the foamability ofsamples.By optimization screening, the formulation of5%lambda-cyhalothrinnanosuspension is that5%lambda-cyhalothrin,0.2%dispersant (SDS: MRES=1:3),1%polyving akohol,3.5%mannitol,0.8%antifoam204and water.3. The mean particle size, D90and PDI of lambda-cyhalothrin nanosuspensionwere14.43±0.13nm,50.00±11.00nm and0.271±0.004. The nano-particles in SEMimage were blow100nm distributed uniformed. The X-ray diffractogram patternshowed that the crystalline state of lambda-cyhalothrin was unchanged after preparingnanosuspension.The article investigated the particle size, PDI, zeta potential, XRD, dispersibility,drainage rate, suspensibility, pourability, foamability, water quality stability, watertemperature, pH and content of lambda-cyhalothrin. These demonstrated that5%lambda-cyhalothrin nanosuspension was physically and chemically stable.