| The toxicity of chlopyrifos, beta-cypermethrin as well as their mixtures with different rations on 3rd Plutella xylostella larvae were determined by immerse leafs method. The optimum ratio additives was determined by using the method of CTC. On this basis, Based on chlopyrifos puls beta-cypermethrin as core materials and biodegradable polylactic acid as wall materials,the sustained-release microspheres of chlopyrifos puls beta-cypermethrin was studied by using emulsion solvent evaporation method, and the relative optimum prescription and process conditions were obtained. The quality detection method was also established.Then prepared of 5% chlopyrifos puls beta-cypermethrin microspheres SC by screening of wetting dispersants, thickening agent, and the anti-freezing agent and carried out laboratory experiments.The degradation dynamics of chlorpyrifos microspheres and EC in water and the toxicity to the larvae of Aedes albopictus were also studied. The main research methods and results were summarized as follows: 1 The screening of optimum ratio of chlopyrifos and beta-cypermethrin mixturesThe toxicity of chlopyrifos,beta-cypermethrin as well as their mixtures with different rations on 3rd Plutella xylostella larvae was determined by immerse leafs method,and calculated their cotoxicity coeffcients,Y. Reverse arcsin transforms (X=arcsin(K)1/2) were computed for the mass fractions, K, of the active ingredients of chlopyrifos.Used software to fit cotoxicity coefficients and arcsine Values.Fitted curveY=-0.0138X2+0.1669X+192.19,If Y’=0,then X=6.047,Pluged X into its mathematical model and X=arcsin (K)1/2, the most significant cotoxicity coefficients of chlopyrifos was 192.695,and its mass fractions, K, of the active ingredients was 0.0547. Pluged K into k:(1-K),the optimum ratio between chlopyrifos and beta-cypermethrin was 1:17. 2 Study on the preparation condition of chlopyrifos puls beta-cypermethrin microspheresThe chlopyrifos puls beta-cypermethrin microspheres was prepared by using emulsion solvent evaporation method, The effects of organic solvent,reaction temperature, emulsifying time,the types of emulsifier and concentration,stirring speed,ratio of oil/water,concentration of PLA,ratio between core materials and wall materials (chlopyrifos puls beta-cypermethrin weight/PLA weight) on the preparation of microspheres were studied by single factor test.The results of microspheres were characterized with drug-loading rate,entrapment rate and morphological characteristics.Choosed core materials and wall materials,concentration of PLA, emulsifier concentration,ratio of oil/water,stirring speed,five important factors influencing microspheres preparation. Used five factors in four levels orthogonal design test to optimize the technology of preparation.The optimum preparation condition was:the core materials and wall materials was 1:3,the concentration of PLA was 120mg/L,the concentration of emulsifier was 1.5%,the ratio of oil/water was 1:20,the emulsifying dispersion speed was 4000rpm/min and kept 0.6min, the magnetic stirring speed was 700rpm/min and kept 3h,the temperature was 30℃.The results of optimum preparation condition showed that the surface of microspheres was smooth,the volume average size of microspheres was 14.26±0.29μm,drug-loading rate was 23.79±0.16%,entrapment rate was 95.15±0.65%.The repeatability of the experiments was good.The differential scanning calorimetry (DSC) determination indicated that chlopyrifos puls beta-cypermethrin and PLA were combined well in the microspheres of chlopyrifos puls beta-cypermethrin.The photochemical stability of chlopyrifos puls beta-cypermethrin microspheres showed that the sustained-release ability of microspheres was significant.3 Determination of chlopyrifos plus beta-cypermethrin microspheres by HPLCThe sample was separated and analyzed quantitatively on Amethyst C18-H column using acetonitrile and water(70:30,by vol) as mobile phase,flow rate 1.0 mL/min and ultraviolet detector wavelength at 230nm. The results demonstrated that the linearity correlation coefficients of chlopyrifos and beta-cypermethrin were 0.9998 and 0.9984 respectively in the range of 0.01-1.0 g/L,the standard deviations were 0.0042 and 0.0253,the variation coefficients were 0.3433% and 0.1137%,the average recoveries were 98.67% and 98.77% respectively. The method was simple, rapid, accurate and suitable for the qualitative and quantitative analysis of chlopyrifos plus beta-cypermethrin microspheres sample.4 Preparation of 5% chlopyrifos plus beta-cypermethrin microspheres suspension concentrateThe formulation of 5% chlopyrifos plus beta-cypermethrin microspheres suspension concentrate was developed by optimizing the recipe with main adjuvants such as wetting-dispersing agents,thickening agents as well as anti-freezing agents. chlopyrifos plus beta-cypermethrin 5%,the wetting-dispersing agents were NNO 2% and 1601# 2%,the thickening agent was Magnesium aluminum silicate 3%, the anti-freezing agent was anti-freezing agent 5%,organic silicon defoamer 0.1% and added water to 100%.Results showed that its physical and chemical properties were not changed significant after the formulation was stored under normal,cold and heating conditions respectively.The toxicity of 5% chlopyrifos plus beta-cypermethrin microspheres SC,48% chlopyrifos EC,4.5%beta-cypermethrin EC.mixture of chlopyrifos plus beta-cyperme-thrin EC in proportion to the larva of Plutella xylostella were evaluated.Results showed that the toxicity of 5% chlopyrifos plus beta-cypermethrin microspheres SC was slightly lower than another three pesticides formulations.5 Degradation dynamics of chlorpyrifos microspheres and EC in water and the toxicity to the larvae of Aedes albopictusUnder the indoor condition,The degradation dynamics of different concentration chlorpyrifos microspheres and chlorpyrifos EC were studied in water. And the toxicity of chlorpyrifos microspheres and chlorpyrifos EC to the 3rd larvae of Aedes albopictus were also evaluated.The results showed that the degradation rate of chlorpyrifos microspheres was slower than chlorpyrifos EC and the half-lives was longer than chlorpyrifos EC. The half-lives of chlorpyrifos microspheres and chlorpyrifos EC at the dosage of 1.2、2、24mg/L were 19.4±2.1d、12.8±1.0d and 27.8±1.6d、16.4±0.9d and 31.0±1.7d、19.7±1.Id,respectively. The toxicity of chlorpyrifos microspheres to the 3rd larvae of Aedes albopictus was better and the duration was longer than chlorpyrifos EC. The killing rate of 1.2mg/L chlorpyrifos microspheres was 76.6% and chlorpyrifos EC was 53.3% after 85days. |
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