Preparation And Properties Of Pyraclostrobin Sodium Alginate Microcapsules

Pyraclostrobin is a fungicide with broad control spectrum and strong internal absorption,but there are defects such as easy photolysis and short duration.In this study,We utilize sodium alginate as the capsule wall,pyraclostrobin as the capsule core.preparing pyraclostrobin SA microcapsules by endogenous emulsification gel method.Taking the particle size and distribution range of microcapsules as the investigation parameters,selection and optimization of solvent types and drug loading conditions;And carried out The performance characterization and indoor toxicity determination of microcapsules,in order to expand the application range of pyraclostrobin,and provide new ideas and technical support for the development of new sustained and controlled-release pesticide dosage forms,the research results are as follows:1.Compared and studied on the particle size and the scope of distribution of microcapsules which prepared by different types of solvents,combined with the solubility of different solvents on the technical,ethyl acetate was selected as the solvent of the capsule core.And based on it,studied on the influence of the drug loading condition including different dosage of sodium alginate、emulsifying time、shear rate、emulsifier types and dosage,etc,on the granulation effect of microcapsules,finally,the optimal ratio of drug loading parameters for the preparation of pyraclostrobin SA microcapsules was screened,namely,adopted 1%sodium alginate,10%emulsifier A-110,emulsified for 10min at a shear rate of 1000 r/min at 25℃,the prepared microcapsules have small and uniform particle size,and the particles show normal distribution.2.Determined the morphological characterization and encapsulation rate of pyraclostrobin SA microcapsules,the results showed that the microcapsules had good encapsulation state,round spherical shape a whole,smooth and round surface,good dispersibility and no adhesion phenomenon.The average particle size of the microcapsules is 17.78μm,the span is 0.596,the encapsulation efficiency is 95.74%、the drug loading is31.64%,which meets the particle size standard of microcapsule preparations and the encapsulation effect is good.3.Studied and compared of the cold and hot storage stability of pyraclostrobin SA microcapsules and the technical,and find that both of them had good stability when stored at 4℃and-20℃;However,when stored at 25℃and high temperature of 54℃,the technical the decomposition rate of the technical is faster.After being stored at 54℃ for 30 d,the decomposition rates of the technical and the microcapsules were 40.25%and16.44%respectively,it indicating that microencapsulation of pyraclostrobin can well delay and reduce the damage of its effective components caused by high temperature.4.The results of the photostability determination of pyraclostrobin SA microcapsules and the technical showed that,the half-lives of the technical and the microcapsules were21.04 min、43.42 min,it indicating that microencapsulation could prolong the half-life of the active ingredients of pyraclostrobin.From the photodegradation dynamic curve,it is found that the degradation rate curve of the technical has a larger slope,the degradation rate curve of microcapsules is relatively gentle.When irradiated with UV light for 60 min,the residual concentrations of active ingredients in the technical and microcapsules were1.384μg/m L、3.778μg/m L,it indicating that microencapsulation could reduce the photolysis rate and photolysis degree of pyraclostrobin,improve the stability of the drug,can achieve the effect of protecting the capsule core technical.5.The release test of pyraclostrobin SA microcapsules in different p H release media showed that the microcapsules were sensitive to acid,in the weak acidic environment,the swelling coefficient of microcapsules decreased was reduced,the burst size of the drugs was decreased,it indicating that the microcapsules had a good controlled release effect.6.The result of efficacy indoor showed that the EC₅₀value of the technical was0.097μg/m L,the maximum inhibition effect on the hypha growth of wheat stem rot fungus was achieved after 12 d of microcapsule treatment,its EC₅₀value was 0.1109μg/m L at this time,it indicating that microencapsulation of pyraclostrobin had a good sustained release effect.