Preparation Of Abamectin B₂ Alginate-Chitosan Embedding Granules By Complex Coacervation

The abamectin B₂ embedding granules was prepared by the complex coacervation method with sodium alginate and chitosan as composite carrier,the influence of various factors and technological conditions on the entrapment granules was investigated.The sustained-release property and release kinetics of abamectin B₂ embedding granules was studied,and the biological evaluation of different particle size embedding granules was carried out with tomato root knot nematode as control object.Effect of concentration of sodium alginate,abamectin B₂ dosage,concentration of emulsifier,oil-water phase ratio in emulsionr and concentration of chitosan,concentration of calcium chloride,pH in crosslinking phase on drug loading and encapsulation efficiency of abamectin B₂ embedding granules was studied by the single factor experiment.It proved that concentration of sodium alginate,concentration of emulsifier,oil-water phase ratio and concentration of chitosan has significant influence on the embedding granules?P<0.05?analyzed by SAS software.Optimization formula was obtained through orthogonal test and verification test using the four factors mentioned above.The optimum formula was as follows:15 g/L of sodium alginate,10 g/L chitosan,7.5 g/L of Tween-20,the dosage of m?Abamectin B₂?:m?alginate?=1:2,oil to water ratio=1:20,10 g/L of calcium chloride and 4.17 of crosslinking phase pH with drug loading of 22.38%±0.25%and the entrapment efficiency was95.26%±0.61%.SEM?Scanning electron microscopy?results showed that the embedding granules?<150?m?were irregular in shape and its surface adhered by dense rodlike Abamectin B₂ crystal.The results of infrared spectroscopy?FI-IR?,differential scanning calorimetry?DSC?,thermogravimetric?TG?and differential thermal analysis?DTG?indicated that the embedding carrier and abamectin B₂ were physically encapsulated,and no chemical reaction happened.The embedding granules was crushed and three kinds of particle size range of embedding granules were obtained?>300?m,150³00?m,<150?m?.The release of embedding granules?>300?m and150³00?m?in soil were accorded with the first-order kinetics equation,The release of embedding granules?150³00?m and<150?m?in soil were accorded with the Higuchi equation.The smaller the particle size,the faster the release of embedding granules.And the temperature and humidity were increased,the release of embedded granules change faster too.Tomato root knot nematode as the prevention and control object,the biological evaluation of abamectin B₂ embedding granules was carried out.The control effect of<150?m embedding granules was 75.9%in the sixtieth day.The results showed that the smaller the particles,the higher the control efficiency.Compared with the dosage of 666.7 g a.i./hm²,500.0 g a.i./hm² was not significant,and333.3 g a.i./hm² was significant in control effect?P<0.05?.The dosage of 500.0g a.i./hm2 was used as the recommended treatment for the embedding granules?<150?m?.