Abstract: Slow-release polymer of avermectin (AVM-QL-SA) was prepared using trimethyl quaternary ammonium salt of lignin-sodium alginate (QL-SA) as carriers by physical blending.Based on the structure elucidation of slow release-polymer through FT-IR, the effects of the factors such as the dosage of crosslink agent and abamectin as well as the pH fluctuation on the drug loading (DL) and the encapsulation efficieney (EE) were discussed.The results indicated that the avermectin was mixed with QL-SA uniformly and no chemical reaction happened.The optimal process conditions of AVM-QL-SA were the dosage of glutaraldehyde 4%(solids content), drug loading of 1%, the pH of reaction system 8.5(washing the product with water to neutral).Under these conditions, the obtained DL and EE were 1.36% and 73.36%, respectively and the particle size of AVM-QL-SA accorded with normal distribution with average particle size of 83.90 μm.AVM-QL-SA had good slow release performance and with the releasing time of 30 h in ethanol/water(1:1).The rate of cumulative release was 88.97% and the residual rate of AVM was 37.75%.Under UV irradiation for 8 h, the residual rate was 6.24%.It was confirmed that AVM-QL-SA had the function of resistance against UV.

Key words: lignin quaternary ammonium salt, polymers, avermectin, slow-release