Preparation of Chlorpyrifos Aqueous Capsule Suspension and Optimization of Encapsulation Conditions

UF-resin was used to encapsulate chlorpyrifos by in-situ polymerization. The effect factors on particle size and distribution of capsule were also investigated. The optimal conditions were as follows:The dosage of dispersant styrene-maleic anhydride(SMA)emulsion was 2.5％ of total system,emulsified for 30 minutes by stirring at the rotating speed of 1 500 r/min,adjusted to pH 2.5 in 60 minutes,the temperature of condensation reaction was controlled at 45℃. The mean diameter of microcapsule suspension was 8.9 μm,and the coefficient of its variance were 0.182 6,which formed satisfied particles size and distribution under the optimum conditions. Its encapsulation efficiencies were 99.54％. Compared with chlorpyrifos EC,the chlorpyrifos CS showed excellent initial efficacy and long residual activity. The original LC50 of chlorpyrifos EC and CS were 2.05 μg/mL and 3.02 μg/mL respectively against 3rd-instar larvae of Bradysia odoriphaga,and their residual LC50 (32 d) under natural conditions were 100.23 μg/mL and 15.63 μg/mL,respectively.