Effect of amphiphilic cholesteryl grafted sodium alginate derivative on the stability of lambda-cyhalothrin in water emulsion

The effect of amphiphilic cholesteryl grafted sodium alginate derivative (CSAD) and nonionic surfactant alkyl poly-glycosides (APG) on the physicochemical properties of pesticide lambda-cyhalothrin in water emulsions was systematically investigated in terms of standing stability, centrifugal stability, dispersion stability,crystallization temperature, droplet size, Zeta potential and viscosity. Results showed that the emulsions with 0.2-1.0 g/L CSAD displayed excellent stability. By using the most optimized concentration of CSAD, the centrifugal stability index of the water emulsions increased to 85.19%. Zeta potential value increased gradually to -41.9 mV followed by a gradual decrease. However, the stability sharply decreased with the increasing polymer concentration. Furthermore, differential scanning calorimetry (DSC) technology was employed to study the freeze-thaw stability of pesticide emulsions. The data showed that the freezing point shifted from -18.06 ℃ to -13.25 ℃ with the addition of CSAD. It revealed that the water emulsions had good stability at low temperature. Therefore, appropriate concentration of CSAD could improve the stability of the emulsion possibly due to the formation of the CSAD-APG complexes.