Effects of processing shear intensity upon droplet size and emulsion stability of oil- in- water emulsion formulation of insecticide Lambda Cyhalothrin

The conventional Emulsifiable Concentrate (EC) formulation of insecticide Lambda Cyhalothrin is being used worldwide for controlling various agricultural insects and mosquitoes. It contains large quantities of petroleum distillate organic solvents and thus has disadvantages of flammability, environmental contamination by evaporation of solvents and penetration into the skin of farmers and spray application workers causing higher dermal toxicity. Water based oil-in-water emulsion (EW) formulation of Lambda Cyhalothrin may be a safer and better alternative to EC formulation. In the present studies, the composition and process for preparing EW formulation were optimized. The process of shear mixing is generally applied for preparing emulsion formulations, but data is not available about the process variables, specially the effects of changes in shear intensity upon the droplet size and emulsion stability, therefore, studies were conducted to examine the effects of changes in processing shear intensity upon droplet size and emulsion stability. The increase in processing shear intensity from 500 rpm to 4000 rpm (at increments of 500 rpm), gradually decreased droplet size from 9.3 microns to 2.22 microns. The emulsion stability increased with increase in processing shear intensity & decrease in droplet size and it was maximum i.e., 99.67 % in the sample prepared at highest shear rate of 4000 rpm. The emulsions prepared with high shear rate and having small droplet size were found stable in mild acidic, alkaline and saline dilution mediums and after accelerated temperature storage. The optimized composition and applying high processing shear intensity were found very effective for preparing stable formulation.