Emulsifiable concentrate formulations are a blend of active ingredient, organic solvent, and surfactants. When the solution is diluted into water, a spontaneous milky emulsion forms with dispersed phase droplets in the size range of 1 to 25 μm. When sprayed, this dilute emulsion gives a uniform and accurate application of active ingredient on the crop, which is essential for effective pest control. The formulation of the active ingredient into an Emulsifiable Concentrate can ensure uniform spreading and wetting under normal spray and weather conditions. The steps involved in formulating a pesticidal Emulsifiable concentrate are as follows:
- Determine the approximate amount of active ingredient (a.i.) required in the concentrate from the amount required in the RTU and the intended dilution factor.
- Screen a range of potentially suitable solvents and assess the solubility of the ai in these at the preferred concentration. Select the most suitable solvent from this screen.
- Combine the ai and solvent in the required ratio leaving a 5% void for emulsifiers.
- Run the solution in (3) through the HLB system to determine the required HLB of the emulsification.
- Having determined the required HLB try blending anionic and nonionic emulsifiers in the formulation in the ratios 10:0, 8:2, 6:4, 4:6, 2:8 and 0:10 which give this HLB.
- Fine tune the anionic/nonionic blend to optimize physical properties (spontaneity, suspensibility, etc.) of the formulation.
- Having established the optimum anionic/nonionic emulsifier ratio in the formulation try different types of emulsifiers in these categories (i.e. different chain lengths, different degrees of ethoxylation etc.).
- If the physical properties of the formulation are not satisfactory go back to step (3) and proceed using a higher level emulsifier.
- Assess the long – term physical and chemical stability of the product.
HLB ranges and their general areas of application.