An international customer came to Battelle with a challenge: they needed to develop a co-formulation of two distinct fungicides with stability and efficacy equal to or better than each of the active ingredients alone. The two active ingredients had very different chemical and physical properties: fungicide A was a high melting point solid with very low solubility, and fungicide B was a low melting point solid with low water solubility. In addition, fungicide A was typically used as a dispersion of fine solid particles in water, but fungicide B needed to be solubilized to achieve biological efficacy.
A suspo-emulsion (SE), where a solution of one fungicide was emulsified into a suspension of the other, was identified as the best option. Solvent selection was key: the solvent needed to have good solvency for one fungicide but poor solvency for the other, and have low water solubility in order to minimize partition into the aqueous phase. We used a solvent screen to identify a solvent that provided good solvency for fungicide B, poor solvency for fungicide A (to prevent crystal growth), and low water solubility to keep fungicide B in solution and maintain its activity.
We developed a stable, suspo-emulsion (SE) co-formulation where a solution of fungicide B was emulsified into a suspension of fungicide A. The resultant formulation had a two-year shelf life, gave good biological efficacy and was both easy to make and easy to use. The new product allowed the agrichemical developer to extend the spectrum of disease control, offer greater convenience to farmers and differentiate their product from competitors. The new co-formulation was delivered to the customer within six months of project initiation, allowing them to get through product testing and registration for an on-time and on-budget product launch.