Physicochemical properties of adjuvants: Values and applications

The physicochemical properties of adjuvants determine their function and im pact upon biological activity. Various physicochemical parameters are key t o modifying both the preretention events and postretention consequences of adjuvant usage, irrespective of whether the adjuvants are tank-mix additive s or built into a formulation. This paper discusses several key adjuvant pa rameters for a range of adjuvant chemistries alone and in mixtures. In addi tion, the misleading use of terms such as nonionic surfactant and hydrophil e-lipophile balance is addressed. From a more coherent understanding of the parameters involved, it can be shown that there are ways of predicting the required properties of an adjuvant to solve specific delivery problems. Th e recognition that different problems often require quite different approac hes illustrates that good adjuvants do not exist per se, only materials tha t should be rationally selected for specific reasons. The chemistry of the herbicide and the nature of its targets will dictate adjuvant selection cri teria.