Inert 'safeners' are applied with herbicides to protect crops from the harmful effects of herbicides. Because millions of pounds of herbicide/safener mixtures are applied across the United States each year, it is important to understand how these compounds behave in the environment. This work examined the adsorption of isoxaflutole (a commercial herbicide applied primarily to corn fields) and cyprosulfamide (a safener commonly paired with isoxaflutole) onto an iron (III) oxide solid, a common mineral in soils. Isoxaflutole is a pro-herbicide meaning it must undergo a transformation in order to generate the active herbicide (a diketonitrile derivative). Because of this, rates of hydrolysis of isoxaflutole and its safener (cyprosulfamide) were also determined in aqueous solutions and in suspensions containing iron (III) oxide. Analytes were monitored and quantified by high performance liquid chromatography (HPLC) with UV-vis detection (Figure 1). Under alkaline conditions, the pseudo-first order rate constant increases for the hydrolysis of isoxaflutole. In contrast, hydrolysis of cyprosulfamide was not observed in our systems. There was a consistent adsorption (65%) of isoxaflutole onto iron (III) oxide across a range of solids loadings (0.2 to 10.9 g/L). With cyprosulfamide, studies show greater adsorption at pH 5.0 and 9.0 relative to pH 7.0. The effects of solvent lipophilicity on rates of isoxaflutole hydrolysis will also be discussed.

Transformations of an herbicide's active (isoxaflutole) and �inert� (cyprosulfamide) ingredients under simulated environmental conditions:  Reactions at the solid-water interface

247th National Meeting (2014)

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