Assessing the potential for pesticides to leech to ground water is an important hurdle for registration of pesticides in the EU. Soil adsorption is a key input parameter in determining the potential of a molecule to reach ground water (defined as a 1 m soil depth). In order to determine the adsorptive potential of a large number of molecules, a high throughput batch equilibrium screening assay was developed and validated. This screening assay is automation friendly and resource conservative. To validate the assay, soil adsorption data were generated using the traditional study design (OECD 106) and a 96-well plate design to assess the accuracy of the screening assay. Precision for the high throughput assay was determined across multiple plates using random positioning of the test compounds in the plate. The output of the high throughput adsorption assay is not a definitive Koc, but a predicted Koc range based on two texturally and physiochemically different soils. This Koc range, when coupled with the complimentary high throughput aerobic soil assay, provides inputs to groundwater models and allows for an early indication of the registerability, particularly in the EU. If the results from the modeling indicate a high leeching potential, i.e. concentrations &gt; 0.1 µg/L, additional higher tier soil sorption and aerobic soil studies will be conducted to refine the ground water model inputs.

Validation of a high throughput screening assay for the determination of pesticide soil adsorption

254th National Meeting (2017)

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