Radiolabeled Nature of the Residue (NOR) studies are a crucial component of pesticide development and stewardship. These studies provide insight into metabolic pathways, residues at harvest in raw agriculture commodities, metabolites that require toxicological evaluation, and metabolites to include in analytical methods. Radiochemical separation and quantification of each metabolite is required to understand its relevance for risk assessment. Complete separation and sufficient recovery of all metabolites is required for accurate radio-profiling as coelution or loss of metabolites can lead to inaccurate quantification, impacting downstream regulatory studies. This research highlights recent advances in analytical radiochemistry that have become standard practice in NOR studies at Corteva Agriscience and provides a rationale for their widespread adoption. In our case studies, offline radio-detection using 96 well plates, liquid scintillation cocktail and a microplate scintillation counter demonstrated increased sensitivity, robustness, and recoveries compared to both online (flow-through) radio-detection and offline radio-detection using plates containing solid scintillant. Due to the decreasing use rates and increasingly complex metabolism of modern active ingredients, UHPLC coupled with offline detection using liquid scintillant is increasingly essential for scientific quality and excellence in agrochemical regulatory science.

Advanced techniques for the separation and quantitation of radioactive metabolites in agrochemical regulatory studies

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ACS Spring 2023

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