Mesotrione, 2-[4-(Methylsulfonyl)-2-nitrobenzoyl]cyclohexane-1,3-dione, is a triketone herbicide that selectively inhibits 4-hydroxyphenylpyruvate dioxygenase (HPPD) and is used for broadleaf weed control, especially in maize. Mesotrione is metabolized primarily to 4-methyl-sulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4-methylsulfonyl benzoic acid (AMBA) in corn. With the development of mesotrione-tolerant crops, use of mesotrione will be expanded. A robust analytical method to determine the residue level of mesotrione and its metabolites in various crop matrices is needed to support the product registration of the herbicide tolerant products. This presentation will focus on the development and optimization of a LC-MS/MS-based analytical method, including sample preparation procedures, to quantitate mesotrione and its metabolites in defined crop groups that include high-starch, high-moisture, high-oil, high-protein and high-acid content. Three primary QuEChERS extraction methods were compared to determine the extraction efficiency of the different approaches using C14-labeled crop matrices for metabolism studies. Several sample clean-up options including solid-phase extractions (SPEs) and dispersive SPEs after QuEChERS-based extraction were evaluated using crop samples spiked with standards. Due to the diverse physicochemical properties of analytes, many commercially available HPLC and SPE columns were screened to select the optimal solution to accommodate the residues of concern in a variety of sample matrices. After evaluation and refinement, a LC-MS/MS-based method was selected that is suitable for various crop matrices. Details of the method and its GLP validation will be presented.

Development and Validation of a LC-MS/MS method for measuring Mesotrione and its metabolites in crop residues

ACS Fall 2021

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