Development of an Enzyme-Linked Immunosorbent Assay for the Detection of Metosulam

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Abstract
A direct enzyme-linked immunosorbent assay (ELISA) was developed to quantitate the herbicide metosulam (N-(2,6-dichloro-3-methylphenyl)-5,7-dimethoxy-1,2,4-triazolo(1,5a)pyrimidine-2-sulfonamide) in soil and water. The ELISA had a detection limit of 0.3 ng·mL-1, a linear working range of 0.5 ng·mL-1 to 10 ng·mL-1, and an IC50 value of 2.8 ng·mL-1. The metosulam antisera cross-reacted with 5-OH and 7-OH metosulam (N-(2,6-dichloro-3-methylphenyl)-5-hydroxy-7-methoxy-1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonamide and N-(2,6-dichloro-3-methylphenyl)-5-methoxy-7-hydroxy-1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonamide, respectively) and the manufacturing intermediate XDE-564 (N-(2,6-dichlorophenyl)-5-ethoxy-7-fluoro[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide). The assay was used to estimate, accurately and precisely, metosulam concentrations in soil and water samples. Water samples were analyzed directly while soil sample analysis required solvent extraction and dilution prior to analysis. Extraction efficiency was 95%. The ELISA estimations in water correlated well with those from HPLC analysis (r2 = 0.99; slope = 0.99), making the ELISA a cheap and reliable alternative to conventional residue analysis techniques for quantification of metosulam. Keywords: Metosulam; ELISA; triazolopyrimidine; herbicide; residue