Matrix-dependent enantioselective degradation and persistence of prothioconazole and prothioconazole-desthio in cereal agroecosystems.

Abstract

BACKGROUND: To elucidate the enantioselective degradation behavior of prothioconazole and its metabolite prothioconazole-desthio in wheat-soil and rice-paddy water-sediment ecosystems, this study conducted degradation experiments under field conditions employing high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) combined with established residue analysis methods. Field trials investigated the degradation kinetics and enantioselectivity differences of the two compounds in different matrices, and final residues in wheat flour, rice grain, and rice husk were determined. RESULTS: Prothioconazole degraded faster than its metabolite in all matrices. The parent compound followed first-order degradation kinetics throughout the entire experimental period, whereas prothioconazole-desthio exhibited a two-phase temporal pattern (formation followed by degradation); first-order kinetics was applied only to the post-peak degradation phase. In wheat plants, wheat field soil, rice plants, paddy water, and sediment, R-(-)-prothioconazole was preferentially degraded, leading to relative accumulation of S-(+)-prothioconazole with enantiomer fraction (EF) values reaching up to 0.64 in wheat plants and soil, and 0.56-0.63 in the rice ecosystem. Prothioconazole-desthio formation and degradation were also enantioselective: R-(+)-prothioconazole-desthio was preferentially formed and S-(-)-prothioconazole-desthio preferentially degraded in wheat plants, rice plants, paddy water, and sediment, with EF values increasing to 0.67 and 0.72 in wheat and rice plants, respectively, whereas no significant enantioselective degradation was observed in soil. Final residues of both prothioconazole and prothioconazole-desthio enantiomers in wheat flour, rice grain, and rice husk were all below the limit of quantification (LOQ = 0.005 mg/kg for these matrices). CONCLUSION: These findings provide data support for environmental risk assessment and scientifically sound application of prothioconazole. © 2026 Society of Chemical Industry.

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