Development and\nApplication of a New QuEChERS Method\nCoupled with UPLC-QTOF-MS/MS for Analysis of Tiafenacil and Its Photolysis\nProducts in Water

This research centered on the novel pyrimidinedione herbicide,\ntiafenacil. Residues of tiafenacil and its three photolysis products\n(PP1 to PP3) in water were analyzed using advanced QuEChERS and UPLC-QTOF-MS/MS\ntechniques, reaching a low limit of quantitation (LOQ) of 10 μg/L.\nCalibration curves exhibited a high degree of linearity (<i>R</i><sup>2</sup> ≥ 0.993) over a concentration range of 0.01 to\n1.00 mg/L. Method validation demonstrated high precision, with intraday\nrelative standard deviation RSDr ≤7.9% and interday RSD<sub>R</sub> ≤ 6.1%, along with high accuracy (recoveries from\n94.4% to 105.0%). Using density functional theory (DFT) at the B3LYP/6-311g\n(d) level, we calculated the electronic properties of tiafenacil and\nits PPs (PP1 to PP3). Additionally, frontier molecular orbital (FMO)\nand fukui function analyses were conducted to explore HOMO–LUMO\nenergies, determine energy band gaps for these substances, and predict\nreactive sites for their electrophilic, nucleophilic, and radical\nreactions. Significantly, ecotoxicity assessment, including ECOSAR\npredictions and acute toxicity tests, revealed that the PPs exhibited\nhigher ecotoxicity to aquatic organisms than tiafenacil. Field experiments\nshowed a half-life of 18.9 days for tiafenacil in water, fitting a\nfirst-order kinetic model (<i>R</i><sup>2</sup> = 0.999),\nwith a degradation of 41.5% after 14 days and approximately 89.2%\nafter 60 days. This study significantly advances our understanding\nof tiafenacil’s environmental fate, evaluates its associated\nrisks, and offers valuable insights for its responsible application.