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Hydrolysis and photolysis of bentazone in aqueous abiotic solutions and identification of its degradation products using quadrupole time-of-flight mass spectrometry

Song, Shiming, Zhang, Cuifang, Chen, Zhaojie, Wei, Jie, Tan, Huihua, Li, Xuesheng
Environmental science and pollution research international 2019 v.26 no.10 pp. 10127-10135
aqueous solutions, bentazon, ethyl acetate, half life, hydrolysis, iron, irradiation, laboratory experimentation, lamps, mass spectrometry, mercury, methanol, pH, photolysis, solvents, temperature, xenon
Hydrolysis and photolysis of bentazone in abiotic aqueous solutions were examined under laboratory conditions. Hydrolysis was studied in different buffer solutions (pH 4.0 ± 0.1, 7.0 ± 0.1, and 9.0 ± 0.1), at different temperatures (15 °C ± 2 °C, 25 °C ± 2 °C, 35 °C ± 2 °C, and 45 °C ± 2 °C), and at different Fe³⁺ concentrations (1, 5, and 10 mg/L). Photolysis was assessed in different buffer solutions and at different solvent (methanol and ethyl acetate) concentrations (10%, 20%, and 30%) or Fe³⁺ (1, 5, and 10 mg/L) concentrations and under mercury or xenon light irradiation. Hydrolysis half-lives ranged 46–99 days at three different conditions. Photolysis half-lives ranged 2.3–7.5 h in three different conditions under mercury and xenon irradiation. Hydrolysis and photolysis of bentazone were accelerated by both alkaline conditions and elevated temperatures, and solvents and Fe³⁺ strongly enhanced bentazone degradation. Photodecomposition was much faster under a mercury lamp than under a xenon lamp. N-methyl bentazone and 6-OH bentazone/8-OH bentazone were identified as degradation products using UPLC-Q-TOF-MS. The data generated from this study could be useful for risk assessment of pesticides in the environment.