The Study Of Flubendiamide Hydrolysis And Photolysis Characteristics

This study was conducted in order to understand the transport, transformation and fate of flubendiamide in the environment, to assess its safety to ecosystems, and eventually to provide theory basis for its proper use under field conditions. In this work, the hydrolysis and photodegradation kinetics of flubendiamide were determined under lab controlled conditions, with the chemical extracted by liquid-liquid partition and detected by HPLC.In the study probing the hydrolysis of flubendiamide, a temperature-controlled incubator was used to provide the required temperature and humidity. The results indicate that the hydrolysis rates of flubendiamide varied substantially in the buffer solutions at pH 4, 7, and 9, respectively, with an order of rates: pH 4 > p H 9 > pH 7. Half-lives were determined to be 73.3 d, 111.6 d, and 81.3 d at buffer pH 4, 7, 9, respectively, which shows flubendiamide was more prone to hydrolysis under acidic and alkaline conditions than neutral conditions. The hydrolysis half-lives of flubendiamide in water at 25 °C, 30 °C, and 40 °C were 111.6 d, 62.5 d, and 31.9 d, respectively, indicating that the hydrolysis of flubendiamide is a temperature dependent process. Distinction of hydrolysis rates was also observed in different water types, the order of hydrolysis rates was identified to be: river water > lake water > tap water > distilled water, with the corresponding half-lives determined to be 40.9 d, 47.3 d, 62.7 d, and 98.5 d, respectively. The results demonstrate that the existence of humic acid stimulated the chemical’s hydrolysis, and the hydrolysis rate was in direct proportion to the concentration of humic acid in water; the hydrolysis rate was also accelerated by the presence of Cu2+ in water, which made a decrease of 48.7 d in half-life compared with that in distilled water.A photo-reactor coupled with a high-vapor mercury lamp and a Xeon lamp was used in understanding the photodegradation behavior of flubendiamide. In three buffer solutions at different pH, the order of photodegradation rates was estimated to be: pH 9 > pH 7 > pH 4. It is noticed that flubendiamide photodecomposed more slowly in alkaline solution, which differentiated from its hydrolysis behavior. The order of photodegradation of flubendiamide in different water types was determined to be: distilled water > tap water > lake water > river water, with the corresponding half-lives calculated to be 0.55 h, 0.75 h, 1.34 h, and 1.87 h, respectively. Flubendiamide in four different solvents photodegraded following the order: acetonitrile > methylene chloride > ethyl acetate > acetone. The photodegradation rate retarded by acetone is probably attributed to its light quenching effect. The results show that nitrate prohibited the photodegradation of flubendiamide, and this trend was more noticeable as its concentration increased. In this study, we also measured the photodegradation rates of flubendiamide affected by different light sources and light intensity. The order of rates was: 500 W mercury lamp > 300 W mercury lamp > Xeon lamp. The photodegradatoin rates of flubendiamide depend on the irradiation energy of the light source as well as its own maximum absorption wavelength.