Morrica P, Barbato F, Della Iacovo R, Seccia S, Ungaro F
Dipartimento di Chimica Farmaceutica e Tossicologica, Università degli Studi di Napoli Federico II, Via D. Montesano 49, 80131 Naples, Italy.
J Agric Food Chem. 2001 Aug;49(8):3816-20. doi: 10.1021/jf010088f.
Knowledge of the kinetics and pathways of hydrolytic degradation is crucial to the prediction of the fate and transport mechanism of chemicals. This work first describes the kinetics of the chemical hydrolysis of imazosulfuron, a new sulfonylurea herbicide, and evaluates the results to propose a degradation pathway. The hydrolysis of imazosulfuron has been studied in aqueous buffers both within the pH range 1.9-12.3 at ambient temperature (thermostated at 25 +/- 2 degrees C) and at pH 3.6 within the temperature range of 15-55 degrees C. The hydrolysis rate of imazosulfuron was characterized by a first-order kinetics, pH- and temperature-dependent, and accelerated by acidic conditions and higher temperatures. The calculated half-lives at pH 4.5 and 5.9 were 36.5 and 578 days, respectively. At pH 6.6, 7.4, 9.2, and 12.3 no significant change in imazosulfuron concentration was observed after 150 days. Half-lives were much lower at pH <4 (= imazosulfuron pK(a)), at which they ranged from 3.3 to 6.3 days. Moreover, a change in temperature from 15 to 25 degrees C in acidic conditions (pH 3.6) decreased the half-life of imazosulfuron by a factor of approximately 4.0; in any case, a 3-5-fold increase in the rate of hydrolysis was found for each 10 degrees C increase in temperature. In acidic conditions the only hydrolysis products were the two molecules resulting from the cleavage of the sulfonylurea bridge.
了解水解降解的动力学和途径对于预测化学物质的归宿和迁移机制至关重要。本研究首先描述了新型磺酰脲类除草剂咪唑磺隆的化学水解动力学，并对结果进行评估以提出降解途径。在环境温度（恒温在25±2℃）下，于pH值1.9 - 12.3的水性缓冲液中以及在15 - 55℃温度范围内、pH值为3.6的条件下研究了咪唑磺隆的水解情况。咪唑磺隆的水解速率符合一级动力学，受pH值和温度影响，在酸性条件和较高温度下加速水解。在pH值4.5和5.9时计算得到的半衰期分别为36.5天和578天。在pH值6.6、7.4、9.2和12.3时，150天后未观察到咪唑磺隆浓度有显著变化。在pH值<4（=咪唑磺隆的pK(a)）时半衰期要短得多，范围为3.3至6.3天。此外，在酸性条件（pH值3.6）下，温度从15℃升至25℃会使咪唑磺隆的半衰期缩短约4.0倍；无论如何，温度每升高10℃，水解速率会提高3 - 5倍。在酸性条件下，唯一的水解产物是由磺酰脲桥断裂产生的两个分子。
