Influence of some organic molecules on the rate and pattern of photolysis of chlorimuron-ethyl.

Abstract

Chlorimuron-ethyl, ethyl-2-(4-chloro-6-methoxy pyrimidine-2-yl-carbamoyl sulfonyl) benzoate, is a post emergence herbicide for the control of important broad-leaf weeds in soybean and maize. Though it is degraded in the agricultural environment primarily via pH-and temperature-dependent chemical hydrolysis, photolysis has also important role to degrade this compound. In this present study, the sensitizing and stabilizing effect of some organic compounds on the photolysis of chlorimuron have been investigated. The calculated half-lives of chlorimuron ethyl in presence of humic acid were 5.11 h in pyrex and 7.53 min in quartz under UV-light, and 5.78 day in quartz under sunlight, which are similar to the half-lives found in distilled water. This indicates that humic acid has no effect on the photolysis of chlorimuron in water. In another experiment, it was observed that 98 % chlorimuron was recovered in the presence of rotenone after 5 h of irradiation in pyrex tube, whereas in presence of riboflavin and benzophenone the degradation was 40.86 and 35.0%, respectively, as compared to 41.33% degradation of chlorimuron without any sensitizer. In presence of nicotine and acetone, the half-lives were 12.32 and 4.58 d, respectively, as compared to that of chlorimuron having no sensitizers in the solution (5.99 d). Thus, riboflavin and benzophenone enhance the rate of photolysis of chlorimuron whereas nicotine and rotenone significantly retard.