The Photolytic And Hydrolyzed Characteristic Study Of Nicosulfuron

Nicosulfuron is a good broad-spectrum postemergence corn herbicide, it has good prospects for development. However, as an efficient herbicide, its conversion and migration in environment have not been studied seriously. So the study of degradation is very necessary. The photolytic and hydrolyzed character of nicosulfuron are studied in this paper, that providing the scientific basis for evaluating the behavior of nicosulfuron in environment, using the drug rationally, and reducing the pollution to the environment. The impact of photolytic and hydrolyzed of nicosulfuron are mesurarated by efficient HLPC-UV in this experiment which is based on indoor cultivated method.At first, the photolytic of nicosulfuron was studied in this paper. The photolysis of nicosulfuron was analyzed under different situations, such as different buffer solutions, organic solvents acetonitrile, isopropyl alcohol, initial concentration, surfactant of sodium dodecyl sulfate, and different light. The results are as follows:(1) The pH buffer solution with 5,7,9 was selected as the medium and mercury was used as experimental light. The half-life of nicosulfuron in different buffer solution were 56.5,10.3,13.2 minutes. It can be see that the photolysis rate of nicosulfuron was the fastest in the neutral conditions, while lowest in the acidic conditions for having a good stability. The photolysis rate was lower than the neutral conditions in alkaline conditions (2) Acetonitrile,isopropyl alcohol were selected as the medium and mercury was used as experimental light. The half-life of nicosulfuron were 56.5,10.3.13.2 minutes. So, the photolysis rate of nicosulfuron was lower than in the water, this two organic solvents obstruction the photolysis rate of nicosulfuron.(3) Acetonitrile was Selected as the medium and mercury was used as experimental light. The initial concentrations were 10 mg-kg-1 and 1 mg-kg-1, the half-life of nicosulfuron were 16.7 and 14.8 minutes. So the effect of initial concentration on the photolysis of nicosulfuron was little.(4) Surfactant of sodium dodecyl sulfate was selected as the medium and mercury was used as experimental light. The results of nicosulfuron showed that the half-life of nicosulfuron was 9.9 minutes in the 1% sodium dodecyl sulfate solution and it was 12.7 minutes in the 0.1% sodium dodecyl sulfate solution. So as the increasing of sodium dodecyl sulfate, the half-life of nicosulfuron was shortened.(5) Mercury and xenon were used as experimental light. The pH buffer solution with 5 and rganic solvents acetonitrile were selected as reaction medium. The results showed under the mercury irradiation, the half-life of nicosulfuron was 10.3 minutes in the suffer solution and in the acetonitrile it was 16.7 minutes. Under the xenon irradiation, the half-life of nicosulfuron was 138.2 minutes in the suffer solution and in the acetonitrile it was 167.8 minutes. So the photolysis rate of nicosulfuron is lower under the xenon irradiation.Hydrolyzed rate of nicosulfron was strongly affected by the chemical constructer, the hydrolysis rate consistent with the first kinetic equation. The results are as follows:(1) In the different buffer solutions, the hydrolyzed rate was quicker in the neutral conditions and acidic conditions, the half-life were not more than 10 days, hydrolyzed rate was slow in the condition of alkaline, the half-life was about 20 days. The half-life were 7.7,5.2,22.5 days.(2) The pH buffer solution with 7 was selected as reaction medium in different temperature. The hydrolyzed rate of nicouslfuron was accelerated with increasing temperature. The half-life were 11.4 days,5.2 days,2.7 days,13.8 minutes in this article with the temperature were 15-45℃(3) The pH buffer solution with 7 was selected as the reaction medium at 25℃. As the concentration increasing, the hydrolysis rate of nicouslfuron slowed down and the half-life were extended. The half-life were 2.6,5.9,7.7 days when the initial concentrations were 1 mg-kg-1,5 mg-kg-1,10 mg-kg-1(4) Studied the influence of metals Cu2+ in this paper. At 25℃, the hydrolysis rate of nicouslfuron was 3.7 days in the 1% Cu2SO4 buffer solution and it was 8.6 days in the 0.1% Cu2SO4 buffer solution, while, the hydrolysis rate of nicouslfuron was 12.3 days in the water. So metals Cu2+ can help the hydrolysis of nicouslfuron and the hydrolysis rate was accelerated with the increasing of concentration.(5) At 25℃, the hydrolyzed rate was 9.9 days in the acetone solution; however, it was 2.6 days in the pH buffer solution with 7. So the acetone was slowed down the rate of hydrolysis.