Studies On The Photodegradation Of Chlorantraniliprole In Solution

In this paper, the photochemical degradation of Chlorantraniliprole in aqueoussolution irradiated by UV lamp, HPML, and sunlight was investigated.The effects of initialconcentrations, pH, water types, H₂O₂,dyes and surfactants on the photodegradation ofChlorantraniliprole were also studied. Photoproducts of Chlorantraniliprole in aqueoussolution were indentified. At the same time, the photolysis kinetics of Chlorantraniliprolewas observed in four organic solvents under UV lamp. The main results were summarizedas following:1. The photochemical degradation rate of Chlorantraniliprole in aqueous solution wasslow under sunlight, and its photodegradation half-life was25.109h. But it degradatedrapidly under UV lamp and HPML lamp, the photodegradation half-lives of which were3.974min and1.898h respectively.2. The photolytic rates of Chlorantraniliprole were negatively correlated with its intialconcentrations ranged from0.3mg·L^-1,0.7mg·L^-1,1.5mg·L^-1,3mg·L^-1and5mg·L^-1, thephotodegradation half-lives of which were3.726min,4.091min,4.485min,4.901min and5.602min respectively. The photolysis of Chlorantraniliprole in alkaline buffer solutionwas slower than the other two buffer solution.The photodegradation half-lives ofChlorantraniliprole were4.127min（pH=5）,4.177min（pH=7）, and4.559min（pH=9）respectively.Water quality also had a significant effect, with a decreasing degradation rateof Chlorantraniliprole in the sequence of Ultra-pure water>tap water>pond water>lakewater>river water. The photodegradation half-lives of Chlorantraniliprole were3.835minin Ultra-pure water,4.239min in tap water,4.506min in pond water,4.580min in lakewater and4.592min in river water.3. When the concentration of H₂O₂was less than3.88mmoL·L^-1, the photodegradati-on speed of Chlorantraniliprole was increasing and its photodegradation half-life decreasedfrom4.218min to1.358min. But with the H₂O₂dosage to7.76mmoL·L^-1, thephotodegradation rate of Chlorantraniliprole was slowed down. Riboflavin, methy blue andmethyl orange had little effects on the photolysis of Chlorantraniliprole with0.3mg·L^-1concentration. However, these three pigments all showed photoquenching effects onChlorantraniliprole with the adding concentration of0.7mg·L^-1so that the half-lives ofChlorantraniliprole prolonged from4.195min to4.348min,4.445min and4.283minrespectively, and the photoquenching effect ranged as: riboflavin>methyl orange>methyl blue.The photoquenching effects of three pigments on photodegradation of Chlorantrani-liprole got stronger with continuing adding their concentrations.4. SDBS and Tween-20had not obviously effects on the photolysis of Chlorantrani-liprole. But CTAB, Tween-80and Nongru2201exhibited photoquenching effects on thephotolysis of Chlorantraniliprole, which made the photodegradation half-lives of Chlorant-raniliprole prolong from3.987min to4.199min,4.067min and4.069min respectively.Photoquenching effects of different dosages of CTAB were no significant differences withthe increasing concentration from1mg·L^-1to25mg·L^-1.When concentrations of Nongru2201were1mg·L^-1and5mg·L^-1, its photoquenching effect also had not change obviously.But Nongru2201enhanced photoquenching effect on Chlorantraniliprole with the addingdosage up to5mg·L^-1, and the photodegradation half-life of Chlorantraniliprole prolongedto4.228min.5. It was found that the photolysis rates of Chlorantraniliprole were very different infour organic solvents under UV lamp. Chlorantraniliprole irradiationed2hours can almostnot be degraded in acetone and its degrdation rate was no more than5%. The order of thephotolysis rate of Chlorantraniliprole in other three organic solvents was acetonitrile>dichloromethane>ethyl acetate with the photodegradation half-lives being9.179min,11.106min and28.755min respectively.6. Two chief photoproducts of Chlorantraniliprole in aqueous solution were indentifi-ed by LC-MS and both of their molecular weights were446. The photoproducts of Chlora-ntraniiprole maybe2-[（2-Bromo-4H-pyrazolo[1,5-d]pyrido[3,2-b][1,4]oxazin-4-ylidene）amino]-5-chloro-N,3-dimethylbenzamide and2-[3-Bromo-1-（3-hydroxy-2-pyridinyl）-1H-pyrazole-5-yl]-6-chloro-3,8-dimethyl-4（3H）-quinazolinone.The major photodegradationpathways of chlorantraniliprole involved in the molecular cyclization and rearrangement.