Chemical and photochemical degradation of chlorantraniliprole and characterization of its transformation products

- Photodegradation of chlorantraniliprole (CAP) was studied in water.
- In the dark, CAP is stable in deionized water but degrades in natural water.
- Photodegradation pattern differs depending on the pH of the water.
- Four main degradation products were characterized by mulitiple methods.
- Dissolved organic matter and nitrate had little effect on CAP photodegradation.

This study aimed at assessing the photodegradation of the insecticide chlorantraniliprole (CAP) in deionized water and in tap water amended with humic acids and nitrate. Photolysis was carried out under simulated solar or UV-A light. CAP (39 μM) photodegradation was slightly faster in tap water than in deionized water with half lives of 4.1 and 5.1 days, respectively. Photodegradation rate of CAP was hardly affected by humic acids (up to 100 mg L−1) and nitrate. Photodegradation pattern was different in slightly acidic (pH = 6.1) deionized water compared to basic (pH = 8.0) tap water. Four main degradation products have been isolated and characterized spectroscopically, and crystal structure was recorded for the first two photodegradation products. CAP also degraded in the dark controls, but only at basic pH (23% loss at pH 8.0 in tap water after 6 days), resulting in the formation of one single degradation product. Our study shows that the degradation of chlorantraniliprole in water is a combination of chemical and photochemical reactions, which are highly dependent on the pH of the solution.