Registration Dossier
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EC number: 428-040-8 | CAS number: 138261-41-3
Phototransformation in water
Administrative data
Link to relevant study record(s)
Description of key information
(2E)-1-[(6-chloropyridin-3-yl)methyl]-N-nitroimidazolidin-2-imine is photolytically degraded in water with an average half-life of 0.76 d.
Key value for chemical safety assessment
- Half-life in water:
- 0.76 d
Additional information
The endpoint “phototransformation in water” is not a data requirement for the registered substance. However, for the sake of completeness this endpoint is covered by a short summary of the available data. There are a total of 2 studies on the phototransformation in water available. Both studies were performed under GLP conditions.
In the first study the photodegradation of (2E)-1-[(6-chloropyridin-3-yl)methyl]-N-nitroimidazolidin-2-imine in buffer pH 7.0 was investigated with artificial sunlight under sterile conditions. The study was conducted according to the respective EPA Guidelines (EPA Ref.: 161-2, Photodegradation Studies in Water) in compliance with the current GLP requirements. During the irradiation period of 2 hours the radioactivity balance was 100.2 ± 1.9 % of the amount at zero time. At a concentration of 5.4 mg/L and a temperature of 23-24.5 °C the test substance was degraded rapidly with a half-life of 0.95 hours. The corresponding rate constant was 0.012 1/min. The environmental half-life was calculated to be 4.2 hours. Under natural sunlight 60 % of the compound were degraded after 4 hours. A large number of photoproducts of different light stability was formed. Two of the major photoproducts were identified. Both photoproducts were stable under the conditions of the experiment. After 120 min of irradiation they represented 9.8 and 17.2 % of the radioactivity according to HPLC.
In the second study the quantum yield of direct photodegradation of (2E)-1-[(6-chloropyridin-3-yl)methyl]-N-nitroimidazolidin-2-imine in pure water was determined according to the ECETOC-method in polychromatic light. From the UV absorption data and the kinetic results of two photo degradation experiments in a merry-go-round irradiation apparatus the quantum yield was calculated to be 0.0142. The resulting quantum yield and UV absorption data were used to estimate the environmental half-life of the test substance concerning direct photodegradation in water by two different simulation models. Estimated half-life ranged from 0.15 d to 16 d (average half-life: 1.48 d).
The results (average half-life of both studies: 0.76 d) indicate that direct photodegradation in water contributes to the overall elimination of the substance in the environment to a great extent and that the half-lives normally are shorter than one day.
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