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Environmental fate & pathways

Hydrolysis

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Description of key information

- DT50 at 10 and 20 degrees Celsius and pH 4: 55 and 11 days; 
- DT50 at 10 and 20 degrees Celsius and pH 7: 20 and 17 days
- DT50 at 10 and 20 degrees Celsius and pH 9: 32 and 21 days

Key value for chemical safety assessment

Half-life for hydrolysis:
20 d
at the temperature of:
10 °C

Additional information

The hydrolytic stability of Fyrolflex RDP was evaluated according to OECD TG 111 (Kendall and Nixon 2000, key study).

Over a 30 day period hydrolysis of Fyrolfkex RDP at pH 4, 7 and 9 at 10°C was observed, resulting in calculated half-lives of 55 days, 20 days and 32 days, respectively. At pH 4, 7 and 9 at 20°C the hydrolysis occurred with calculated half-lives of 11 days, 17 days and 21 days, respectively.

 

According to the authors these data clearly suggest that the hydrolytic stability of Fyrolflex RDP is temperature and pH dependent. At pH 4, coefficients of determination of 0.7854 and 0.9936 at 10°C and 20°C, respectively indicate that the hydrolysis process proceeds further towards completion due to elevated temperature. This likewise, correlates well with the large disparity in half-lives between the samples incubated at 10°C and 20°C. The data from the pH 7 and 9 test systems do not show this large temperature-dependent difference. The data additionally indicate that the hydrolysis rate of Fyrolflex RDP at each pH and temperature does not strictly follow first-order kinetics. Rather, it appears that following approximately 15-17 days, the concentration of Fyroflex RDP reaches a plateau, thereby suggesting an equilibrium process between parent and degradation product(s). Overall, Fyrolflex RDP appears to be least stable at neutral pH and/or at elevated temperature

 

The study was carried out according under GLP. As there were some deviations from the OECD TG 111, the study was rated Reliability 2.

In a key study according to OECD TG 111 under GLP, the half-life (hydrolysis) of Fyrolflex RDP at 20 degrees Celsius and pH 4, 7 and 9 was found to be 11, 17 and 21 days respectively.