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Environmental fate & pathways

Hydrolysis

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Description of key information

Hydrolytic half life at ca. 23 °C (19F NMR method similar to OECD TG111):
pH 4: > 7 days
pH 7: 72.9 ± 2.0 hours
pH 9: 24.1 ± 0.6 hours

Key value for chemical safety assessment

Additional information

The key study was equivalent to OECD TG111 and was conducted taking PBSF's volatility into account. The system was buffered sufficiently to neutralize all all acid products assuming 100% hydrolysis (ca. 500 mM buffer). Detection was by 19F NMR and the method had a limit of detection sufficient to determine 0.09% hydrolysis of starting material. Extent of hydrolysis was followed by monitoring the expected hydrolysis product perfluorobutanesulfonic acid. The study was conducted under ISO9001/2008 guidelines and was done using sound scientific principles similar to OECD TG111. The study is reliable with restrictions and is suitable for assessing hydrolysis of PBSF. The supporting study was done according to EPA OPPTS 835.2110 and was GLP compliant. However, in several cases tested at lower concentrations, PBSF was lost from the test bottles without appearance of hydrolysis products. At higher concentrations, PBSF was not lost but significant hydrolysis was not observed. The test vials in the supporting study do not appear to have been shaken during the experiment and were only mixed on initial setup. Buffer concentrations in the supporting study were less than 10% (6-25 mM) of those in the key study. It is believed that the test substance was lost by volatilization during the experimental and/or analytical phases of the supporting study. The supporting study suggests that volatilization may be more important than hydrolysis under some circumstances. Further, the lack of hydrolysis in less buffered, unmixed vials as compared to extensive hydrolysis in highly buffered, well-mixed vials suggests that ionic strength and/or extent of mixing has a strong impact on hydrolysis rate. Since PBSF is insoluble (< 0.274 mg/L) in water, it is likely that the latter is the case.