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Hydrolysis

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Description of key information

Based on the results of a reliable study performed according to OECD 111, the test substance is stable to hydrolysis.

Key value for chemical safety assessment

Additional information

Hydrolysis of C12/C14 alkyl dimethylamine oxide (AO) was investigated at pH 4, 7 and 9 according to OECD Test Guideline 111 and EU Method C.7 [Analytico Medinet B.V. (2002)]. AO was tested at a nominal concentration of 4167 µg/L for 5 days at 50 °C.

Both the C12 and C14 homologues of the test substance were evaluated. Analytical samples were taken at time 0 and after 5 days of incubation at 50 °C and protected from light to prevent photolysis. Samples were analyzed by atmospheric pressure ionization interfaced with flow injection/mass spectrometry (FI-MS/MS). Internal calibration standards were prepared from deuterated test substance. Results of the test solutions at pH 4, 7 and 9 showed no significant decrease of concentration after 5 days of incubation at 50 °C for the C12 homologue. For the C14 homologue, the same results were obtained at pH 7 and 9. However, at pH 4 a significant decrease of concentration of 27.5% was observed. Re-analysis of the extracts confirmed these results. No explanation could be found for this possible hydrolysis of the C14 homologue at pH 4, especially because the C12 homologue didn't show any significant decrease of concentration at pH 4. Therefore, the 5-day test at pH 4 was repeated. In the repeat test, the C12 homologue showed similar results to the initial test. However, the duplicate of the repeated test for the C14 homologue showed inconsistent results. One test solution showed a decrease of 44.3% and the duplicate showed a decrease of 5.6%. Results of the C14 homologue showed that the analytical method used for the determination of the C14 homologue was not consistent. As a result, conclusions were based on the C12 homologue results only.

The test solutions at pH 4, 7 and 9 showed no significant decrease in concentration of the C12 homologue after 5 days of incubation. Further testing at these pH levels was not required according to the EEC Directive 92/69 EEC Annex V, Part C.7 criteria; therefore, it can be stated that the test substance is hydrolytically stable. Because AO is hydrolytically stable, rate constants for hydrolysis were not calculated.