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Description of key information

Experimental investigation, EU C.7/OECD 111, 25 °C, pH 4 and 7: hydrolytically stable; pH 9: half-life of 52.3 h, rate constant: 5.52 x 10E-4/h

Key value for chemical safety assessment

Half-life for hydrolysis:
52.3 d
at the temperature of:
25 °C

Additional information

An investigation of the hydrolytic behaviour of the test substance as function of pH was carried out at pH 4, 7 and 9 in an experiment following the principles of EU Method C.7 / OECD Guideline 111 (Tarran, 2012). Hydrolysis occurs, when a substance reacts with water. The kinetics were consistent with pseudo-first order reactions, since the graphs of log concentration versus time are straight lines. The substance concentration is determined as a function of time. High Performance Liquid Chromatography (HPLC) was the analytical method of choice. The test was performed under sterile conditions and in vessels shielded from light. Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 0.1 g/L for the preliminary test and 1 g/L for all other tests in the three buffer solutions. In the preliminary test, the sample solutions were maintained at 50 +/- 0.5 °C for a period of 5 days. The results showed that it was necessary to undertake further testing (Tier 2) at all pH values at various temperatures, since more than 10 % hydrolysis had occurred. Tier 2 testing was sufficient for pH 4 and 9, concluding that the test substance will be stable. At pH 7, approximately 15 % hydrolysis was recorded at 70 °C after 5 days; while 30 % hydrolysis had occurred after 5 days at 50 °C in the preliminary test before. Therefore, the Tier 1 testing was repeated. As final result, the test substance has to be considered as stable at pH 4 and 7, since the half-lives were calculated as > 1 year at 25 °C. No rate constants can be derived. The half-life at pH 9 at 25 °C will be 52.3 days with a rate constant of 5.52 x 10E-4/h. As the substance was determined to be hydrolytically stable under acidic conditions, no additional testing at pH 1.2 and 37 +/- 0.5 °C was performed (optional test under OECD 111).