REAKTIV OLIV F00-149

Hydrolysis

Description of key information

A study was performed  according to EU method C.7 and in compliance with GLP to measure the rate of hydrolysis of the test substance Reactive Olive F00-0149. At pH 7 the rate constant at 38°C was calculated to 7.147E-03 h-1 and the corresponding half-life of the test substance was 26.92 h at pH 7 and 42.55 hours at pH 4. The half-life at 25 °C was not determined within the study. However, the rate constant at 25 °C was extrapolated using the Arrhenius equation, and the corresponding half-life calculated during subsequent study evaluation following the EU Technical Guidance Document on Risk Assessment. The calculated half-life time is 76.16 hours at 25°C.

Key value for chemical safety assessment

Half-life for hydrolysis:

76.16 h

at the temperature of:

25 °C

Additional information

The hydrolysis rate of the test substance was determined in accordance with EU method C.7, and in compliance with GLP. The test substance was dissolved in standard buffer (~ 2 g/l) and its concentration measured at specific sampling times. HPLC was used to analyse the test substance concentration. A preliminary test was carried out to assess the rate of hydrolysis at pH 4, 7 and 9 at 50 °C; as a consequence, the main test at pH 9 were not performed due to low hydrolysis at pH 9.

The main test was carried out at pH 4 and 7 at 50 °C initially. A linear dependence of the log₁₀-transformed test substance concentration on time was observed, i.e. the hydrolysis followed pseudo first order kinetics. Therefore, further tests were carried out at pH 4 and 7 at 38 °C. From the measurement results the rate constants and the half-lives of the test substance were calculated at:

pH 4, 50 °C: Kobs = 0.0317 h^-1, t1/2 = 21.89 hours

pH 4, 38 °C: Kobs = 0.0163 h^-1, t1/2 = 42.55 hours

pH 7, 50 °C: Kobs = 0.0767 h^-1, t1/2 = 9.04 hours

pH 7, 38 °C: Kobs = 0.0257 h^-1, t1/2 = 26.92 hours

The Arrhenius equation was used to calculate the rate constant at 25 °C. At pH 7 the rate constant was calculated at 7.147 ×10^-3h^-1.

The half-life for the test substance at pH 7 and 25 °C was not determined and not extrapolated within the study.

For this reason equation 25 from the Technical Guidance Document on Risk Assessment Part II from the Institute for Health and Consumer Protection - European Chemicals Bureau was used do derive the half-life value at 25°C:

DT50(X°C) = DT50(T) * e^(0.08*(T-X))

DT50(X°C) = Half-life time at desired temperature (here: X = 25°C)

DT50(T) = Half-life time at measured temperature (here: T = 38°C)

T = 38°C, X = 25°C.

The resulting calculated half-life time is 76.16 hours at 25°C.