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Description of key information

Half-lives (DT50) at 25°C:
- t1/2 (pH4) > 1 year
- t1/2 (pH7) = 280 day(s)
- t1/2 (pH9) = 68.4 hour(s)

Key value for chemical safety assessment

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

Additional information

The rate of hydrolysis increases with an increase in pH, whereas the following half-lives (at 25°C) were obtained [For pH 7 and pH 9 graphs of the common logarithm of the concentration (g/L) versus time (hours) were plotted and the rate constant and half-life calculated. By plotting the natural logarithm of the rate constants against the reciprocal of the temperature (K), the rate constant and half-lives at 25°C were obtained by either interpolation or extrapolation.(Mullee, 2005)]:

- t1/2(pH4) > 1 year

Sample solutions at pH 4 were maintained at 50.0 ± 0.5°C for a period of 120 hours.Result: Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.

- t1/2(pH7) = 280 day(s)

Sample solutions at pH 7 were maintained at 50.0 ± 0.5°C for a period of 360 hours. Result: The extent of hydrolysis after 360 hours indicated that a further test (with solutions being maintained at 60 and 70 ± 0.5°C) was required to estimate the rate constant and half-life. Results: t1/2 = 69 h at 60 °C and t1/2 = 23.7 h at 70 °C.

- t1/2(pH9) = 68.4 hour(s)

Due to the anticipated rapid hydrolysis at pH 9, solutions were maintained at 20 and 30 ± 0.5°C. Results: t1/2 = 133 h at 20 °C and t1/2 = 36 h at 30 °C.