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Hydrolysis

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Description of key information

Hydrolysis as a function of pH

Key value for chemical safety assessment

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

Additional information

For the preliminary study, the hydrolytic stability of TCP was evaluated at pH 4,7 and 9, at 50°C over a five day period. Degradation of TCP was observed at pH 4,7 and 9. For the definitive study, the hydrolytic stability of TCP was evaluated and degradation was observed at pH 4,7 and pH 9, at 15°C and 25°C, over a 30-day period. Degradation of TCP at pH 4 was observed at both temperatures resulting in calculated half-lives of 79.8 days at 15°C and 61.6 days at 25°C. Degradation of TCP at pH 7 was observed at both temperatures resulting in calculated half-lives of 49.4 days at 15°C and 44.4 days at 25°C. Degradation of TCP at pH 9 was observed at both temperatures resulting in calculated half-lives of 15.3 days at 15°C and 6.56 days at 25°C. These data clearly indicate the hydrolysis rate of TCP is both pH and temperature dependent. No details of specific hydrolysis products are specified within the study.

 

TCP has been found to degrade rapidly in lake water; after an initial lag period of approximately 48 h, the substance was shown by GLC-FPD to have completely disappeared after 120 h.

Given the age of the main study and the known composition of the material offered commercially at this time, the composition is proposed as follows:

tri-m-tolyl phosphate EC no.: 209-241-8 at >= 10.0 — <= 35.0 % (w/w)

Di-m Cresyl p Cresyl Phosphate at >= 28.0 — <= 45.0 % (w/w)

Di-p Cresyl m Cresyl Phosphate at >= 11.0 — <= 36.0 % (w/w)

tri-o-tolyl phosphate EC no.: 201-103-5 at 0.0 — < 0.07 % (w/w)

Tri-cresyl-phosphate impurities containing mono-ortho- tolyl, di-ortho-tolyl, and tri-ortho tolyl groups < 0.15% (w/w)

Plus various unidentified low level impurities.

 

No specific information on the hydrolysis of the individual above components is available; however assessment using the EPISUITE HYDROWIN v2.00 tool provides the following results:

 

pH

Estimated half life

tri-m-tolyl phosphate

Di-m Cresyl p Cresyl Phosphate

Di-p Cresyl m Cresyl Phosphate

5

170.7 years

210.9 years

259.1 years

6

18.02 years

21.89 years

26.59 years

7

1.812 years

2.198 years

2.666 years

8

66.17 days

80.25 days

97.33 days

9

6.617 days

8.025 days

9.733 days

10

15.88 hrs

19.26 hrs

23.36 hrs

 

The above QSAR results endorse the conclusion of the test conducted that the hydrolysis of commercial TCP products are pH dependant, but are somewhat longer for results at pH 7 than those noted within the test. Additionally the QSAR indicates that the behaviour of different TCP isomers during hydrolysis is comparable.

 

Finally, in accordance with REACH Annex VIII Section 9.2.2.1., the study does not need to be conducted if the substance is readily biodegradable or highly insoluble in water. It can be demonstrated that the substance is considered to be readily biodegradable, and is only sparingly soluble. Hence waiving of this test is applicable under the conditions of Section 9.2.2.1.

 

In conclusion, hydrolytic effects attributed to the substance are proposed to contribute to removal, in addition to the effects of biodegradation.

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