1,3-bis(trimethylsilyl)urea

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Jul - 20 Dec 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

13 April 2004

Deviations:

yes

Remarks:

The rapid hydrolysis meant that following the test guidelines completely was not applicable.

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Version / remarks:

30 May 2008

Deviations:

yes

Remarks:

The rapid hydrolysis meant that following the test guidelines completely was not applicable.

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom (19 Nov 2018)

Radiolabelling:

no

Analytical monitoring:

yes

Remarks:

HPLC-MS

Details on sampling:

- Sampling method: For pH 4, pH 7 and pH 9 a sample solution was prepared at 20 mg/L using the 2000 mg/L stock solution in dried acetonitrile, that had been used to prepare the 20 mg/L standard solution, and diluted to volume with the relevant buffer solution. The resulting samples contained 1% of the acetonitrile co-solvent. Immediately after preparation, the samples were injected on the LC-MS.
- Sampling intervals/times for pH measurements: 10 min (second injection) and 50 min (third injection for pH 9)
- Standard solution: To demonstrate identification and stability of the test item, a standard solution was prepared in dried acetonitrile at 20 mg/L and analysed using HPLC-MS. The acetonitrile was dried using anhydrous sodium suphate and filtered before use. Injections of the 20 mg/L standard solution were performed to bracket the sample injections to demonstrate the test item was still detectable and at a consistent sensitivity. There was no significant change in the intensity of the test item peak in the standard solution.

Buffers:

- pH: 4, 7 and 9

Duration:

10 min

pH:

4

Temp.:

20 °C

Duration:

10 min

pH:

7

Temp.:

20 °C

Duration:

50 min

pH:

9

Temp.:

20 °C

Transformation products:

yes

No.:

#1

No.:

#2

Details on hydrolysis and appearance of transformation product(s):

Based on the chemical structure of the test item, the primary hydrolysis products would be urea and trimethylsilanol.

% Recovery:

0

pH:

4

Temp.:

20 °C

Duration:

ca. 0 - <= 10 min

% Recovery:

0

pH:

7

Temp.:

20 °C

Duration:

ca. 0 - <= 10 min

% Recovery:

21

pH:

9

Temp.:

20 °C

Duration:

ca. 0 min

% Recovery:

5

pH:

9

Temp.:

20 °C

Duration:

ca. 10 min

% Recovery:

0

pH:

9

Temp.:

20 °C

Duration:

ca. 50 min

pH:

4

Temp.:

20 °C

DT50:

< 10 min

pH:

7

Temp.:

20 °C

DT50:

< 10 min

pH:

9

Temp.:

20 °C

DT50:

< 10 min

Details on results:

TEST CONDITIONS
- pH maintained throughout the study: Yes, the measured pH values were 4.0, 7.0 and 8.9, respectively

RESULTS AT PH 4 AND PH 7

No peak was observed in the chromatography immediately after sample preparation and after 10 min.

This indicated that the test item essentially hydrolysed immediately on contact with water at pH 4 and pH 7. Therefore, the half-life at 20 °C (laboratory temperature the samples were prepared at) was concluded to be less than 10 min at pH 4 and pH 7.

RESULTS AT PH 9

A peak for the test item was observed in the injection immediately after sample preparation and after approximately 10 min but both were significantly reduced in size compared to the 20 mg/L standard solution. The amount of test item remaining in these two injections was approximately 21% and 5%, respectively. After approximately 50 min, no peak for the test item was observed in the chromatography. Therefore, the half-life at 20 °C was concluded to be less than 10 min at pH 9.

Description of key information

DT50 < 10 min (at pH 4, 7 and 9, 20 °C, OECD 111)

Key value for chemical safety assessment

Half-life for hydrolysis:

10 min

at the temperature of:

20 °C

Additional information

The hydrolytic stability of 1,3-bis(trimethylsilyl)urea (CAS No. 18297-63-7) was experimentally assessed according to OECD guideline 111.

Substance identity and stability was analysed by high performance liquid chromatography-mass spectrometry (LC-MS) at pH 4, 7 and 9. Samples were prepared at 20 mg/L using a 2000 mg/L stock solution (in dried acetronitrile) and were diluted to volume with the relevant buffer solution (final acetronitrile content: 1%). The samples were injected on the LC-MS immediately after sample preparation and after 10 min. For pH 9 a third injection was performed after approximately 50 minutes.

The half-lives at pH 4 and pH 7 are < 10 min based on the obtained chromatograms (no peaks up to 10 min). At pH 9, a peak for the test item was observed immediately after preparation and after approximately 10 min, but both were significantly reduced in size compared to the 20 mg/L standard solution. The amount of test item remaining in these two injections was approximately 21% and 5%, respectively. After approximately 50 min, no peak for the test item was observed. Therefore, it was concluded that the half-life at pH 9 is < 10 min.

It is concluded that the DT50 of the substance is < 10 min at pH 4, 7 and 9. Based on the chemical structure of the test item, the primary hydrolysis products are urea and trimethylsilanol.