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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-09-03 to 2013-02-05
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP study according to OECD TG 111, but results are probably not based on hydrolysis as no pH dependence was observed and no qualtitative or quantitative determination of the hydrolysis products was done
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
2004
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent products: in the main test, samples were taken after 0, 4, 24, 48, 72, 96 and 120 hours at 50 °C, after 0, 1, 2, 4, 6, 20 and 28 hours at 60 °C and after 0, 24, 48, 120, 216, 288, 384, 456, 552 and 720 hours at 25 °C under all pH conditions
- Sampling method: test flasks containing the sample solutions were taken from the water bath at various times
- Sampling intervals/times for pH measurements: the pH value of each sampled solution was recorded
- Sampling intervals/times for sterility check: not performed
- Sample storage conditions before analysis: it was not reported that samples were stored before analysis
Buffers:
- pH 4: buffer solution was prepared potassium hydrogen phthalate (0.005 mol/dm3)
- pH 7: buffer solution was prepared from disodium hydrogen orthophosphate (anhydrous, 3 mmol/dm3), potassium dihydrogen orthophosphate (2 mmol/dm3) and sodium chloride (2 mmol/dm3)
- pH 9: buffer solution was prepared from disodium tetraborate (1 mmol/dm3) and sodium chloride (2 mmol/dm3)
Details on test conditions:
TEST SYSTEM
- System: distilled water
- Type, material and volume of test flasks, other equipment used: stoppered glass flasks
- Sterilisation method: not reported
- Lighting: not reported
- Measures taken to avoid photolytic effects: incubation in the dark
- Measures to exclude oxygen: ultrasonication and degassing with nitrogen to minimise dissolved oxygen content
- Details on test procedure for unstable compounds: none
- Details of traps for volatile, if any: none
- If no traps were used: closed system was used
- there was no evidence that the substance adsorbed to the walls of the flask

TEST MEDIUM
- Volume used/treatment: not reported
- Kind and purity of water: not reported
- Preparation of test medium: substance was dissolved in water
- Identity and concentration of co-solvent: 1% co-solvent of tetrahydrofuran

OTHER TEST CONDITIONS
- Adjustment of pH: none
- Dissolved oxygen: not reported
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
0.476 - 0.486 mg/L
Duration:
28 h
pH:
4
Temp.:
60 °C
Initial conc. measured:
0.409 - 0.42 mg/L
Duration:
720 h
pH:
4
Temp.:
25 °C
Initial conc. measured:
0.416 - 0.455 mg/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
0.487 - 0.49 mg/L
Duration:
48 h
pH:
7
Temp.:
60 °C
Initial conc. measured:
0.469 - 0.497 mg/L
Duration:
720 h
pH:
7
Temp.:
25 °C
Initial conc. measured:
0.456 - 0.5 mg/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.471 - 0.48 mg/L
Duration:
48 h
pH:
9
Temp.:
60 °C
Initial conc. measured:
0.448 - 0.471 mg/L
Duration:
720 h
pH:
9
Temp.:
30 °C
Initial conc. measured:
0.396 - 0.442 mg/L
Number of replicates:
One sample per time point per pH value per temperature
Positive controls:
no
Negative controls:
no
Preliminary study:
Greater than 10% hydrolysis was observed after 120 hours at all pH values at 50 °C test temperature triggering a tier 2 assessment.
Test performance:
The results from the experiments at 50 and 60 °C in the tier 2 test showed abnormal hydrolysis behaviour with faster loss of test item at lower temperature. Therefore the rate of hydrolysis was assessed directly at 25 °C for pH 4, 7 and 9.
Transformation products:
not measured
No.:
#1
No.:
#2
No.:
#3
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.002 h-1
DT50:
299 h
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.003 h-1
DT50:
259 h
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0.003 h-1
DT50:
243 h
Type:
(pseudo-)first order (= half-life)
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered: the tier 2 tests at 50 and 60 °C showed abnormal hydrolysis behaviour and the hydrolysis was assessed directly at 25 °C

MAJOR TRANSFORMATION PRODUCTS
From structural information provided by the sponsor on the test item, the expected products of hydrolysis are cyclododecanol, formaldehyde and ethanol.

INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS: none

VOLATILIZATION (at end of study): not reported

PATHWAYS OF HYDROLYSIS: not reported

No qualitative or quantitative determination of hydrolysis products was done. Therefore it was not possible to prove that the dissipation of the substance is due to hydrolysis and not adsorption or volatility. The missing pH dependence of T1/2 indicates that hydrolysis might not be the relevant dissipation process.

Validity criteria fulfilled:
yes
Conclusions:
The substance was found to hydrolyse under environmental conditions with a half life of 259 h at 25 °C and pH 7 (pseudo-first order reaction kinetics).
Executive summary:

The hydrolysis of the substance (ethoxymethoxy)cyclododecane was tested under GLP in accordance with OECD TG 111. First, a preliminary test was undertaken, in which sample solutions were maintained at 50 °C ± 0.5 °C for a period of 24 hours. The results from this preliminary test showed that it was necessary to conduct a main test at pH 4, pH 7 and pH 9 with solutions being maintained at 50 and 60 °C. As the substance showed abnormal behaviour with faster hydrolysis at lower temperature, the hydrolysis was directly assessed at 25 °C. In the main test, sample solutions were taken from the tempered water baths at various time points, the pH of each solution was recorded and the concentration of the test substance was determined by gas chromatography. To this end, duplicate aliquots of each sample were extracted with hexane. The kinetics of the hydrolysis reaction has been determined to be consistent with that of a pseudo-first order reaction. The rate constant and half-life of hydrolysis at 25 °C was directly determined from the experimental data. The rate constants at 25 °C were 0.00232 hr-1 at pH 4, 0.00268 hr-1 at pH 7 and 0.00286 hr-1 at pH 9, which corresponds to half-lives of 299, 259 and 243 hours, respectively.

No qualitative or quantitative determination of hydrolysis products was done. Therefore it was not possible to prove that the dissipation of the substance is due to hydrolysis and not adsorption or volatility. The missing pH dependence of T1/2 indicates that hydrolysis might not be the relevant dissipation process.

Description of key information

The substance was found to dissipate under environmental conditions with a half life of 259 h at 25 °C and pH 7 (pseudo-first order reaction kinetics).

Key value for chemical safety assessment

Half-life for hydrolysis:
259 h
at the temperature of:
25 °C

Additional information

A hydrolysis study in accordance with OECD TG 111 was conducted. The results of a preliminary test indicated that further testing is required and the hydrolysis was studied in a main test at pH 4, pH 7 and pH 9 with sample solutions being maintained at 50 and 60 °C. As the substance showed abnormal behaviour with faster hydrolysis at lower temperature, the hydrolysis was directly assessed at 25 °C. It was found that the substance was hydrolysed under all test conditions and that the reaction followed pseudo-first order kinetics. The rate constants for the reaction at 25 °C were derived from the experimental data and were 0.00232 hr-1 at pH 4, 0.00268 hr-1 at pH 7 and 0.00299 hr-1 at pH 9. This corresponds to half-lives of 299, 259 and 243 hours, respectively.

No qualitative or quantitative determination of hydrolysis products was done. Therefore it was not possible to prove that the dissipation of the substance is due to hydrolysis and not adsorption or volatility. The missing pH dependence of T1/2 indicates that hydrolysis might not be the relevant dissipation process.