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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:
from 02 February 2017 to 14 March 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
2008
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
2004
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
PREPARATION OF THE SAMPLES
- Test item was spiked to the buffers at a target concentration of 5.4 mg/L.
- For each sampling time, duplicate vessels were filled under vacuum with 6 mL test solution (Tier 1) or completely filled with test solution (Tier 2).
- The vessels were placed in a temperature controlled environment (50°C).
- Blank buffers were treated similarly as the test samples.

SAMPLING DETAILS
- Samples for analysis were taken immediately after preparation (t=0).
- Samples for analysis (except for the blanks) were taken at t= 5 days (Tier 1) or at several sampling points after t=0 (Tier 2).
- Samples taken from solutions with a temperature > 20°C were cooled to room temperature using running tap water.

pH MEASUREMENTS
The pH of the test solutions (except for the blanks) was determined at each sampling time.

QC SAMPLES TIER 2 STUDY
QC samples were prepared at each pH to evaluate a possible matrix effect. An aliquot of 3 mL blank buffer at each relevant pH was spiked in duplicate with the test item at a target concentration of 0.1 or 10 mg/L.



Buffers:
- Buffer pH 4: 16.7% 0.1 M sodium acetate and 83.3% 0.1 M acetic acid in water.
- Buffer pH 7: 0.1 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 10 N sodium hydroxide.
- Buffer pH 9: 0.1 M boric acid and 0.1 M potassium chloride in water adjusted to pH 9 using 10 N sodium hydroxide.







Details on test conditions:
TEST SYSTEM
- Sterilisation method: Each buffer was filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman) and transferred into a sterile vessel. The blank and test solutions were prepared in sterile vessels.
- Measures to exclude oxygen: nitrogen gas was purged through the sterile buffers for 5 minutes.
- Measures taken to avoid photolytic effects: the test vessels were kept in the dark.

TEST MEDIUM
- Kind of water: tap water purified by a purification system (Milli-Q, Millipore)
- Identity and concentration of co-solvent: a spiking solution of 4 g/L in acetone was used. The spiking volume was < 1% of the sample volume. The test concentrations were not corrected for the spiking volume.
- Each buffer contained 0.0009% (w/v) sodium azide.





Duration:
144.32 h
pH:
4
Temp.:
50.1 °C
Initial conc. measured:
2.6 mg/L
Remarks:
mean of duplicate samples
Duration:
144.08 h
pH:
7
Temp.:
50.1 °C
Initial conc. measured:
3.1 mg/L
Remarks:
mean of duplicate samples
Duration:
118.33 h
pH:
9
Temp.:
50.1 °C
Initial conc. measured:
2.9 mg/L
Remarks:
mean of duplicate samples
Number of replicates:
Two
Positive controls:
no
Negative controls:
no
Preliminary study:
At pH 4, pH 7 and pH 9, a decrease in concentration of > 10% (i.e. 98%) was observed after 5 days at 50°C. The higher Tier test was required according to the guidelines. Recoveries in the range from 49% to 72% were obtained. Based on these results, evaporation of the substance was expected to occur. Tier 2 was therefore performed under minimized headspace.
Test performance:
RECOVERIES (TIER 2)
- Recovery is the concentration analysed at t=0 relative to the nominal concentration.
- The mean recovery at each pH was calculated from duplicate samples (see below).
- The concentrations analysed in the test samples were not corrected for recovery.

Despite the precautions (minimized headspace) taken to avoid evaporation of the test item, the mean recoveries were below the acceptable range of 90-110%. Since the study samples were calculated on relative to t=0 concentrations, the low recoveries had no influence on the results.

QC SAMPLES
The accuracies of the QC samples prepared at 0.1 and 10 mg/L (for each pH value) fell within the criterion range of 70 – 110%. The analytical method was therefore demonstrated to be adequate to support the hydrolysis study on the test item.
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
There was no decrease in concentration in time (see picture below). The degree of hydrolyis was < 10% after 5 days at pH 4, 7 and 9 and 50°C. This corresponds with a half-life time at 25°C of > 1 year; the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Formation and decline of each transformation product during test: not applicable
% Recovery:
48
pH:
4
Temp.:
50.1 °C
Duration:
0 h
Remarks on result:
other: Expected to be due to volatility
% Recovery:
56
pH:
7
Temp.:
50.1 °C
Duration:
0 h
Remarks on result:
other: Expected to be due to volatility
% Recovery:
53
pH:
9
Temp.:
50.1 °C
Duration:
0 h
Remarks on result:
other: Expected to be due to volatility
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
other: hydrolytically stable based on Tier 2 test
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
other: hydrolytically stable based on Tier 2 test
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
other: hydrolytically stable based on Tier 2 test
Details on results:
TEST CONDITIONS
- Tier 1 : pH: 4.0, 7.0 and 9.0; 50.0 ± 0.1°C
- Tier 2 : pH: 3.9 - 4.0, 7.0 - 7.1 and 9.0; 50.1 ± 0.2°C






Validity criteria fulfilled:
yes
Remarks:
Test is performed according to the guideline.
Conclusions:
The substance is hydrolytically stable at pH 4, 7 and 9 (half-life time at 25°C of > 1 year).
Executive summary:

A GLP-compliant hydrolysis study was performed according to OECD 111. In the preliminary Tier 1 study, a decrease in concentration of >10% (i.e. 98%) was observed after 5 days at 50°C at pH 4, 7 and 9, likely due to volatility. Therefore a Tier 2 study was performed. using minimum headspace in the test vessels. The test substance was stable in this test: < 10% hydrolysis after 5 days at 50°C was observed at pH 4, 7 and 9 in the Tier 2 test. This corresponds with a half-life time at 25°C of > 1 year and the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Description of key information

A GLP-compliant hydrolysis study was performed according to OECD 111. In the preliminary Tier 1 study, a decrease in concentration of >10% (i.e. 98%) was observed after 5 days at 50°C at pH 4, 7 and 9, likely due to volatility. Therefore a Tier 2 study was performed. using minimum headspace in the test vessels. The test substance was stable in this test: < 10% hydrolysis after 5 days at 50°C was observed at pH 4, 7 and 9 in the Tier 2 test. This corresponds with a half-life time at 25°C of > 1 year and the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information