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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
16 November 2016 to 13 December 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
SAMPLING
- Duplicate sample solutions were taken initially and from the water bath at various time points.
- The pH of each solution was recorded.
Buffers:
TEST SYSTEM
- The test system consisted of buffer solutions at pH’s 4, 7 and 9 (see Table 1, below).
- The buffer solutions were passed through a 0.2 μm membrane filter to sterilise and subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen.
Details on test conditions:
PREPARATION OF TEST SOLUTIONS
- Stock solutions of test item were prepared at a nominal concentration of 1.0 x 10E03 mg/L in the three buffer solutions. At this concentration the pH 4 stock precipitated. It was therefore passed through a filter paper and the filtrate diluted by a factor of 2 with the pH 4 buffer solution. This produced a stock solution than was half saturation as required by the test guidelines.
- The stock solutions were split into individual glass vessels, sealed with minimal headspace, for each data point. These sample solutions were shielded from light whilst maintained at the test temperature.

PRELIMINARY TEST / TIER 1
- Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 120 hours.

EVALUATION OF DATA
- The response factors of the standard peak areas (unit peak area per mg/L) were calculated using the equation RFstd = Rstd / Cstd where RFstd = response factor of the standard solution; Rstd = peak area of the standard solution; Cstd = concentration of the standard solution (mg/L).
- Each sample solution concentration (mg/L) was calculated using the equation C = (Rspl / RFstd) * D where C = sample solution concentration (mg/L); Rspl = mean peak area of the sample solution; RFstd = mean response factor of the standard solutions (unit peak area per mg/L); D = dilution factor (0.05 for pH 4 samples only to account for injection volume).

DEGREE OF HYDROLYSIS
- The decrease in concentration as a percentage of initial concentration was calculated using the equation Percentage of initial = (Ct / C0) * 100 where Ct = concentration of the test solution at time t (g/L); C0 = concentration of the test solution at time 0 (g/L).
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
0.001 mg/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
0.001 mg/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
0.001 mg/L
Number of replicates:
Two
Positive controls:
no
Negative controls:
no
Transformation products:
no
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
other: < 10% hydrolysis after 5 days at 50 °C (equivalent to half-life > 1 yr at 25 °C)
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
other: < 10% hydrolysis after 5 days at 50 °C (equivalent to half-life > 1 yr at 25 °C)
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Remarks on result:
other: < 10% hydrolysis after 5 days at 50 °C (equivalent to half-life > 1 yr at 25 °C)
Details on results:
RESULTS
- Typical chromatography is presented in Appendix 1 (attached).
- The mean peak areas relating to the standard and sample solutions are shown in Table 2 (attached).
- Test item concentrations at given time points are shown Tables 3, 4 and 5 (attached).
- Result for pH 4 at 50 °C: Less than 10% hydrolysis after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25 °C.
- Result for pH 7 at 50 °C: Less than 10% hydrolysis after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25 °C.
- Results for pH 9 at 50 °C: Less than 10% hydrolysis after 5 days at 50 °C, equivalent to a half-life greater than 1 year at 25 °C.

VALIDATION

- The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 120 to 1.20 x 10E03 mg/L.

- The results were satisfactory with a correlation coefficient (r) of 0.999 being obtained.

Validity criteria fulfilled:
yes
Conclusions:
The estimated half-life at 25 °C of the test item was shown to be greater than 1 year at pH 4, 7 and 9.
Executive summary:

GUIDELINE

Assessment of hydrolytic stability was carried out using Method C.7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004.

 

METHODS

The test system consisted of buffer solutions at pH 4, 7 and 9. The buffer solutions were passed through a 0.2 μm membrane filter to sterilise and subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen. Duplicate sample solutions were taken initially and from the water bath at various time points. The pH of each solution recorded. The concentration of test item in the sample solutions was determined by high performance liquid chromatography (HPLC).

 

Stock solutions of test item were prepared at a nominal concentration of 1.0 x10E03 mg/L in the three buffer solutions. At this concentration the pH 4 stock precipitated. It was therefore passed through a filter paper and the filtrate diluted by a factor of 2 with the pH 4 buffer solution. This produced a stock solution than was half saturation as required by the test guidelines.

 

The stock solutions were split into individual glass vessels, sealed with minimal headspace, for each data point. These sample solutions were shielded from light whilst maintained at the test temperature.Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 120 hours.

 

RESULTS

The estimated half-life at 25 °C of the test item was shown to be greater than 1 year at pH 4, 7 and 9.

Description of key information

The estimated half-life at 25 °C of the research material was shown to be greater than 1 year at pH 4, 7 and 9 (OECD 111 and EU Method C.7).

Key value for chemical safety assessment

Additional information

GUIDELINE

Assessment of hydrolytic stability was carried out using Method C.7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004.

 

METHODS

The test system consisted of buffer solutions at pH 4, 7 and 9. The buffer solutions were passed through a 0.2 μm membrane filter to sterilise and subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen. Duplicate sample solutions were taken initially and from the water bath at various time points. The pH of each solution recorded. The concentration of test item in the sample solutions was determined by high performance liquid chromatography (HPLC).

 

Stock solutions of test item were prepared at a nominal concentration of 1.0 x10E03 mg/L in the three buffer solutions. At this concentration the pH 4 stock precipitated. It was therefore passed through a filter paper and the filtrate diluted by a factor of 2 with the pH 4 buffer solution. This produced a stock solution than was half saturation as required by the test guidelines.

 

The stock solutions were split into individual glass vessels, sealed with minimal headspace, for each data point. These sample solutions were shielded from light whilst maintained at the test temperature.Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 120 hours.

 

RESULTS

The estimated half-life at 25 °C of the test item was shown to be greater than 1 year at pH 4, 7 and 9.