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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2004
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Study conducted according to OECD 111. In compliance with GLP. No degradation products identified.
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Principles of method if other than guideline:
NA
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
NA
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
No data
Buffers:
No data
Estimation method (if used):
NA
Details on test conditions:
Test was conducted at 25 degrees celcius and at 3 different pH (4, 7 and 9)
Number of replicates:
no data
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
no data
Preliminary study:
The half life of OBSH at 25 degrees celcius was:
pH 4: 9.2 h
pH 7: 7.9 h
pH 9: 5.8 h
At 37 degrees celcius the half life > 5 days
Transformation products:
not specified
Details on hydrolysis and appearance of transformation product(s):
Hydrolysis products are not identified in this study.
pH:
4
Temp.:
20 °C
DT50:
23.1 h
pH:
7
Temp.:
20 °C
DT50:
17.2 h
pH:
9
Temp.:
20 °C
DT50:
13.9 h
pH:
4
Temp.:
25 °C
DT50:
9.2 h
pH:
7
Temp.:
25 °C
DT50:
7.9 h
pH:
9
Temp.:
25 °C
DT50:
5.8 h
pH:
4
Temp.:
30 °C
DT50:
3.76 h
pH:
7
Temp.:
30 °C
DT50:
3.72 h
pH:
9
Temp.:
30 °C
DT50:
2.46 h
Other kinetic parameters:
no data
Details on results:
The half life of OBSH at 25 degrees celcius was:
9.2 h at pH 4
7.9 h at pH 7
5.8 h at pH 9
However, hydrolysis products are not identified in this study.
Validity criteria fulfilled:
not specified
Conclusions:
The half life of OBSH at 25 degrees celcius was:
9.2 h at pH 4
7.9 h at pH 7
5.8 h at pH 9
These data suggest that OBSH is hydrolytically unstable over a range of environmentally relevant pH and temperature conditions.
Executive summary:

The stability of OBSH was tested applying the OECD Guideline no 111. Three different pH were tested (4,7 and 9) at one temperature (25 degrees celcius).

The half life of OBSH at 25 degrees celcius was:

9.2 h at pH 4

7.9 h at pH 7

5.8 h at pH 9

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
7 OCT 2020 to 7 JUNE 2021
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: Guideline for testing of chemcial, National Institute of Environmental Research (Notice No. 2020-28 (19, August 2020) - South Korea
Deviations:
no
Principles of method if other than guideline:
NA
GLP compliance:
yes
Specific details on test material used for the study:
- Chemicall name: 4,4´-Oxybis(benzenesulfonyl hydrazide) (OBSH)
- CAS No: 80-51-3
- Lot No: 202007001
- Facility code No: 2020/00054
- Received date: 09 September 2020
- Manufacture date: 02 July 2020
- Expiration date: 01 July 2021
- Received quantity: 180.68 g (incl. container weight)
- Molecular formular: C12H14N4O5S2
- Molecular weight: 358.39 g/mol
- Apperance: white fine powder
- Purity: 98.1%
- Solubility: DMSO, DMF
- Storage conditions: Room temperature, protect from light, no exposure to high temperatures
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Analysis of the test substance:
Tier 1: The concentration of the test substance for all samples was measured for 5 days at 24 hour intervals.
Tier 2: The concentration of the test substance for all samples was analyzed in time at a minimum of six points normally between 10 % and 90 % hydrolysis of
the test substance.
Tier 3: Identification of hydrolysis products was not performed.
Buffers:
Buffer solution:
The sterilized buffer solutions of different pH values (pH 4.00, 7.00 and 9.00)
were prepared from the annex (Buffer mixtures of Clark and Lubs) of the OECD test guideline. This buffer solutions were aerated to free from nitrogen for 5 minutes before preparation of the test solution. The pH of each buffer solution was checked with a calibrated pH meter before exposure to the test substance.
Estimation method (if used):
NA
Details on test conditions:
Test conditions
Temperature:
- Tier 1: nominal temperature : 50.0±0.5 ℃, actual temperature : 49.8~50.1 ℃
- Tier 2: nominal temperature : 25.0±0.5 ℃, 50.0±0.5 ℃, 70.0±0.5 ℃, actual temperature : 25.1~25.2 ℃, 50.1~50.2 ℃, 69.9~70.1 ℃.

The Tier 2 was performed in a dark and sterile condition in a series of procedures to prevent photolytic effect and biodegradation of the test substance.

Test methods
Tier 1
- Test concentration : 8.2×10-4 M (300.000 mg/L) for pH 4.00, 7.00, 9.00
- Replicate : Duplicate per test sample (pH 4.00, 7.00 and 9.00)
- Temperature : 50.0±0.5 ℃
- Test duration : 5 days
- Test solution : 250 mL per replicate

Tier 2
- Test concentration : 8.2×10-4 M (300.000 mg/L) for pH 4.00, 7.00, 9.00
- Replicate : Duplicate per test sample (pH 4.00, 7.00 and 9.00)
- Temperature : 25.0±0.5 ℃, 50.0±0.5 ℃, 70.0±0.5 ℃

Preparation of test solution:
- Tier 1 (Preliminary test): Considering the purity of the test substance (98.1 %) and solubility (1.69×10^-3 M, 604.7 mg/L, 1 % DMSO), the test solution of nominal concentration (8.2×10^-4 M, 300.000 mg/L) was prepared by dissolving the test substance in the buffer solutions (pH 4.00, 7.00 and 9.00) of 1,000 mL. Nominal concentration of the test substance was not exceed half of the solubility concentration. The test solution of nominal concentration was prepared on the day of exposure.

- Tier 2 (Hydrolysis of unstable substances): Considering the purity of test substance (98.1 %) and solubility (1.69×10^-3 M, 604.700 mg/L, 1 % DMSO), the test solution of nominal concentration (8.2×10^-4 M, 300.000 mg/L) was prepared by dissolving the test substance in the buffer solutions (pH 4.00, 7.00 and 9.00) of 2,000 mL. Nominal concentration of the test substance did not exceed half of the solubility concentration. The test solution of nominal concentration was prepared on the day of exposure.

- Tier 3 (Identification of hydrolysis products)
According to information provided by the sponsor, it is expected that Hydrazine monohydrate and 4,4’-oxybis(benzenesulfonic acid) are the main hydrolysis products. This is based on the molecular structure of 4,4’-Oxybis(benzenesulfonylhydrazide)(OBSH) and available hydrolysis data from previous testing. An analytical method for quantification of Hydrazine monohydrate was conducted in a pilot study using HPLC. However, validation of the analytical method of Hydrazine monohydrate was not possible, because the sensitivity was not good enough (LOD: 32.044 mg/L, LOQ: 97.104 mg/L). Therefore, analytical quantification of hydrazine monohydrate was technically not feasible. Based on molecular formula (H6H2O) and molecular weight (50.06 g/mol), the theoretical concentration of Hydrazine monohydrate is 4.1×10^-5 mg/L when 4,4’-Oxybis(benzenesulfonylhydrazide) (OBSH) is completely hydrolyzed at nominal concentration of 8.2×10^-4 M (300 mg/L) and converted to Hydrazine monohydrate. Since no analytical standard for 4,4’-oxybis(benzenesulfonic acid) can be purchased, it was not possible to analytically quantify the substance in this study. A Tier 3 test was not performed, because it was technically not feasible to analytically quantify the degradation products Hydrazine monohydrate and 4,4’-oxybis(benzenesulfonic acid).

For another analysis of hydrolysis product 4,4’-oxybis(benzenesulfonic acid) (non-GLP), the samples for each pH were collected in conical tubes (about 5 ml) at the end of the Tier 2 test and delivered to an external lab (please refer to the attached document for details). Since analytical standard for 4,4'-oxybis(benzenesulfonicacid) could not be purchased, the structure was predicted using both a liquid-chromatography mass spectrometer(LC-MS) (please refer to the attached document). 4,4'-oxybis(benzenesulfonicacid) was monitored using a positive and negative electrospray mode recording set at m/z 330.9 and 328.9 respectively, which are consistent with [M+H]+ and [M-H]- molecular ions.
Duration:
5 d
pH:
4
Temp.:
25 °C
Initial conc. measured:
ca. 300 mg/L
Remarks:
Nominal concentration: 8.2×10-4 M (300 mg/L); Also tested at 50 and 70 °C
Duration:
5 d
pH:
7
Temp.:
25 °C
Initial conc. measured:
ca. 300 mg/L
Remarks:
Nominal concentration: 8.2×10-4 M (300 mg/L); Also tested at 50 and 70 °C
Duration:
5 d
pH:
9
Temp.:
25 °C
Initial conc. measured:
ca. 300 mg/L
Remarks:
Nominal concentration: 8.2×10-4 M (300 mg/L); Also tested at 50 and 70 °C
Number of replicates:
duplicate per test sample (pH 4, 7 and 9)
Positive controls:
no
Negative controls:
no
Statistical methods:
no
Test performance:
An analytical method for quantification of Hydrazine monohydrate was conducted in a pilot study using HPLC. However, validation of the analytical method of Hydrazine monohydrate was not possible, because the sensitivity was not good enough (LOD: 32.044 mg/L, LOQ: 97.104 mg/L). Therefore, analytical quantification of hydrazine monohydrate was technically not feasible.


Since analytical standard for 4,4'-oxybis(benzenesulfonicacid) could not be purchased, the structure was predicted using both a liquid-chromatography mass spectrometer(LC-MS) (please refer to the attached document). As a result, no mass values(m/z) of the substance were detected, and no expected fragmentation values were detected. Therefore, the measurement results showed that structural interpretation linkage and interpretation were not possible and that the substance could not be quantified properly.
Transformation products:
not measured
Remarks:
technically not feasible
No.:
#1
No.:
#2
Details on hydrolysis and appearance of transformation product(s):
Hydrolysis products could not be analytically identified. However, theoretical concentration of the two hydrolysis products can be calculated (25°C) using the measured rate constants. Please refer to the Executive Summary.
Key result
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0.059 h-1
DT50:
ca. 11.7 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.079 h-1
DT50:
ca. 8.8 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
70 °C
Hydrolysis rate constant:
ca. 0.104 h-1
DT50:
ca. 6.7 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0.088 h-1
DT50:
ca. 7.9 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.1 h-1
DT50:
ca. 6.9 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
70 °C
Hydrolysis rate constant:
ca. 0.133 h-1
DT50:
ca. 5.2 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
ca. 0.118 h-1
DT50:
ca. 5.9 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
ca. 0.15 h-1
DT50:
ca. 4.6 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
70 °C
Hydrolysis rate constant:
ca. 0.273 h-1
DT50:
ca. 2.5 h
Type:
(pseudo-)first order (= half-life)
Other kinetic parameters:
NA
Details on results:
Results of Tier 1:

The half life of OBSH at 25 degrees celcius was:
pH 4: 11.7 h
pH 7: 7.9 h
pH 9: 5.9 h

The half life of OBSH at 50 degrees celcius was:
pH 4: 8.8 h
pH 7: 6.9 h
pH 9: 4.6 h

The half life of OBSH at 70 degrees celcius was:
pH 4: 6.7 h
pH 7: 5.2 h
pH 9: 2.5 h

Results of Tier 2:
During the test period, the actual temperature values in water bath for 25.0 (pH 4.00, 7.00 and 9.00), 50.0 (pH 4.00, 7.00 and 9.00) and 70.0 ℃ (pH 4.00, 7.00 and 9.00) were maintained constantly in range of 25.1~25.2 ℃, 50.1~50.2 ℃ and 69.9~70.1 ℃, respectively.The pH values of the test solution for pH 4.00 (25.0, 50.0 and 70.0 ℃), 7.00 (25.0, 50.0 and 70.0 ℃) and 9.00 (25.0, 50.0 and 70.0 ℃) were 4.02~4.09, 7.03~7.05 and 8.94~9.07, respectively.

The hydrolysis rate constant (kobs) and half-life (t0.5) for the exposure conditions (25, 50 and 70 ℃ for pH 4.00, 7.00 and 9.00) of the test substance were calculated by the concentration of the test substance according to the
exposure time (see table on key results above).
Results with reference substance:
NA

Specific identification of hydrolysis products was not possible. Based on the molecular structure of OBSH and available hydrolysis data from previous tests (see 5.1.2 – hydrolysis), it is expected that hydrazine and 4,4’-oxybis(benzenesulfonic acid) are the main hydrolysis products. It was not possible to analyse for 4,4’-oxybis(benzenesulfonic acid).

Evaluation of hydrazine was performed using Hydrazine monohydrate as standard. Hydrazine monohydrate was dissolved in the buffer solution (pH 4, 7, 9) and then analyzed. But the degradation occurred quite rapidly, and it seems that the peak of the target was overlapped with the buffer solution. Also, the detection limit was higher than the real concentration, so it was concluded that the analysis was impossible and technically unfeasible.

Specifically, Hydrazine monohydrate was analyzed by HPLC as a hydrolysis product of OBSH. As a result of the analysis of Hydrazine monohydrate, the sensitivity was not good when it was analyzed by HPLC, the LOD was 32.044 mg/L and the LOQ was 97.104 mg/L.

Overall, the following results was derived: 

- OBSH concentration: 8.2×10-4 M(300 mg/L)

- Hydrazine monohydrate molecular weight: 50.06 g/mol

- When OBSH is completely hydrolysed and converted to Hydrazine monohydrate, the concentration is 4.1×10-5 mg/L.

Validity criteria fulfilled:
not specified
Conclusions:
The stability of OBSH was tested applying the OECD Guideline no 111. Three different pH were tested (4, 7 and 9) at 3 temperatures (25 °C, 50°C and 70°C).

The hydrolysis half-life of OBSH at 25 °C was 11.7 hours (pH 4); 7.0 hours (pH 7) and 5.9 hours (pH 9).
The hydrolysis half-life of OBSH at 50 °C was 8.8 hours (pH 4); 6.9 hours (pH 7) and 4.6 hours (pH 9).
The hydrolysis half-life of OBSH at 70 °C was 6.7 hours (pH 4); 5.2 hours (pH 7) and 2.5 hours (pH 9).

The results from this key study is in agreement with the reported half-lives in the study reported in the OECD SIDS document (section 5.1.12 - Hydrolysis.03).

Based on the molecular structure of OBSH and available hydrolysis data from previous tests (section 5.1.2 – hydrolysis), it is expected that hydrazine and 4,4’-oxybis(benzenesulfonic acid) are the main hydrolysis products. This is in agreement with the assessments stated in the recent CLH report for harmonized classification of OBSH.

No standard form for 4,4’-oxybis(benzenesulfonic acid) can be purchased, so it was not possible to analyse for the substance.

Evaluation of hydrazine was performed using Hydrazine monohydrate as standard. Hydrazine monohydrate was dissolved in the buffer solutions (pH 4, 7, 9) and then analyzed using HPLC. A quite poor sensitivity was found for this substance with a LOD of 32.044 mg/L and a LOQ of 97.104 mg/L. The hydrazine is not expected to dissipate to a very high degree during the study (it will in natural surface waters), so would be expected that at detection but not a quantification of the hydrazine would be expected. Even so, there has been analytical problems for a proper identification of hydrazine in the samples after hydrolysis.

Executive summary:

Hydrolysis rates:


The stability of OBSH was tested applying the OECD Guideline no 111. Three different pH were tested (4, 7 and 9) at 3 temperatures (25 °C, 50°C and 70°C).


 


The hydrolysis half-life of OBSH at 25 °C was 11.7 hours (pH 4); 7.0 hours (pH 7) and 5.9 hours (pH 9).


The hydrolysis half-life of OBSH at 50 °C was 8.8 hours (pH 4); 6.9 hours (pH 7) and 4.6 hours (pH 9).


The hydrolysis half-life of OBSH at 70 °C was 6.7 hours (pH 4); 5.2 hours (pH 7) and 2.5 hours (pH 9).


 


The results from this key study is in agreement with the reported half-lives in the study reported in the OECD SIDS document (section 5.1.12 - entry Hydrolysis.03).


 


This enables the estimation of the coefficient for the rate constant expression of hydrolysis:


 


khydrolysis= kalkaline×[OH-]+kneutral+kacid×[H+]






























Temperature (°C(



*kH(hr-1(mol/l)-1



KOH(hr-1(mol/l)-1



kN(hr-1)



25



-282



3001.463



0.087



40



-212



5071.421



0.010



70



-284



14538.71



0.132



*the negative kH actual indicates that there is no acid catalyzed hydrolysis.


 


And dependency of temperature according to an Arrhenius equation:


 


khydrolysis= khydrolysis,0×exp(-A/T), T being the absolute temperature.


























pH



khydrolysis,0 (hr-1)



A (K)



4



1.3732



1255.6



7



0.6248



920.77



9



4.1035



1882.7



 


Hydrolysis products:


Based on the molecular structure of OBSH and available hydrolysis data from previous tests (section 5.1.2 – hydrolysis), it is expected that hydrazine and 4,4’-oxybis(benzenesulfonic acid) are the main hydrolysis products. This is in agreement with the assessments stated in the recent CLH report for harmonized classification of OBSH.


 


After the 5 days study at an initial concentration of OBSH of 300 mg/L, the below degree of degradation of OBSH and theoretical concentration of the two hydrolysis products can be calculated (25°C) using the measured rate constants:


 


































pH



-



4



7



9



OBSH



Mg/L



0.25



0.0080



0.00023



Hydrazine



Mg/L



83.7



83.8



83.8



4,4’-oxybis(benzenesulfonic acid)



Mg/L



276



277



277



 


No standard form for 4,4’-oxybis(benzenesulfonic acid) can be purchased, so it was not possible to analyse for the substance.


 


Evaluation of hydrazine was performed using Hydrazine monohydrate as standard. Hydrazine monohydrate was dissolved in the buffer solutions (pH 4, 7, 9) and then analyzed using HPLC. A quite poor sensitivity was found for this substance with a LOD of 32.044 mg/L and a LOQ of 97.104 mg/L. The hydrazine is not expected to dissipate to a very high degree during the study (it will in natural surface waters), so would be expected that at detection but not a quantification of the hydrazine would be expected. Even so, there has been analytical problems for a proper identification of hydrazine in the samples after hydrolysis.

Description of key information

The stability of OBSH was tested applying the OECD Guideline no 111. Three different pH were tested (4,7 and 9) at one temperature (25 degrees celcius). The half life of OBSH at 25 degrees celcius was:
11.7 h at pH 4
7.9 h at pH 7
5.9 h at pH 9

Key value for chemical safety assessment

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

Additional information

Data from a new study is available supporting the already available data on hydrolysis of OBSH.


Hydrolysis rates


The stability of OBSH was tested applying the OECD Guideline no 111. Three different pH were tested (4, 7 and 9) at 3 temperatures (25 °C, 50°C and 70°C).


The hydrolysis half-life of OBSH at 25 °C was 11.7 hours (pH 4); 7.0 hours (pH 7) and 5.9 hours (pH 9).


The hydrolysis half-life of OBSH at 50 °C was 8.8 hours (pH 4); 6.9 hours (pH 7) and 4.6 hours (pH 9).


The hydrolysis half-life of OBSH at 70 °C was 6.7 hours (pH 4); 5.2 hours (pH 7) and 2.5 hours (pH 9).


The results from the key study is in agreement with the reported half-lives in the study reported in the SIDS document (entry Hydrolysis.03).


This enables the estimation of the coefficient for the rate constant expression of hydrolysis.


khydrolysis= kalkaline×[OH-]+kneutral+kacid×[H+]






























Temperature (°C(



*kH(hr-1(mol/l)-1



KOH(hr-1(mol/l)-1



kN(hr-1)



25



-282



3001.463



0.087



40



-212



5071.421



0.010



70



-284



14538.71



0.132



*the negative kH actual indicates that there is no acid catalyzed hydrolysis.


And dependency of temperature according to an Arrhenius equation:


khydrolysis= khydrolysis,0×exp(-A/T), T being the absolute temperature.


























pH



khydrolysis,0 (hr-1)



A (K)



4



1.3732



1255.6



7



0.6248



920.77



9



4.1035



1882.7



 


Hydrolysis products


Based on the molecular structure of OBSH and available hydrolysis data from previous tests (see 5.1.2 – hydrolysis), it is expected that hydrazine and 4,4’-oxybis(benzenesulfonic acid) are the main hydrolysis products. This is in agreement with the assessments stated in the recent CLH report for harmonized classification of OBSH.


After the 5 days study at an initial concentration of OBSH of 300 mg/L, the below degree of degradation of OBSH and theoretical concentration of the two hydrolysis products can be calculated (25°C) using the measured rate constants:


 


































pH



-



4



7



9



OBSH



Mg/L



0.25



0.0080



0.00023



Hydrazine



Mg/L



83.7



83.8



83.8



4,4’-oxybis(benzenesulfonic acid)



Mg/L



276



277



277



 


No standard form for 4,4’-oxybis(benzenesulfonic acid) can be purchased, so it was not possible to analyse for the substance.


Evaluation of hydrazine was performed using Hydrazine monohydrate as standard. Hydrazine monohydrate was dissolved in the buffer solutions (pH 4, 7, 9) and then analyzed using HPLC. A quite poor sensitivity was found for this substance with a LOD of 32.044 mg/L and a LOQ of 97.104 mg/L. The hydrazine is not expected to dissipate to a very high degree during the study (it will in natural surface waters), so would be expected that at detection but not a quantification of the hydrazine would be expected. Even so, there has been analytical problems in a proper identification of hydrazine in the samples after hydrolysis.