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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015-09-30
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
The main structure of the read-across substance is the same of the CJ304, only the salt form is different. However, this difference does not influence the toxicity of the CJ304. CJ304 contains Li/Na salt form and the read-across substances contains only Na salt. This will not lead to difference on the toxicity results.
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Identification: FAT 41001/H TE
Physical State/Appearance: Dark blue Solid
Commercial Name: Reactive Blue 049
EC No: 276-481-8
CAS No: 72214-18-7
Batch: BOP 01-12 (Lot: BS-1106872)
Purity: 77.3 %
Expiry: 31 January 2017
Storage Conditions: Frozen in the dark
Radiolabelling:
no
Analytical monitoring:
yes
Remarks:
The concentration of the sample solution was determined by high performance liquid chromatography (HPLC).
Details on sampling:
Duplicate aliquots (A and B) of each sample solution were diluted by a factor of 10 using dimethyl sulfoxide (DMSO).
Buffers:
- Buffer solution pH 4 : Citric acid 0.006 mol dmE-3, Sodium chloride 0.004 mol dmE-3, Sodium hydroxide 0.007 mol dmE-3.
- Buffer solution pH 7 : Disodium hydrogen orthophosphate (anhydrous) 0.003 mol dmE-3, Potassium dihydrogen orthophosphate 0.002 mol dmE-3, Sodium chloride 0.002mol dmE-3.
- Buffer solution pH 9 : Disodium tetraborate 0.001 mol dmE-3, Sodium chloride 0.002 mol dmE-3.
Details on test conditions:

Performance of the Test
Preparation of the Test Solutions
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 5 g/L in the three buffer solutions.
The concentration of each solution did not exceed the lesser of 0.01 mol/L or half the water solubility.
The test solutions were split into individual vessels for each data point.
The solutions were shielded from light whilst maintained at the test temperature.

Preliminary Test
Sample solutions were prepared at a nominal concentration of 5 g/L at pH 4, 7 and 9 and maintained at 50.0 ± 0.5 °C for a period of 120 hours.

Tier 2
Results from the Preliminary test showed it was necessary to undertake further testing at pH 4, with solutions being maintained at 50.0 ± 0.5 °C, 60.0 ± 0.5 °C and 70.0 ± 0.5 °C for a period of 720, 408 and 360 hours respectively.
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
5 g/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
5 g/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
5 g/L
Duration:
720 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
5 g/L
Duration:
408 h
pH:
4
Temp.:
60 °C
Initial conc. measured:
5 g/L
Duration:
360 h
pH:
4
Temp.:
70 °C
Initial conc. measured:
5 g/L
Number of replicates:
two
Positive controls:
no
Negative controls:
no
Preliminary study:
The extent of hydrolysis after 120 hours indicated that further tests (Tier 2), conducted at 40 ± 0.5 °C, 50 ± 0.5 °C and 60 ± 0.5 °C, were required to estimate the rate constant and half-life at 25 °C.

Preliminary pH 7 Test at 50.0 ± 0.5 ºC
Less than 10% hydrolysis after 5 days at 50.0 ± 0.5 °C, equivalent to a half-life greater than 1 year at 25 °C.

Preliminary pH 9 Test at 50.0 ± 0.5 ºC
Less than 10% hydrolysis after 5 days at 50.0 ± 0.5 °C, equivalent to a half-life greater than 1 year at 25 °C.
Test performance:
No data
Transformation products:
not measured
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
> 0 - < 0 s-1
DT50:
> 110 - < 126 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Details on results:
pH 4 Test at 50.0 ± 0.5 ºC - Tier 2– Peak 1
Slope = -6.49E-04
kobs = 1.49E-03 hour-1
= 4.15E-07 second-1
t½ = 464 hours
= 19.3 days


pH 4 Test at 50.0 ± 0.5 ºC - Tier 2– Peak 2
Slope = -7.02E-04
kobs = 1.62E-03 hour-1
= 4.49E-07 second-1
t½ = 429 hours
= 17.9 days

pH 4 Test at 60.0 ± 0.5 ºC - Tier 2– Peak 1
Slope = -1.30E-03
kobs = 3.00E-03 hour-1
= 8.34E-07 second-1
t½ = 231 hours
= 9.62 days

pH 4 Test at 60.0 ± 0.5 ºC - Tier 2– Peak 2
Slope = -1.36E-03
kobs = 3.13E-03 hour-1
= 8.69E-07 second-1
t½ = 222 hours
= 9.23 days

pH 4 Test at 70.0 ± 0.5 ºC - Tier 2– Peak 1
Slope = -2.40E-03
kobs = 5.23E-03 hour-1
= 1.5E-06 second-1
t½ = 125 hours
= 5.22 days

pH 4 Test at 70.0 ± 0.5 ºC - Tier 2– Peak 2
Slope =-2.48E-03
kobs = 5.72E-03 hour-1
= 1.59E-06 second-1
t½ = 121 hours
= 5.05 days

pH 4 Arrhenius Data – Peak 1
From the graph of the data, the rate constant and half-life at 25 °C have been estimated to be as follows:

kobs = 2.29E-04 hour-1
= 6.36E-08 second-1
t½ = 3.03E+03 hours
= 126 days

pH 4 Arrhenius Data – Peak 2
From the graph of the data, the rate constant and half-life at 25 °C have been estimated to be as follows:

kobs = 2.63E-04 hour-1
= 7.31E-08 second-1
t½ = 2.63E+03 hours
= 110 days
Validity criteria fulfilled:
yes
Conclusions:
The rate constant and estimated half-life at 25 °C of the test item are:
At pH 4 the rate constant (peak 1) was 6.36E-08 s-1 at 25 °C
At pH 4 the rate constant (peak 2) was 7.31E-08 s-1 at 25 °C

The estimated half life at pH 4 at 25 °C (peak 1) was 126 days.
The estimated half life at pH 4 at 25 °C (peak 2) was 110 days.
The estimated half life at pH 7 at 25 °C was > 1 year.
The estimated half life at pH 9 at 25 °C was > 1 year.
Executive summary:

Assessment of hydrolytic stability was carried out using a procedure designed to be compatible with Method C7 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.

The test substance was evaluated at pH 4 for 120 h, 360 h, 480 h and 720 h. For pH 7 and 9 the duration was 120 h. All tests were carried out at 50 °C. The concentration used was 5 g/L.

Based on the findings of the study,

The rate constant and estimated half-life at 25 °C of the test item are:

At pH 4 the rate constant (peak 1) was 6.36 x 10-8 s-1 at 25 °C

At pH 4 the rate constant (peak 2) was 7.31 x 10-8 s-1 at 25 °C

The estimated half life at pH 4 at 25 °C (peak 1) was 126 days.

The estimated half life at pH 4 at 25 °C (peak 2) was 110 days.

The estimated half life at pH 7 at 25 °C was >1 year.

The estimated half life at pH 9 at 25 °C was >1 year.

Description of key information

A study was performed to measure the abiotic degradation of the test article according to OECD guideline 111 at 50 °C ± 0.1 °C at each of pH 4.0, pH 7.0, and pH 9.0.

The results of pH 7.0 and pH 9.0 showed no significant degradation of FAT 41'001/H. In conclusion, FAT 41001/H was considered to be hydrolytically stable at pH 7.0 and pH 9.0.

The results at pH 4.0 showed that FAT 41001/H is not stable at this pH range. Therefore, according to the guidelines advanced testing of FAT 41001/H was performed to determine the rate constant (K25) of the FAT 41001/H hydrolysis reaction at pH 4.0. As a result of all observations, it can be stated that the hydrolysis reaction of FAT 41001/H at pH 4.0 and 25 °C was estimated to be relative slow (t1/2 (25 °C) about 110 days)

Key value for chemical safety assessment

Half-life for hydrolysis:
110 d
at the temperature of:
25 °C

Additional information