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Environmental fate & pathways

Hydrolysis

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Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Start of experimental work : 26th March 2013. End of experimental work 31st May 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Meets the criteria as reliable without restriction according to Klimisch et al (1997).

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report date:
2013

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
lithium 3-((3,4-dicyanophenyl)thio)propane-1-sulfonate
EC Number:
700-787-7
Cas Number:
769953-18-6
Molecular formula:
C11H9N2O3S2Li
IUPAC Name:
lithium 3-((3,4-dicyanophenyl)thio)propane-1-sulfonate
Test material form:
solid: particulate/powder
Radiolabelling:
no

Study design

Details on sampling:
Preliminary Hydrolysis Test

For the initial HPLC analysis, the test solutions were left to reach room temperature and then 0.6 ml of each hydrolysis test was diluted to 10.0 ml with sample diluent.

For the 5 days hydrolysis analysis, one vial of each test was removed from the oven at 50 ºC +/- 0.5ºC after 5 days and allowed to cool to room temperature. 0.6 ml of each test was diluted to 10.0 ml with sample diluent.

Full Hydrolysis Test at pH 9

For the initial analysis at each temperature, each of the remaining aliquots was left to reach room temperature and then 0.6 ml of each hydrolysis test was diluted to 10.0 ml with sample diluent. A buffer blank solution was prepared at the same time by taking 0.6 ml of the pH 9 buffer solution and diluting to 10.0 ml with sample diluent.

For the other time points, one vial of each of the test solutions was removed from each oven at each time point. The test solutions were allowed to reach room temperature before diluting 0.6 ml of each test solution to a separate 10.0 ml volumetric flask and make up to volume with pH sample diluent. A blank solution was prepared at each time point as described above.

Buffers:
Preparation of Buffer Solutions

Three buffer solutions were prepared for preliminary test. The pH 9 buffer solution for the full hydrolysis study was prepared as for the pH 9 buffer in the preliminary test.

pH 4.0 Buffer Solution
164ml of 0.2M acetic acid solution was added to 36ml of 0.2M sodium acetate and diluted to 1 litre with ELGA Ultrapure water. The solution was degassed with helium.

pH 7.0 Buffer Solution
296ml of 0.1N sodium hydroxide solution was added to 500ml of 0.1M monopotassium phosphate solution and diluted to 1 litre with ELGA Ultrapure water. The solution was degassed with helium.

pH 9.0 Buffer Solution
213ml of 0.1N sodium hydroxide solution was added to 500ml of 0.1M boric acid in 0.1M potassium chloride and diluted to 1 litre with ELGA Ultrapure water. The solution was degassed with helium.

All buffers were autocalved at 121ºC for 15 min and then placed in a 50ºC oven to warm overnight before use.

Buffer blanks were also run to demonstrate specificity.
Details on test conditions:
TEST SYSTEM
- Sterilisation method: All glassware used during the analysis was autoclaved before use.

OTHER TEST CONDITIONS
- Adjustment of pH: The pH of each buffer solution was measured prior to use and no pH adjustment was required. The initial pH's of all test solutions were within 0.1 pH units of required pH, therefore no pH adjustment was necessary.
Duration of testopen allclose all
Duration:
5 d
pH:
4
Initial conc. measured:
2 321 mg/L
Duration:
5 d
pH:
4
Initial conc. measured:
2 178 mg/L
Duration:
5 d
pH:
7
Initial conc. measured:
2 230 mg/L
Duration:
5 d
pH:
7
Initial conc. measured:
2 416 mg/L
Duration:
5 d
pH:
9
Initial conc. measured:
2 224 mg/L
Duration:
5 d
pH:
9
Initial conc. measured:
2 316 mg/L
Number of replicates:
Two replicates per pH.
Positive controls:
no
Negative controls:
no

Results and discussion

Preliminary study:
The pH 4.0 and 7.0 hydrolysis tests showed that there was been less than 10% hydrolysis after 5 days at 50°C ±0.5°C versus the initial time point and therefore no futher testing was required.

The pH 9.0 hydrolysis test showed approximately 30% hydrolysis after 5 days at 50°C ±0.5°C versus the initial time point and further testing was required at pH9.0 as stipulated in the test method.

Transformation products:
yes
Identity of transformation productsopen allclose all
No.:
#1
Reference
Reference substance name:
Unnamed
IUPAC name:
3-((3,4-dicarbamoylphenyl)thio)propane-1-sulfonic acid
Molecular formula:
C11H14N2O5S2 [318.362 gr/mol]
Molecular weight:
ca. 318
SMILES notation:
C1=C(C=CC(=C1C(=O)N)C(=O)N)SCCC[S](=O)(=O)O
No.:
#2
Reference
Reference substance name:
Unnamed
IUPAC name:
2-carbamoyl-5-((3-sulfopropyl)thio)benzoic acid
Molecular formula:
C11H13NO6S2 [319.347 gr/mol]
Molecular weight:
ca. 319
SMILES notation:
C1=C(C=CC(=C1C(=O)N)C(=O)O)SCCC[S](=O)(=O)O
No.:
#3
Reference
Reference substance name:
Unnamed
IUPAC name:
2-carbamoyl-4-((3-sulfopropyl)thio)benzoic acid
Molecular weight:
ca. 319
SMILES notation:
C11H13NO6S2 [319.347 gr/mol]
Details on hydrolysis and appearance of transformation product(s):
See attached background material for hydrolysis products.
Total recovery of test substance (in %)open allclose all
% Recovery:
100.5
pH:
4
Temp.:
50 °C
Duration:
5 d
% Recovery:
100.7
pH:
4
Temp.:
50 °C
Duration:
5 d
% Recovery:
99.9
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
98.6
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
70
pH:
9
Temp.:
50 °C
Duration:
5 d
% Recovery:
69.6
pH:
9
Temp.:
50 °C
Duration:
5 d
Dissipation DT50 of parent compoundopen allclose all
pH:
9
Temp.:
40 °C
DT50:
41.1 d
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
DT50:
9.9 d
Type:
(pseudo-)first order (= half-life)

Any other information on results incl. tables

Results

 Preliminary Test - Individual Results of Hydrolysis Tests

     

Test

Concentration mg/L

 

Initial result mg/L

 

Result after 5 days mg/L

% Recovery after 5 days

 

% Loss

pH4-1

2368

2309

2321

100.5

None

pH4-2

2214

2163

2178

100.7

None

pH7-1

2210

2232

2230

99.9

0.1

pH7-2

2416

2451

2416

98.6

1.4

pH9-1

2222

2224

1556

70.0

30.0

pH9-2

2296

2316

1612

69.6

30.4

 

The buffer blanks gave no interferences at or around the retention time of the analyte peaks and specificity in buffer for hydrolysis testing was deemed acceptable.

 

The results of the initial HPLC analysis show that hydrolysis did not occur immediately. At pH 4.0 and 7.0 there has been less than 10% hydrolysis after 5 days at 50°C ± 0.5°C versus the initial time point. As stipulated in the test guideline no further testing is required at these pH's.

 

At pH 9.0 there was approximately 30% hydrolysis after 5 days at 50°C ± 0.5°C versus the initial time point and thus further hydrolysis testing is required as stated in the test guideline.

Full Hydrolysis Test Results at pH 9

 

For the hydrolysis at pH 9 at 20±0.5ºC, 40±0.5ºC and 50±0.5ºC, the plot of the log transformed data of the test solutions concentrations versus time is a straight line (r>0.99), therefore the reaction is pseudo-first order. See below for the first order rate constant, Kobs, for each temperature and the predicted first order rate constant at 25°C:

 

pH 9 Kobs at 20 ± 0.5°C not applicable as less than 10% hydrolysis

pH 9 Kobs at 40 ± 0.5°C = 0.01685 days-1 (1456 secs-1)

pH 9 Kobs at 50 ± 0.5°C = 0.0702 days-1 (6066 secs-1)

pH 9 Kobs at 25°C = 0.002 days-1

 

Test Item Half-life

pH 9 at 20.0°C±0.5°CTest

not applicable as less than 10% hydrolysis

pH 9 at 40.0°C±0.5°C Test

Half life, t0.5, is 41.1 days (987.1 hours)

pH 9 at 50.0°C±0.5°C Test

Half life, t0.5, is 9.9 days (236.9 hours)

 

Individual Results at pH 9 at 40.0 ºC±0.5ºC

All of the time points were included for the calculation of the rate constant, Kobs, see the table below:

 

40°C test-1

40°C test-2

Time (days)

C0(mg/l)

Ct(mg/l)

ln(C0/Ct)

Time (days)

C0(mg/l)

Ct(mg/l)

ln(C0/Ct)

0

2473

2473

0.0000

0

2529

2529

0.0000

3

2473

2372

0.0417

3

2529

2416

0.0457

7

2473

2189

0.1220

7

2529

2256

0.1142

10

2473

2110

0.1587

10

2529

2176

0.1503

14

2473

1950

0.2376

14

2529

1996

0.2367

18

2473

1849

0.2908

18

2529

1909

0.2812

24

2473

1628

0.4181

24

2529

1692

0.4019

30

2473

1487

0.5087

30

2529

1548

0.4909

 

 

 

Rates of formation of the major hydrolysis products

 

The hydrolysis rate constant of the major hydrolysis products could not be determined as the formation rates were not first order.


From the data acquired during the full hydrolysis at pH9, it was noted the formation of three major hydrolysis products (>10%) with retention times of 6.6, 7.1 and 13.6 minutes.

 

 Identification of Hydrolysis Products by Electrospray LCMS

 

The major hydrolysis products observed during full hydrolysis testing at pH 9.0 were identified by Negative Electrospray LCMS using a Waters ZQ with Waters Alliance 2695 LC with UV and negative ion detection. The peaks were assigned on the basis of their relative retention times. See the attached background material section for the suggested structures.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
At pH 4.0 and 7.0 the test item under goes less than 10% hydrolysis after 5 days at 50°C ±0.5°C. In the preliminary test, at pH 9.0 the test item showed approximately 30% hydrolysis after 5 days at 50°C ±0.5°C versus the initial time point. In the higher tier tests hydrolysis was found to be pseudo first- order. Three major hydrolysis products were identified.
Executive summary:

Introduction

Hydrolysis as a function of pH was determined for the test item using a method designed to be compliant with OECD text Method 111 Hydrolysis as a function of pH)

Method

Hydrolysis was measured at pH 4.0, pH 7.0 and pH 9.0 using a preliminary test.  The pH 9.0 preliminary hydrolysis tests showed approximately 30% hydrolysis after 5 days at 50°C ±0.5°C and as stipulated in the test guideline higher tier hydrolysis testing of the test item at pH 9 was undertaken to determine if hydrolysis followed first-order kinetic behaviour. Major hydrolysis products at pH9 were also identified using electrospray LCMS.

 Results and Conclusion

At pH 4.0 and 7.0 the test item under goes less than 10% hydrolysis after 5 days at 50°C ±0.5°C. In the preliminary test, at pH 9.0 the test item showed approximately 30% hydrolysis after 5 days at 50°C ±0.5°C versus the initial time point. In the higher tier tests hydrolysis was found to be pseudo first- order. Three major hydrolysis products were identified from electrospray LCMS.

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