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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 2017-08-29 to 2018-
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:
yes
Remarks:
The pre-test (Tier 1) was perfoemd at 20 °C, insted of 50 °C.
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
yes
Remarks:
The pre-test (Tier 1) was perfoemd at 20 °C, insted of 50 °C.
Principles of method if other than guideline:
The performance of the test at 20 °C (instead of 50 °C) was regarded to provide more suitable information regarding the hydrolysis at conditions relevant for other studies conducted in aqueous media (e.g OECD 117, OECD 105). The pre-test (Tier 1) was performed only.
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Remarks:
GC/MSD
Details on sampling:
- Sampling intervals for the parent/transformation products: after 0, 6 and 118.5 hours in the test item vessels; after 0 and 118.5 hours in the blank vessels
Buffers:
- All buffers were filtered through 0.2 µm sterile PTFE filters.
- pH: 4
- Composition of buffer: 2M CH3COOH, CH3COONa, Demineralised water
- pH: 7
- Composition of buffer: KH2PO4, Demineralised water, 2M NaOH
- pH: 9
- Composition of buffer: H3BO3, KCl, Demineralised water, 2M NaOH
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 50 mL glass flasks
- Sterilisation method: All glassware and filters were sterilised and purged with argon before use.

TEST MEDIUM
- Volume used/treatment: 1000 mL
- Kind and purity of water: sterilised demineralised water

OTHER TEST CONDITIONS
- Temperature: 19.4 - 20.4 °C
Duration:
118.5 h
pH:
4
Temp.:
20 °C
Initial conc. measured:
0.75 g/L
Duration:
118.5 h
pH:
7
Temp.:
20 °C
Initial conc. measured:
0.75 g/L
Duration:
118.5 h
pH:
9
Temp.:
20 °C
Initial conc. measured:
0.75 g/L
Number of replicates:
3 blank replicates
3 replicates for each test item + buffer solution
Positive controls:
no
Negative controls:
yes
Preliminary study:
Only the pre-test (Tier 1) was perfomed. All results are based on this test.
Transformation products:
yes
No.:
#1
No.:
#2
% Recovery:
0
pH:
4
Temp.:
20 °C
Duration:
0 h
% Recovery:
0
pH:
7
Temp.:
20 °C
Duration:
0 h
% Recovery:
0
pH:
9
Temp.:
20 °C
Duration:
0 h
pH:
4
Temp.:
20 °C
DT50:
< 1 min
Key result
pH:
7
Temp.:
20 °C
DT50:
< 1 min
pH:
9
Temp.:
20 °C
DT50:
< 1 min

Calibration Data Ethanol

Table 1. Calibration parameters of linear calibration of Ethanol

Slope (b)

239.029

counts*min / mg/L

Intercept y-axis (a)

-1471.92

counts*min

Method variation coefficient

2.21

%

Correlation coefficient r

0.999630

-

Coefficientofdeterminationr2

0.999261

-

The concentration of ethanol was calculated using the following equation:

Conc. [mg/L] = (Area + a) / b

with:

a =Intercept y-axis

b = Slope

Recovery rate = 98.8 - 109.2 %

Calibration Data Ethyl Acetate

Table 2. Calibration parameters of quadratic calibration of Ethyl Acetate

c (quadratic term)

-4.1077

counts*min / (mg/L)2

b (linear term)

11857.3

counts*min / mg/L

a (constant)

-33420.4

counts*min

Method variation coefficient

2.92

%

Correlation coefficient r

0.999512

-

Coefficientofdeterminationr2

0.999024

-

The concentration of ethyl acetate was calculated using the following equation:

Concentration [mg/L] = -b/2c -√[(b/2c)^2-((a-peak area)/c)]

with:

c =quadratic term

b =linear term

a =constant

Recovery rate: 96 - 103.8 %

Recovery rate

Ethanol - 95 % in buffer pH 4 and 100 % in buffer pH 9

Ethyl Acetate - 102 % in buffer pH 4 and 98 % in buffer pH 9  

One replicate of each buffer solution (pH 4 and 9) was additionally filtrated via 0.45 µm PTFE filters and measured in duplicate via GC/MSD (headspace):

Ethanol - 95 % in buffer pH 4 and 90 % in buffer pH 9

Ethyl Acetate - 91 % in buffer pH 4 and 86 % in buffer pH 9  

The condition for recovery rate “100 ± 5 %” was fulfilled for both buffer solutions pH 4 and pH 9 for both reference items.

The recovery rate of ethanol after filtration lay outside the range of “100 ± 5 %” in pH 9 buffer solution only. The recovery rate of ethyl acetate lay outside the range of “100 ± 5 %” after filtration of both solutions pH 4 and pH 9 with the concentration of 400 mg/L.

Therefore, no filtration of the test solution was performed during the hydrolysis test.

LOQ/LOD

As no signals were observed in buffer solutions for ethanol (and thus calculation of LOD and LOQ from the areas in medium extracts was not possible), the lowest concentration of the calibration function (50 mg/L) was stated as limit of detection and quantification.

For the calculation of ethyl acetate in the test solutions the quadratic calibration function was used; therefore, the calculation of LOQ/LOD was also not possible. The lowest concentration of the calibration (50 mg/L) was stated as limit of detection and quantification, too.

Results

Following the equation of the hydrolysis of the test item in water, from 1 mole test item, 1 mole ethyl acetate and 2 mole ethanol are formed. Therefore, after complete hydrolysis of 750 mg/L test item, 423 mg/L ethanol and 407 mg/L ethyl acetate should be measured in the test solutions. Therefore, the measured values were compared with the theoretical concentration of ethanol and ethyl acetate after complete hydrolysis.

Table. 1 Results for Ethanol

Buffer solution

Time[h]

Replicate #

Area[counts*min]

Concentration[mg/L]

Mean Concentration [mg/L]

Recovery from

theoretical Conc. 423 mg/L [%]

pH 4

0 h

1

92125

391.6

366.6

87

2

80167

341.5

6 h

1

74858

319.3

310.9

74

2

70831

302.5

118.5

1

77022

328.4

331.7

78

2

78600

335.0

pH 7

0 h

1

84505

359.7

358.0

85

2

83701

356.3

6 h

1

83367

354.9

350.7

83

2

81357

346.5

118.5

1

81929

348.9

344.2

81

2

79654

339.4

pH 9

0 h

1

80798

344.2

361.6

85

2

89145

379.1

6 h

1

80969

344.9

331.8

78

2

74696

318.7

118.5

1

92481

393.1

403.9

95

2

97639

414.6

Table 2. Results for Ethyl Acetate

Buffer solution

Time[h]

Replicate #

Area[counts*min]

Concentration[mg/L]

Mean Concentration [mg/L]

Recovery from

theoretical Conc. 407 mg/L [%]

pH 4

0 h

1

3548104

401.2

380.2

93

2

3219726

359.3

6 h

1

3185843

355.1

356.0

87

2

3200151

356.9

118.5

1

2890056

355.6

365.4

90

2

3033656

375.2

pH 7

0 h

1

3522875

397.9

397.5

98

2

3516944

397.1

6 h

1

3341656

374.7

367.1

90

2

3221134

359.5

118.5

1

3234959

403.1

392.0

96

2

3075119

380.9

pH 9

0 h

1

3200758

357.0

368.0

90

2

3376434

379.1

6 h

1

3236141

361.4

353.7

87

2

3112943

346.0

118.5

1

2276938

274.5

282.7

69

2

2403078

290.8

The blank solutions were measured at 0 h and after 118.5 h. The measured values lay below the LOQ of ethanol and ethyl acetate: < 50 mg/L. 85 – 87 % Ethanol and 90 – 98 % ethyl acetate were measured at the beginning of the test relating to theoretical amounts in case of a complete hydrolysis of the test item. As a reason for the deviation of 13 – 15 % of ethanol from theoretical value could be a volatility of ethanol. The concentration of ethyl acetate in pH 9 buffer solution after 5 days was lower than at the beginning of the test as ethyl acetate is possible hydrolysed at pH 9 to ethanol and acetic acid. This is also the reason for higher ethanol value after 118.5 h in pH 9 buffer solution in comparison to the beginning of the test.

Therefore, the test item has completely hydrolysed after addition of the test item to water.

Validity criteria fulfilled:
yes
Conclusions:
In conclusion, the test item has completely hydrolysed after addition of the test item to water.
Executive summary:

A hydrolysis study with the test item was performed according to OECD 111 and Regulation (EC) No. 440/2008 Method C.7 under GLP. A 1.5 g/L solution of the test item in sterilised water was mixed with sterilised buffer solutions (pH values: 4, 7, and 9). The resulting solutions were stored at 19.9 ± 0.5 °C for a period of five days. Samples were taken at 0 h, 6 h and after 5 days.

Following the equation of the hydrolysis of the test item in water, from 1 mole test item, 1 mole ethyl acetate and 2 mole ethanol are formed. Therefore, after complete hydrolysis of 750 mg/L test item, 423 mg/L ethanol and 407 mg/L ethyl acetate should be measured in the test solutions.

During the hydrolysis test, 85 – 87 % ethanol and 90 – 98 % ethyl acetate were measured in all buffer solutions at the beginning of the test relating to theoretical amounts in case of a complete hydrolysis of the test item. As a reason for the deviation of 13 – 15 % of ethanol from theoretical value could be a volatility of ethanol. The concentration of ethyl acetate in pH 9 buffer solution after 5 days was lower than at the beginning of the test as ethyl acetate is possible hydrolysed at pH 9 to ethanol and acetic acid. This is also the reason for higher ethanol value after 118.5 h in pH 9 buffer solution in comparison to the beginning of the test. Therefore, the test item has completely hydrolysed after addition of the test item to water.

Description of key information

The test item was completely hydrolysed after addition of the test item to water. The half-life of the test item in water is <1 min at 20 °C.

Key value for chemical safety assessment

Additional information

A hydrolysis study with the test item was performed according to OECD 111 and Regulation (EC) No. 440/2008 Method C.7 under GLP. A 1.5 g/L solution of the test item in sterilised water was mixed with sterilised buffer solutions (pH values: 4, 7, and 9). The resulting solutions were stored at 19.9 ± 0.5 °C for a period of five days. Samples were taken at 0 h, 6 h and after 5 days.

Following the equation of the hydrolysis of the test item in water, from 1 mole test item, 1 mole ethyl acetate and 2 mole ethanol are formed. Therefore, after complete hydrolysis of 750 mg/L test item, 423 mg/L ethanol and 407 mg/L ethyl acetate should be measured in the test solutions.

During the hydrolysis test, 85 – 87 % ethanol and 90 – 98 % ethyl acetate were measured in all buffer solutions at the beginning of the test relating to theoretical amounts in case of a complete hydrolysis of the test item. As a reason for the deviation of 13 – 15 % of ethanol from theoretical value could be a volatility of ethanol. The concentration of ethyl acetate in pH 9 buffer solution after 5 days was lower than at the beginning of the test as ethyl acetate is possible hydrolysed at pH 9 to ethanol and acetic acid. This is also the reason for higher ethanol value after 118.5 h in pH 9 buffer solution in comparison to the beginning of the test. Therefore, the test item has completely hydrolysed after addition of the test item to water.