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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
25 May - 31 Jul 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)
Version / remarks:
April 13, 2004
Deviations:
yes
Remarks:
For the performance of the hydrolysis main test (pH 4 at 40 °C), the temperature was not controlled within 0.5 °C (i.e. 0.6 °C) and slightly above the criteria. Impact on the result were unlikely.
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
March 04, 2016
Deviations:
yes
Remarks:
For the performance of the hydrolysis main test (pH 4 at 40 °C), the temperature was not controlled within 0.5 °C (i.e. 0.6 °C) and slightly above the criteria. Impact on the result were unlikely.
Qualifier:
according to
Guideline:
EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)
Version / remarks:
October 2008
Deviations:
yes
Remarks:
For the performance of the hydrolysis main test (pH 4 at 40 °C), the temperature was not controlled within 0.5 °C (i.e. 0.6 °C) and slightly above the criteria. Impact on the result were unlikely.
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Analysis was performed on subsamples of 10 µL. The samples were 100-fold diluted with 0.1% formic acid in ISO-medium. The samples were further diluted by a factor 10 or 50 with 0.1% formic acid in ISO-medium to obtain concentration levels within the calibrated range. The blank solutions were 100-fold diluted with 0.1% formic acid in ISO-medium and analyzed. The concentrations of the test item were determined immediately after preparation (t=0) and at several sampling points after t=0.
Buffers:
- pH: 4, 7, 9
- Type and final molarity of buffer: Acetate buffer 0.01 M and 0.1 M, Phosphate buffer 0.01 M and 0.1 M, Borate buffer 0.01 M and 0.1 M
- Composition of buffer:
Acetate buffer pH 4, 0.01 M Solution of 16.7% 0.01 M sodium acetate in water and 83.3% 0.01 M acetic acid in water. Buffer contained 0.0009% (w/v) sodium azide.
Phosphate buffer pH 7, 0.01 M Solution of 0.01 M potassium di-hydrogen-phosphate in water adjusted to pH 7 using 1N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
Borate buffer pH 9, 0.01 M Solution of 0.01 M boric acid in water and 0.01 M potassium chloride in water adjusted to pH 9 using 1N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
Acetate buffer pH 4, 0.1 M Solution of 16.7% 0.1 M sodium acetate in water and 83.3% 0.1 M acetic acid in water. Buffer contained 0.0009% (w/v) sodium azide.
Phosphate buffer pH 7, 0.1 M Solution of 0.1 M potassium di-hydrogen-phosphate in water adjusted to pH 7 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
Borate buffer pH 9, 0.1 M Solution of 0.1 M boric acid in water and 0.1 M potassium chloride in water adjusted to pH 9 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.
Estimation method (if used):
The Arrhenius equation was used to determine the rate constant and half-life time at 25 °C.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: sterile vessel
- Sterilisation method: Each test solution was filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany)
- Lighting: to avoid photolytic effects, the incubations were performed in the dark.
- Measures to exclude oxygen: to exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution
- If no traps were used, is the test system closed/open: closed

TEST MEDIUM
- Volume used/treatment: Test item solutions were prepared in the 0.1 M buffer solutions at a target concentration of 1000 mg/L. Analysis was performed on subsamples of 10 µL. The samples were 100-fold diluted with 0.1% Trifluoroacetic acid in water (Main test); Blank buffer solutions were treated similarly as the test samples and analyzed at t=0.
- Kind and purity of water: Tap water purified by a Milli-Q water purification system (Millipore, Bedford, MA, USA)
- Preparation of test medium: ISO-medium Adjusted ISO-medium, formulated using RO-water (tap-water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands) with the following composition: CaCl2.2H2O: 211.5 mg/L; MgSO4.7H2O: 88.8 mg/L; NaHCO3: 46.7 mg/L; KCl: 4.2 mg/L
- Identity and concentration of co-solvent: Sodium azide (Merck), all buffer contained 0.0009% (w/v) sodium azide.
Duration:
5 d
pH:
4
Temp.:
20 °C
Initial conc. measured:
65.9 mg/L
Duration:
5 d
pH:
4
Temp.:
40 °C
Initial conc. measured:
95.8 mg/L
Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
33.4 mg/L
Duration:
5 d
pH:
7
Temp.:
20 °C
Initial conc. measured:
69 mg/L
Duration:
5 d
pH:
7
Temp.:
40 °C
Initial conc. measured:
57.4 mg/L
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
21.9 mg/L
Duration:
5 d
pH:
9
Temp.:
20 °C
Initial conc. measured:
72.9 mg/L
Duration:
5 d
pH:
9
Temp.:
40 °C
Initial conc. measured:
14.8 mg/L
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
66 mg/L
Number of replicates:
duplicates
Positive controls:
no
Negative controls:
no
Statistical methods:
All logarithms of the relative concentrations were correlated with time using linear regression analysis.
Transformation products:
not measured
% Recovery:
>= 100
pH:
9
Temp.:
20 °C
Duration:
313.32 h
% Recovery:
>= 100
pH:
9
Temp.:
40 °C
Duration:
288.13 h
% Recovery:
>= 100
pH:
9
Temp.:
50 °C
Duration:
46.95 h
% Recovery:
> 99 - < 100
pH:
7
Temp.:
20 °C
Duration:
142.8 h
% Recovery:
>= 100
pH:
7
Temp.:
40 °C
Duration:
93.13 h
% Recovery:
>= 100
pH:
7
Temp.:
50 °C
Duration:
69.35 h
% Recovery:
>= 100
pH:
4
Temp.:
20 °C
Duration:
503.33 h
% Recovery:
>= 100
pH:
4
Temp.:
40 °C
Duration:
69.7 h
% Recovery:
>= 100
pH:
4
Temp.:
50 °C
Duration:
116.97 h
pH:
4
Temp.:
20 °C
DT50:
5.1 d
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
25 °C
DT50:
3.2 d
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
40 °C
DT50:
0.81 d
Type:
(pseudo-)first order (= half-life)
pH:
4
Temp.:
50 °C
DT50:
1 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
20 °C
DT50:
1.5 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
DT50:
1.3 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
40 °C
DT50:
0.93 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
50 °C
DT50:
0.58 d
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
20 °C
DT50:
3.5 d
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
25 °C
DT50:
3 d
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
40 °C
DT50:
2.1 d
Type:
(pseudo-)first order (= half-life)
pH:
9
Temp.:
50 °C
DT50:
0.57 d
Type:
(pseudo-)first order (= half-life)

Conclusion

The main test (Tier 2) was used for the determination of the rate of hydrolysis of the substance at pH values 4 -9. The test item hydrolysis at a temperature range of 20 to 50 °C at pH 4 in a range of 0.81 to 5.1 days, at pH 7 in a range of 0.58 to 1.5 days and at pH 9 in a range of 0.57 to 3.5 days. The hydrolytic half-life at 25 °C was estimated to be 3.2 days at pH4, 1.3 days at pH7 and 3.0 days at pH9.

Table 1: Main Test pH 4: Rate Constants (kobs) and Half-life Time(t½)

Temperature [°C]

kobs [hours-1]


20

5.69 x 10-3

5.1 days

25

9.08 x 10-3

3.2 days (Arrhenius equation was used to determine this value)

40

3.58 x 10-2

0.81 days

50

2.78 x 10-2

1.0 days

 

Table 2: Main Test pH 7: Rate Constants (kobs) and Half-life Time (t½)

Temperature [°C]

kobs [hours-1]


20

1.87 x 10-2

1.5 days

25

2.15 x 10 -2

1.3 days (Arrhenius equation was used to determine this value)

40

3.09 x 10-2

0.93 days

50

4.99 x 10-2

0.58 days

 

Table 3: Main Test pH 9: Rate Constants (kobs) and Half-life Time (t½)

Temperature [°C]

kobs [hours-1]


20

8.29 x 10-3

3.5 days

25

9.61 x 10-3

3.0 days (Arrhenius equation was used to determine this value)

40

1.37 x 10-2

2.1 days

50

5.09 x 10-2

0.57 days

Description of key information

DT50 at 25 °C at pH 4 = 3.2 days (OECD 111, EU C.7; OPPTS 835.2120, estimated based on Arrhenius equation)

DT50 at 25 °C at pH 7 = 1.3 days (OECD 111, EU C.7; OPPTS 835.2120, estimated based on Arrhenius equation)

DT50 at 25 °C at pH 9 = 3 days (OECD 111, EU C.7; OPPTS 835.2120, estimated based on Arrhenius equation)

Key value for chemical safety assessment

Additional information

One study is available investigating the hydrolysis of the test item as a function of pH according to OECD guideline 111 under GLP conditions (Ciric, 20018). The hydrolytic degradation was studied in sterile aqueous buffer solutions at pH 4, pH 7 and pH 9 in the dark with a nominal test concentration of 1000 mg/L at 20, 40 and 50.0 °C. The concentrations of the test item were determined immediately after preparation (t=0) and at several sampling points after t=0. Analysis was performed on subsamples of 10 µL. The samples were 100-fold diluted with 0.1% TFA in water to obtain concentration levels within the calibrated range. Blank buffer solutions were treated similarly as the test samples and analyzed at t=0. The pH of each of the test solutions (except for the blanks) was determined at least at the beginning and at the end of the test. The results show that the hydrolytic degradation of the test item under sterile conditions strongly depends on the temperature and the pH value. The test item hydrolysis at a temperature range of 20 to 50 °C at pH 4 in a range of 0.81 to 5.1 days, at pH 7 in a range of 0.58 to 1.5 days and at pH 9 in a range of 0.57 to 3.5 days. The hydrolytic half-life at 25°C was estimated to be 3.2 days at pH4, 1.3 days at pH7 and 3.0 days at pH9.