2-hydroxy-3-(prop-2-enoyloxy)propyl 2-methyl-2-propylhexanoate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From October 14, 2016 to December 09, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

on the study plan but they were assessed, documented and signed by the study director

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

on the study plan but they were assessed, documented and signed by the study director

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch no.: JBGJ0045R
Purity: 100% (UVCB)
Appearance: clear yellowish liquid
Composition: 2-Propenoic acid, reaction products with glycidyl tert-decanoate

Analytical monitoring:

yes

Details on sampling:

No sample preparation was performed

Buffers:

Chemicals and reagents:
- Water: deionised water with total organic carbon < 1 ppm and conductivity below 0.1 µS/cm was used.
- Buffer Solutions
Composition was taken from the annex of the OECD method (buffer solutions 7 and 9) resp. Küster et al. (buffer solution 4). All chemicals used were of analytical grade. The pH was measured with a pH-meter with an uncertainty of 0.01 units and pH was adjusted to the nominal pH value ± 0.03 units.
- Buffer at pH 4
Acetic acid, 2 M, CH3COOH, p.A., concentration 2 mol/L
Sodium acetate solution, 1 M, CH3COONa, p.A., concentration 1 mol/L
Buffer-Solution, pH 4, used for tier 1: CH3COOH, 2 M (80.0 mL), CH3COONa, 1 M (40.0 mL), and water ad 1000 mL. The pH was adjusted to pH 4.02. Before performance of tier 1 the pH was confirmed with 4.03.
- Buffer at pH 7
Potassium dihydrogen phosphate KH2PO4, p.A.
Sodium hydroxide solution, 2 M, NaOH, p.A., 2 mol/L
Buffer-Solution, pH 7, used for tier 1 and tier 2: KH2PO4 (8.7085 g), water (250 mL), NaOH, 2 M (14.9 mL) and water ad 1000 mL. pH was adjusted to pH 6.97. Before performance of tier 1 this pH was confirmed. Before performance of tier 2 the pH was confirmed with 7.00.
- Buffer at pH 9
Boric acid, H3BO3, p.A.
Potassium chloride, KCl, p.A.
Buffer-Solution, pH 9, used for tier 1 and tier 2: H3BO3 (3.0930 g), KCl (3.7290 g), water (500 mL), NaOH, 2 M (10.75 mL) and water ad 1000 mL. The pH was adjusted to pH 8.99. Before performance of tier 1 this pH was confirmed with 9.00. Before performance of tier 2 this pH was confirmed with 9.03.
- Inert Gas: argon 4.6 was used.

Estimation method (if used):

-

Details on test conditions:

This study was performed in order to determine the hydrolysis behaviour of the test substance in dependence of the pH. This study consisted of a laboratory test method to assess abiotic hydrolytic transformations of chemicals in aquatic systems at pH values normally found in the environment (pH 4 - 9). Aqueous buffer solutions of different pH values (pH 4, 7 and 9) were treated with the test substance, sterilised by filtration and incubated in the dark under controlled laboratory conditions (at constant temperatures). After appropriate time intervals, buffer solutions were analysed for the test substance.
Performance of the study (details):
- Tier 1:
A test substance solution with a concentration of 50 mg/L was prepared by dilution from a stock solution 5000 mg/L. The stock solution was prepared by filling up 109.7 mg test substance to 21.94 mL with acetonitrile. After treatment with ultrasonic, the solution was diluted by filling up 1 mL of the stock solution to 100 mL with demineralised water in a flask. 10 mL test substance solution was mixed with 10 mL of each hydrolysis buffer solution, resulting in 25 mg/L test substance in hydrolysis buffer. These mixtures were drawn into syringes, and sterile filtrated into sterile HPLC vessels (filled nearly to the top). The pH values after mixing with the test substance were 4.03, 7.02 and 8.97, respectively. The pH values after mixing with demineralised water (resulting in blanks) were 4.03, 7.03 and 8.98, respectively.
The solutions were purged with sterilised argon to remove oxygen, closed tightly and incubated for 120h at 50 ± 0.5°C in an incubation chamber. Four vials were prepared for each pH, one for analysis at t = 0h and three for t = 120h.
- Tier 2:
A test substance solution with a concentration of 50 mg/L was prepared by dilution from a stock solution 5000 mg/L. The stock solution was prepared by filling up 102.8 mg test substance to 20.56 mL with acetonitrile. After treatment with ultrasonic, the solution was diluted by filling up 1 mL of the stock solution to 100 mL with demineralised water in a flask. 25 mL test substance solution was mixed with 25 mL of each hydrolysis buffer solution, resulting in 25 mg/L test substance in hydrolysis buffer. These mixtures were drawn into syringes, and sterile filtrated into sterile HPLC vessels (filled nearly to the top). The pH values after mixing with the test substance were 8.97 – 8.98 resp. 6.99 – 7.01. Preparation of the vessels and performance of the study was the same as in tier 1, except for the sampling times, which were adjusted to the results of previous sampling times. The test was performed until maximum 90% hydrolysis was reached, at the longest for 30 days.
Tier 2 (repetition at pH 9, storage at 50°C):
A test substance solution with a concentration of 50 mg/L was prepared by dilution from a stock solution 5000 mg/L. The stock solution was prepared by filling up 50.0 mg test substance to 10.0 mL with acetonitrile. After treatment with ultrasonic, the solution was diluted by filling up 1 mL of the stock solution to 100 mL with demineralised water in a flask. 25 mL test substance solution was mixed with 25 mL of hydrolysis buffer solution pH 9, resulting in 25 mg/L test substance in hydrolysis buffer.
- Further treatment of solutions:
Blanks (demineralised water mixed with hydrolysis buffer solutions) were prepared and incubated identi-cally.
 

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 1

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 1

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 1

Duration:

30 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 2

Duration:

30 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 2

Duration:

30 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 2

Duration:

30 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 2

Duration:

30 d

pH:

7

Temp.:

12 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 2

Duration:

30 d

pH:

9

Temp.:

12 °C

Initial conc. measured:

25 mg/L

Remarks:

Tier 2

Number of replicates:

Tier 1: 4 per pH
Tier 2: duplicate

Positive controls:

no

Negative controls:

no

Statistical methods:

- The concentration of the test substance in the solutions was determined using the following equation: Concentration [mg/L] = (Peak area - a) / b * correction factor * sensitivity correction
- Hydrolysis in % was calculated

Preliminary study:

Hydrolysis behaviour of the test substance was examined at three different pH values and three different temperatures. At pH = 4, no signs of hydrolysis were was observed in the preliminary study (Tier 1). Therefore, the test substance can be considered as hydrolytically stable at this pH value.

Transformation products:

not measured

Details on hydrolysis and appearance of transformation product(s):

-

% Recovery:

99

pH:

4

Temp.:

50 °C

Duration:

120 h

Remarks on result:

hydrolytically stable based on preliminary test

Remarks:

Tier 1

% Recovery:

73.4

pH:

7

Temp.:

50 °C

Duration:

120 h

Remarks on result:

other: significant hydrolysis

Remarks:

Tier 1

% Recovery:

< 10

pH:

9

Temp.:

50 °C

Duration:

120 h

Remarks on result:

other: significant hydrolysis

Remarks:

Tier 1

Key result

pH:

7

Temp.:

12 °C

Remarks on result:

not determinable

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

ca. 0 h-1

DT50:

ca. 3 374.1 h

Remarks on result:

other: half-life = 140.6 days (weak hydrolysis)

Key result

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0.003 h-1

DT50:

ca. 234.8 h

Remarks on result:

other: half-life=9.78 days (marked hydrolysis)

Key result

pH:

9

Temp.:

12 °C

Hydrolysis rate constant:

>= 0.002 h-1

DT50:

ca. 364.5 h

Remarks on result:

other: half-life= 15.18 days (marked hydrolysis)

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

ca. 0.01 h-1

DT50:

ca. 67.2 h

Remarks on result:

other: half-life= 2.8 days (marked hydrolysis)

Key result

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0.141 h-1

DT50:

ca. 4.9 h

Remarks on result:

other: half-life=0.2 days (marked hydrolysis)

Key result

Temp.:

20 °C

Hydrolysis rate constant:

0.005 h-1

DT50:

126.9 h

Type:

other: pseudo-first order pattern

Remarks on result:

other: at pH 7 and 9

Other kinetic parameters:

-

Details on results:

- Hydrolysis behaviour of the test substance was examined at three different pH values and three different temperatures. At pH = 4, no hydrolysis was observed in the preliminary study (Tier 1). Therefore, the test substance can be considered as hydrolytically stable at this pH value. For pH = 7 at 12 °C, no hydrolysis above 10% was noticed. At 25 °C only weak hydrolysis was observed at pH 7. At pH = 9, marked hydrolysis was observed with increasing hydrolysis rates at higher temperatures.
- All validity criteria regarding the analytical methods and determination of hydrolysis were met: repeatability of the values was very good, and coefficients of determination all lay ≥ 0.95 (rounded values). The measurements of the test at pH 7 and 12 °C couldn’t be evaluated because of the lack of evaluable data points during the test period. Temperature dependency of the hydrolysis constants fits very well the Arrhenius equation indicating that the reaction is indeed following a pseudo-first order pattern.

Results with reference substance:

-

Table 1. The measured concentrations and the decrease in Tier 1 (mean concentration in mg/L)

	pH 4	pH 7	pH 9
t = 0h	25.381	23.817	25.860
t = 120h	25.123	17.486	<LOQ
Recovery after 120h (%)	99.0	73.4	<10
Change over 120h (%)	-1.0	-26.6	>-90

Table 2. Kobs and Half-life values in Tier 2

Temperature (°C)	pH	Kobs (h-1) (pH)	Half-life (h)	Kobs (h-1) (total)	Half-life (h) (total)
12	7	not evaluable	not evaluable	0.001902	364.5
12	9	0.001902	364.5
25	7	0.000205	3371.4	0.010519	65.9
25	9	0.010314	67.2
50	7	0.002952	234.8	0.143938	4.8
50	9	0.140986	4.9

Kobs: hydrolysis as a function of temperature

- Using the experimentally determined k_obsfor each pH and temperature, temperature dependency was calculated, using the relation ln k vs. 1/T.

- With these parameters, k_obs(total) and half-life at 20°C were calculated, using the Arrhenius equation with:

 

K_obs= e^25.94*e^-10261/293+ e^30.24*e^-10392/293= 0.005464; correlating to t_1/2= 126.9 h

 

Validity criteria fulfilled:

yes

Conclusions:

Under the study conditions, the respective half-livesat at 12, 25 and 50°C were determined to be not evaluable, 3374 and 234.8 h at pH 7 and 364.5, 67.2 and 4.9 h at pH 9.

Executive summary:

A study was conducted to determine the hydrolysis as a function of pH of the test substance according to OECD Guideline 111 and EU Method C.7. Two experiments were performed. In Tier 1, a solution of the test substance in sterilised water was mixed with buffer solutions (pH values: 4, 7 and 9), sterilised by filtration with sterilised filters and treated with argon to remove oxygen. The resulting solutions were stored at 50°C for a period of five days. Samples were taken at the beginning and after five days. At pH = 4, the decrease of test substance concentration after 5 days was found to be 1%. The analysis of the samples at pH = 7 and pH = 9 showed however significant changes in the concentration of the test substance after five days (decrease: 26.6 and >90 %).The test substance was considered stable at pH 4 and 50°C. Therefore a second experiment had to be performed for pH 7 and pH 9. In Tier 2, a solution of the test substance in deionised water was mixed with buffer solutions (pH values: 7 and 9), sterilised by filtration with sterilised filters and treated with argon to remove oxygen. The resulting solutions were stored at 12, 25, and 50°C. Sampling was performed in suitable time intervals in order to monitor the hydrolysis behaviour of the test substance at the different temperatures and pH-values. Analysis of the samples was performed with HPLC/UV. For pH 7 at 12 °C, no hydrolysis above 10% was noticed. At 25 °C only weak hydrolysis was observed at pH 7. At pH = 9, marked hydrolysis was observed with increasing hydrolysis rates at higher temperatures. Using the Arrhenius equation, parameters were calculated for hydrolytical behaviour of the test substance at 20°C and were measured to beK_obs= 0.005464 and t_1/2= 126.9 h. The respective half-livesat at 12, 25 and 50°C were determined to be not evaluable, 3374 and 234.8 h at pH 7 and 364.5, 67.2 and 4.9 h at pH 9 (Brinkmann, 2017). Therefore, under the conditions of the study, the test substance is considered to undergo no or weak hydrolysis at relevant environmental conditions (i.e., at 12 or 25 °C and pH7), which indicates primary removal of the test substance from the environment will be via the biotic degradation pathway.

Description of key information

The test substance was found to undergo no or weak hydrolysis at relevant environmental conditions (i.e., at 12 or 25 °C and pH7), which indicates primary removal of the test substance from the environment will be via the biotic degradation pathway. Therefore, the half-life at pH 7 and 25 °C has been considered further for risk assessment.

Key value for chemical safety assessment

Half-life for hydrolysis:

3 374.1 h

at the temperature of:

25 °C

Additional information

A study was conducted to determine the hydrolysis as a function of pH of the test substance according to OECD Guideline 111 and EU Method C.7. Two experiments were performed. In Tier 1, a solution of the test substance in sterilised water was mixed with buffer solutions (pH values: 4, 7 and 9), sterilised by filtration with sterilised filters and treated with argon to remove oxygen. The resulting solutions were stored at 50°C for a period of five days. Samples were taken at the beginning and after five days. At pH = 4, the decrease of test substance concentration after 5 days was found to be 1%. The analysis of the samples at pH = 7 and pH = 9 showed however significant changes in the concentration of the test substance after five days (decrease: 26.6 and >90 %). The test substance was considered stable at pH 4 and 50°C. Therefore a second experiment had to be performed for pH 7 and pH 9. In Tier 2, a solution of the test substance in deionised water was mixed with buffer solutions (pH values: 7 and 9), sterilised by filtration with sterilised filters and treated with argon to remove oxygen. The resulting solutions were stored at 12, 25, and 50°C. Sampling was performed in suitable time intervals in order to monitor the hydrolysis behaviour of the test substance at the different temperatures and pH-values. Analysis of the samples was performed with HPLC/UV. For pH 7 at 12 °C, no hydrolysis above 10% was noticed. At 25 °C only weak hydrolysis was observed at pH 7. At pH = 9, marked hydrolysis was observed with increasing hydrolysis rates at higher temperatures. Using the Arrhenius equation, parameters were calculated for hydrolytical behaviour of the test substance at 20°C and were measured to be K_obs= 0.005464 and t_1/2= 126.9 h. The respective half-lives at at 12, 25 and 50°C were determined to be not evaluable, 3374 and 234.8 h at pH 7 and 364.5, 67.2 and 4.9 h at pH 9 (Brinkmann, 2017). Therefore, under the conditions of the study, the test substance is considered to undergo no or weak hydrolysis at relevant environmental conditions (i.e., at 12 or 25 °C and pH7), which indicates primary removal of the test substance from the environment will be via the biotic degradation pathway.