2-[[(butylamino)carbonyl]oxy]ethyl acrylate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Tier 1: 20 - 25 Apr 2015, Tier 2: 20 Jul - 24 Sep 2015

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)

Version / remarks:

13 Apr 2004

Deviations:

yes

Remarks:

(1) Tier 2 study: An 8 h temperature deviation (< 24 °C) occurred on the 2nd sampling day. (2) Tier 2 study: Hydrolysis was investigated at one temperature only (25 °C) instead of the minimum of three temperatures (per pH value) required by the guideline.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

30 May 2008

GLP compliance:

yes (incl. QA statement)

Remarks:

Federal Office for the Environment (FOEN), Bern, Switzerland

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: Tier 1: daily, during 5 d. Tier 2: 10 - 12 sampling time points over a period of 30 d.
- Sampling method: Sampling was performed in sterile conditions (Bunsen burner, hood). For sampling, the test vessels were removed from the thermostat cabinet and 5 mL were transferred with a sterile pipette tip into a test tube. Then, sterile filtered N2 was injected into the headspace and the test vessel was immediatley closed with the screw cap and placed back onto the stirring device in the thermostat cabinet.
- Sampling intervals/times for pH measurements: At every sampling. The pH (precision ± 0.1 unit) was measured in the test tube with the remaining sample volume (after removal of volume required for HPLC).
- Sampling intervals/times for sterility check: In the Tier 1 study no sterility test was conducted at the end of the incubation period. In the Tier 2 study sterility tests were conducted at the end of the test on the pooled replicate test vessels to confirm that the degradation of the test item did not occur through biological processes. The number of colony forming units per mL (CFU/mL) was determined in the pooled replicate test vessels according to European Pharmacopoeia. The sterility tests were performed by a third laboratory in accordance with ISO/IEC 17025.
- Sample storage conditions before analysis: Either immediate HPLC measurement (with max. half (2.5 mL) of the sampled volume) or storage in freezer. In the Tier 1 study samples wer not frozen before HPLC analysis. In the Tier 2 study part of the HPLC analyses were not conducted directly after sampling. Instead, the samples were frozen in order to measure several sampling time points at once, whenever possible. To ensure the stability of the test item in the freezer, a test was performed.

Buffers:

- pH: 4, 7, and 9
- Type and final molarity of buffer: (a) pH 4: mixture of 0.1 M potassium biphthalate and 0.1 N NaOH. (b) pH 7: mixture of 0.1 M monopotassium phosphate and 0.1 N NaOH. (c) pH 9: mixture of 0.1 M H3BO3 in 0.1 M KCl and 0.1 N NaOH.
- Composition of buffer: pH 4: 0.4 mL 0.1 N NaOH + 50 mL 0.1 M potassium biphtalate to 100 mL Milli-Q water. pH 7: 29.63 mL 0.1 N NaOH + 50 mL 0.1 M monopotassium phosphate to 100 mL MQ. pH 9: 21.30 mL 0.1 N NaOH + 50 mL 0.1 M H3BO3 to 100 mL MQ. Prepared according to Annex 3 of the guideline for a temperature of 20 °C.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 100 mL vessels with screw cap (Schott, Duran). The buffers were prepared in separate, larger glass vessels.
- Sterilisation method: Test solutions were filter-sterilized. The test and blank vessels (inlcuding a magnetic rod for stirring) were sterilized by autoclaving before use. Sampling was conducted under sterile conditions (Bunsen burner, hood) to ensure the sterility of the test vessels throughout the test.
- Lighting: None. The test vessels were placed in the thermostat cabinet in the dark.
- Measures to exclude oxygen: In the Tier 1 study the three freshly prepared buffers were sparged with N2 for about 5 min to minimize reaction of the test item with oxygen and then placed at 25 °C for at least 3 h to allow for temperature equilibration. In the Tier 2 study, the freshly prepared pH buffers were not sparged with nitrogen for 5 min. However, no influence on the initial test item concentrations were observed, which were about 50 mg/L as planned. After sampling sterilie filtered N2 was injected into the headspace before recapping the test vessels.
- If no traps were used, is the test system closed/open: Closed, with screw caps.

TEST MEDIUM
- Volume used/treatment: 50 mL
- Kind and purity of water: Milli-Q
- Preparation of test medium: The freshly prepared buffers were used to prepared test solutions of 50 mg/L test item. After stirring at least 10 min to ensure full dissolution of the test item in the thermostat cabinet at 25 °C, the pH was adjusted with a precision of ± 0.1 pH unit. The vessels were again taken out the the cabinet and were filter-sterilized under sterile conditions and then filled into the test and blank vessels.
- Renewal of test solution: No

OTHER TEST CONDITIONS
- Adjustment of pH: Yes, with a precision of ± 0.1 pH unit.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

50.6 mg/L

Remarks:

Tier 1 study

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

47.7 mg/L

Remarks:

Tier 1 study

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

48.2 mg/L

Remarks:

Tier 1 study

Duration:

30 d

pH:

4

Temp.:

25 °C

Initial conc. measured:

47.7 mg/L

Remarks:

Tier 2 study

Duration:

30 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

48.2 mg/L

Remarks:

Tier 2 study

Duration:

30 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

46.7 mg/L

Remarks:

Tier 2 study

Number of replicates:

2 test vessels (buffer + test item) and 1 blank vessel (buffer without test item) per pH value

Positive controls:

no

Negative controls:

no

Statistical methods:

The 95% confidence intervals (CI) of the hydrolysis rate constant were calculated using the "Regression" module of the "Data Analysis" Tool of Excel, Microsoft Office 10.

Transformation products:

no

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0.002 d-1

DT50:

313 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Hydrolysis rate constant: Lower CI: 0.00182 d^-1, Upper CI: 0.00262 d^-1

Remarks:

Half-Life: Lower CI: 265 d, Upper CI: 381 d

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.005 d-1

DT50:

132 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Hydrolysis rate constant: Lower CI: 0.00484 d^-1, Upper CI: 0.00567 d^-1

Remarks:

Half-Life: Lower CI: 122 d. Upper CI: 143 d

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.012 h-1

DT50:

55.7 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Hydrolysis Rate Constant: Lower CI: 0.0122 d^-1, Upper CI: 0.0127 d^-1

Remarks:

Half-Life: Lower CI: 55 d. Upper CI: 57 d.

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

The Tier 1 study indicated that the test substance is stable at pH 4 but hydrolyses at pH 7 (roughly estimated half-life of 6.6 d) and pH 9 (roughly estimated half-life < 1 d).

Description of key information

Half-life (pH 4): 313 d, 95% CI: 265 – 381 d (OECD 111, 25 °C, 30 d)

Half-life (pH 7): 132 d, 95% CI: 122 – 143 d (OECD 111, 25 °C, 30 d)

Half-life (pH 9): 55.7 h, 95% CI: 55 – 57 h (OECD 111, 25 °C, 30 d)

Key value for chemical safety assessment

Half-life for hydrolysis:

132 d

at the temperature of:

25 °C

Additional information

There is one GLP study available, in which the hydrolysis of the substance was investigated according to the OECD guideline 111.

Hydrolysis was investigated in a two-tiered approach at pH 4, 7, and 9 at 50 °C (tier 1) and 25 °C (tier 2). Hydrolysis was monitored for a maximum of 30 d or until 90% hydrolysis was observed. For the test, sterile test solutions containing the test item (50 mg/L, nominal) in three different buffers were prepared in closed test vessels, which were placed on a stirring device in a thermostat cabinet in the dark. Samples were taken at regular intervals and hydrolysis was monitored by HPLC analysis. Sterility was maintained throughout the test.

The Tier 1 study indicated that the test substance is stable at pH 4, but hydrolyses at pH 7 (roughly estimated half-life of 6.6 d) and 9 (roughly estimated half-life < 1 d). In the Tier 2 study, the test item concentration showed a constant decrease over time, which was very slow at pH 4, slightly faster at pH 7 and fastest at pH 9. Since all plots of the log-transformed concentration vs. time yielded a linear function, it was assumed that hydrolysis follows a pseudo-first order reaction and that the hydrolysis rate constant (Kobs) as well as half-life (t0.5) could be calculated in the standard way. The hydrolysis rate constant Kobs as well as the calculated half-life (including 95% confidence intervals) were 0.00222 d^-1 and 313 d (265 – 381 d) at pH 4 (25 °C), 0.0056 d^-1 and 132 d (122 – 143 d) at pH 7 and 0.0124 ^h-1 and 55.7 h (55 – 57 h) at pH 9.