Registration Dossier

Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02 December 2010–27 June 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2011
Report date:
2011

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
Bis(2-ethylhexyl) fumarate
EC Number:
205-448-2
EC Name:
Bis(2-ethylhexyl) fumarate
Cas Number:
141-02-6
Molecular formula:
C20H36O4
IUPAC Name:
1,4-bis(2-ethylhexyl) (2E)-but-2-enedioate
Details on test material:
Name: "Dioctylfumarate"
Chemical names: Fumaric acid bis-(2-ethylhexyl) ester
Hill formula: C20H36O4
CAS No.: 141-02-6
Batch No.: LEDF1B5012
Appearance: Colourless liquid
Purity: See the Certificate of Analysis in Appendix 1
Conditions of storage: Room temperature
Expiry date: September 2011
Radiolabelling:
no

Study design

Details on sampling:
In the preliminary test, solutions of < 50 % saturation respectively <0.01 mol/L of the test substance in buffers with pH values of 4, 7 and 9 (precision ± 0.1) were kept at 50 ± 0.5 °C and the concentration of dioctylfumarate was determined after various times up to a maximum of 5 days. If less than 10 % of hydrolysis is observed after 5 days (half-life at 25 °C is greater than one year), the test substance is considered hydrolytically stable and no additional testing is required.
The water solubility of the test substance is 1.2 mg/L (see separate Seibersdorf Labor GmbH report on the water solubility of "Dioctylfumarate").
pH 4, pH7 and pH 9
A stock solution was prepared by weighing 10.2 mg of the test substance in 100 mL methanol (Sigma-Aldrich, Lot. No. SZBA071S). Volumes of the stock solution between 0.65 mL and 0.80 mL were filled up to 250 mL with appropriate sterile buffer solutions (see Appendix 3) and methanol (total content methanol 0.75 %). The recovery of each pH was determined immediately using HPLC. Afterwards the solutions were divided into 10 amber
screw cap vials (total 30 vials a 10 mL) and nitrogen was bubbled through the solutions to exclude oxygen. The concentration of the resulting solutions were lower than 50 % saturation respectively < 0.01 mol/L.
The vials were kept in a water bath (DL 30 V26 1, Haake, Germany) at the test temperature in the dark. The temperature (calibrated glass/mercury thermometer No. 249) was recorded during the test. The pH values of the solutions were determined with a pH-meter (ino Lab pH Level 2; WTW).
Due to the results of the preliminary tests, see chapter 7, a main test was performed at pH 9 and no main tests were performed at pH 4 and pH 7 in agreement with the guidelines.
In the main test, solutions of < 50 % saturation (< 0.01 mol/L) of the test substance in buffers were kept at 24 °C and 70 °C at pH 9. The concentrations of dioctylfumarate were determined at different times (a minimum of six spaced data points normally between 10 % and 90 % hydrolysis of the test substance).
The tests were performed in duplicate (contained in separate reaction vessels) for both temperatures at pH 9.
Temperatures (calibrated glass/mercury thermometer No. 249) and pH (pH-meter InoLab pH Level 2, WTW, Germany) were recorded at each analysis.
Sterility confirmation tests were conducted at the end of the higher Tier test.
Test pH 9 at 24 °C
A stock solution was prepared by weighing 15.0 mg of the test substance in 100 mL methanol (Sigma-Aldrich, Lot. No. SZBA071S). 1.5 mL of the stock solution was filled up to 500 mL with buffer pH 9 (see Appendix 3) and methanol (total content methanol 0.75 %).
The concentration of the resulting solutions was lower than 50 % saturation respectively <0.01 mol/L. Afterwards the solution was divided into 2 × 15 amber screw cap vials (total 30 vials a 10 mL) and nitrogen was bubbled through the solutions to exclude oxygen. The recovery of two samples was determined immediately using HPLC. The vials were kept in a peltier-cooled incubator (IPP200, Memmert, Germany) at the test temperature in the dark.
The bio burden of one sample were checked at the end of the test using a test kit (Envirocheck Contact TVC, Merck, Lot. No. 1355188).
Test pH 9 at 70 °C
A stock solution was prepared by weighing 15.1 mg of the test substance in 100 mL methanol (Sigma-Aldrich, Lot. No. SZBA071S). 1.5 mL of the stock solution was filled up to 500 mL with buffer pH 9 (see Appendix 3) and methanol (total content methanol 0.75 %). The concentration of the resulting solutions was lower than 50 % saturation respectively <0.01 mol/L. The recovery was determined immediately using HPLC. Afterwards the solution
was divided into 2 × 15 amber screw cap vials (total 30 vials a 10 mL) and nitrogen was bubbled through the solutions to exclude oxygen. The vials were kept in a water bath (DL 30 V26 1, Haake, Germany) at the test temperature in the dark.
The bio burden of one sample were checked at the end of the test using a test kit (Envirocheck Contact TVC, Merck, Lot. No. 1355188).
The hydrolysis products of "Dioctylfumarate" at basic pH-values are 2-ethyl-1-hexanol (CAS 104-76-7), fumaric acid (CAS 110-17-8) and 2-ethylhexylfumarate (intermediate stage), according to the sponsor.

Results and discussion

Preliminary study:
Less than 10 % of the test substance at pH 4 and pH 7 hydrolysed within 5 days at 50 °C. According to the guideline it is estimated that the half-life of dioctylfumarate in aqueous solution at 25 °C is greater than one year for pH 4 and pH 7.
Dioctylfumarate is stable to hydrolysis at pH 4 and pH 7 and no main tests were performed.
At pH 9 more than 10 % of the test substance hydrolysed within 5 days at 50 °C. The half-life time at 25 °C is assumed to be lower than 1 year. Therefore, according to the guideline, a main test at pH 9 was performed.
Transformation products:
not measured
Dissipation DT50 of parent compound
Key result
pH:
9
Temp.:
25 °C
DT50:
240 h
Type:
(pseudo-)first order (= half-life)
Details on results:
Dioctylfumarate hydrolysed at pH 9 with a half life time of 240 hours at 25 °C. The kinetic of the hydrolysis of dioctylfumarate was of first order at pH 9.
The rate constant of the hydrolysis of dioctylfumarate was determined at:
- pH4: Preliminary test at 50 °C,
- pH7: Preliminary test at 50 °C,
- pH9: Preliminary test at 50 °C and main test at 24 °C and at 70 °C.
Less than 10 % of the test substance at pH 4 and pH 7 hydrolysed within 5 days at 50 °C. According to the guideline it is estimated that the half-life of dioctylfumarate in aqueous solution at 25 °C is greater than one year for pH 4 and pH 7.
Dioctylfumarate is stable to hydrolysis at pH 4 and pH 7 and hydrolysed at pH 9 with a half life time of 240 hours at 25 °C. The kinetic of the hydrolysis of dioctylfumarate was of first order at pH 9.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
Less than 10 % of the test substance at pH 4 and pH 7 hydrolysed within 5 days at 50 °C. According to the guideline it is estimated that the half-life of "Dioctylfumarate" in aqueous solution at 25 °C is greater than one year for pH 4 and pH 7.
"Dioctylfumarate" is stable to hydrolysis at pH 4 and pH 7 and hydrolysed at pH 9 with a half life time of 240 hours at 25 °C. The kinetic of the hydrolysis of dioctylfumarate was of first order at pH 9.
Executive summary:

Aim of the study

The objective of the study was to determine the rate of hydrolysis of dioctylfumarate as a function of pH for evaluating its abiotic degradation behaviour according to EU chemical notification requirements.

Methods

The applied methods are in accordance with the methods described in:

  • Regulation (EC) No 440/2008, method C.7
  • OECD Guideline for the testing of chemicals guideline 111, adopted on 13 April 2004.

The rate constant of the hydrolysis of "Dioctylfumarate" was determined at:

  • pH 4: Preliminary test at 50 °C,
  • pH 7: Preliminary test at 50 °C,
  • pH 9: Preliminary test at 50 °C and main test at 24 °C and at 70 °C.

Results and discussion

The following hydrolytic properties of dioctylfumarate were obtained:

* estimated according to the guideline.

** Recoveries should range from 90 % to 110 %.

Less than 10 % of the test substance at pH 4 and pH 7 hydrolysed within 5 days at 50 °C. According to the guideline it is estimated that the half-life of dioctylfumarate in aqueous solution at 25 °C is greater than one year for pH 4 and pH 7.

Dioctylfumarate is stable to hydrolysis at pH 4 and pH 7 and hydrolysed at pH 9 with a half life time of 240 hours at 25 °C. The kinetics of the hydrolysis of dioctylfumarate was of first order at pH 9.

  • pH 4: Preliminary test at 50 °C
  • pH 7: Preliminary test at 50 °C
  • pH 9: Preliminary test at 50 °C and main test at 24 °C and at 70 °C.