Benzenepropanal, 2-methyl-4-(2-methylpropyl)-

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

May 27, 2015 to December 09, 2015

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name (as stated in the report): GR-88-0778
Lot No: Batch 6
Aspect: Colourless liquid
Expiration date: March 29, 2017

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

1) Preliminary test at 50°C (Tier 1)
Solutions of GR-88-0778 in the different buffer solutions were prepared as described above. For each pH, a minimum of 24 amber glass crimp cap vials (20 ml) were filled with 10 ml of the respective solution, sealed with Teflon coated rubber septa crimp cap, and placed in the water bath at 50°C. After temperature equilibration, a first pair of vials was extracted for each pH.
This is time zero of the experiment. At given times, namely after 6h and 120 h, other two vials per buffer solution were sacrificed for analysis.

2) Main test (Tier 2)
The main test at pH 9 the main test was performed at 40.0°C, 50.0°C and 60.0°C. The test was conducted in conditions similar to the conditions described for the preliminary test. The test temperatures and sampling times were chosen and adapted in function of the observed hydrolysis rate.
pH9 at 40°C - Sampling times - 0 hrs, 6, 24, 48, 72, 144, 150 and 336 hours;
pH9 at 50°C - Sampling times - 0 hrs, 6, 120, 126, 144, 150, 168, 174, 240, 246, 264, 270, 288 and 294 hours;
pH9 at 60°C - Sampling times - 0 hrs, 6, 24, 48, 72, 144, 150 and 336 hours.

Buffers:

pH 4: Ready-made concentrate (Titrisol®, MERCK, Darmstadt, Germany, art. No. 9884, citrate / hydrochloric acid buffer) pH 4.00 ± 0.02 at 20°C,
pH 7: Ready-made concentrate (Titrisol®, MERCK, Darmstadt, Germany, art. No. 9887, phosphate buffer) pH 7.00 ± 0.02 at 20°C,
pH 9: Ready-made concentrate (Titrisol®, MERCK, Darmstadt, Germany, art. No. 9889,
boric acid / potassium chloride / sodium hydroxide buffer) pH 9.00 ± 0.02 at 20°C,

In order to avoid any unnecessary excess of inorganic salts that could reduce the solubility of the test substance, these buffer solutions were diluted to 10% with ultrapure water before being used as test media.

Estimation method (if used):

A GC analysis method using MTBE, containing dodecane as an internal standard, as solvent for liquid-liquid extraction was used for specific analysis of GR-88-0778. Extraction from aqueous samples with MTBE containing the internal standard (dodecane) was performed as follows:
- un-cap the vial containing 10 ml of aqueous phase
- add 10 ml of MTBE containing the internal standard (dodecane) to the vessel
- re-cap the vial with a crimp cap
- shake vigorously by hand during 30 seconds
- allow a few minutes for proper decantation
- check that both phases are clear
- sample 2 ml of the upper (organic) phase into a GC-vial
- analyze the organic phase by GC-FID

Number of replicates:

Duplicate samples analysed at each sampling point.

Positive controls:

no

Negative controls:

no

Preliminary study:

The criterion given in the guidelines for the preliminary test is:

If less than 10 % degradation after 120 h (equivalent to a half-life time higher than 1 year at 25°C) is observed, no further testing is necessary.

This criterion is fulfilled for pH 4 and pH 7: <10% degradation was observed at 50°C over a 120 h period (0 h to 120 h).

For pH 9 concentrations higher than at t = 0 h were observed, at t = 6 h, at t = 120 h and at t = 126 h. The results could not be exploited.

For this reason the test was continued in the conditions of the main test for pH 9.

Transformation products:

not measured

% Recovery:

95.2

pH:

4

Temp.:

50 °C

Duration:

120 h

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

93.4

pH:

7

Temp.:

50 °C

Duration:

120 h

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

62.9

pH:

9

Temp.:

40 °C

Duration:

336 h

% Recovery:

27

pH:

9

Temp.:

50 °C

Duration:

294 h

% Recovery:

34.3

pH:

9

Temp.:

60 °C

Duration:

336 h

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

131.7 d

Validity criteria fulfilled:

yes

Conclusions:

An abiotic degradation study (hydrolysis as a function of pH) was carried out with GR-88-0778 according to OECD guideline n° 111.

Only the preliminary test needed to be performed at pH 4 and pH 7 since, at 50°C, less than 10% hydrolysis occurred after 120 h. A hydrolysis of less than 10% after 120 h, or more, at 50°C corresponds to a half-life time of more than one year at 25°C.

For pH 9 a main test was conducted at 40°C, 50°C and 60°C.
Temperature correlation is weak, with the test substance concentration decreasing faster at 50°C than at 60°C. From this observation, and from the fact that the test substance does not contain hydrolysable groups, it was concluded that processes other than hydrolysis contribute to, or are sole pathways of dissipation of the test substance.

If, despite this conclusion, all dissipation at pH 9 is assumed to be due to hydrolysis, a half-life time of 3161 h (= 131.7 d) at 25°C can be calculated.

Executive summary:

Half-Life of GR-88 -0778 / NYMPHEAL in an OECD 111 Hydrolysis as a Function of pH study at 25°C :

pH4 > 1 -year

pH7 > 1 -year

pH9 = 131.7 days

Description of key information

An abiotic degradation study (hydrolysis as a function of pH) was carried out with GR-88-0778 according to OECD guideline n° 111.

Only the preliminary test needed to be performed at pH 4 and pH 7 since, at 50°C, less than 10% hydrolysis occurred after 120 h. A hydrolysis of less than 10% after 120 h, or more, at 50°C corresponds to a half-life time of more than one year at 25°C.

For pH 9 a main test was conducted at 40°C, 50°C and 60°C.

Temperature correlation is weak, with the test substance concentration decreasing faster at 50°C than at 60°C. From this observation, and from the fact that the test substance does not contain hydrolysable groups, it was concluded that processes other than hydrolysis contribute to, or are sole pathways of dissipation of the test substance. If, despite this conclusion, all dissipation at pH 9 is assumed to be due to hydrolysis, a half-life time of 3161 h (= 131.7 d) at 25°C can be calculated.

Since pH4 and pH7 are also relevant environmental pHs, the key value for abiotic degradation by Hydolysis as a function of pH is set to > 1-year at 25 °C.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C