cis-2-tert-butylcyclohexyl acetate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

9 Dec 2011 to 31 Aug 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Preliminary test: The concentration of the test substance in the test samples was determined immediately after preparation (t=0) and after 5 days. The samples taken at t=5 days were cooled to room temperature using running tap water. Aliquots of 3 mL were extracted with 4.5 mL DCM. The shaking time was 30 seconds. Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analysed at t=0. The pH of each of the test solutions (except for the blanks) was determined at each sampling time.
- Main test: The concentrations of the test substance were determined immediately after preparation (t=0) and at several sampling points after t=0. Blank buffer solutions were treated similarly as the test samples and analysed 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.

Buffers:

- Acetate buffer pH 4, 0.01 M: Solution of 16.6 % 0.01 M sodium acetate and 83.4 % 0.01 M acetic acid. The buffer contains 0.0009 % (w/v) sodium azide.
- Phosphate buffer pH 7, 0.01 M: Solution of 0.01 M potassium di-hydrogenphosphate adjusted to pH 7 using 1 N sodium hydroxide. The buffer contains 0.0009 % (w/v) sodium azide.
- Borate buffer pH 9, 0.01 M solution of 0.01 M boric acid and 0.01 M potassium chloride adjusted to pH 9 using 1 N sodium hydroxide. The buffer contains 0.0009 % (w/v) sodium azide.

Details on test conditions:

- Preliminary test: The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test substance was spiked to the solutions at a target concentration of 1 mg/L using a spiking solution in acetone. For each sampling time, duplicate sterile vessels under vacuum were completely filled with test solution and placed in the dark in a temperature controlled environment at 50 ± 0.1 °C. The spiking volume was < 1 % of the sample volume. Nominal concentrations were not corrected for the spiking volume.
- Main study: To minimize the effect of evaporation the main study on the hydrolysis of the test substance was performed at 20 °C and 25 °C directly. Test samples were prepared and treated similarly as during the preliminary test.

Duration:

5 d

Number of replicates:

Test samples were analysed by single injection.

Positive controls:

not specified

Negative controls:

not specified

Preliminary study:

At pH 4, pH 7 and pH 9 a degree of hydrolysis of ≥ 10 % after 5 days was observed. With additional samples at 2.4 hours it was found that the degree of hydrolysis was not linear related to the results of the test samples at 120 hours. The reason for this was most likely that the test substance had evaporated from the test solutions at the test temperature of 50 °C. To minimize the effect of evaporation in the main test on the hydrolysis of the test substance was performed directly at 20 °C and 25 °C. No test substance was detected in the blank buffer solutions. The mean recoveries of the buffer solutions at pH 7 and pH 9 fell within the criterion range of 90-110 %. The mean recovery of the buffer solution at pH 4 was 112 %. The value was slightly higher than the criterion range. It was considered that results demonstrated that the analytical method was adequate to demonstrate the degradation of the test substance in the preliminary test of the hydrolysis study.

Transformation products:

not measured

pH:

4

Temp.:

20 °C

Hydrolysis rate constant:

0.016 h-1

DT50:

44 h

Type:

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

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0.015 h-1

DT50:

47 h

Type:

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

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

0.015 h-1

DT50:

46 h

Type:

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

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.016 h-1

DT50:

42 h

Type:

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

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0.016 h-1

DT50:

44 h

Type:

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

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.014 h-1

DT50:

49 h

Type:

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

Details on results:

- At all pH, no test substance was detected in the blank buffer solutions.
- The mean recoveries of the buffer solutions fell within the criterion range of 70-110 % at pH 4 and within 90-110 % at pH 7 and 9. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance.
- For testing of pseudo-first order kinetics the mean logarithms of the relative concentrations between 10 % and 90 % were plotted against time. At both temperatures linear relationships were obtained within the first 80 hours of the experiment. After this time, the apparent rate of hydrolysis decreased, possibly due to formation of an equilibrium in the hydrolysis reaction. The half-life times of the test substance were determined according to the model for pseudo-first order reactions of the samples taken within the first 80 hours of the experiment.

Validity criteria fulfilled:

yes

Conclusions:

The rate of degradation of the test substance at 20 °C and 25 °C was similar at pH 4, 7, ang 9 and ranged within 42-49 hours.

Executive summary:

In a GLP hydrolysis study performed according to OECD guideline 111, hydrolysis of the test substance was tested at varying temperatures and as a function of pH. In a preliminary test hydrolysis was measured at 50 °C at pH 4, 7 and 9. In the main test half-lives were determined at pH 4, 7 and 9, at 20 and 25 °C. Residual test substance was determined by a gas chromatographic method with flame ionization detection. In the preliminary test a degree of hydrolysis of ≥10 % after 5 days was observed. With additional samples at 2.4 hours it was found that the degree of hydrolysis was not linear related to the results of the test samples at 120 hours, probably due to the fact that the test substance had evaporated from the test solutions. Therefore, the main test was performed at 20 °C and 25 °C. From the main study, the rate of degradation of the test substance at 20 °C and 25 °C was similar at pH 4, 7, and 9 and ranged within 42-49 hours.

Description of key information

In a GLP hydrolysis study performed according to OECD guideline 111, hydrolysis of the test substance was tested at varying temperatures and as a function of pH. In a preliminary test hydrolysis was measured at 50°C at pH 4, 7 and 9. In the main test half-lives were determined at pH 4, 7 and 9, at 20 and 25°C. Residual test substance was determined by a gas chromatographic method with flame ionization detection. In the preliminary test a degree of hydrolysis of ≥10% after 5 days was observed. With additional samples at 2.4 hours it was found that the degree of hydrolysis was not linear related to the results of the test samples at 120 hours, probably due to the fact that the test substance had evaporated from the test solutions. Therefore, the main test was performed at 20°C and 25°C. From the main study, the rate of degradation of the test substance at 20 °C and 25 °C was similar at pH 4, 7, and 9 and ranged within 42-49 hours.

Key value for chemical safety assessment

Half-life for hydrolysis:

49 h

at the temperature of:

25 °C