trans-(5RS,6SR)-6-amino-2,2-dimethyl-1,3-dioxepan-5-ol

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

03 Dez 1993 - 11 Feb 1994

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)

Version / remarks:

92/69

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Remarks:

GC

Details on sampling:

- Sampling intervals for the parent compound:
Preliminary test (50 °C):
pH 4: 0, 2, 4, 6, 7, 8 h
pH 7+9: 0, 24, 72, 144, 168, 240, 312, 408, 480 h
further testing:
pH 4 (30 °C): 0, 4, 6, 24, 29, 32, 48 h
pH 7 (65 °C): 0, 24, 48, 72, 144, 168 h
pH 7 (55 °C): 0, 24, 72, 144, 192, 240 h
- Sampling method: For determination of the initial test substance concentration three 2-mL aliquots were removed from the hydrolysis solutions and each extracted and analyzed by GC.
- Sampling intervals/times for pH measurements: same as for sampling

Buffers:

- pH: 4
- Type: acetate buffer, 0.02 M
- Composition of buffer: 0.00225 mol sodium acetate anhydrous p.a (M= 82.03 g/mol); approx. 0.5 mL = approx. 0.009 mol acetic acid 100 % p.a. were dissolved to 250 mL with double distilled water. 200 mL of this solution was diluted to 500 mL with double distilled water. The pH was adjusted to 4.00 with 0.1 N sodium hydroxide solution.

- pH: 7
- Type: phosphate buffer, 0.02 M
- Composition of buffer: 8.68 g = 0.061 mol disodium hydrogen phosphate (M= 141.96 g/mol); 5.28 g = 0.039 mol potassium dihydrogen phosphate (M= 136.09 g/mol) were dissolved to 1000 mL with double distilled water. 200 mL of this solution was diluted to 1000 mL with double distilled water and the pH was adjusted to 7.00 with 10% phosphoric acid.

- pH: 9
- Type: borate buffer, 0.02 M
- Composition of buffer: 7.10 g = 0.019 mol disodium tetraborate (M= 381.37 g/mol); 1.58 g = 0.026 mol boric acid (M- 61.83) were dissolved to 1000 mL with double distilled water. 200 mL of this solution was diluted to 1000 mL with double distilled water and the pH was adjusted to 9.25 with 1 N sodium hydroxide solution.

Details on test conditions:

TESTSYSTEM
- Type, material and volume of test flasks, other equipment used: 5 mL vials sealed gas-tight with septa, stainless steel thermostatic bath with metal lid.
- Sterilization procedure: All experiments were performed using sterilized glassware, sample vials, and buffer solutions (sterilization method not specified).
- Measures to avoid photolytic effects: Possible photolytic degradation of the test substance was prevented by light exclusion.
- Oxygen exclusion measures: Buffer solutions were kept at equilibrium for one hour at the respective experimental temperatures (T= 30 °C, 50 °C, 55 °C, 65 °C) and then purged with nitrogen to remove dissolved oxygen.
- If no traps were used, the test system is closed/open: closed.

TEST MEDIUM
- Type and purity of water: double distilled water
- Preparation of test medium: three test solutions buffered to pH 4, 7 or 9 were prepared by adding a stock solution of the test substance in the appropriate buffer solution to a volumetric flask containing the appropriate buffer solution.

OTHER TEST CONDITIONS
- Adjustment of the pH value: according to the buffer solutions
- Dissolved oxygen: removed by flushing with nitrogen

Duration:

240 h

pH:

7

Temp.:

55 °C

Initial conc. measured:

100 mg/L

Duration:

168 h

pH:

7

Temp.:

65 °C

Initial conc. measured:

100 mg/L

Duration:

48 h

pH:

4

Temp.:

30 °C

Initial conc. measured:

100 mg/L

Duration:

480 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

100 mg/L

Remarks:

Preliminary test

Duration:

480 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

100 mg/L

Remarks:

Preliminary test

Duration:

8 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

100 mg/L

Remarks:

Preliminary test

Number of replicates:

1 replicate for each pH value and temperature.

Positive controls:

no

Negative controls:

no

Statistical methods:

With the aid of the experimentally determined rate constants kobs for hydrolysis at pH 4 and pH 7, the activation energy Ea can be determined using the Arrhenius equation. From the Arrhenius equation, the rate constant k 25°C for hydrolysis at T = 25 °C is determined for the respective pH value, and from this the half-life t 0.5 is determined. The graphical representation of In kobs versus 1/T in Kelvin yields a straight line with the intercept ln A and the slope -Ea/R

Preliminary study:

A preliminary study was performed at pH 4, pH 7, and pH 9. The data for the hydrolysis solution at pH 9 indicated that the test substance is hydrolytically stable at pH 9 and no further study was performed at this pH value. Results for the test solutions at pH 4 and pH 7 showed that more than 50% of the test substance was degraded within 4 h and 312 h, respectively. Therefore, hydrolysis tests were carried out at at two elevated temperatures (pH 4: 30 °C and pH 7: 55 °C, 65 °C).

Transformation products:

not specified

% Recovery:

37

pH:

7

Temp.:

55 °C

Duration:

240 h

% Recovery:

14

pH:

7

Temp.:

65 °C

Duration:

168 h

% Recovery:

32

pH:

4

Temp.:

30 °C

Duration:

48 h

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0.011 h-1

DT50:

2.52 d

Type:

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

Remarks on result:

other: extrapolation to the hydrolysis rate constant and half-life at 25 °C was conducted by applying the Arrhenius equation.

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

316 d

Type:

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

Remarks on result:

other: extrapolation to the hydrolysis rate constant and half-life at 25 °C was conducted by applying the Arrhenius equation.

pH:

7

Temp.:

55 °C

Hydrolysis rate constant:

0.004 h-1

DT50:

7.5 d

Type:

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

pH:

7

Temp.:

65 °C

Hydrolysis rate constant:

0.012 h-1

DT50:

2.37 d

Type:

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

pH:

4

Temp.:

30 °C

Hydrolysis rate constant:

0.021 h-1

DT50:

1.35 d

Type:

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

Details on results:

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

Validity criteria for the hydrolysis study:

Target condition according to guideline:	Actual condition according to the study:	Validity criteria met:
The analytical method used will depend on the nature of the substance and must be sufficiently precise and sensitive to detect a reduction of 10 % of the initial concentration.	Analysis via GC-FID is senstive enough to detect a reduction of 10% of the initial concentration.	Yes
A sufficient number of samples (not less than four) should be chosen to cover the range 20 to 70 % of hydrolysis to test for pseudo-first order behaviour at the specified pH values.	pH 9: not hydrolytically degraded pH 7: Pre-test 4 measurements, further tests 5 measurements pH 4: Pre-test and further test each 4 measurements	Yes
Confidence intervals should be computed and presented for all regression coefficients, rateconstants, half-lives, and any other kinetic parameters (e.g. DT50).	All relevant parameters are reported within the study.	Yes

Validity criteria fulfilled:

yes

Remarks:

See 'Any other information on results incl. tables'

Conclusions:

Based on experimental data, the hydrolytical half-lives at 25 °C were extrapolated using the Arrhenius equation and accounted to 2.52 d (pH 4) and 316 d (pH 7). The test substance is not hydrolytically degraded at pH 9.

Executive summary:

The study was conducted to determine the hydrolysis of the test substance as a function of pH in accordance with EU Directive 92/69/EEC C.7. A preliminary study was performed at pH 4, 7 and 9. The data for the hydrolysis solution at pH 9 showed that there was no hydrolytic degradation. Therefore, according to the test guideline, no further testing was required at this pH. Hydrolysis experiments at pH 4 and pH 7 showed that more than 50% of the test substance was degraded within 4 h and 312 h, respectively. Therefore, hydrolysis tests were carried out at at two elevated temperatures (pH 4: 30 °C and pH 7: 55 °C, 65 °C). The extrapolation to the hydrolysis rate constant and half-life at 25 °C was conducted by applying the Arrhenius equationand respective half-lives were 2.52 d at pH 4 and 316 d at pH 7.

Description of key information

The study was conducted to determine the hydrolysis of the test substance as a function of pH in accordance with EU Directive 92/69/EEC C.7. A preliminary study was performed at pH 4, 7 and 9. The data for the hydrolysis solution at pH 9 showed that there was no hydrolytic degradation. Therefore, according to the test guideline, no further testing was required at this pH. Hydrolysis experiments at pH 4 and pH 7 showed that more than 50% of the test substance was degraded within 4 h and 312 h, respectively. Therefore, hydrolysis tests were carried out at at two elevated temperatures (pH 4: 30 °C and pH 7: 55 °C, 65 °C). The extrapolation to the hydrolysis rate constant and half-life at 25 °C was conducted by applying the Arrhenius equationand respective half-lives were 2.52 d at pH 4 and 316 d at pH 7.

Key value for chemical safety assessment

Half-life for hydrolysis:

316 d

at the temperature of:

25 °C