3-methoxyoestra-1,3,5(10)-trien-17-one

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

at the beginning (0 h) and the end of testing (120 h)

Buffers:

- 0.05 M acetate buffer solution pH 4
0.68 g = 0.008 mol sodium acetate p.a. Merck Art. 6268 (M = 82.03 g/mol) and 2.4 mL = 0.042 mol acetic acid 100 % p.a. Merck Art. 63 E (M = 60.05 g/mol, density = 1.05 g/mL) were dissolved to 1000 mL with double distilled water. The pH value was adjusted to 4 by adding acetic acid 100 % p.a. (Merck Art. 63 E).
- 0.05 M phosphate buffer solution pH 7
4.35 g = 0.031 mol disodium hydrogen phosphate Merck Art. 6589 (M = 141.96 g/mol) and 2.65 g = 0.019 mol potassium dihydrogen phosphate Merck Art. 4881 (M = 136.09 g/mol) were dissolved to 1000 mL with double distilled water.
- 0.05 M borate buffer solution pH 9
4.77 g = 0.012 mol disodium tetraborate-decahydrate Merck Art. 6315 (M = 381.37 g/mol) and 46 mL = 0.0046 mol hydrochloric acid Titrisol Merck Art. 9973 (0.1 M) were dissolved to 1000 mL with double distilled water. As the pH value of borate buffer solutions decreases with increasing temperature, the pH value was adjusted to 9.2 at 25°C with 1 M sodium hydroxide solution to obtain a pH value of 9.00 at 50°C.
- for calibration of pH meter and electrode:
standard buffer solutions pH 4 (Art. 33543), pH 7 (Art. 33546) and pH 9 (Art. 33548), Riedel-de Haen

Details on test conditions:

Preparation of the test solutions
Three test solutions, buffered to pH values of 4, 7 and 9, each with a test substance concentration of approx 0.2 mg/L were prepared by adding a stock solution of test substance in acetonitrile to the corresponding buffer solution which had been equilibrated at 50°C for one hour followed by purging with nitrogen to remove dissolved oxygen.

Procedures for incubation and sampling
Aliquots of the test solutions were filled into three sterilized 5 mL autosampler vials which were tightly closed with screw caps. The vials were incubated in a themostatic water bath at 50 +- 0.1 °C.
The inital test substance concentration was measured in triplicate on the test solutions of pH 4, 7 and 9. Aliquots of the samples were diluted 1:1 by volume with acetonitrile prior to analysis in order to avoid solubility problems. The pH values in aliquots of the test solutions were then measured in a separate vessel at the test temperature of 50°C at the start of incubation and at the end of the hydrolysis experiment.
During the incubation of the test solutions possible photolytic degradation of the test substance was prevented by exclusion of light from the hydrolysis solutions by using a thermostatic bath made of stainless stell with a metal cover.
After five days of incubation, the vials from each of the hydrolysis solutions at pH 4, 7 and 9 were removed from the thermostatic bath. Aliquots of each vessel were worked up like the start solutions and analyzed by HPLC.

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

0.244 mg/L

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

0.247 mg/L

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

0.241 mg/L

Number of replicates:

Three replicates/pH value

Preliminary study:

Less than 10 % hydrolysis of the test substance were observed in a preliminary test at 50 °C and pH values of 4, 7 and 9.

Transformation products:

no

% Recovery:

93.9

pH:

4

Temp.:

50 °C

Duration:

120 h

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

95.1

pH:

7

Temp.:

50 °C

Duration:

120 h

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

98.3

pH:

9

Temp.:

50 °C

Duration:

120 h

Remarks on result:

hydrolytically stable based on preliminary test

pH:

4

Remarks on result:

hydrolytically stable based on preliminary test

pH:

7

Remarks on result:

hydrolytically stable based on preliminary test

pH:

9

Remarks on result:

hydrolytically stable based on preliminary test

Conclusions:

Estron-Methylether is hydrolytically stable at pH 4, 7 and 9 and 25 °C.

Executive summary:

The rate of hydrolysis of Estron-Methylether in aqueous solutions buffered to pH valuse of 4, 7 and 9 was studied according to guideline EC C.7

A preliminary test at 50 °C was perfomed. Three test solutions, buffered to pH values of 4, 7 and 9, each with a test substance concentration of approx 0.2 mg/L were prepared by adding a stock solution of test substance in acetonitrile to the corresponding buffer solution which had been equilibrated at 50°C for one hour followed by purging with nitrogen to remove dissolved oxygen.

Aliquots of the test solutions were filled into three sterilized 5 mL autosampler vials which were tightly closed with screw caps. The vials were incubated in a themostatic water bath at 50 +- 0.1 °C.

The inital test substance concentration was measured in triplicate on the test solutions of pH 4, 7 and 9. The pH values in aliquots of the test solutions were measured in a separate vessel at the test temperature of 50°C at the start of incubation and at the end of the hydrolysis experiment. During the incubation of the test solutions possible photolytic degradation of the test substance was prevented by exclusion of light from the hydrolysis solutions by using a thermostatic bath made of stainless stell with a metal cover.

After five days of incubation, the vials from each of the hydrolysis solutions at pH 4, 7 and 9 were removed from the thermostatic bath. Aliquots of each vessel were analyzed by HPLC.

As less than 10 % hydrolytic degradation within 5 days at 50 °C was observed, Estron-Methylether is hydrolytically stabe at pH 4, 7 and 9 at 25 °C.

Description of key information

The rate of hydrolysis of Estron-Methylether in aqueous solutions buffered to pH valuse of 4, 7 and 9 was studied according to guideline EC C.7

A preliminary test at 50 °C was perfomed. Three test solutions, buffered to pH values of 4, 7 and 9, each with a test substance concentration of approx 0.2 mg/L were prepared by adding a stock solution of test substance in acetonitrile to the corresponding buffer solution which had been equilibrated at 50°C for one hour followed by purging with nitrogen to remove dissolved oxygen.

The solutions were incubated in a themostatic water bath at 50 +- 0.1 °C. The inital test substance concentration was measured in triplicate on the test solutions of pH 4, 7 and 9.

After five days of incubation, the vials from each of the hydrolysis solutions at pH 4, 7 and 9 were removed from the thermostatic bath. Aliquots of each vessel were analyzed by HPLC.

As less than 10 % hydrolytic degradation within 5 days at 50 °C was observed, Estron-Methylether is hydrolytically stabe at pH 4, 7 and 9 at 25 °C.