Estradiol

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Environmental Assessment Technical Assistance Handbook (US Food and Drug Administration, FDA, 1987), Technical Assistance Documents-Environmental Fate Testing (TAD), no. 3.09

Deviations:

yes

Remarks:

According to FDA-TAD no. 3.09, triplicate samples are to be analyzed at each sampling time. After 5 days only duplicate samples were analyzed.

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

not applicable

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

SAMPLING SCHEDULE:
- Day 0: The test concentration was measured in triplicate on the stock solutions of pH 5, 7 and 9
- Day 5: The test concentration was measured in duplicate on the stock solutions of pH 5, 7 and 9

Buffers:

I. Buffer solution pH 5:
- 0. 0158 M acetate buffer solution pH 5: 0.82 g sodium acetate (Merck Art. 106268; MG 82.03 g/mol) were dissolved to 1000 ml with double distilled water; the pH value was adjusted to 5 by adding acetic acid (100%; Merck Art. 100063)

II. Buffer solution pH 7:
- 0.0067 M phosphate buffer solution pH 7: 0.584 g disodium hydrogen phosphate (Merck Art. 106566; (MG 141 .96 g/mol) and 0.354 g potassium dihydrogen phosphate (Merck Art. 105108; MG 136.09 g/mol) were dissolved to 1000 ml with double distilled water; the pH value was adjusted to 7 by
adding phosphoric acid 10 %

III. Buffer solution pH 9
- 0. 1 M borate buffer solution pH 9: 5.03 g disodium tetraborate (Merck Art. 1 06309) and 92ml hydrochloric acid (Titrisol Merck Art. 109973, 0.1 M)
were dissolved to 1000 ml with double distilled water; the pH value was adjusted to 9.20 by adding 1 M sodium hydroxide solution (Titrisol Merck Art. 109959) in order to take into account the temperature dependence of the pH of this buffer solution

Details on test conditions:

EXPERIMENTAL DESIGN:

I. Preparation of test solution:
- Three stock solutions, buffered to pH values of 5, 7 and 9, each with a test concentration of approx. 1 mg/1 buffer solution containing 1 % acetonitrile, were prepared using sterilized equipment, buffer solutions and double distilled water

II. Procedures for incubation and sampling:
- Aliquots of the test solutions were filled into sterilized 5 mL autosampler vials which were tightly closed with screw caps
- The vials were incubated in a thermostatic water bath at 50± 0.1 °C
- After a hydrolysis time of approx. 5 days two vials from each of the hydrolysis solutions at pH 5, 7 and 9 were removed from the thermostatic bath and analyzed
- The pH values of the test solutions were measured in a separate vessel at the test temperature of 50 °C at the start and at the end of incubation
- During the hydrolysis experiment 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 steel with a metal cover

III. Apparatus:
- Analytical balance MC 210 P-OCE (Sartorius)
- Thermostatic bath DC 3 I W 19 (Haake)
- Pt 100 resistance thermometer (Knick), graded by a calibrated thermometer, connected to digital pH meter 647 (Knick) with recorder 1100 (W+W) for registration of temperature
- pH meter 766 (Knick) with calibrated glass electrode 00554106 (Metrohm)
- HPLC system

Duration:

5 d

pH:

5

Temp.:

50

Initial conc. measured:

0.977 mg/L

Duration:

5 d

pH:

7

Temp.:

50

Initial conc. measured:

0.971 mg/L

Duration:

5 d

pH:

9

Temp.:

50

Initial conc. measured:

0.974 mg/L

Transformation products:

no

% Recovery:

97.7

pH:

5

Temp.:

50 °C

Duration:

5 d

% Recovery:

97.5

pH:

7

Temp.:

50 °C

Duration:

5 d

% Recovery:

95

pH:

9

Temp.:

50 °C

Duration:

5 d

pH:

5

Temp.:

25 °C

DT50:

> 1 yr

Type:

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

Remarks on result:

other: estimated (see "Details for result")

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Type:

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

Remarks on result:

other: estimated (see "Details for result")

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Type:

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

Remarks on result:

other: estimated (see "Details for result")

Details on results:

The data indicate that less than 10 % of the test substance are hydrolyzed at 50 °C within 5 days of observation at pH 5, 7 and 9. Therefore the substance can be considered hydrolytically stable, i.e. ty, > 1 year at 25 °C and no further testing is required.

The acid dissociation constant of estradiol is 10. 71 (Lewis, K. M., Archer, R. D.; Steroids, 34, 5, p. 485-499 (1979)).

Validity criteria fulfilled:

yes

Conclusions:

No hydrolytic degradation was observed within 5 days at pH 5, 7 and 9 at 50 ± 0.1 °C (pretest). Therefore no further testing was required and estradiol can be considered to be hydrolytically stable at pH 5, 7 and 9 and 25 °C, i.e. t1/2 > 1 year.

Executive summary:

The rate of hydrolysis in aqueous solutions buffered to pH values of 5, 7 and 9 was studied in a preliminary test according to FDA Technical Asisstance Documents-Environmental Fate Testing (TAD), No. 3.09 in agreement with EU testing guideline C.7. No hydrolytic degradation was observed within 5 days at pH 5, 7 and 9 at 50 ± 0.1 °C (pretest). Therefore no further testing was required and estradiol can be considered to be hydrolytically stable at pH 5, 7 and 9 and 25 °C, i.e. t_1/2> 1 year.

Description of key information

The substance is hydrolytically stable at pH 5, pH7 and pH9 (25°C).

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

"Should read: > 1 year at 25 °C"

No hydrolytic degradation was observed within 5 days at pH 5, 7 and 9 at 50 ± 0.1 °C (pretest). Therefore no further testing was required and the substance can be considered to be hydrolytically stable at pH 5, 7 and 9 and 25 °C.