5-bromo-5-nitro-1,3-dioxane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05-Nov-2018 to 25-Feb-2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

None of the deviations were considered to have impacted the overall integrity of the study or the interpretation of the study results and conclusions.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification: 5-Bromo-5-nitro-1,3-dioxane
Batch (Lot) Number: 201807021
Expiry date: 30 Jun 2020 (expiry date) (taken from label)
Physical Description: White crystal powder
Purity/Composition: See Certificate of Analysis
Storage Conditions: At room temperature
Stability at higher temperatures: Stable, maximum temperature: 50°C, maximum duration: 120 minutes

Radiolabelling:

not specified

Analytical monitoring:

yes

Details on sampling:

Preliminary Test - Tier 1
For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment at 50.1°C ± 0.2°C.
The concentration of the test item in the test samples was determined immediately after preparation (t=0) and after 2.4 hours and 5 days. The samples taken at t=2.4 hours and t=5 days were cooled to room temperature using running tap water. Analysis was performed on subsamples of 800 µL. The samples and the blank buffer solutions were diluted in a 4:1 (v:v) ratio with acetonitrile and analyzed. The pH of each of the test solutions (except for the blanks) was determined at each sampling time.

Stability of Stock Solutions
Stock solutions of the test item were stored at room temperature for at least 12 hours. Additional calibration solutions were prepared and analyzed by single injection. The stock solutions were found to be stable if the coefficient of variation on the response factors of the calibration solutions prepared with fresh and stored stock solutions was ≤ 10%.

Main Study - Tier 2
For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment. The spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume. Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analyzed 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, 0.1 M
Solution of 16.7% 0.1 M sodium acetate in water and 83.3% 0.1 M acetic acid in water. Buffer contained 0.0009% (w/v) sodium azide.

Phosphate buffer pH 7, 0.1 M
Solution of 0.1 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.

Borate buffer pH 9, 0.1 M
Solution of 0.1 M boric acid in water and 0.1 M potassium chloride in water adjusted to pH 9 using 10N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.

Details on test conditions:

Performance of the Study
The rate of hydrolysis of the test item as a function of pH was determined at pH values normally found in the environment (pH 4-9). All solutions containing the test item were protected from light.

Preliminary Test - Tier 1
Test item solutions were prepared in the buffer solutions at a target concentration of 76.0, 91.8 and 108 mg/L. Each solution was filter-sterilised through a 0.2 µm FP 30/0.2 CAS filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment at 50.1°C ± 0.2°C. The concentration of the test item in the test samples was determined immediately after preparation (t=0) and after 2.4 hours and 5 days. The samples taken at t=2.4 hours and t=5 days were cooled to room temperature using running tap water. Analysis was performed on subsamples of 800 µL. The samples and the blank buffer solutions were diluted in a 4:1 (v:v) ratio with acetonitrile and analyzed. The pH of each of the test solutions (except for the blanks) was determined at each sampling time.

Main Study - Tier 2
The buffer solutions at pH 7 and pH 9 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 item was spiked to the solutions at a target concentration of 10 mg/L using a spiking solution in acetonitrile. For each sampling time, duplicate sterile vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment. The spiking volume was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume. Blank buffer solutions containing a similar content of blank spiking solution were treated similarly as the test samples and analyzed 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. The study was performed at the following temperatures.

pH code Temperature I Temperature II Temperature III
pH 7 19.8°C +/- 0.5°C 40.4°C +/- 0.6°C 50.0°C +/- 0.1°C
pH 9 19.8°C +/- 0.5°C 40.4°C +/- 0.6°C 50.0°C +/- 0.1°C

Positive controls:

not specified

Negative controls:

not specified

Statistical methods:

The rate constant (kobs) and half-life time of the test item at each temperature was obtained. The Arrhenius equation was used to determine the rate constant and half-life time.

Calibration Curve Statistical Parameters
Slope: 7.81 X 10E3
Intercept: 6.62
Weighting factor: 1/concentration2
r: 0.9995 8

Preliminary study:

At pH 7 and pH 9, a degree of hydrolysis of ≥ 10% was observed after 5 days. According to the guideline, the higher Tier test was required to determine the half-life time of the test item. A degree of hydrolysis of < 10% was observed at pH 4 after 5 days. It demonstrated that the half-life time of the test item at 25°C is > 1 year. According to the guideline, no further tests were required. No test item was detected in the blank buffer solutions. The mean recoveries of the test item containing buffer solutions at t=0 fell below the criterion range of 90-110%. Therefore in the main study a lower concentration as nominal concentration was used and the buffer solutions were spiked with the test item.

Test performance:

The mean recoveries of the test item containing buffer solutions at t=0 fell below the criterion range of 90-110%. Therefore in the main study a lower concentration as nominal concentration was used and the buffer solutions were spiked with the test item.

Transformation products:

not specified

% Recovery:

> 100

pH:

7

Temp.:

20 °C

% Recovery:

> 100

pH:

7

Temp.:

40 °C

% Recovery:

> 100

pH:

7

Temp.:

50 °C

% Recovery:

> 100

pH:

9

Temp.:

20 °C

% Recovery:

> 100

pH:

9

Temp.:

40 °C

% Recovery:

> 50

pH:

9

Temp.:

50 °C

pH:

4

Remarks on result:

hydrolytically stable based on preliminary test

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

ca. 0 h-1

DT50:

ca. 349 d

Type:

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

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

ca. 0 h-1

DT50:

ca. 284 d

Type:

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

pH:

7

Temp.:

40 °C

Hydrolysis rate constant:

ca. 0 h-1

DT50:

ca. 77 d

Type:

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

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0.001 h-1

DT50:

ca. 34 d

Type:

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

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

ca. 0 h-1

DT50:

ca. 269 d

Type:

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

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

ca. 0 h-1

DT50:

ca. 487 d

Type:

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

pH:

9

Temp.:

40 °C

Hydrolysis rate constant:

ca. 0.001 h-1

DT50:

ca. 41 d

Type:

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

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0.003 h-1

DT50:

ca. 9 d

Type:

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

Details on results:

Preliminary Test - Tier 1
At pH 7 and pH 9, a degree of hydrolysis of ≥ 10% was observed after 5 days. According to the guideline, the higher Tier test was required to determine the half-life time of the test item. A degree of hydrolysis of < 10% was observed at pH 4 after 5 days. It demonstrated that the half-life time of the test item at 25°C is > 1 year. According to the guideline, no further tests were required. No test item was detected in the blank buffer solutions. The mean recoveries of the test item containing buffer solutions at t=0 fell below the criterion range of 90-110%. Therefore in the main study a lower concentration as nominal concentration was used and the buffer solutions were spiked with the test item.

Main Study - Tier 2
No test item was detected in the blank buffer solutions. The mean recoveries of the test item containing buffer solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test item.

For testing of pseudo-first order kinetics the mean logarithms of the relative concentrations between 10% and 90% were plotted against time. At all temperatures linear relationships were obtained. The half-life times of the test item were determined according to the model for pseudo-first order reactions. All logarithms of the relative concentrations were correlated with time using linear regression analysis.

The rate constant (kobs) and half-life time of the test item at each temperature was obtained. The Arrhenius equation was used to determine the rate constant and half-life time at 25°C using results at 40°C and 50°C, since no hydrolysis was detected at 20°C.

pH 9
No test item was detected in the blank buffer solutions. The mean recoveries of the test item containing buffer solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test item.

Validity criteria fulfilled:

yes

Conclusions:

The preliminary test (Tier 1) and main study (Tier 2) were performed for the determination of the rate of hydrolysis of 5-Bromo-5-nitro-1,3-dioxane at pH values normally found in the environment (pH 4-9). The half-life times of the test item were as follows: pH 7 at 25°C = 284 days (key result)

Executive summary:

The objective of this study was to determine physico-chemical properties for  5-Bromo-5-nitro-1,3-dioxane.

The summary of the results is listed below:

Information                            Guideline(s)                                                               Result

Hydrolysis at pH 4               EC C.7, OECD 111, OPPTS 835.2120                     pH 4: t½ > 1 year

Hydrolysis at pH 7              EC C.7, OECD 111, OPPTS 835.2120              t½ = 349 days at 20°C

t½ = 284 days at 25°C

t½ = 77 days at 40°C

t½ =34 days at 50°C

Hydrolysis at pH 9              EC C.7, OECD 111, OPPTS 835.2120            t½ = 269 days at 20°C

t½ = 487 days at 25°C

t½ = 41 days at 40°C

t½ = 9 days at 50°C

Description of key information

The preliminary test (Tier 1) and main study (Tier 2) were performed for the determination of the rate of hydrolysis of the test substance at pH values normally found in the environment (pH 4-9). The half-life times of the test item were as follows: pH 7 at 25°C = 284 days (key result)

Key value for chemical safety assessment

Half-life for hydrolysis:

284 d

at the temperature of:

25 °C