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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
23 July 2012 - 11 January 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
EC No. 440/2008
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
GLP certificate: June 2012
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling method: At each sampling time, duplicate vials were removed from the waterbath and the entire volume was extracted with three portions (5 ml) of dichloromethane. The extracts were combined and evaporated to dryness under nitrogen and the residue redissolved in acetonitrile (1 mL) for analysis by high performance liquid chromatography (HPLC).
- Sampling intervals/times for pH measurements: Immediately and then after 2.4 hours
- Sample storage conditions before analysis: The samples were placed in a waterbath at 50°C in the dark until sampling was required (immediately and then after 2.4 hours, for pH 4 and pH 7)
Buffers:
- pH: 4, 7 and 9
- Composition of buffer:
pH 4: 0.2M aqueous potassium dihydrogen orthophosphate (550 mL) was mixed with 0.07M aqueous disodium hydrogen orthophosphate dodecahydrate (1250 mL) and purified water (3200 mL). The pH was adjusted to 4.0 +/- 0.05 with orthophosphoric acid.
pH 7: 0.2M aqueous potassium dihydrogen orthophosphate (1250 mL) was mixed with 1M sodium hydroxide (150 mL) and purified water (3600 mL). The pH was adjusted to 7.0 +/- 0.05 with 1M hydrochloric acid/1M sodium hydroxide, as required.
pH 9: 0.1M boric acid in 0.1M aqueous potassium chloride (2500 mL) was mixed with 1M sodium hydroxide (105 mL) and purified water (2400 mL). The pH was adjusted to 9.0 +/- 0.05 with 1M hydrochloric acid/1M sodium hydroxide, as required.

Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks: Wheaton vials containing buffer solution (9 mL). Vials were purged with nitrogen and pre-equilibrated at test temperatures (50 °C)
- Extended testing at pH 4 and pH 7:
* Separate tests were conducted at temperatures of 10, 25 and 40 °C in the dark. Duplicate samples were taken immediately to serve as t0 samples, and then several pairs of samples were analysed in the range of 10 to 90% hydrolysis to test for pseudo-first order behaviour.
- Extended testing at pH 9:
* As the hydrolysis rate was extremely rapid, testing was conducted at the single reporting temperature of 25 °C and with reduced sampling (four samples at each of t0 and t5minutes).
Number of replicates:
2 at each sampling time
Preliminary study:
The preliminary study showed that at each of pH 4, pH 7 and pH 9 at 50 ± 0.5°C, more than 10% hydrolysis had occurred after 2.4 hours.
Transformation products:
not measured
pH:
4
Temp.:
25 °C
DT50:
12 h
Key result
pH:
7
Temp.:
25 °C
DT50:
2 h
pH:
9
Temp.:
25 °C
DT50:
< 5 min
Details on results:
- Extended testing at pH 4: At pH 4, definitive tests were conducted at temperatures of 10, 25 and 40˚C, and the hydrolysis rate constant (k) and DT50 at 25˚C were extrapolated from the measured values of log10k at the selected temperatures using the Arrhenius relationship. A DT50 value of 12 hours was obtained at this pH value. The hydrolysis reactions for BMI at pH 4 were shown to follow pseudo-first order behaviour.
- Extended testing at pH 7: At pH 7, definitive tests were conducted at temperatures of 10, 25 and 40˚C, and the hydrolysis rate constant (k) and DT50 at 25˚C were interpolated from the measured values of log10k at the selected temperatures using the Arrhenius relationship. A DT50 value of 2 hours was obtained at this pH value. The hydrolysis reactions for BMI at pH 7 were shown to follow pseudo-first order behaviour.
- At pH 9, testing was conducted at the single temperature of 25˚C. The DT50 value of less than 5 minutes was obtained at this pH value.
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this test BMI was determined to be hydrolytically unstable under acidic, neutral and basic conditions, the rate of the reaction increasing with increase in pH.
Executive summary:

A study was performed to determine the rate of hydrolysis of BMI as a function of pH. The study was performed according to GLP principles and met the requirements of Commission Regulation (EC) No. 440/2008, Method C.7, and the OECD Guidelines for Testing of Chemicals, Method 111.

Under the conditions of this test BMI was determined to be hydrolytically unstable under acidic, neutral and basic conditions, the rate of the reaction increasing with increase in pH. A DT50 value of 12 hours was obtained at pH 4, 2 hours at pH 7 and a DT50 value of less than 5 minutes was obtained at pH 9.

Description of key information

pH 9: DT50 = < 5 mins at 25 °C

pH 7: DT50 = 2 hours at 25 °C

pH 4: DT50 = 12 hours at 25 °C

Key value for chemical safety assessment

Half-life for hydrolysis:
2 h
at the temperature of:
25 °C

Additional information

A study was performed to determine the rate of hydrolysis of BMI as a function of pH. The study was performed according to GLP principles and met the requirements of Commission Regulation (EC) No. 440/2008, Method C.7, and the OECD Guidelines for Testing of Chemicals, Method 111.

Under the conditions of this test BMI was determined to be hydrolytically unstable under acidic, neutral and basic conditions, the rate of the reaction increasing with increase in pH. A DT50 value of 12 hours was obtained at pH 4, 2 hours at pH 7 and a DT50 value of less than 5 minutes was obtained at pH 9.