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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02 July to 30 July 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)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: The samples, of nominal concentration approximately 0.9 mg/l, were placed in a 50°C waterbath in the dark until sampling was required (immediately, and then after 2.4, 120 and 240 hours).
- Sampling method: At each sampling time, two samples were removed from the bath and an aliquot (2.5 ml) of each was diluted to volume (5 ml) with methanol for analysis by high performance liquid chromatography (HPLC).
- Sampling intervals/times for pH measurements: Sample pH and incubation temperature were monitored over the period of the test.

Buffers:
- pH: 4, 7 and 9
- Type and final molarity of buffer: pH 4: 0.2M aqueous potassium dihydrogen orthophosphate, pH 7: 0.2M aqueous potassium dihydrogen orthophosphate, pH 9: 0.1M boric acid in 0.1M aqueous potassium chloride.

- Composition of buffer:

pH 4: 0.2M aqueous potassium dihydrogen orthophosphate (110 ml) was mixed with 0.07M aqueous disodium hydrogen orthophosphate dodecahydrate (250 ml) and purified water (640 ml). The pH was adjusted to 4.0 ± 0.05 with orthophosphoric acid.

pH 7: 0.2M aqueous potassium dihydrogen orthophosphate (250 ml) was mixed with 1M sodium hydroxide (30 ml) and purified water (720 ml). The pH was adjusted to 7.0 ± 0.05 with 1M sodium hydroxide/1M hydrochloric acid as required.

pH 9: 0.1M boric acid in 0.1M aqueous potassium chloride (500 ml) was mixed with 1M sodium hydroxide (21 ml) and purified water (480 ml). The pH was adjusted to 9.0 ± 0.05 with 1M sodium hydroxide/1M hydrochloric acid as required.
Estimation method (if used):
Not used
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 10 ml Wheaton vials
- Sterilisation method: autoclave, 120°C, 1hour
- Lighting: none
- Measures taken to avoid photolytic effects: samples kept in the dark duruing test period
- Measures to exclude oxygen: test solutions deaeration by bubbling nitrogen gas through sterilized 0.2µm membrane filters for 5 minutes
- Details on test procedure for unstable compounds: not applicable
- If no traps were used, is the test system closed/open: closed (Weaton vials)


TEST MEDIUM
- Volume used: 10ml
- Kind and purity of water: purified sterilised water

- Preparation of test solution: Aliquots (1.5 ml) of a stock solution of TCD in acetonitrile (approximately 5 mg/l) were added to separate 10 ml Wheaton vials containing buffer solution (7.5 ml), which had been purged with nitrogen and pre-equilibrated at test temperature (50 ± 0.5°C). In an initial test, a
smaller quantity of acetonitrile (1% v/v) had been used as co-solvent, but volatilisation of TCD was evident at the test temperature and it was considered that additional solvent was required to maintain the test substance in solution.

- Renewal of test solution: not applicable
- Identity and concentration of co-solvent: acetonitrile

OTHER TEST CONDITIONS
The prepared test solutions were held in a thermostatic water bath set at 50°C for the duration of the test.
Duration:
0.1 d
Temp.:
50 °C
Initial conc. measured:
0.9 mg/L
Duration:
5 d
Temp.:
50 °C
Initial conc. measured:
0.9 mg/L
Duration:
10 d
Temp.:
50 °C
Initial conc. measured:
0.9 mg/L
Number of replicates:
1
Positive controls:
no
Negative controls:
no
Statistical methods:
Not applicable
Preliminary study:
The preliminary study showed that the test substance was stable in water at pH 4, 7 and 9.
The main study was not required.


Transformation products:
not measured
Details on hydrolysis and appearance of transformation product(s):
Not applicable - no measurable hydrolysis was seen during the study

% Recovery:
94
pH:
4
Temp.:
50 °C
Duration:
5 d
% Recovery:
95
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
91
pH:
9
Temp.:
50 °C
Duration:
5 d
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Other kinetic parameters:
Not applicable no measurable hydrolysis was seen during the study

Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): volatilisation of TCD was evident at the test temperature using 1% acetonitrile co-solvent and it was considered that additional solvent (15%) was required to maintain the test substance in solution.

MAJOR TRANSFORMATION PRODUCTS
Not applicable, the substance is stable to hydrolysis

MINOR TRANSFORMATION PRODUCTS
Not applicable, the substance is stable to hydrolysis

INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS:
Not applicable, the substance is stable to hydrolysis

PATHWAYS OF HYDROLYSIS
Not applicable, the substance is stable to hydrolysis

SUPPLEMENTARY EXPERIMENT (if any): RESULTS:
Not applicable, the substance is stable to hydrolysis

There were no significant changes in pH and temperature with time. The slightly elevated pH values were due to the presence of the cosolvent (samples prepared at the same concentration, but with 1% v/v co-solvent, were generally within ± 0.1 units of nominal pH value).

Nominal: pH 4, measured: pH 4.4 (initial and final)

Nominal pH 7, measured: pH 7.4 (initial and final)

Nominal pH 9, measured: pH 9.5 (initial and final)

Validity criteria fulfilled:
yes
Conclusions:
TCD was determined to be hydrolytically stable under acidic, neutral and basic conditions.

Description of key information

TCD was determined to be hydrolytically stable under acidic, neutral and basic conditions.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

The substance is stable to hydrolysis for 5 days at 50°C in a preliminary hydrolysis test carried out in accordance with OECD test Guideline 111 (Huntingdon Life Sciences, 2013, Study number VHJ0055).

Further work is not undertaken as it can be concluded from the results of the preliminary test that the substance will have a half-life time of greater than 1 year at 25°C at pH 4, 7 and 9.