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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
26 November, 2017 - 15 March, 2018
Reliability:
1 (reliable without restriction)
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:
- Identity: DNAN
- Appearance: Pale yellow powder
- Storage conditions: Room temperature (15 to 25°C), dark
- Batch number: 55503625
- Purity: 100%
- Expiry date: 28 April 2019
- :Date received: 28 April 2017


Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The following procedure was carried out at each of pH 4, 7 and 9:

Aliquots (0.1 mL) of a stock solution of DNAN in acetonitrile (7.5 g/L) were added to separate Wheaton vials containing buffer solution (10 mL), which had been purged with nitrogen and pre-equilibrated at test temperature (50 ± 0.5°C).

The samples, of nominal concentration 75 mg/L, were placed in a 50°C oven in the dark until sampling was required (immediately, and then after 2.4, 24 and 120 hours).

At each sampling time, two samples were removed from the bath and an aliquot (1 mL) of each was diluted to volume (20 mL) with mobile phase for analysis by high performance liquid chromatography (HPLC).

Sample pH and incubation temperature were monitored over the period of the test.
Buffers:
Buffer solutions were prepared as follows:
- 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 (3660 mL). The pH was adjusted to 7.0 ± 0.05 with 1M hydrochloric acid.
- 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 (2395 mL). The pH was adjusted to 9.0 ± 0.05 with 1M hydrochloric acid or 1M sodium hydroxide, as required.
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
74.8 mg/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
75.6 mg/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
74.3 mg/L
Number of replicates:
2
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
The concentration of DNAN in the analysed solution (CA) was calculated from standards introduced before and after samples (bracketing standards) by the following equation:
CA (mg/L) = sample peak area x standard concentration (mg/L) / mean peak area of bracketing standards

The concentration of DNAN in each test solution (CB) was then determined thus:
CB (mg/L) = CA (mg/L) x dilution factor

where the dilution factor was 20 for all samples.
Preliminary study:
The preliminary study showed that at each of pH 4, 7 and 9 and 50 ± 0.5ºC, less than 10% hydrolysis had occurred after 120 hours (5 days), equivalent to a half-life of greater than 1 year under environmental conditions (25°C). No further testing was considered necessary.
Test performance:
Using the conditions described, the calibration of DNAN was found to be linear over the range 0 to 15 mg/L with a regression coefficient of 1.0000.
It was considered that the analytical method was sufficiently sensitive to quantify test item concentrations down to 10% or less of the initial concentration.
Transformation products:
not specified
Details on hydrolysis and appearance of transformation product(s):
None
Key result
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Validity criteria fulfilled:
yes
Conclusions:
DNAN was determined to be hydrolytically stable under acidic, neutral and basic conditions.
Executive summary:

A study was performed to determine the rate of hydrolysis of DNAN as a function of pH. The test was conducted in accordance with the preliminary test as described in EC Method C.7 and the OECD Method 111.

The preliminary study showed that at each of pH 4, 7 and 9 and 50±0.5ºC, less than 10% hydrolysis had occurred after 5 days, equivalent to a half-life of greater than 1 year under environmental conditions (25°C). No further testing was considered necessary.

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

Description of key information

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

Key value for chemical safety assessment

Additional information

A study was performed to determine the rate of hydrolysis of DNAN as a function of pH (Envigo CRS Limited, QT77HM, 2018). The test was conducted in accordance with the preliminary test as described in EC Method C.7 and the OECD Method 111, and in compliance with GLP.

The preliminary study showed that at each of pH 4, 7 and 9 and 50±0.5°C, less than 10% hydrolysis had occurred after 5 days, equivalent to a half-life of greater than 1 year under environmental conditions (25°C). No further testing was considered necessary.

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