2-(2,6-diethyl-4-methyl-phenyl)propanediamide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 August 2003 to 03 September 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: 2.4 hours, 2 days and 5 days. After an initial period of about 1 hour, to ensure that the test item had completely dissolved in the buffer solution and that the solutions were at test temperature, the first aliquot for analysis was removed and the concentration of the test material determined by high performance liquid chromatography. This aliquot was designated t0.
- Sampling intervals/times for pH measurements: pH was measured with the final aliquot taken for analysis
- Sample preparation: 2.0 mL from the hydrolysis solution were diluted with the mobile phase to reach concentrations within those of the reference solutions.

Buffers:

- pH: 4.0
- Type of buffer: citrate buffer
- Composition and final molarity of buffer: 20 mM sodium citrate

- pH: 7.0
- Type of buffer: phosphate buffer
- Composition and final molarity of buffer: 20 mM sodium phosphate

- pH: 9.0
- Type of buffer: borax buffer
- Composition and final molarity of buffer: 20 mM sodium tetraborate

The buffer solutions were prepared under clean room conditions, filtered through a 0.2 µm membrane filter and were sterile.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: amber 100 mL volumetric flasks.
- Measures taken to avoid photolytic effects: To exclude light from the test system, the water bath was covered in aluminium foil. As a further precautionary measure, amber volumetric flasks were used. This gave protection during the times that flasks were exposed to light, such as sampling.

TEST MEDIUM
- Preparation of test medium: Approximately 40 mg of the test material were accurately weighed into six individual flasks. Approximately 100 ml of the appropriate sterile buffer solution were added to the flasks. The flasks were then placed in a thermostatically controlled water bath at 50 °C ± 0.1 °C with continuous stirring.

OTHER TEST CONDITIONS
- Dissolved oxygen: Dissolved oxygen was removed from the system by bubbling a stream of argon gas through each solution for approximately five minutes

Duration:

5 d

pH:

3.8

Temp.:

50 °C

Initial conc. measured:

420.715 - 445.881 mg/L

Duration:

5 d

pH:

7.1

Temp.:

50 °C

Initial conc. measured:

402.279 - 447.261 mg/L

Duration:

5 d

pH:

9.1

Temp.:

50 °C

Initial conc. measured:

433.56 - 468.756 mg/L

Number of replicates:

Two per pH tested

Positive controls:

no

Negative controls:

no

Test performance:

The results indicated that less than 10 % of the test item had hydrolysed at any pH value after the five days at 50 °C, including the pH 9.0 buffer solution, in which slight decomposition had occurred. According to the standardised guidelines followed, when less than 10 % of the the test substance has hydrolysed after five days at 50 °C, then no further testing is required.

Transformation products:

not measured

pH:

3.8

Temp.:

50 °C

DT50:

> 1 yr

pH:

7.1

Temp.:

50 °C

DT50:

> 1 yr

pH:

9.1

Temp.:

50 °C

DT50:

> 1 yr

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

Table 1: Results

Hydrolysis solution	H41	H42	H71	H72	H91	H92
Concentration [mg/L] at time t0
1st determination	447.135	419.773	401.936	445.625	465.409	433.390
2nd determination	444.627	421.656	402.622	448.896	472.102	433.729
Average	445.881	420.715	402.279	447.261	468.756	433.560
Concentration [mg/L] at time2.4h
1st determination	456.540	420.041	406.222	443.133	452.910	416.380
2nd determination	455.822	426.099	411.730	440.056	457.506	415.315
Average	456.181	423.070	408.976	441.595	455.208	415.848
Concentration change [%]	2.310	0.560	1.665	-1.267	-2.890	-4.085
Average concentration change	1.4		0.2		-3.5
Concentration [mg/L] at time2d
1st determination	456.093	424.568	398.527	438.195	436.242	402.160
2nd determination	436.910	410.195	397.879	437.685	435.728	396.732
Average	446.502	417.382	398.203	437.940	435.985	399.446
Concentration change [%]	0.139	-0.792	-1.013	-2.084	-6.991	-7.868
Average concentration change	-0.3		-1.5		-7.4
Concentration [mg/L] at t5d
1st determination	445.369	408.433	390.359	418.098	432.500	400.701
2nd determination	446.657	412.456	393.426	420.264	429.606	400.456
Concentration change [%]	0.030	-2.441	-2.582	-6.278	-8.043	-7.607
Average concentration change	-1.2		-4.4		-7.8
pH at 50 ºC	3.81	3.81	7.09	7.10	9.14	9.12
Average pH	3.8		7.1		9.1

Validity criteria fulfilled:

yes

Remarks:

The study meets that quality criteria as defined in standardised guidelines.

Conclusions:

Under the conditions of the test, the half-life of the test material (t1/2) was estimated from the preliminary test as greater than 1 year at pH 3.8, 7.1 and 9.1 at 25 °C. The study is considered to be reliable, relevant and adequate for risk assessment purposes.

Executive summary:

The rate of hydrolysis of the test material was determined at three pH values in accordance with the standardised guidelines OECD 111 and EU Method C.7. After five days at 50 °C less than 10 % of the test item had hydrolysed at any of the three investigated pH values. Therefore, in accordance with the test method used, the half-life time t_1/2 of the test material may be estimated from the preliminary test to be:

t_1/2 >1 year at 25 °C and pH 3.8

t_1/2 >1 year at 25 °C and pH 7.1

t_1/2 >1 year at 25 °C and pH 9.1

Description of key information

Hydrolysis Half-life >1 year, pH 3.8, 7.1 and 9.1, 25 ºC, OECD 111, EU Method C.7, Das 2003

Additional information

The rate of hydrolysis of the test material was determined at three pH values in accordance with the standardised guidelines OECD 111 and EU Method C.7. After five days at 50 °C less than 10% of the test item had hydrolysed at any of the three investigated pH values. Therefore, in accordance with the test method used, the half-life time t_1/2of the test material may be estimated from the preliminary test to be:

t_1/2>1 year at 25 °C and pH 3.8

t_1/2>1 year at 25 °C and pH 7.1

t_1/2>1 year at 25 °C and pH 9.1