Dimethyl(octyl)amine

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 Nov 2015 to 21 Jul 2017

Reliability:

1 (reliable without restriction)

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 (incl. QA statement)

Radiolabelling:

no

Details on sampling:

As the content of N,N-dimethyloctylamine in AD 1 is not known exactly (purity is given to be > 95 % (w/w)), for calculations the purity was assumed to be 100 % (w/w). This has no influence on the analytical result, as the test item is also used for calibration and only a change in concentration has to be determined.
A spike solution containing 20.00 g/L of the test item was prepared in acetonitrile.
The test solutions were prepared by transferring 0.5 mL of the spike solution into a 100 mL volumetric flask. The flasks were brought to volume with the respective buffer solutions. The concentration of the test item in the test solutions was 100 mg/L and did not exceed 0.01 M or the half saturation concentration. Under argon atmosphere 3.0 mL of the test solutions were given into several glass vials. The vials were closed with Teflon sealed crimp caps.
The samples taken at t0 were stored deep frozen until the sampling date after 5 days. After the last sampling date the samples were brought to room temperature and 1.0 mL acetonitrile were added (dilution factor: 4/3). Finally the samples were brought to a pH value of about 12 by adding a suitable amount of a 10 M sodium hydroxide solution:

• pH 4: 31 µL of 10 M sodium hydroxide solution were added
• pH 7: 20 µL of 10 M sodium hydroxide solution were added
• pH 9: 12 µL of 10 M sodium hydroxide solution were added

The nominal content of the test item in the measuring solution was 75 mg/L. The analytical method was specific for determination of the test item at the test solution concentrations. The validation of the analytical method is presented in Appendix 3 of this report.

Buffers:

Citrate buffer pH 4 (0.05 M):
Per 1000 mL ultra-pure grade water 10.514 g citric acid monohydrate had to be weighed and 59 mL of sodium hydroxide solution (1 M) had to be added to reach pH 4.
The pH value of the buffer solution was determined to be 4.00.

Phosphate buffer pH 7 (0.05 M):
Per 1000 mL ultra-pure grade water 6.818 g Potassium dihydrogenphosphate had to be weighed and 29 mL of sodium hydroxide solution (1 M) had to be added to reach pH 7.
The pH value of the buffer solution was determined to be 7.00.

Borate buffer pH 9 (0.05 M):
Per 1000 mL ultra-pure grade water 3.748 g potassium chloride and 3.102 g boric acid had to be weighed and 21 mL of sodium hydroxide solution (1 M) had to be added to reach pH 9.
The pH value of the buffer solution was determined to be 9.00.

The pH values of the buffer solutions used during the test were determined with a calibrated pH meter with a precision of 0.01 pH units.

Details on test conditions:

The preliminary test was carried out using a thermostatically controlled water bath at 50 °C +- 0.5 °C. Photolytic interference was avoided. All suitable precautions were taken to exclude dissolved oxygen (degassing the buffers with argon for at least five minutes and purging the vessels with argon before preparing the test solution). Sterile buffer solutions were used.

Duration:

0 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

101.1 mg/L

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

101.9 mg/L

Duration:

0 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

99.5 mg/L

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

99.2 mg/L

Duration:

0 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

85.9 mg/L

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

80.6 mg/L

Number of replicates:

Two replicates per pH and sampling time

Positive controls:

not specified

Negative controls:

not specified

Preliminary study:

The time courses of the test item concentration at 50 °C and three different pH values were determined. The determined temperatures during the entire period of the test were in the range of 50.0 °C ± 0.5 °C. Two samples were taken at each pH and each sampling date.
Samples were taken at the beginning of the test and after 120 hours at pH 4, pH 7 and pH 9. The concentrations in buffer solutions were determined by HPLC-UV analysis. At pH 4, pH 7 and pH 9 less than 10 % of the test item were hydrolysed within 120 hours at 50 °C.

Transformation products:

not measured

Details on hydrolysis and appearance of transformation product(s):

At pH 4, pH 7 and pH 9 less than 10 % of the test item were hydrolysed within 120 hours at 50 °C.

% Recovery:

100.8

pH:

4

Temp.:

50 °C

Duration:

120 h

% Recovery:

99.7

pH:

7

Temp.:

50 °C

Duration:

120 h

% Recovery:

93.8

pH:

9

Temp.:

50 °C

Duration:

120 h

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

 

Table1:     Time course of AD 1 concentration at pH 4 at 50 °C

Time [h]	Determined Content ofAD 1in Sample [mg/L]^(1	Mean Determined Content ofAD 1in Sample [mg/L]^(1)	Actual concentration in % of initial concentration
0	101.0	101.1	---
	101.2
120	102.7	101.9	100.8
	101.1

⁽¹⁾: regardinga dilution factor of 4/3

Table2:     Time course of AD 1 concentration at pH 7 at 50 °C

Time [h]	Determined Content ofAD 1in Sample [mg/L]^(1	Mean Determined Content ofAD 1in Sample [mg/L]^(1)	Actual concentration in % of initial concentration
0	98.9	99.5	---
	100.0
120	98.6	99.2	99.7
	99.7

⁽¹⁾: regardinga dilution factor of 4/3

Table3:     Time course of AD 1 concentration at pH 9 at 50 °C

Time [h]	Determined Content ofAD 1in Sample [mg/L]^(1	Mean Determined Content ofAD 1in Sample [mg/L]^(1)	Actual concentration in % of initial concentration
0	86.6	85.9	---
	85.2
120	80.5	80.6	93.8
	80.7

⁽¹⁾: regardinga dilution factor of 4/3

Validity criteria fulfilled:

yes

Remarks:

validated according to guideline SANCO/3029/99 rev. 4

Conclusions:

The abiotic degradation of AD 1 as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (440/2008).

The hydrolysis of AD 1 is negligible at pH 4, pH 7 and pH 9. The degradation of AD 1 was less than 10 % at pH 4, pH 7 and pH 9 at 50 °C over a period of 120 hours. Therefore the corresponding half-life time can be estimated to be longer than one year at 25 °C.

Executive summary:

Report: Bär, C. (2017): Abiotic Degradation - Hydrolysis as Function of pH of AD 1

Source: Eurofins Agroscience Services EcoChem GmbH / Eurofins Agroscience Services Ecotox GmbH,Eutinger Straße 24,
D – 75223 Niefern-Öschelbronn, Germany; unpublished Report: S15 -05586

Guidelines: OECD guideline 111 and EC method C.7 (440/2008)

Deviations:no

GLP:yes (incl. certificate)

Study period: 30 November 2015 to 21 July 2017

Results: The degradation of AD 1was less than 10 % at pH 4, pH 7 and pH 9 at 50 °C over a period of 120 hours. Therefore the corresponding half-life time can be estimated to be longer than one year at 25 °C.

Description of key information

The hydrolysis of AD 1 is negligible at pH 4, pH 7 and pH 9. The degradation of AD 1 was less than 10 % at pH 4, pH 7 and pH 9 at 50 °C over a period of 120 hours. Therefore the corresponding half-life time can be estimated to be longer than one year at 25 °C.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C