[2-(1-ethoxyethoxy)ethyl]benzene

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 February 2017 - 12 July 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Remarks:

LC-UV

Details on sampling:

PREPARATION OF THE SAMPLES
- Tier 1 (pH 4, 7 and 9) and tier 2 (pH 4 and 7) tests were performed.
- Test item was spiked to each sterile and oxygen-free buffer using a spiking solution in acetonitrile. Target concentration: 10 mg/L
- For each sampling time, duplicate vessels under nitrogen were filled with test solution.
- The vessels were placed in a temperature controlled environment.
- Blank buffers containing a similar content of co-solvent were treated similarly as the test samples.

SAMPLING DETAILS
- Samples for analysis were taken immediately after preparation (t=0).
- Samples for analysis (except for the blanks) were taken after 5 days (Tier 1) or at several sampling points after t=0 (Tier 2).
- Samples taken from solutions with a temperature > 20°C were cooled to room temperature using running tap water.

pH MEASUREMENTS
The pH of the test solutions (except for the blanks) was determined at least at the beginning and at the end of each test.

Buffers:

- Buffer pH 4: aqueous solution of 16.7% 0.1 M sodium acetate and 83.3% 0.1 M acetic acid. Sodium azide content: 0.0009% (w/v).
- Buffer pH 7: aqueous solution of 0.1 M potassium di-hydrogenphosphate adjusted to pH 7 using 10 N sodium hydroxide. Sodium azide content: 0.0009% (w/v).
- Buffer pH 9: aqueous solution of 0.1 M boric acid and 0.1 M potassium chloride adjusted to pH 9 using 10 N sodium hydroxide. Sodium azide content: 0.0009% (w/v).

Details on test conditions:

TEST SYSTEM
- Sterilisation method: Each buffer was filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman) and transferred into a sterile vessel.
- Measures to exclude oxygen: nitrogen gas was purged through the sterile buffers for 5 minutes.
- Measures taken to avoid photolytic effects: the test vessels were kept in the dark.
- The samples not analysed on the sampling day were stored in the freezer for max. 13 days (stability has been demonstrated over this period). On the day of analysis, the frozen samples were defrosted at room temperature, treated and analysed.

TEST MEDIUM
- Kind of water used for the buffers: tap water purified by a purification system (Milli-Q, Millipore)
- Identity and concentration of co-solvent: acetonitrile. The volume of the co-solvent was < 1% of the sample volume. The nominal concentrations were not corrected for this.

ACTUAL TEMPERATURES
Tier 1
pH 4, 7 and 9: 49.3°C ± 0.7°C

Tier 2
pH 4: 19.8°C ± 0.1°C, 30.1°C ± 0.1°C and 50.1°C ± 0.1°C
pH 7: 19.7°C ± 0.5°C, 49.6°C ± 0.5°C and 59.9°C ± 0.1°C

Duration:

24.23 h

pH:

4

Temp.:

20 °C

Initial conc. measured:

9.83 mg/L

Remarks:

mean (n=2) conc.

Duration:

4.33 h

pH:

4

Temp.:

30 °C

Initial conc. measured:

9.93 mg/L

Remarks:

mean (n=2) conc.

Duration:

2.42 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

10.6 mg/L

Remarks:

mean (n=2) conc.

Duration:

720.98 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

10.6 mg/L

Remarks:

mean (n=2) conc.

Duration:

332.33 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

10.45 mg/L

Remarks:

mean (n=2) conc.

Duration:

167.63 h

pH:

7

Temp.:

60 °C

Initial conc. measured:

10.8 mg/L

Remarks:

mean (n=2) conc.

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Preliminary study:

At pH 4 and pH 7, a degree of hydrolysis of > 10% (100% and 64%, respectively) was observed after 5 days at 50°C. According to the guideline, the higher tier test was required.

At pH 9, hydrolysis of < 10% (6.2%) was observed after 5 days at 50°C (half-life time at 25°C is > 1 year). No further tests were required.

Test performance:

RECOVERIES
- Recovery is the concentration analysed at t=0 relative to the nominal concentration.
- The mean (n=2) recovery at each pH and temperature was calculated (see table below).
- The mean recoveries fell within the criterion range of 90-110% (98-106% at pH 4 test and 105-108% at pH 7 test).
- The concentrations analysed in the test samples were not corrected for recovery.

Transformation products:

not specified

% Recovery:

98

pH:

4

Temp.:

20 °C

Remarks on result:

other: Tier 2

% Recovery:

99

pH:

4

Temp.:

30 °C

Remarks on result:

other: Tier 2

% Recovery:

106

pH:

4

Temp.:

50 °C

Remarks on result:

other: Tier 2

% Recovery:

106

pH:

7

Temp.:

20 °C

Remarks on result:

other: Tier 2

% Recovery:

105

pH:

7

Temp.:

50 °C

Remarks on result:

other: Tier 2

% Recovery:

108

pH:

7

Temp.:

60 °C

Remarks on result:

other: Tier 2

% Recovery:

99

pH:

4

Temp.:

50 °C

Remarks on result:

other: Tier 1

% Recovery:

100

pH:

7

Temp.:

50 °C

Remarks on result:

other: Tier 1

% Recovery:

103

pH:

9

Temp.:

50 °C

Remarks on result:

other: Tier 1

pH:

4

Temp.:

20 °C

Hydrolysis rate constant:

0.186 h-1

DT50:

3.7 h

Type:

(pseudo-)first order (= half-life)

pH:

4

Temp.:

30 °C

Hydrolysis rate constant:

0.649 h-1

DT50:

1.1 h

Type:

(pseudo-)first order (= half-life)

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

5.86 h-1

DT50:

0.12 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0.35 h-1

DT50:

2 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: calculated from the Arrhenius equation

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

0 h-1

DT50:

99 d

Type:

(pseudo-)first order (= half-life)

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.008 h-1

DT50:

89 h

Type:

(pseudo-)first order (= half-life)

pH:

7

Temp.:

60 °C

Hydrolysis rate constant:

0.021 h-1

DT50:

33 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

55 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: calculated from the Arrhenius equation

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Table: Preliminary test (Tier 1) results

 

pH code	Sampling time	Analyzed concentration [mg/L]	Degree of hydrolysis [%]		pH
			Individual	Mean
pH 4	0 hours	9.89			4.0
		9.92			4.0
	5 days	not detected	100	100	4.0
		not detected	100		4.0
pH 7	0 hours	10.0			7.0
		10.0			7.0
	5 days	3.47	65	64	7.1
		3.72	63		7.1
pH 9	0 hours	10.3			9.0
		10.3			9.0
	5 days	9.59	7.0	6.2	9.0
		9.75	5.4		9.0

Validity criteria fulfilled:

yes

Remarks:

The mean recoveries fell within the criterion range of 90-110% (98-106% at pH 4 test and 105-108% at pH 7 test).

Conclusions:

The half-life time of the substance at 25°C at pH 4, pH 7 and pH 9 was determined to be 2.0 hours, 55 days and > 1 year, respectively.

Executive summary:

The rate of hydrolysis of the substance at pH values normally found in the environment (pH 4-9) was determined in a GLP-compliant study according to OECD 111.

A degree of hydrolysis of < 10% was observed at pH 9 after 5 days at 50°C (tier 1). This corresponds with a half-life time at 25°C of > 1 year and the substance can be considered hydrolytically stable at pH 9.

Hydrolysis of > 10% was determined at pH 4 and pH 7 after 5 days and 50°C. Hydrolysis rates at 20, 30 and 50°C (pH 4) and at 20, 50 and 60°C (pH 7) were determined in a tier 2 study. The substance was shown to degrade by a pseudo-first order behaviour. Half-life times at 25°C were determined from the Arrhenius equation: 2.0 hours at pH 4 and 55 days at pH 7. This leads to the conclusion that Hyacinth body has a half-life of 55 days at an environmental pH of 7.

Description of key information

Hydrolysis: (OECD TG 111): DT50 is 55 days at pH 7. The substance is hydrolytically stable at pH 9 (half-life time at 25°C of > 1 year), hydrolytically unstable at pH 7 (half-life time at 25°C of 55 days) and hydrolytically unstable at pH 4 (half-life time at 25°C of 2.0 hours).

Key value for chemical safety assessment

Half-life for hydrolysis:

55 d

at the temperature of:

25 °C

Additional information

The rate of hydrolysis of the substance at pH values normally found in the environment (pH 4-9) was determined in a GLP-compliant study according to OECD 111.

A degree of hydrolysis of < 10% was observed at pH 9 after 5 days at 50°C (tier 1). This corresponds with a half-life time at 25°C of > 1 year and the substance can be considered hydrolytically stable at pH 9.

Hydrolysis of > 10% was determined at pH 4 and pH 7 after 5 days and 50°C. Hydrolysis rates at 20, 30 and 50°C (pH 4) and at 20, 50 and 60°C (pH 7) were determined in a tier 2 study. The substance was shown to degrade by a pseudo-first order behaviour. Half-life times at 25°C were determined from the Arrhenius equation: 2.0 hours at pH 4 and 55 days at pH 7. This leads to the conclusion that Hyacinth body has a half-life of 55 days at an environmental pH of 7.