Ethyl 2-ethylhexanoate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sewage treatment plant Hochdahl, Germany

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

act. ingr.

Initial conc.:

5 mg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: no data
- Solubilising agent (type and concentration if used): Disponil NP 9.5EO 10PO
- Test temperature: 20±1°C
- pH: no data
- Continuous darkness: no data

TEST SYSTEM
- Culturing apparatus: conical shoulder bottle
- Number of culture flasks/concentration: 2 (inoculum blank: 4)
- Measuring equipment: iodometric oxygen measurement, Winkler method
- closed system


SAMPLING
- Sampling frequency: 7, 14, 21, 28 d

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: no
- Other: O2 control (mineral medium without inoculum and test substance)
- Solubilising agent control (mineral medium, solubilising agent, inoculum)

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

67

Sampling time:

28 d

Remarks on result:

other: 2 mg/L test substance

Parameter:

% degradation (O2 consumption)

Value:

67

Sampling time:

28 d

Remarks on result:

other: 5 mg/L test substance; at the end of the test period O2 depletion was observed, thus, the result represents minimum degradation

Results with reference substance:

Sodium benzoate was degradednormally: 73% after 7 d, 80% after 14d, 76% after 21 d, 80% after 28 d

	Concentration [mg/L]	% BOD/COD
		7 d	14 d	21 d	28 d
Test substance	2	5	49	67	67
	5	2	39	65	67 (O2 depletion)
Reference substance	2	73	80	76	80

 

Oxygen consumption

	Concentration [mg/L]	Oxygen concentration [mg/L]
		7 d	14 d	21 d	28 d
Test substance	2	9.98 9.96	7.17 6.24	5.57 5.64	5.47 5.48
	5	8.77 8.80	1.82 6.24	1.12 0.17	0.21 0.37
Reference substance	2	6.55 6.72	6.35 6.56	6.66 6.21	6.21 6.22
Inoculum blank	---	9.12 9.13 9.05 8.97	90.1 9.29 9.05 9.15	8.89 8.98 9.03 9.01	8.88 8.76 8.90 9.01

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

2-Ethyl ethyl capronate was readily biodegradable in this closed bottle test.

Executive summary:

The biodegradation of 2-Ethyl ethyl capronate (100% a.i.) was investigated in a study conducted according to OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test) over a period of 28 days using activated sludge sampled from a municipal sewage treatment plant as inoculum. Due to the low water solubility of the test substance, Disponil NP 9.5EO 10PO was used as solubilising agent.

The biodegradation rate was determined by measurement of O2 consumption. Inoculum blank, O2 control (mineral medium without inoculum and test substance), solubilising agent control (mineral medium, solubilising agent, inoculum) and procedural/functional control with the reference substance Sodium benzoate were performed. The test was performed with 2 and 5 mg/L test substance concentration.

The functional control reached the pass level >60% after 7 d (73%).

The biodegradation of the test substance was 67% (at 2 mg/L) and 67% (at 5 mg /L) after 28 days. However, in the 5 mg/L samples oxygen depletion was observed during the test. Thus, these values represent only minimum biodegradation.

According to the OECD guideline, the values obtained in a 14 d window would be acceptable in the Closed Bottle method if it is considered that the number of bottles necessary to evaluate the 10-d window causes the test to become too unwieldy.

The 14 d window started > 7 d; after 21 d > 60% degradation was reached. Thus, the test substance can be considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable