Isopropyl 2-ethylhexanoate

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 31, 2017 to January 12, 2018.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Version / remarks:

adopted 23.03.2006, corrected 26.09.2014

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Isopropyl 2-ethylhexanoate

EC Number:

266-549-5

EC Name:

Isopropyl 2-ethylhexanoate

Cas Number:

67024-46-8

Molecular formula:

C11H22O2

IUPAC Name:

isopropyl 2-ethylhexanoate

Test material form:

liquid

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

The study was performed with aerobic activated sewage sludge from the aeration stage of the local wastewater treatment plant, ARA Birs (Birsfelden / Switzerland), which treats predominantly domestic sewage.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

17.2 mg/L

Based on:

IC (inorganic carbon)

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Immediately before use, sufficient inoculated mineral medium was prepared by adding diluted
activated sludge (see Section 5.1.2) to mineral medium. Aliquots of inoculated medium (well
mixed) were dispensed into replicate bottles to give a headspace to liquid ratio of 1:4.9 (i.e.
133 mL medium into 160 mL-capacity bottles).
The test item (3.8 μL) was injected into sealed bottles containing the inoculated mineral
medium using a high precision syringe.
The blank bottles were treated in a similar fashion, but excluding the test item.

Reference substance

Reference substance:

other: Octan-1-ol.

Results and discussion

% Degradation

% Degradation 1

Key result

Parameter:

% degradation (CO2 evolution)

Value:

3.5

Sampling time:

5 d

% Degradation 2

Parameter:

% degradation (CO2 evolution)

Value:

58.5

Sampling time:

11 d

% Degradation 3

Parameter:

% degradation (CO2 evolution)

Value:

67.6

Sampling time:

21 d

% Degradation 4

Key result

Parameter:

% degradation (CO2 evolution)

Value:

74.6

Sampling time:

28 d

Details on results:

The inorganic carbon (IC) production of Isopropyl 2-ethylhexanoate in the test medium
significantly increased from Exposure Day 5 until Day 14, when a mean biodegradation level
of 63 % of the theoretical maximum IC production (ThIC) was obtained. Afterwards the
biodegradation continued to increase to a lesser extent until the end of the 28-day exposure
period. At the end of the test the mean percentage biodegradation of the five test item bottles
sampled was 75 % with a 95 % confidence interval of ± 3.6 %.
The pass level for ready biodegradability, i.e. an IC production of at least 60 % of the ThIC in
a 10-day window within the 28-day period of the test was reached approximately on Exposure
Day 12.
In conclusion, Isopropyl 2-ethylhexanoate was found to be readily biodegradable under the test
conditions within 28 days.
In the procedure control, the reference item 1-octanol was degraded by an average of 79 % and
88 % by Exposure Day 7 and 14, respectively, thus confirming suitability of the activated
sludge (> 60 % degradation by Exposure Day 14). At the end of the 28-day exposure period,
the mean percentage biodegradation of the five procedure control bottles sampled was 91 %
with a 95 % confidence interval of ± 1.9 %.
In the toxicity control, containing both the test item and the reference item, no inhibitory effect
on the biodegradation of the reference item was determined. Thus, Isopropyl 2-ethylhexanoate
had no inhibitory effect on the activity of activated sludge microorganisms at the tested
concentration of 24.3 mg/L.
The validity criteria of the test were met.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Isopropyl 2-ethylhexanoate was found to be readily biodegradable under the test
conditions within 28 days.