Isobutyl phenylacetate

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 2002 - January 2003.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to a recognised guideline and is GLP compliant.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Isobutyl phenyl acetate

IUPAC Name:

Isobutyl phenyl acetate

Test material form:

liquid

Details on test material:

Identification: Isobutyl phenyl acetate
Commercial name: Isobutyl phenyl acetate
Chemical nature: 2-methylpropyl phenylacetate
Empirical formula: C12H16O2
Molecular weight: 192.2 g/mol
CAS No.: 102-13-6
Appearance/physical state: Colorless liquid
Lot No: 9000466715
Purity: 99.9%
Expiry date: 14 April 2004

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Peney-Dessous) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

35 d

Initial test substance concentration

Initial conc.:

100 mg/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Test substance samples (25 mg, corresponding to 100 mg/l in a 250-ml flask) were weighed in small aluminium boats and added directly to the test flasks of the SAPROMAT, whereas reference substance samples (sodium benzoate)were added as 1.0 ml of a 25 mg/ml solution in mineral medium.
All flasks were filled with 250 ml of mineral medium. Samples of test or reference substance, or both, were added. Then, a volume of suspended sludge corresponding to 7.5 mg dry weight (as determined from 3.6, generally 1 to 3 ml) was added.
About 2 g of soda lime is placed in an attachment of the stopper, the flasks are closed and placed in the water bath of the SAPROMAT. After temperature and pressure equilibration, the oxygen-meters of the instrument are set to zero (time zero of the experiment).

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Preliminary study:

Not applicable

Test performance:

Oxygen uptakes, as read on the SAPROMAT meters, were corrected to account for the small differences between actual and nominal concentrations of test and reference substances.
Degradation of sodium benzoate exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified (validity criterion).

% Degradation

% Degradation 1

Key result

Parameter:

% degradation (O2 consumption)

Value:

83

Sampling time:

28 d

% Degradation 2

Parameter:

% degradation (O2 consumption)

Value:

84

Sampling time:

35 d

Details on results:

Isobutyl Phenylacetate underwent 83% biodegradation after 28 days (84% after 35 days) in the test conditions. Biodegradation starts on day 2 and reaches 78% at the end of the 10-day window (days 2 to 12).
The curves obtained with the reference substance alone and with Isobutyl Phenylacetate + reference substance show no toxic effect of Isobutyl Phenylacetate to the micro-organisms at the test concentration (100 mg/l).
Thus, Isobutyl Phenylacetate should be regarded as readily biodegradable according to this test.

BOD5 / COD results

Results with reference substance:

Degradation of sodium benzoate exceeded 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified (validity criterion).

Any other information on results incl. tables

Table 1: Measured concentrations and pH values for test and reference substances

Flask no.	Concentrations (mg/L		pH
	Test subst.	Ref. Subst.	Initial	Final
1/9	0	0	7.44	7.52
1/10	0	0	7.44	7.39
1/11	0	100.1	7.44	7.74
1/12	0	100.1	7.44	7.92
2/9	103.0	100.1	7.44	7.99
2/10	104.4	100.1	7.44	7.99
2/11	105.2	0	7.44	7.49
2/12	105.7	0	7.44	7.45

Table 2: Biological oxygen demand (BOD) and % degradation

	Days	2	7	12	21	28	35
BOD Sludge	1^stflask	9.0	20.0	25.0	29.0	31.0	33.0
	2^ndflask	8.0	20.0	26.0	34.0	40.0	48.0
	mean	8.5	20.0	25.5	31.5	35.5	40.5
BOD Test Subs.	1^stflask	81.2	206.3	227.5	244.0	248.0	253.9
	2^ndflask	78.0	193.2	213.3	231.6	239.4	246.3
	1^stflask corrected	72.7	186.3	202.0	212.5	212.5	213.4
	2^ndflask corrected	69.5	173.2	187.8	200.1	203.9	205.8
% degr.	1^stflask	29	75	81	85	85	85
	2^ndflask	28	69	75	80	82	82
	mean	28	72	78	83	83	84

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Isobutyl Phenylacetate was 83% biodegraded after 28 days, and the 10-day window was met. Therefore, Isobutyl Phenylacetate is regarded as readily biodegradable according to this study.

Executive summary:

The ready biodegradability of Isobutyl Phenylacetate was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method No. 301 F. Isobutyl Phenylacetate undergoes 83% biodegradation after 28 days (84% after 35 days) in the test conditions. Biodegradation starts on day 2 and reaches 78% at the end of the 10-day window (days 2 to 12). The curves obtained with the reference substance alone and with Isobutyl Phenylacetate + reference substance show no toxic effect of Isobutyl Phenylacetate to the micro-organisms at the test concentration (100 mg/l). Thus, Isobutyl Phenylacetate should be regarded as readily biodegradable according to this test.