4-tert-butyl-3-hydroxy-2,6-xylylacetonitrile

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study in compliance with GLP-criteria.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

4-tert-butyl-3-hydroxy-2,6-xylylacetonitrile

EC Number:

259-766-1

EC Name:

4-tert-butyl-3-hydroxy-2,6-xylylacetonitrile

Cas Number:

55699-10-0

Molecular formula:

C14H19NO

IUPAC Name:

2-(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)acetonitrile

Details on test material:

- Name of test material (as cited in study report): 4-tert-Butyl-3-hydroxy-2,6-xylylacetonitrile
- Physical state/ Appearance: Solid / white to yellowish
- Homogeneity: Homogeneous
- Storage conditions: Storage at room temperature

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Municipal activated sludge from the wastewater treatment plant of Mannheim/Baden Württemberg (Germany). The inoculum was collected on 08 October 2007 from the aeration tank of the plant and aerated in the laboratory until use. A suitable aliquot of the activated sludge suspension was sieved by a finely woven mesh with a mesh size of about 1 mm. After settling the supernatant was discarded and the sludge suspension was filled up with tap water. The sludge of the suspension was adjusted to a concentration of 6.0 g/L dry weight and then added to the test vessels to obtain a sludge concentration of 30 mg/L dry substance. Finally the activated sludge suspension in the test vessels was pre-aerated for about 24 hours at a temperature of 22 ± 2 °C. Total pre-aeration time: about 24 hours.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST SYSTEM:
The Carbon Dioxide Evolution Test was performed in 2 L incubation bottles filled up to a volume of 1.5 L. The bottles were connected to two serial scrubbing bottles (total volume 250 mL) filled with 100 mL 0.05 mol sodium hydroxide solution for the adsorption of carbon dioxide from biodegradation processes. Usually twice a week the Total Inorganic Carbon (TIC) values of the adsorption solutions of the first trap were determined and used for the calculation of the produced carbon dioxide. After each sampling the second trap was moved forward and the new trap with fresh sodium hydroxide solution was placed into the second position. Each trap was analyzed separately. The test was performed at 22±2°C.
The TIC-value of the freshly prepared sodium hydroxide solution was determined and considered by the calculation of biogenic produced carbon dioxide amount. The incubation bottles were stirred on magnetic stirrers; the aeration was performed with carbon dioxide free air at a flow of approximately 800 mL per hour.

PREPARATION OF TEST ASSAYS:
For preparation of the test assays, first the required volume of distilled water was dosed to the test vessels. After adding of solutions of mineral salts, the pH-values of the test media were adjusted to 7.4 ± 0.2. The stock solution of activated sludge was added and the test assays were aerated at 22 ± 2 °C for about 24 hours. On next day the test- respectively reference substance were added in the required concentrations to the test vessels and the pH-values of the test assays were measured once again. The blank control assays (BC) contain only mineral medium and activated sludge. The test substance assays (TS) contain the test substance with concentration of 20 mg/L Total Organic Carbon (TOC), the reference substance assay (RS) contains aniline with a concentration of 20 mg/L TOC, The assay for inhibition control (IH) contains the test substance and the reference substance in the same concentration in relation to its total organic carbon contents. The test vessels were connected with an aeration unit and aerated by bubble aeration with carbon dioxide free air. The exposure phase was started by connection of the several test vessels with the absorption units.
At the end of exposure, the pH values were measured in each test vessel. For stripping of carbon dioxide, dissolved in the test medium, each test vessel was acidified by adding 2 mL of concentrated hydrochloric acid. The concentration of dissolved organic carbon in the blank controls and reference substance assays was determined at the beginning and end of exposure. However, since the test substance was insufficiently soluble in water, no useful measurements could be recorded from the inhibition control and test substance assays. The aeration was continued for about 24 hours and the released carbon dioxide amounts in both traps of each test vessel were determined and added to the calculated amount of day 28.

ANALYSIS OF TIC AND DOC:
Samples for the TIC- and DOC-analysis were performed as repeat determination, using a TOC-analyzer equipped with an auto sampler (Shimadzu TOC-5000A). The system works with a combustion/non-disperse infrared gas analysis method. For calibration of the TOCAnalyzer, standard samples were measured before start of measurements to prove the conformity with the calibration curve. The samples for TIC-analysis (absorption solution) were measured without further treatment. The samples for DOC-analysis were centrifuged for about 15 minutes at 4000 rpm. The samples were analyzed on the day of sampling.

Reference substance

Reference substance:

aniline

Results and discussion

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

< 10

Sampling time:

28 d

Details on results:

SUMMARY OF RESULTS:
- Duration of the adaptation phase (days): --
- Degradation of the test subst. at the end of the ten-day window (% CO2/ThCO2): --
- Degradation degree of the test subst. at the end of exposure (% CO2/ThCO2), mean value: <10
- Degradation degree of the reference substance after 14 days (% CO2/ThCO2): 83
- Degradation degree in the inhibition control after 14 days (% CO2/ThCO2): 40