Potassium isobutyrate

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

Study period:

09 Jan 2019 - 12 Feb 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted 17. Jul. 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

30 May 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Sponsor / 181101001
- Expiration date of the lot/batch: 31. Oct. 2020
- Purity test date: 01. Nov. 2018

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room Temperature (20 ± 5 °C); Keep away from humidity
- Stability under test conditions: Stable
- Solubility and stability of the test substance in the solvent/vehicle:
Stability in solvents: H2O: 96h; EtOH: unknown; acetone: unknown; CH3CN: unknown; DMSO: unknown
Stability in solvents: H2O: > 1 g/L; EtOH: unknown; acetone: unknown; CH3CN: unknown; DMSO: unknown

Pre-treatment: A stock solution containing 5001 mg/L in deionised water was prepared. Its organic carbon was determined in order to estimate the amount to be added to the test flasks.
The TOC was 2002.22 mg/L, giving an organic carbon content of 40.04 %.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, 67435 NW-Lachen-Speyerdorf.
Date of collection: 11. Jan. 2019, batch no: 20190111.

- Pretreatment: The sludge was filtrated, washed with test medium (2x) and re-suspended in test medium. It was then aerated until use. The dry matter was determined to contain 4800 mg of suspended solids/L.

Duration of test (contact time):

28 d

Initial conc.:

50 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: The medium was prepared from the stock solutions. The stock solution of the positive control was prepared and its DOC was measured. The stock solution of the test item was prepared and its DOC was measured. The inoculum was taken from its source, washed, aerated and the dry matter was determined.
- Test temperature: 19.7 – 20.9 °C without direct lighting
- pH:
Test 1: 7.9
Test 2: 7.9
- pH adjusted: no
- Aeration of dilution water: The test vessels were filled with medium and inoculum. Then, all flasks were aerated for 72 hours with puri-fied, CO2-free, moistened air to purge the system of CO2.
- Suspended solids concentration: The dry matter was determined to contain 4800 mg of suspended solids/L.
- Continuous darkness: yes - no direct lighting
- Other: The test was performed with a nominal start concentration of 20 mg organic carbon/L of the test item.

TEST SYSTEM
- Culturing apparatus:
The test vessels were aerated with purified (by activated charcoal), CO2-scrubbed, moistened air. The scrub-bing of carbon dioxide was achieved by bubbling the purified air through a flask containing 1.5 M NaOH. To control the absence of CO2, the air was then led through a flask containing a solution of Ba(OH)2 before reaching the test vessels.
Magnetic stirrers were used to prevent deposition of inoculum.
The emitted CO2 was trapped in 0.25 M NaOH. Two scrubbers containing 100 mL each were connected in series to the test vessels. The initial IC value of the 0.25 M NaOH was separately determined in each flask.

- Number of culture flasks/concentration: 2

- Measuring equipment:
Analyses of the emitted CO2 were made by IC measurement using the carbon analyser TOC multi N/C 2100S, Analytik Jena. Each sample was measured in duplicate or triplicate, respectively (depending on the variation between the measured values). The carbon analyser was calibrated with freshly prepared reference solutions containing potassium hydrogen phthalate (TC), sodium hydrogen carbonate and sodium carbonate (IC). Quali-ty control samples were measured daily.

Trap used: The emitted CO2 was trapped in 0.25 M NaOH. Two scrubbers containing 100 mL each were connected in series to the test vessels. The initial IC value of the 0.25 M NaOH was separately determined in each flask.

SAMPLING
- Sampling frequency: From each front scrubber flask, 10 samples were taken in order to determine the emitted CO2 (on day 0, 2, 4, 7, 9, 11, 14, 18, 23 and 29).
- Sampling method: The sample volume was 1 mL. The resulting change in the volume of the front flask was considered in the calculation of emitted CO2. On day 28, 5 mL HCl 2 M was added to each test flask in order to drive off dissolved CO2. On day 29, samples from both scrubber flasks were taken.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2, containing mineral medium and inoculum
- Abiotic sterile control: 1, containing test item, mineral medium and HgCl2
- Toxicity control: 1, containing test item, positive control, mineral medium and inoculum
- Apparatus blanks: 2, containing mineral medium only
- Positive control flasks: 2, containing positive control, mineral medium and inoculum
- Test flasks: 2, containing test item, mineral medium and inoculum

Reference substance:

aniline

Remarks:

positive control

Key result

Parameter:

% degradation (CO2 evolution)

Value:

85

Sampling time:

28 d

Potassium isobutyrate is considered as “not readily biodegradable”

 Potassium isobutyrate is considered as “ultimately biodegradable within 28 days”.

¨          

 

All validity parameters and values are presented in the following table:

Parameter	Criterion	Found	Assessment
IC content of test item solution in medium	< 5% of TC	0 %	valid
CO2emitted by the controls	< 70 mg/L	14.2 mg/L	valid
Difference within replicates	< 20%	3.4 %	valid
Degradation of positive control > 60%	≤14 days	7 days	valid
Degradation in the toxicity flask on day 14	> 25%	39.1 %	non - toxic

 

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The following data were determined for the test item Potassium isobutyrate:
10-day-window: day 3 – 13 degradation at the end of 10-day-window 52 % degradation at the end of the test 85 % pass level following guideline: 60 % at the end of 10-day-window for pure substances
respective 60 % at the end of the test for mixtures
Therefore, when applying the 10-day-window, the test item Potassium isobutyrate is not readily biodegradable following OECD 301B and EU C.4-C respectively. As degradation surpassed 60% in the course of the test, Potassium isobutyrate is considered as ultimately biodegradable, within 28 days.

Executive summary:

Title of Study: Determination of the aerobic ready biodegradability of Potassium isobutyrate in the CO2 Evolution Test following OECD 301B resp. EU C.4-C

Findings and Results:

The test item Potassium isobutyrate was tested using a concentration of nominally 20 mg organic car-bon/L Potassium isobutyrate in test medium following OECD 301B and EU-Method C.4-C.

Aniline was chosen as positive control.

Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L). The test was left running for 28 days.

All validity criteria were met. Degradation of the positive control surpassed the pass level of 60 % after 7 days.

The following data were determined for the test item Potassium isobutyrate:

10-day-window:       day 3 – 13        

degradation at the end of 10-day-window:       52 %

degradation at the end of the test:       85 %

pass level following guideline:        60 % at the end of 10-day-window for pure substances  respective 60 % at the end of the test for mixtures

Therefore, when applying the 10-day-window, the test item Potassium isobutyrate is not readily biode-gradable following OECD 301B and EU C.4-C respectively. As degradation surpassed 60% in the course of the test, Potassium isobutyrate is considered as ultimately biodegradable, within 28 days.

Description of key information

One key study was performed according to OECD 301B under the conditions of GLP.

Key value for chemical safety assessment

Type of water:

freshwater

Additional information

Potassium isobutyrateis considered as “not readily biodegradable”

 Potassium isobutyrateis considered as “ultimately biodegradable within 28 days”.