2,2,6,6-tetramethylpiperidinooxy

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:

2009-08-20 to 2010-02-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Version / remarks:

(1992)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge was collected, prepared and controlled by the test institute.
- Laboratory culture: The activated sludge, which was cultivated for 21.5 hours after the synthetic sewage had been added, was used.
- Method of cultivation: Preparation of synthetic sewage with glucose, peptone and potassium dihydrogenphosphate, pH adjustment to 7.0.
- Preparation of inoculum for exposure: suspended solid concentration was measured.
- Concentration of sludge: 30 mg/L as the concentration of suspended solid
- Water filtered: purified water

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

Biochemical oxygen demand

Parameter followed for biodegradation estimation:

DOC removal

Remarks:

Dissolved organic carbon (DOC) has been determined at test end.

Parameter followed for biodegradation estimation:

test mat. analysis

Remarks:

Analysis of the test item concentration by HPLC at the end of the test.

Details on study design:

TEST CONDITIONS
- Composition of medium: preparation of culture medium according to japanese industrial standards (JIS) K 0102-2008 section 21, pH 7.0
- Test temperature: 25 +/- 1°C
- pH: 7.0
- pH adjusted: measured before test start
- Suspended solids concentration: 30 mg/L in the test vessels
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: test vessels, volume 300 mL
- Number of culture flasks/concentration: 3 vessels for test substance concentration
- Method used to create aerobic conditions: The test solution was stirred by a magnetic stirrer.
- Measuring equipment: Closed system oxygen consumption measuring apparatus for BOD measurement
- Details of trap for CO2 and volatile organics if used: Soda lime as absorbent for carbon dioxide

SAMPLING
- Sampling frequency: The appearance of the test solution (e.g. color) was checked once a day.
- Sampling method: Measurement of BOD by using a closed system oxygen consumption measuring apparatus.


CONTROL AND BLANK SYSTEM
- Inoculum blank: Test vessel without test item (1 vessel)
- Abiotic sterile control: test item and water, no acitivated sludge (1 vessel)
-Reference control: Sludge and aniline (1 vessel)

Reference substance:

aniline

Remarks:

100 mg/L

Preliminary study:

Converted products were expected due to the results from a preliminary test.

Test performance:

The reference substance was used to confirm that the sludge is sufficiently active.

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Percentage biodegradation by BOD.

Parameter:

% degradation (DOC removal)

Value:

0

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Percentage biodegradation by DOC.

Parameter:

% degradation (test mat. analysis)

Value:

28

Sampling time:

28 d

Remarks on result:

other:

Remarks:

percentage biodegradation of test item.

Details on results:

Each of the average percentage biodegradations by BOD and by DOC was 0%. The growth of the sludge was not observed at the end of the cultivation. These results showed that the test item was not biodegraded by microorganisms.

Approximately theoretical amount of the test item remained in the test solution (water +test item). On the other hand, the percentage residue of the test item was low as 69-72% in the test solutions (sludge + test item). These result suggested that converted products corresponding to decrease of the test item were produced in the test solutions (sludge + test item). However, no peak corresponding to converted products was detected on the HPLC chromatograms in all test solutions.

As some of the test item was thought to be converted during the cultivation in the test solutions (sludge + test item), the qualitative analysis of converted products by LC-MS was performed. As a result, one peak corresponding to a converted product was detected and the converted product was presumed as 1-hydroxy-2,2,6,6-tetramethylpiperidine, which was produced by hydroxylation of oxyl group of the test item.

The percentage production of 1-hydroxy-2,2,6,6-tetramethylpiperidine was estimated as 28-32% which was calculated from the difference between the percentage residues of the test item and DOC. 1-Hydroxy-2,2,6,6-tetramethylpiperidine and the rest of the test item were not biodegraded by microorganisms and remained in the test solutions.

Results with reference substance:

The reference substance aniline showed 71 % degradation after 7 days and 78 % degradation after 14 days. At test end 80 % of the reference substance has been degraded.

Validity criteria fulfilled:

yes

Remarks:

Oxygen uptake in inoculum blank was below 60 mg/L in 28 days. The difference of degradation in the test substance replicates was <20 %. Degradation of aniline was 71% after 7 days (criteria >40%) and 78 % after 28 days (Criteria >65%).

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the test conditions, some of the test substance has been converted into 1-hydroxy-2,2,6,6-tetramethylpiperidine in presence of microorganisms. The test substance and the converted were not biodegraded by microorganisms.

Description of key information

In a biodegradation test according to guideline OECD 310C, some of the test substance has been converted into 1-hydroxy-2,2,6,6-tetramethylpiperidine in presence of microorganisms. The test substance and the converted were not biodegraded by microorganisms under the test conditions.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Biodegradation of the test substance has been examined in a GLP-conform guideline test according to OECD 301C (MITI test). Activated slugde was incubated for 28 days with the test substance. The biochemical oxygen demand has been determined with a closed system oxygen consumption measuring aparatus and the dissolved oxygen concentration has been determined by total organic carbon analysis. furthermore the test substance has been monitored by HPLC analysis. The biodegradation according to BOD and DOC has been 0% after 28 days and shows that the test item was not biodegraded by microorganisms. Under the test conditions of this study, some of the test item was converted into 1-hydroxy-2,2,6,6-tetramethylpiperidine under the presence of microorganisms. The percentage production of 1-hydroxy-2,2,6,6-tetramethylpiperidine was estimated to be 28-32%. 1-Hydroxy-2,2,6,6-tetramethylpiperidine and the rest of the test item were not biodegraded by microorganisms and remained in the test solutions.