1-methyl-N,N',N''-tris(1-methylpropyl)silanetriamine

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:

2016-04-04 to 2016-08-04

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)

Deviations:

no

Remarks:

Study plan deviations are listed; a different batch of the reference item was used for the test but the study integrity was not adversely affected by these deviations

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: activated sludge freshly obtained from a municipal sewage treatment plant (Netherlands), receiving predominantly domestic sewage.
- Method of cultivation: The freshly obtained sludge was kept under continuous aeration until further treatment.
- Concentration of sludge: 3.4 g of suspended solids in 1 L of concentrated sludge
- Preparation of inoculum for exposure: the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium
- Storage length: the sludge was allowed to settle for 44 min before use

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

test mat.

Initial conc.:

12 mg/L

Based on:

TOC

Remarks:

based on the molecular formula

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS

- Composition of medium: test material, sludge inoculum and mineral media (mineral components and Milli-RO water). The day before the start of the test, mineral components, Milli-RO water (ca.80% of final volume) and inoculum (1% of final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2. At the start of the test (day 0), weighted amounts of test and reference item (test item bottle A: 39.2 mg; test item bottle B: 40.4 mg and toxicity control bottle: 39.4 mg) were added to the bottles containing the microbial organisms and mineral components. The volumes of suspensions were made up to 2 litres with Milli-RO water. Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle.
The test solutions were continuously stirred during the test, to ensure optimal contact between the test item and the test organisms.
- Additional substrate: no
- Solubilising agent (type and concentration if used): no
- Test temperature: 21.4 to 22.9°C
- pH: 7.9 (before addition of concentrated HCL) - 7.6 in control blank and test bottles (Phenolphthalein (1% solution in ethanol, Merck) was used as pH-indicator.)
- pH adjusted: yes (using 1 M HCL)
- Continuous darkness: yes

TEST SYSTEM

- Culturing apparatus: 2L Glass brown coloured bottles
- Number of culture flasks/concentration: 2 bottles for the test suspension (test item and inoculum), 2 bottles for the inoculum blank, 1 bottle for the positive control (containing reference item and inoculum) and 1 bottle for the toxicity control (containing test item, reference item and inoculum).
- Measuring equipment: not specified (device for determination of carbon dioxide titrimetrically)
- Details of trap for CO2 and volatile organics if used: A mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. The synthetic air was sparged through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min). The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate.

SAMPLING

- Sampling frequency: every 2nd or 3rd day during the first 10 days and thereafter at least every fifth day until day 28 for the inoculum blank and test suspension.
- Sampling method: Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series. The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardized HCl.


CONTROL AND BLANK SYSTEM

- Inoculum blank: Yes. 2 bottles of 2L containing only inoculum.
- Reference control: Yes: Positive (reference and inoculum) and Toxicity control (test item, reference item and inoculum). 1001.0 mg of sodium acetate in Milli-RO water up to a total volume of 250 mL was prepared as stock solution. 20 mL of this stock solution were added to 2L of the test medium of the positive and the toxicity control bottles, resulting in a final concentration of 40 mg sodium acetate/L (12 mg TOC/L).

Reference substance:

other: sodium acetate

Key result

Parameter:

% degradation (CO2 evolution)

Remarks:

bottle A

Value:

30

Sampling time:

29 d

Remarks on result:

other: based on ThCO2

Key result

Parameter:

% degradation (CO2 evolution)

Remarks:

bottle B

Value:

39

Sampling time:

29 d

Remarks on result:

other: based on ThCO2

Results with reference substance:

The positive control item was biodegraded by at least 60% (61%) within 14 days (a first test has been disregarded because the positive control did not meet the acceptability criterion)

Table 1 : CO2 production and percentage biodegradation of the test item (bottle A)

 

Day	HCL (0.05N) titrated (mL)	HCL (0.05N) titrated (mL)	Produced CO2 (mL HCL)	Produced CO2 (mg)	Cumulative CO2 (mg)	Biodegradation (%)*
	Blank (mean)	Bottle A
2	47.52	47.00	0.52	0.6	0.6	1
5	45.56	45.86	0.00	0.0	0.6	1
7	45.46	45.66	0.00	0.0	0.6	1
9	45.98	45.86	0.12	0.1	0.7	1
14	46.25	45.23	1.02	1.1	1.8	2
19	44.12	38.23	5.89	6.5	8.3	10
23	44.38	35.56	8.82	9.7	18.0	21
27	45.77	39.96	5.81	6.4	24.4	28
29	45.15	43.68	1.47	1.6	26.0	30
29	46.91	47.15	0.00	0.0	26.0	30
29	48.24	48.66	0.00	0.0	26.0	30

*= Calculated as the ratio between CO2 produced (cumulative) and the ThCO2 of the test item: 86.2 mg CO2/2L

Table 2 : CO2 production and percentage biodegradation of the test item (bottle B)

Day	HCL (0.05N) titrated (mL)	HCL (0.05N) titrated (mL)	Produced CO2 (mL HCL)	Produced CO2 (mg)	Cumulative CO2 (mg)	Biodegradation (%)*
	Blank (mean)	Bottle B
2	47.52	47.56	0.00	0.0	0.0	0
5	45.56	45.45	0.11	0.1	0.1	0
7	45.46	44.53	0.93	1.0	1.1	1
9	45.98	45.93	0.05	0.1	1.2	1
14	46.25	44.68	1.57	1.7	2.9	3
19	44.12	29.48	14.64	16.1	19.0	21
23	44.38	37.28	7.10	7.8	26.8	30
27	45.77	41.41	4.36	4.8	31.6	36
29	45.15	42.86	2.29	2.5	34.1	38
29	46.91	46.76	0.15	0.2	34.3	39
29	48.24	48.23	0.01	0.0	34.3	39

*Calculated as the ratio between CO2 produced (cumulative) and the ThCO2 of the test item: 88.9 mg CO2/2L

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Ready biodegradation values of 30 and 39% were obtained for the test substance in 28 days using an appropriate test procedure. Since at least 60% biodegradation was not reached within 10 days immediately following the attainment of 10% biodegradation (10-day window), the criterion for ready biodegradability was not met. Thus, under the conditions of this test 1-methyl-N,N’,N’’-tris(1-methylpropyl)silantriamine was not readily biodegradable.

Description of key information

Biodegradation in water screening tests: 30% and 39% (ThCO₂) biodegradation in 29 days (OECD 301B). 1 -Methyl-N,N’,N’’-tris(1-methylpropyl)silantriamine is not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

1 -Methyl-N,N’,N’’-tris(1-methylpropyl)silantriamine (CAS 37697-65-7) hydrolyses within the timescale of the ready biodegradation study (half-lives at 25°C of <2 min at pH 4 at pH 7 and 5 min at pH 9) to form methylsilanetriol (CAS 2445-53-6) and sec-butylamine (CAS 13952-84-6). The biodegradation observed in the study is attributable to the biodegradation of the sec-butylamine. No significant biodegradation is expected for the silanol hydrolysis product.

The key study is the only biodegradation study available for the substance. In a test conducted in accordance with OECD 301B (CO₂ Evolution Test) and in compliance with GLP, biodegradation values of 30% and 39% were obtained for the test substance in 29 days. Since at least 60% biodegradation was not reached within 10 days immediately following the attainment of 10% biodegradation (10-day window), the criterion for ready biodegradability was not met. Thus, under the conditions of this test 1-methyl-N,N’,N’’-tris(1-methylpropyl)silantriamine was not readily biodegradable.