Triethoxy(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2005-04-26 to 2004-05-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Kurume Laboratory of Chemicals Evaluation and Research Institute, Japan

- Date of receipt: 2005-04-14

- Culturing: Once a day, about one third of the medium was removed and an equal volume of 0.1% synthetic waste water was added

- Mixed Liquor Suspended Solid (MLSS): 4700 mg/l

Duration of test (contact time):

ca. 28 - ca. 29 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The test substance was exposed to activated sludge in an automatic BOD meter. The biological oxygen demand (BOD) was measured for 28 days. After the completion of BOD measurement, dissolved organic carbon (DOC) and residential test substance were measured. Biodegradability of the test substance was assessed based on the results of these measurements.

Reference substance:

aniline

Key result

Parameter:

% degradation (DOC removal)

Value:

7

Sampling time:

28 d

Details on results:

The calculation of the degradation curve was performed with the help of a computer program contained in WordPerfect.

On day 28, the remaining dissolved CO2 was expelled by acidifying the samples. No further biological degradation occured since the microorganisms were killed by acidification. The degradation values obtained on day 29 (end of incubation) were therefore assigned to day 28.

The test substance achieved a degradation of 9% within 28 days (mean of two test substance samples).

Results with reference substance:

The degradation of aniline based on BOD was 79% on day 14.

pH measured

After the completion of BOD measurement, the pH values of the test solutions was all 7.2 in the test suspensions 1, 2 and 3 and was similar to that on the initiation of BOD measurement (pH = 6.9)

 

Table 1: pH measurement

Bottle no	Substance	pH
		Day 0	Day 28
1	Aniline	-	8.0
2	-	6.9	7.2
3	Dynasylan F8261	-	7.2
4	Dynasylan F8261	-	7.2
5	Dynasylan F8261	-	7.2
6	Dynasylan F8261	8.0	8.1

 

BOD Measurement

On day 28, while ThOD was 28.2 mg, BOD was 1.9, 0.6 and 3.7 mg (corrected values with BOD of the inoculum blank) in the test suspension 1, 2 and 3 respectively and 2.5 mg in the abiotic control. Degradability based on BOD was 7, 2, 13%, the average was 7% and the difference of maximum and minimum was 11% and below 20%.

 

Table 2: BOD measurement

Bottle No	Substance	ThOD (mg)	Day 7			Day 14			Day 21			Day 28
			BOD (mg)	∆BOD (mg)	Degradability (%)	BOD (mg)	∆BOD (mg)	Degradability (%)	BOD (mg)	∆BOD (mg)	Degradability (%)	BOD (mg)	∆BOD (mg)	Degradability (%)
1	Aniline	90.2	63.3	59.5	66	75.4	70.9	79	76.6	71.5	79	77.5	71.3	79
2	-	-	3.8	-	-	4.5	-	-	5.1	-	-	6.2	-	-
3	Dynasylan F8261	28.2	5.2	1.4	5	6.1	1.6	6	6.8	1.7	6	8.1	1.9	7
4	Dynasylan F8261	28.2	4.4	0.6	2	5.0	0.5	2	5.6	0.5	2	6.8	0.6	2
5	Dynasylan F8261	28.2	5.8	2.0	7	6.5	2.0	7	8.0	2.9	10	9.9	3.7	13
6	Dynasylan F8261	28.2	2.5	-	-	2.5	-	-	2.5	-	-	2.5	-	-
									Average (%) (bottle no. 3, 4, 5)					7
									Standard deviation (%)(bottle no. 3, 4, 5)					5.5
									Difference between maximum and minimum value (%)(bottle no. 3, 4, 5)					11

∆BOD = [BOD of bottle no 3, 4, 5] – [BOD of bottle no 2]

 

DOC measurement

On day 28, while the theoretical organic carbon (TOC) concentration was 9.9 mg, DOC was 0(-0.1), 0(-0.1) and 0 mg (corrected values with DOC of the inoculum blank) in the test suspension 1, 2 and 3 respectively and 5.3 mg in the abiotic control. Where DOC was calculated to be negative, this value is shown in parenthesis.

Degradability based on DOC was not calculated because the guttiform test substance was precipitated and insoluble in test suspension.

 

Table 3: DOC measurement

Bottle No	Test substance	Test substance added (mg)	Day 28
			TC (mg/l)	IC (mg/l)	DOC (mg/l)	DOC (mg)	∆DOC (mg)
2	-	-	0.9	0.0	0.9	0.3	-
3	Dynasylan F8261	9.9	0.6	0.0	0.6	0.2	0(-0.1)*
4	Dynasylan F8261	9.9	0.7	0.0	0.7	0.02	0(-0.1)*
5	Dynasylan F8261	9.9	0.9	0.0	0.9	0.3	0.0
6	Dynasylan F8261	9.9	17.5	0.0	17.5	5.3	-

∆BOD = [BOD of bottle no 3, 4, 5] – [BOD of bottle no 2]

*where ∆DOC was calculated to be negative, this value in parenthesis

 

Measurement of residual test substance (table 4)

The correlation coefficient of the analytical curve concentration and peak area was 0.99971, this indicate good relationship.

On day 28, compared with the standard solution, no new peaks/chromatograms where found for the test suspensions. Average disappearance rates of the test substance was 8% and in the abiotic control, it was 99%.

 

Table 4: Residual test substance measurement

Bottle No	Test substance	Test substance added (mg)	Day 28
			Test substance			Disappearance (%)
			Measured value (mg/l)	Correction value (mg/l)*	mg
3	Dynasylan F8261	30.0	90.2	100.2	30.1	0
4	Dynasylan F8261	30.0	89.8	99.8	29.9	0
5	Dynasylan F8261	30.0	68.5	76.1	22.8	24
6	Dynasylan F8261	30.0	1.1	1.2	0.4	99
Average (%) (bottle no 3, 4, 5)						8
Standard deviation (%) (bottle no 3, 4, 5)						13.9

*measured values of the concentration of the test substance in the test solutions were corrected with the recovery rate

(measured value) x 100/96 = correction value

 

 

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

7% biodegradation in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1997-03-18 to 1997-04-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Modified sturm test

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The activate sludge was obtained from a communal sewage treatment plant. 20 ml was used to inoculate the test samples. The suspended solids content of the test samples was 29.7 mg/L and the dry solids content of the inoculate used was 4.4 g/L. The bacterial count of the inoculate was 122 x10E4 colony-forming units/ml

Duration of test (contact time):

29 d

Initial conc.:

45.8 mg/L

Based on:

test mat.

Initial conc.:

45.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The test substance was added to the liquid medium that had been inoculated with activated sludge and aerated. The evolved carbon dioxide was bound in sodium hydroxide in the form of sodium carbonate. The degradation was followed for a test duration of 29 days, and the bound CO2 was checked by TOC analysis after 0,3,6,9,15,24,28 and 29 days.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

9

Sampling time:

28 d

Remarks on result:

other: Mean of two batches.

Details on results:

The calculation of the degradation curve was performed with the help of a computer program contained in WordPerfect.

On day 28, the remaining dissolved CO2 was expelled by acidifying the samples. No further biological degradation occured since the microorganisms were killed by acidification. The degradation values obtained on day 29 (end of incubation) were therefore assigned to day 28.

The test substance achieved a degradation of 9% within 28 days (mean of two test substance samples).

Results with reference substance:

The control substance, sodium benzoate obtained a degradation of 92% within 28 days. The proportional degradation of the control substance reached the plateau for ready biodegradability within 14 days. Therefore, the test methodology was considered valid for assessment.

Table 1: TOC analysis for blank, control and test substance

mg TOC/L 0.05 M NaOH
Time (days)	Blank A	Blank B	Avg. of blank A and B	Control	Test substance A	Test substance B
30 min	1.19	1.44	1.32	1.34	1.40	1.63
3	5.31	4.95	5.13	27.70	5.60	5.93
6	8.72	7.76	8.24	40.45	9.00	9.46
9	11.84	11.20	11.52	47.95	13.56	13.42
15	15.81	15.06	15.44	54.53	19.86	19.65
20	18.36	17.64	18.00	57.75	21.72	22.83
24	18.90	18.27	18.59	58.80	22.17	23.19
28	20.07	19.74	19.91	59.78	23.97	23.91
29	20.16	19.77	19.97	60.34	23.67	24.39

 

Table 2: Calculation of degradation for control substance

Theoretical CO₂ production: 53.6 mg/l

 

Test duration	TOC mg/l NaOH (0.05 M)			CO2 mg/l sample	Degradation (%)
	Sodium benzoate	Avg of blanks	Difference/3 (3 L test vessel used)	Correction for molecular weight of C and CO2
30 min	1.34	1.32	0.01	0.04	0
3	27.70	5.13	7.52	27.60	51
6	40.45	8.24	10.74	39.42	74
9	47.95	11.52	12.14	44.55	83
15	54.53	15.44	13.03	47.82	89
20	57.75	18.00	13.25	48.63	91
24	58.80	18.59	13.40	49.18	92
28	59.78	19.91	13.29	48.77	91
29 after acidification	60.34	19.97	13.46	49.40	92

 

Table 3: Calculation of degradation for sample A

Theoretical CO₂ production: 55.4 mg/l

 

Test duration	TOC mg/l NaOH			CO2 mg/l sample	Degradation (%)
	Test substance	Avg of blanks	Difference/3 (3 L test vessel used)	Correction for molecular weight of C and CO2
30 min	1.40	1.32	0.03	0.11	0
3	5.60	5.13	0.16	0.59	1
6	9.00	8.24	0.25	0.92	2
9	13.56	11.52	0.68	2.50	5
15	19.86	15.44	1.47	5.39	10
20	21.72	18.00	1.24	4.55	8
24	22.17	18.59	1.19	4.37	8
28	23.97	19.91	1.35	4.95	9
29 after acidification	23.67	19.97	1.23	4.51	8

 

Table 4: Calculation of degradation for sample B

Theoretical CO₂ production: 55.1 mg/l

 

Test duration	TOC mg/l NaOH			CO2mg/l sample	Degradation (%)
	Test substance	Avg of blanks	Difference/3 (3 L test vessel used)	Correction for molecular weight of C and CO2
30 min	1.63	1.32	0.10	0.37	1
3	5.93	5.13	0.27	0.99	2
6	9.46	8.24	0.41	1.50	3
9	13.42	11.52	0.63	2.31	4
15	19.65	15.44	1.40	5.14	9
20	22.83	18.00	1.61	5.91	11
24	23.19	18.59	1.53	5.62	10
28	23.91	19.91	1.33	4.88	9
29 after acidification	24.39	19.97	1.47	5.39	10

 

Table 5: Mean calculation of sample A and sample B

Determination of the mean degradation of the test substance (%)

 

Degradation after day	Vessel 11 (%)	Vessel 12 (%)	Mean value of Vessel 11 and Vessel 12 (%)
30 min	0	1	1
3	1	2	2
6	2	3	3
9	5	4	5
15	10	9	10
20	8	11	10
24	8	10	9
28	9	9	9
29 after acidification	8	10	9

 

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

9% biodegradation in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Biodegradation in water (screening tests): 7% and 9% in 28 days (EU Method C.4-C, MITI test). The silanol hydrolysis product, [2-(perfluorohexyl)ethyl]silanetriol, is not expected to biodegrade to any significant extent.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Additional information

Two reliable ready biodegradation studies are available for the registration substance. In the first study (Diefenbach, 1997), ready biodegradation study was conducted for the registration substance in accordance with EU Method C.4 and in compliance with GLP. A biodegradation value of 9% in 28 days was obtained for the substance. Similarly, in the second study (Omura, 2005), a biodegradation value of 7% DOC removal in 28 days was determined for the substance using a relevant test method and in compliance with GLP. The results are considered to be reliable and are used as weight of evidence.

 

[2-(Perfluorohexyl)ethyl]triethoxysilane hydrolyses moderately rapidly to form [2-(perfluorohexyl)ethyl]silanetriol and ethanol. [2-(Perfluorohexyl)ethyl]silanetriol is not expected to biodegrade to any significant extent.

 

Ethanol is readily biodegradable (OECD, 2004).

 

The measured biodegradation of the registration substance is lower than expected based on hydrolysis within the time period of the biodegradation studies, followed by biodegradation of the ethanol hydrolysis product. A total degradation of approximately 43% is expected, due to degradation of ethanol. The lower measured biodegradation of the substance may be related to its low water solubility and the high loading rate in the study, limiting its hydrolysis.

 

 

Reference:

OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.