2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2012-08-02 to 2012-08-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

GLP compliance:

yes (incl. QA statement)

Type of method:

column elution method

Water solubility:

> 0 - < 0 g/L

Remarks on result:

not determinable

Remarks:

Water concentrations ranged from a low of 7.20E-06 g/L to a high of 5.25E-05 g/L.

	Measured Concentration (mg/L) Column flow rate
Date	25 mL/hr	pH	12.5 mL/hr	pH	6 mL/hr	pH
06 August 2012	0.0525 ± 0.0396	5.0	0.0847 ± 0.0285	5.0
07 August 2012					0.0269 ± 0.0147	5.5
09 August 2012			0.0092 ± 0.0011	5.5
10 August 2012					0.0072 ± 0.0012	5.5
14 August 2012			0.0189 ± 0.0039	5.5
	Mean		0.0376		0.0171
	Standard Deviation		0.0411		0.0139

The mean concentration of 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cylclotrisiloxane was determined to be 5.25E-05 ± 3.96E-05 g/L at a flow rate of approximately 25 mL/hour. The mean concentration of 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cylclotrisiloxane was determined to be 8.47E-05 ± 2.85E-05 g/L, at a flow rate of approximately 12.5 mL/hour. Since the results for the two flow rates were not within the required reproducibility (less than 30% for column elution), a third flow rate was added at 6 mL/hour. The mean concentration of 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl) cylclotrisiloxane was determined to be 2.69E-05 ± 1.47E-05 g/L at a flow rate of approximately 6 mL/hr. This result did not agree within ± 30% with the 12.5 mL/hr flow. Due to the inconsistencies with the results it was decided to perform two more elutions, one at 12.5 mL/hr and one at 6 mL/hr. The results for these elutions were 9.20E-06 ± 1.10E-06 g/L and 7.20E-06 ± 1.20E-06 g/L respectively. These results agree within the required 30%, however due to a procedural error with the creation of the QC samples the QC sample recoveries were outside of acceptance criteria. One additional elution was performed at 12 mL/hr which produced a result of 1.89E-05 ± 3.90 E-06 g/L. This final result disagreed with the previous 12 and 6 mL/hr results.

The results of the column elution study were highly variable and therefore inconclusive. The concentrations ranged from a low of 7.20E-06 g/L to a high of 5.25E-05 g/L. The results did not increase with decreasing flow rate which is expected when the test system has not achieved equilibrium. Instead the results generally decreased with decreasing flow rate, which is indicative of the test substance migrating off the column as particulate or colloidal material, in an insoluble form. Turbidity values for the fractions collected ranged from 0.05 to 0.14 NTU. These values indicate minimal colloidal material in the eluate. These results appear to be contradictory to the concentration results discussed above. However, it is known that turbidity measurement for the analysis of the presence of colloidal material is highly variable; colloidal particles of different sizes will generate different results when present at the same concentration. Any result less than 1.0 NTU is regarded to be below LOQ. Therefore, colloidal material could be present in sufficient quantities to create the observed results while not being detected by the turbidity analysis.

Conclusions:

The results of the column elution study were highly variable and therefore inconclusive. Water concentrations ranged from a low of 7.20E-06 g/L to a high of 5.25E-05 g/L.

Reference 3

Endpoint:

water solubility

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

See attached QMRF/QPRF

Principles of method if other than guideline:

The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).

The model is an adaptation of the existing SRC model WaterNT v 1.01, aka WaterFrag, which is a component of the EPI Suite. This model is based on fragment values. That is, the chemical structure is broken down into its constituent functional groups, and the contribution of each group toward the overall solubility is calculated. Certain correction factors may also apply. Whilst this method is good in principle, it suffers from not having reliable fragment values for substances containing Si-O bonds. Therefore, multiple linear regression on a set of organosilicon compounds has been used to generate new fragment values for silicon and oxygen bound to silicon (with separate values for –OH and other oxygen). The adapted model applies to substances containing Si-O bonds.

Water solubility:

0 mg/L

Temp.:

20 °C

pH:

7

Conclusions:

A water solubility of 1.3E-06 mg/l at 20°C was obtained for the test substance using an appropriate calculation method. The result is considered reliable.

Description of key information

Water solubility [2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane]: 1.3E-06 mg/l at 20°C (QSAR)

Key value for chemical safety assessment

Water solubility:

0 mg/L

at the temperature of:

20 °C

Additional information

The water solubility study for the substance, 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (F-D3), was considered technically not feasible because of the very low solubility estimated for the substance. An attempt to conduct a water solubility study using the column elution method (OECD 105) was unsuccessful because the result of the study yielded aqueous solubilities that significantly differed outside the required variation (<30%). The tentative solubility ranged down to <0.007 mg/l. The limit of quantification of the validated analytical method was determined to be 0.005 mg/l.

A predicted water solubility of 1.3E-06 mg/l at 20°C was determined for F-D3 using a QSAR estimation method. There is some additional uncertainty associated with the result as there are no highly fluorinated compounds in the training/test set. However, the prediction is considered sufficient to indicate that the water solubility of F-D3 is very low.

In addition to information from attempts at measuring and estimating water solubility of F-D3, a measured water solubility for dodecamethylcyclohexasiloxane (D6, CAS 540-97-6) is available. D6 has a molecular weight of 444.9 g/mol and a measured water solubility of 0.005 mg/l (Varaprath et al 1996) and F-D3 has a slightly greater molecular weight of 468.5 g/mol. However, the structure of the latter has fewer oxygen atoms to engage in polar interactions with water that likely enhance the solubility of the former. At the same time, while both molecules contain the same number of carbon atoms, the larger and non-polar trifluoropropyl groups should act to reduce solubility relative to the methyl substitution on D6. Therefore, it is chemically reasonable that F-D3 should have water solubility that is significantly less than D6. This conclusion, based on a simple consideration of the factors that govern aqueous solubility – molecular size and capacity for polar interactions – is in quantitative agreement with estimated water solubility of F-D3.

Therefore, it is concluded that it is not technically feasible to measure the water solubility of F-D3 and the water solubility is likely to be in the parts per trillion range.

Predicted water solubility values of 4.9E-04 mg/L and 1.3E+04 mg/L are estimated for the intermediate degradation product (1,5-dihydroxy-1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)trisiloxane) and ultimate degradation product (3,3,3-trifluoropropylmethysilanediol) respectively.