Trimethoxy(3,3,3-trifluoropropyl)silane

Water solubility

Administrative data

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental starting date: 24 September 2019, Experimental completion date: 11 March 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Test material

Test material information

Constituent 1

Reference substance name:

Trimethoxy(3,3,3-trifluoropropyl)silane

EC Number:

207-059-3

EC Name:

Trimethoxy(3,3,3-trifluoropropyl)silane

Cas Number:

429-60-7

Molecular formula:

C6H13F3O3Si

IUPAC Name:

trimethoxy(3,3,3-trifluoropropyl)silane

Test material form:

liquid

Specific details on test material used for the study:

Identification: ST2092NM
Appearance/Physical state: clear, colourless, liquid
Batch: 802496
Purity: 100%
Expiry / Retest date: 31 October 2020
Storage conditions: room temperature, in the dark

Results and discussion

Water solubility

Water solubility:

<= 13.8 mg/L

Conc. based on:

test mat.

Incubation duration:

>= 1 - <= 3 h

Temp.:

20 °C

pH:

>= 6.7 - <= 7

Remarks on result:

other: potential water solubility may be higher than this but due to the hydrolytic instability of the test item a higher concentration would not persist.

Any other information on results incl. tables

Preliminary Test:

The preliminary estimate of the water solubility at 20.0 ± 0.5 °C was 13.8 mg/L. The solution had a pH of 6.2.

Definitive Test:

The concentration (g/L) of test item in the sample solutions is shown in the following table:

Sample Number	Time Shaken at ~20 ºC (hours)	Concentration (mg/L)	Solution pH
Sample blank	n/a	0.609	n/a
1	1	11.8	7.0
2	2	0.861	6.7
3	3	1.06	7.0

Overall concentration:           11.8 g/L at 20.0 ± 0.5 ºC

Validation:

The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 5 to 200 mg/L. The results were satisfactory with a correlation coefficient (r) of 1.00 being obtained.

Assessment of the sample recovery procedure was performed and proved adequate for the test; at a nominal concentration of 25 mg/L, a mean percentage recovery of 68.5% was obtained (range 67.9 to 68.8%). Test sample concentrations have not been corrected for the recovery of analysis (see Discussion).

Discussion:

On completion of the equilibration period, the samples were clear and colorless with excess test item present on the base of the test vessels. After centrifugation, the supernatants were visually observed to be clear, colorless solutions free from un-dissolved test item and had no Tyndall beam effect.

The Sponsor initially indicated that the test item was unstable in water. With knowledge of this hydrolytic instability, it was decided to reduce the shaking period of the samples. The preliminary sample was shaken at 30 °C for 3 hours and equilibrated at 20 °C for 1 hour. For the definitive test it was decided to shake the samples directly at 20 °C. The samples were extracted into hexane as the test item was stable in this solvent. 

It was decided not to correct the sample results for the recovery result (68.5%) even though this was significantly lower than 100% and the individual results were consistent. This is because the loss of test item could have been mostly due to hydrolysis during sample preparation rather than incomplete extraction. As the time period the test item was in contact with water for the recoveries and test would not have been the same, a direct comparison could not be made. However, the recovery procedure does demonstrate that the majority of the test item could be recovered from an aqueous sample.

Sample 3A proved difficult to integrate among the baseline noise due to its small size. The peak was of a similar size to, possibly slight smaller than, the sample matrix blank. It was therefore decided to report the peak as a limit value based on the area of the sample matrix blank.

For the definitive test, only Sample 1 indicated a definitive presence of test item. Samples 2 and 3 were not significantly greater than the sample matrix blank. This could suggest that their shaking periods caused additional hydrolysis of the test item and that longer shaking periods would not result in a higher water solubility result. It could suggest that shaking for less than the 1 hour at 20 °C as for Sample 1 would result in a higher result. However, the test is not applicable to test items that hydrolyse that rapidly and therefore additional testing was considered not required.

The results of the preliminary test sample and Sample 1 were similar, being 13.8 mg/L and 11.8 mg/L respectively. Although the preliminary test sample was shaken at 30 °C for 3 hours, it too had a period of 1 hour at 20 °C. Given a reduced work up time, a higher result may have been possible but wouldn’t be any more meaningful given the rapid reduction in the concentration of test item due to hydrolysis. Any concentration higher than the ones measured would only persist for a very short period of time, impractically short for long term environmental considerations. Therefore being the highest measured, the preliminary test result will be used as the overall result with a caveat about stability.

As a comparison, the estimated water solubility using WSKOW v1.42 (September 2010), © 2000 U.S. Environmental Protection Agency was 8430 mg/L using its own estimated log P_owof 0.73. If the partition coefficient test result of 2.81 is used, this reduces the estimated water solubility to just 140 mg/L.

Applicant's summary and conclusion

Conclusions:

The water solubility of the test item has been measured up to 13.8 mg/L at 20.0 ± 0.5 °C. However, the potential water solubility may be higher than this but due to the hydrolytic instability of the test item a higher concentration would not persist. The concentration of 13.8 mg/L would also decrease over time.

Executive summary:

The water solubility of the test item has been measured up to 13.8 mg/L at 20.0 ± 0.5 °C using the flask method, designed to be compatible with Method A.6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 105 of the OECD Guidelines for Testing of Chemicals, 27 July 1995. However, the potential water solubility may be higher than this but due to the hydrolytic instability of the test item a higher concentration would not persist. The concentration of 13.8 mg/L would also decrease over time.