Reaction mass of 1,3-dimethyl-1,1,3,3-tetraphenyldisiloxane and 1,3,3,5-tetramethyl-1,1,5,5-tetraphenyltrisiloxane and 1,3,3,5,5,7-hexamethyl-1,1,7,7-tetraphenyltetrasiloxane

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Key result

Water solubility:

0.61 mg/L

Conc. based on:

other: Si content

Loading of aqueous phase:

1 g/L

Incubation duration:

> 24 - < 72 h

Temp.:

20.5 °C

pH:

> 6 - < 7

Key result

Water solubility:

1.89 mg/L

Conc. based on:

other: Si content

Loading of aqueous phase:

10 g/L

Incubation duration:

> 24 - < 72 h

Temp.:

20.5 °C

pH:

> 6 - < 7

Preparation of test vessels:

Flask No.       Amount test item in mg     Amount test item in mL   Volume H2O in mL   Resulting nominal concentration in mg/L

1A                            3                                   2.80                                    500                           6.0

1B                            3                                   2.80                                    500                           6.0

1C                            3                                   2.80                                    500                           6.0

2                            0.5                                   0.47                                    500                           1.0

3                               2                                   1.87                                    500                           4.0

4                               5                                   4.67                                    500                          10.0

Five vessels (blank, flask 1C (for the sampling point 72 h) and flasks 2 – 4) were set onto the stirrer immediately and the stirring at 100 rpm was started. After 24 ± 2 hours, flask 1B (for the sampling point 48 h) and after 48 ± 2 hours, flask 1A (for the sampling point 24 h) were set on the stirrer and all flasks were stirred for further 24 ± 2 hours at room temperature).

Then, flasks 1A-C were taken from the stirrer and tempered at 20.0 ± 0.5 °C. As the test item was located in the low phase (bottom of the flask), the aliquots were taken out of replicates 1A-C using a syringe. A slight Tyndall effect was observed in each solution. The same result was observed after centrifugation of the test solutions at 6000 rpm for 15 minutes. Therefore, the solutions were membrane filtrated using 0.45 µm PTFE filter and measured via ICP-OES for Si. Because of a difference of less than 15 % in the con-centrations on days 2 and 3 and no upward tendency, the test was finished on day 3.

The final measurement was performed as determination from flasks 2 – 4. The sample preparation was performed as described above.

The element Si was measured via ICP-OES in the saturated aqueous solutions. All filtrated test solutions showed no Tyndall effect in the filtrated solutions.

Results: Measurements during Equilibration

Day     Flask #       Temperature [°C]  pH*       Intensity       Conc. Si** [µg/L]   Concentration test item [mg/L]     Difference to previous sample [%]

1         1A                 20.5                  6-7       540.96              250.7                           1.466                                          -

2         1B                 20.5                  6-7       594.45              275.1                            1.609                                          +9.7

3         1C                 20.5                  6-7       594.13              274.9                            1.608                                          -0.1

3         blank              20.5                 6-7       43.56                < 30                                -                                                 -

Results: Measurements at Plateau

Flask#     pH*       Temperature [°C]    Intensity       Conc. Si** [µg/L]    Concentration test item [mg/L]

2              5.41          20.5                     222.28           104.2                         0.609

3              5.40          20.5                     479.94            220.8                         1.291

4              5.60          20.5                     704.31           322.4                          1.885

Conclusions:

The solubility range for the tested nominal concentrations 1 – 10 g/L was 0.61 – 1.89 mg/L at 20.5 °C, corresponding to 0.02 – 0.06 % of the test item relating to the nominal concentration of the test item.

Executive summary:

The solubility of the test item in water was determined according to OECD 105 resp. EU A.6.

The solubility of the test item in water was determined from the measured concentrations of Si in the filtrated test solutions. The concentration of the test item was calculated from the measured Si concentrations and the content of Si in the test item of 17.1 % (calculated from the molecular mass of each component).

Dependency of the solubility on the amount of the test item (nominal load) was perceived in the preliminary and the main test. The blank value was below the LOQ of Si (< 30 µg/L Si).

As the solubility was dependent on the nominal concentration, no exact value for the solubility of the test item in water can be stated. The solubility range for the tested nominal concentrations 1 – 10 g/L was 0.61 – 1.89 mg/L at 20.5 °C, corresponding to 0.02 – 0.06 % of the test item relating to the nominal concentration of the test item.

No observations arousing doubts concerning the accuracy of the results and the validity of the study were made.

Description of key information

The solubility range for the tested nominal concentrations 1 – 10 g/L was 0.61 – 1.89 mg/L at 20.5 °C, corresponding to 0.02 – 0.06 % of the test item relating to the nominal concentration of the test item.