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Physical & Chemical properties

Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)
GLP compliance:
yes
Type of method:
slow-stirring method
Partition coefficient type:
octanol-water
Key result
Type:
log Pow
Partition coefficient:
6.488
Temp.:
25.1 °C
Remarks on result:
other: No pH stated
Details on results:
6.488 ± 0.017 (1SD, n=3)

Results for test vessel A

Sampling Time, h

Average Concentration D4(oct),μg/ml

Replicate Difference D4(oct),μg/mL

Average Concentration D4(aq), ng/mL

Replicate difference D4(aq), ng/mL

Log Kow

24.3

393.5

4.6

0.1348

0.0077

6.4654

 29.3

 390.5

 0.1

 0.1209

0.0048

6.5093

 48.2

 390.7

 0.5

 0.1227

0.0015

6.5029

53.3

392.3

0.4

0.1375

0.0036

6.4553

71.9

389.1

2.1

0.1308

0.0106

6.4736

Average

391.2

0.1293

 

6.4813

Std Dev

1.7

1.6

0.0073

0.0046

0.0237

Results for test vessel B

Sampling Time, h

Average Concentration D4(oct),μg/ml

Replicate Difference D4(oct),μg/mL

Average Concentration D4(aq), ng/mL

Replicate difference D4(aq), ng/mL

Log Kow

24.9

393.8

0.6

0.1211

0.0072

6.5120

30.0

392.4

0.5

0.1259

0.0084

6.4936

48.8

391.9

1.9

0.1225

0.0012

6.5050

54.0

395.1

8.3

0.1316

0.0116

6.4776

72.7

386.3

6.4

0.1278

0.0041

6.4805

Average

391.9

0.1258

 

6.4938

Std Dev

3.4

3.4

0.0042

0.0053

0.0150

Results for test vessel C

Sampling Time, h

Average Concentration D4(oct),μg/ml

Replicate Difference D4(oct),μg/mL

Average Concentration D4(aq), ng/mL

Replicate difference D4(aq), ng/mL

Log Kow

25.6

395.5

1.9

0.1247

0.0013

6.5011

30.7

394.9

0.9

0.1315

0.0083

6.4776

49.5

395.1

0.3

0.1278

0.0023

6.4901

54.7

394.1

1.7

0.1301

0.0054

6.4812

73.5

394.5

1.8

0.1261

0.0006

6.4952

Average

394.8

0.1281

 

6.4891

Std Dev

0.5

1.0

0.0028

0.0033

0.0097

Conclusions:
A partition coefficient value of 6.49 was determined at 25.1°C in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

log Kow [octamethylcyclotetrasiloxane]: 6.49 at 25.1°C (OECD 123) log Koa [octamethylcyclotetrasiloxane]: 4.22 at 24°C

Key value for chemical safety assessment

Log Kow (Log Pow):
6.49
at the temperature of:
25.1 °C

Additional information

Two reliable studies are available for the n-octanol-water partition coefficient of the substance. A measured log Kow of 6.49 at 25.1°C was determined for the substance in accordance with OECD 123, slow-stirring method. The result is considered to be reliable and selected as key study. This value is supported by another measured log Kow of 6.98 at 21.7°C using a syringe method.

A log Kow value of 5.1 was also determined for the substance using the HPLC method, however, this method is considered unsuitable for silicon-type substances as such was disregarded. In a secondary source to which reliability could not be assigned, log Kow value of 5.1 was reported for the substance.

A log Koa value of 4.22 at 24°C was determined for the substance in a reliable study conducted according to scientifically sound method and in compliance with GLP.