Octamethylcyclotetrasiloxane

Partition coefficient

Link to relevant study record(s)

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

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 K_oa 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.