Decamethylcyclopentasiloxane

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

supporting 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:

other: syringe method

Partition coefficient type:

octanol-water

Analytical method:

other: GC-MS

Type:

log Pow

Partition coefficient:

8.023

Temp.:

25.3 °C

Remarks on result:

other: pH not stated

Tabulated results for Test Vessel A

Sampling Time, h	Average concentration D5(oct)μg/ml	Replicate difference D5(oct)μg/ml	Average concentration D5(aq)ng/ml	Replicate difference D5(aq)ng/ml	Log Kow
27.6	4740	392	0.04084	0.00010	8.0647
52.3	4572	50	0.03924	0.00034	8.0663
73.5	4606	42	0.04419	0.00024	8.0180
98.5	4707	197	0.04700	0.00079	8.0006
Average	4656		0.04282		8.0374
Std Dev	80	157	0.00347	0.00032	0.0332

abulated results for Test Vessel B

Sampling Time, h	Average concentration D5(oct)μg/ml	Replicate difference D5(oct)μg/ml	Average concentration D5(aq)ng/ml	Replicate difference D5(aq)ng/ml	Log Kow
28.1	4568	145	0.04288	0.00029	8.0275
51.1	4584	270	0.04379	0.00290	8.0198
72.7	4654	160	0.04798	0.0095	7.9868
99.5	4714	29	0.04459	0.00104	8.0241
Average	4630		0.04481		8.0145
Std Dev	67	123	0.00222	0.00151	0.0188

Tabulated results for Test Vessel C

Sampling Time, h	Average concentration D5(oct)μg/ml	Replicate difference D5(oct)μg/ml	Average concentration D5(aq)ng/ml	Replicate difference D5(aq)ng/ml	Log Kow
28.7	4518	30	0.04185	0.00768	8.0332
51.2	4478	80	0.03943	0.00141	8.0553
74.1	4556	238	0.04323	0.00072	8.0228
97.3	4496	179	0.04486	0.00105	8.0010
Average	4512		0.0423		8.0280
Std Dev	33	109	0.00230	0.00185	0.0226

Conclusions:

A partition coefficient value of 8.023 ±0.006 was determined at 25.3°C in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Partition coefficient: (log Kow) 8.07 at 24.6 °C

Key value for chemical safety assessment

Log Kow (Log Pow):

8.07

at the temperature of:

24.6 °C

Additional information

Two reliable studies are available for the n-octanol-water partition coefficient of D5; a syringe method gave a log Kow of 8.07 at 24.6°C (SEHSC 2007) and a slow-stirring method gave a log Kow of 8.02 at 25.3°C (DCC 2007). The syringe method is selected as key study, since it allows for the establishment of octanol/air/water three-phase equilibrium and is considered to be the most appropriate method for this substance. The two results are very similar.

Earlier measurements gave log Kow values in the range 4.8 to 5.2. However, it is likely that in all cases the methodology was not appropriate for the substance.

A log Koa value of 4.96 was determined in a reliable study conducted according to scientifically sound methods, and in compliance with GLP.

A log Kaw value of 3.13 has been determined in a reliable study (presented in Section 5.4.2).