cyclohexadecanone

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18 August to 02 November 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)

Deviations:

yes

Remarks:

The determination of the low log Pow was made by the HPLC method extending the foreseen upper range given in the guideline to higher log Pow values, as allowed by the guideline in exceptional cases.

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

7.77

Temp.:

25 °C

pH:

7.185

Results and Discussion

 A preliminary test showed that the test item eluted after DDT, which is the reference compound with the highest log Pow as cited in the guideline. Under the conditions of the preliminary test, with each single injection of the reference item mixture and test item solution, the linear extrapolation of the calibration resulted in a log Pow of the test item of 7.71.

At this log Pow value, normally the slow-stirring method according to OECD 123 would apply. However, this method was assumed not to be appropriate for the test item due to the following consideration: the maximum concentration of the test item to be used in each phase is 0.1 M. This corresponds to a starting concentration of the test item in n-octanol of 23.8 g/L. With the log Pow as given above, a concentration of the test item in the aqueous phase of 0.46 μg/L would be obtained. The limit of quantification for analysis of the test item in water by using GC/MS as derived from the lowest detectable standard solution measured in the water solubility study of the test item, was found to be 30 μg/L. Thus, the concentration in the aqueous phase in a slow-stirring experiment would be far below the limit of quantification of the analytical method. Therefore, it was concluded that the slow-stirring method (OECD 123) is not suitable for the determination of the log Pow.

The determination of the low Pow was made by the HPLC method extending the foreseen upper range given in the guideline to higher log Pow values, as allowed by the guideline in exceptional cases.

In a first main test the reference item decachlorobiphenyl was included as a reference item with a very high log Pow above the tentative log Pow of the test item. However, due to an insufficient R2 fit of the calibration curve this system could not be used for the determination of the log Pow.

In a second main test, the reference item dibenz[a,c]anthracene was used as a reference item with a high log Pow.

Based on the 2nd main test, the log Pow-value of the test item was found to be 7.77. The data are given in the table below.

 

Results of Log Pow-Values of the test item

Test Item		Retention Time [min]	Log k'	Log Pow	Mean	Overall Mean
Solution 1	1st run	7.427	0.8458	7.770	7.77	7.77 ± 0.00
	2nd run	7.420	0.8454	7.767
Solution 2	1st run	7.427	0.8458	7.770	7.77
	2nd run	7.427	0.8458	7.770

Conclusions:

A log Pow of 7.77 at 25°C was determined for the test substance according to OECD 117.

Executive summary:

During this study, the partition coefficient (n-octanol/water) of the test item was determined using the HPLC method. The log Pow-value was found to be 7.77.

The foreseen upper range of the HPLC method was extended to higher log Pow values, since the slow-stirring method (OECD 123) deemed not to be suitable for the determination of the log Pow of the test item.

Description of key information

Log Kow: 7.77 at 25 °C (OECD 117, HPLC method)

Key value for chemical safety assessment

Log Kow (Log Pow):

7.77

at the temperature of:

25 °C

Additional information

During this study, the partition coefficient (n-octanol/water) of the test item was determined using the HPLC method. The log Pow-value was found to be 7.77.

The foreseen upper range of the HPLC method was extended to higher log Pow values, since the slow-stirring method (OECD 123) deemed not to be suitable for the determination of the log Pow of the test item.