[ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids

Partition coefficient

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

partition coefficient

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Study period:

August, 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

See attached QMRF and QPRF documents.

Qualifier:

equivalent or similar to guideline

Guideline:

other: Fragment constant calculation method

Version / remarks:

Use of QSAR model is consistent with ECHA "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals".

Deviations:

not applicable

Principles of method if other than guideline:

See attached QMRF and QPRF documents.

Type of method:

calculation method (fragments)

Partition coefficient type:

octanol-water

Specific details on test material used for the study:

Partition coefficient was predicted based on the weighted average of eight individual constituents of the UVCB substance. These components, along with water, comprise ca. 98% of the quantified constituents and ca. 78% of the total composition.

Key result

Type:

log Pow

Partition coefficient:

ca. 5.6

Remarks on result:

other: Predicted using QSAR model

Details on results:

The range of predicted constituent partition coefficients is 4.92 – 7.94. However, the lowest and highest predicted values are associated with constituents that comprise <1.5% of the typical UVCB composition. Since the partition coefficient is a ratio of the concentrations of the UVCB mixture in octanol and water, the logKow of the mixture can be appropriately predicted by calculating the weighted average of the constituent partition coefficients. The average partition coefficient weighted by each constituent’s typical concentration in the mixture is logKow = 5.6.

The partition coefficient value can be considered to represent the value(s) at an unspecified, probably ambient temperature (ca. 20°C), since no mention is made in the guidelines of the temperature at which the reference substance’s log Pow values were determined. Partition coefficients of the test and reference substances are assumed to vary with temperature in the same way.

Conclusions:

The partition coefficient (logKow) of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids is determined to be 5.6.

Executive summary:

The n-octanol/water partition coefficient of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids was predicted based on measured and estimated logKow values of eight (8) individual UVCB constituents obtained using the ECOSAR (Ecological Structure-Activity Relationship) Class Program version 2.0. These constituents, along with water, comprise more than ca. 98% of the quantified constituents and ca. 78% of the total UVCB composition.

Since the partition coefficient is a ratio of the concentrations of the UVCB mixture in octanol and water, the logKow of the mixture is appropriately predicted by calculating the weighted average of the constituent partition coefficients. The average partition coefficient weighted by each constituent’s typical concentration in the mixture is logKow = 5.6. This value is consistent with the measured partition coefficient of a similar read-across substance (EC/List number 943-164-7).

Reference 2

Endpoint:

partition coefficient

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Study period:

19 December 2016 - 18 April 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The partition coefficient of a read-across substance (EC/List number 943-164-7) was assessed according to OECD method 117. The read-across substance was produced by the same E. coli fermentation process as [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids, but was extracted using a different solvent.

Qualifier:

according to guideline

Guideline:

other: EU Method A.24 Partition Coefficient (n-octanol/water): High Performance Liquid Chromatography (HPLC) Method

Version / remarks:

2016

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 830.7570 (Partition Coefficient, n-octanol / H2O, Estimation by Liquid Chromatography)

Version / remarks:

1996

Deviations:

no

GLP compliance:

yes

Type of method:

HPLC method

Partition coefficient type:

octanol-water

Key result

Type:

log Pow

Partition coefficient:

3.1

Temp.:

20 °C

Remarks on result:

other: Peak 1 (Peak area of 14%). Non-buffered mobile phase

Key result

Type:

log Pow

Partition coefficient:

5.2

Temp.:

20 °C

Remarks on result:

other: Peak 2 (Peak area of 7.9%)

Key result

Type:

log Pow

Partition coefficient:

5.5

Temp.:

20 °C

Remarks on result:

other: Peak 3 (Peak area of 78%)

Details on results:

- Retention times of reference substances used for calibration: see table below
- Details of fitted regression line: log k' = 0.326 x log Pow – 0.830 (r = 0.996, n=14)
- Graph of regression line and chromatograms: see attachment
- Both chromatograms of the test item showed one major peak (78% area) and severall small peaks. The small peaks with peak areas of 14 and 7.9% were also used for logPow calculations.
- Average retention data for test item: see table below
- The value of log Pow obtained from duplicate measurements was within ± 0.1 log units.

Table: Results Partition coefficient n-octanol-water (HPLC method)

Substance	tr,1 [min]	tr,2 [min]	mean tr (n=2)	log Pow	Pow	Area %
Formamide (t0)	0.602	0.603	0.603
Benzylalcohol	0.771	0.773		1.1
Bromobenzene	1.551	1.550		3.0
Biphenyl	2.575	2.571		4.0
Dibenzyl	4.278	4.263		4.8
Triphenylamine	7.827	7.784		5.7
4,4’-DDT	11.239	11.167		6.5
Benzo[ghi]perylene	18.096	17.948		7.2
Test item – peak 1	1.496	1.491	1.494	3.1	1.2E03	14
Test item – peak 2	5.128	5.118	5.123	5.2	1.7E05	7.9
Test item – peak 3	6.069	6.060	6.065	5.5	3.0E05	78

Remark: the log Pow values of the reference substances are according to OECD TG 117.

Conclusions:

The log Pow value was determined to be 5.5 based on the peak of the main test item.

Executive summary:

The log Pow of the substance was determined using the HPLC method in a GLP study according to EC A.8, OECD 117 and OPPTS 830.7570. The mobile phase was a gradient with 75/25 (v/v) methanol/water and methanol and the wavelength of detection 210 nm.

Formamide was used as unretained substance. Duplicate injections of unretained substance, reference substances and test item. Both chromatograms of the test item showed one major peak and severall small peaks. The log Pow value for the peaks with areas of 14%, 7.9% and 78% was determined to be 3.1, 5.2 and 5.5, respectively. The log Pow of the UVCB substance is determined to be 5.5 based on the peak of the main test item.

Description of key information

The logKow of the UVCB substance is predicted by calculating the average of the constituent partition coefficients weighted by their typical concentration in the mixture. The weighted average partition coefficient is logKow = 5.6. This value is consistent with the measured partition coefficient of a similar read-across substance (EC/List number 943-164-7).

Key value for chemical safety assessment

Log Kow (Log Pow):

5.6