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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
Study period:
2012-10-09 to 2013-01-28
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)
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient)
GLP compliance:
yes
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
>= 6.24 - 9.4
Temp.:
40 °C
pH:
6.6
Remarks on result:
other: Overall Log Pow 6.24 to > 9.4
Details on results:
Preliminary estimate
The Log Pow was calculated to be 5.35, 10.62 and higher for larger components.

Definitive study
The result from the preliminary test indicated that the HPLC method was the most suitable for determination of partition coefficient for this test item.
The test item had no dissociation constants within the environmentally relevant pH range and therefore, was tested in an unadjusted mobile phase at an approximately neuutral pH.
The sample was prepared in tetrahydrofuran that had been shaken with anhydrous sodium sulphate in an attempt to remove residual water and reduce any potential hydrolysis that may occur while in solution prior to analysis.
In comparison to the chromatography produced for the water solubility test, the chromatography for the partition coefficient used a tetrahydrofuran gradient over a longer time period that highlighted that the test item was composed of multicomponents.

See attached document.

Table 1: Reference - Dead time

Dead Time

Retention times (mins)

Mean Retention Time (mins)

Injection 1

Injection 2

Thiourea

0.870

0.870

0.870

 

Table 2: Retention time of calibration standards

Standard

Retention time (mins)

Mean Retention Time (mins)

Log10 k'

Log10 Pow

Injection 1

Injection 2

Capacity factor (k')

Benzyl alcohol

1.01

1.006

1.008

0.159

-0.800

1.1

Triphenylamine

2.517

2.517

2.517

1.89

-0.277

5.7

1-Phenylnonane

5.534

5.534

5.534

5.36

0.729

7.1

1-Phenyldecane

8.785

8.785

8.785

9.10

0.959

8.1

1-Phenyldodecane

11.229

11.224

11.227

11.9

1.08

8.7

1-Phenyltridcane

14.383

14.378

14.381

15.5

1.19

9.4

 

Table 3: Results

Peak number

Injection

Retention Time (mins)

Capacity factor (k)

Log10 k'

log10 Pow

% Peak area

1

1

3.401

2.91

0.464

6.24

54.7

2

3.397

2.91

0.463

6.24

2 to 9

1

≥24.022

>15.5

>1.19

>9.4

45.3

2

≥24.021

>15.5

>1.19

>9.4

Conclusions:
The log Pow value of the test material is 6.24 to > 9.4
Executive summary:

Test Guidance

OECD Guideline 117 and EC Method A8

Method and materials

A preliminary estimate of the partition coefficient was calculated using KOWWIN v 1.68.

The definitive test was performed by HPLC. The HPLC was calibrated with 6 standards using the Log Pow of standards given in OECD 117 guideline. Standards were prepared in methanol. Column dead time was determined from the retention dime of thiourea.

Capacity factors were calculated from retention times of the standards. Capacity factors were correlated to log Pow via a calibration graph. The log Pow of the test material was determined by interpolation from the calibration graph.

Results

The partition coefficient of the test item has been determined to be in the range 1.74E06 to > 2.5E09, log Pow 6.24 to > 9.4

Description of key information

The log Pow value of the test material is 6.24 to > 9.4.

Key value for chemical safety assessment

Log Kow (Log Pow):
9.4
at the temperature of:
40 °C

Additional information

The log Pow value of the test material is 6.24 to > 9.4

The experimentally derived value of > 9.4 is taken to be representative of the substance due to the uncertainty regarding the validity of the value of 6.24 for one component of the UVCB. It should be noted that the HPLC method for determination of Log Pow is not applicable if the substance has a high surface activity or does not dissolve in water. If the substance hydrolyses it is questionable if the hydrolysis products should be tested instead. The test material is hydrophobic and has a low experimentally derived water solubility (0.17 mg/L). Furthermore, there is potential for the boric acid groups to hydrolyse if they are exposed to water, whilst the substance structures show a potential for surface activity. Based on this evidence it is possible that the measurement of of the log Pow for certain components may have been underestimated due to their physicochemical properties in association with water. Calculated BCF values for the components show no indication for biaccumulation (BCF< 500) and the Koc determination indicates a high absorption to organic matter. On a weight of evidence approach it is considered that the Log Kow value > 9.4 is valid for this substance.