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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30/03/2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
GLP study performed using an accepted method
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient - Shake Flask Method)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
gas chromatography
Key result
Type:
Pow
Partition coefficient:
0.264
Temp.:
22.2 °C
pH:
ca. 11.9
Details on results:
The test item has predicted dissociation constants of 5.1 ± 0.7 (tertiary amine group), 8.9 ± 0.4 (tertiary amine group) and 14.9 ± 0.5 (alcohol group) using the I-Lab 2.0 prediction software from Advanced Chemistry Development Inc. (Algorithm version 5.0.0.184). Hence, the stock solution was adjusted to pH 11.9 ± 0.5, to ensure the test item was partitioned in its non-ionized form.

The partition coefficient determined for each sample is shown in the following table:

Sample

Organic/ aqueous volume ratio

Partition

coefficient

Log10 Pow

Mean partition coefficient

1

1:2

0.293

-0.533

0.286

2

0.279

-0.554

3

1:1

0.297

-0.528

0.298

4

0.298

-0.525

5

2:1

0.185

-0.734

0.209

6

0.234

-0.630

 

Overall Pow: 0.264

Overall log10 Pow: -0.584

The determination of partition coefficient was performed using the shake flask method. This choice was supported by the estimated partition coefficient obtained in the preliminary estimation. The stock solution was prepared in n-octanol saturated water in place of water saturated n-octanol due to the insolubility of the test item in the organic phase. This deviation to the guidelines has been considered to have a negligible impact on the overall result, as it was more appropriate to use this solvent to obtain a more realistic partition coefficient value. The linearity of the detector response with respect to concentration was satisfactory, with goodness of fit coefficients greater than 0.99 being obtained for both the organic and the aqueous matrices. Also, the peak areas obtained for the analysed QC standards showed that the response of the instrument was stable throughout each run.

The individual log Pow results were all within ± 0.3 units, as specified by the guidelines. The results were therefore considered satisfactory.

Conclusions:
The partition coefficient of the test item has been determined to be 0.264 at 22.2 ± 0.5 °C, log10 Pow -0.584.
Executive summary:

The n-octanol/water partition coefficient of the test item was determined to be 0.264 at 22.2 ± 0.5 °C (log10 Pow -0.584) using the shake flask method, designed to be compatible with Method A.8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 107 of the OECD Guidelines for Testing of Chemicals, 27 July 1995.

Description of key information

The n-octanol/water partition coefficient of the test item was determined to be 0.264 at 22.2 ± 0.5 °C (log10 Pow -0.584), using the shake flask method, designed to be compatible with Method A.8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 107 of the OECD Guidelines for Testing of Chemicals, 27 July 1995.

Key value for chemical safety assessment

Log Kow (Log Pow):
-0.584
at the temperature of:
22.2 °C

Additional information