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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:
27.07.-28.07.16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Version / remarks:
2004
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
2.3
Temp.:
25 °C
Remarks on result:
other: HPLC screening; pH not determined

Capacity factor, log Capacity Factor, log Pow test item peaks

Peak

Measurement No.

K

log K

log POW

1

1

0.6984

-0.1559

1.133

2

0.6968

-0.1569

1.131

3

0.6977

-0.1563

1.132

Mean

 

 

1.132

Standard Deviation

 

 

0.001

2

1

2.1164

0.3256

2.273

2

2.1154

0.3254

2.273

3

2.1165

0.3256

2.274

Mean

 

 

2.273

Standard Deviation

 

 

0.000

3

1

2.5204

0.4015

2.453

2

2.5202

0.4014

2.453

3

2.5173

0.4009

2.452

Mean

 

 

2.453

Standard Deviation

 

 

0.001

4

1

4.7732

0.6788

3.110

2

4.7691

0.6784

3.109

3

4.7800

0.6794

3.111

Mean

 

 

3.110

Standard Deviation

 

 

0.001

Conclusions:
Variations in the retention times of reference items and test item are very small. Therefore a stable configuration of the HPLC-column can be assumed.
The correlation log K/log POW is good: the coefficient of determination r2 was calculated with 0.9582. This value was considered as sufficiently high to use the calibration function for the de-termination of the log POW of the test item 2,2'-Azobis (4-methoxy-2,4-dimethyl valeronitrile).
As peaks 1, 3 and 4 showed a relative area < 5 %, they were considered as minor peaks. Alt-hough area is not necessarily correlated to absolute concentration if UV detection is used, it is assumed that the test item 2,2'-Azobis (4-methoxy-2,4-dimethyl valeronitrile) consists mainly of the second peak, indicating that the log POW should be regarded as 2.3.
No observations were made which might cause doubts concerning the validity of the study outcome.
Executive summary:

The study was performed using a HPLC with a C18 column. Seven reference items with different retention times and thiourea for the determination of the dead time were used to produce a calibration curve, since retention time on hydrophobic columns and POWare correlated. The reference items were chosen based on the results of the pre-test.


One vial was filled with the reference item mix and one vial with the test item solution. The vials were analysed using the HPLC with the program described below. First one injection from the solvent blank methanol/water 65/35 %(v/v) was made.
Then three injections were measured from the reference item mix, three injections from the test item and again three injections from the reference item mix.


For each reference item, the capacity factor K was calculated from the retention time of thiourea and the retention time of the respective reference item.

A calibration function (log K versus log POW, linear fit) was determined using the literature values for POWof the reference items and the retention times in the six determinations.

 

The chromatogram of the test item gave one major and three minor peaks. With the calibration function log K versus log POW, the corresponding log POWs of the major peaks were determined with:

Peak

Mean Area
[mAU*min]
[1]

Relative Area
[%]

Mean Retention Time
[min]

log POW
±Standard Deviation

1

0.151

1.24

2.319

1.1 ± 0.0

2

10.917

89.65

4.257

2.3 ± 0.0

3

0.161

1.32

4.808

2.5 ± 0.0

4

0.292

2.40

7.888

3.1 ± 0.0


[1]mAU = milli absorbance units

These values are the means ± standard deviations of three independent determinations

As peaks 1, 3 and 4 showed a relative area < 5 %, they were considered as minor peaks. Although area is not necessarily correlated to absolute concentration if UV detection is used, it is assumed that the test item2,2'-Azobis (4-methoxy-2,4-dimethyl valeronitrile) consists mainly of the second peak, indicating that the log POWshould be regarded as 2.3.

Description of key information

Based on the findings in the available guideline study the value of 2.3 is selected as key value for the further chemical safety assessment.

Key value for chemical safety assessment

Log Kow (Log Pow):
2.3
at the temperature of:
25 °C

Additional information