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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:
14 - 19 Jul 2017
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)
GLP compliance:
yes (incl. certificate)
Remarks:
Swiss Federal Office of Public Health
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
>= 5.71 - <= 6.04
Temp.:
20 °C
pH:
7.6
Remarks on result:
other: evaluation based on six peaks representing >90% of the test item

Results of the calibration

The R² fit of the calibration curve used was 0.9955. The deviations of calculated log Pow values from actual log Pow values were 3 % at maximum. This reflects the linear correlation between the logarithms of the capacity factors of the HPLC system and the log Pow values of the reference items in the applied range of 2.7 to 6.5.

 

 

Results of the partition coefficient determination for the test item

The test item showed a chromatographic profile consisting of several peaks. It could be verified that the six peaks with retention times between 16.8 and 20.8 minutes are representing more than 90 % of the test item (area %). The evaluation was based on these peaks. The log Pow values for the compounds relating to these peaks were found to be 5.71 (Peak 1), 5.75 (Peak 2), 5.81 (Peak 3), 5.92 (Peak 4), 5.97 (Peak 5) and 6.04 (Peak 6). The data are given in the following table.

 

Peak Number

Solution

Run

Retention Time [min]

log k’

Log POW

Mean

Standard Deviation

Peak 1

Solution 1

1strun

16.773

1.132

5.714

5.71

±0.01

2ndrun

16.767

1.132

5.714

Solution 2

1strun

16.767

1.129

5.705

2ndrun

16.747

1.128

5.703

Peak 2

Solution 1

1strun

17.220

1.144

5.755

5.75

±0.01

2ndrun

17.213

1.144

5.754

Solution 2

1strun

17.213

1.141

5.745

2ndrun

17.187

1.140

5.742

Peak 3

Solution 1

1strun

17.960

1.164

5.819

5.81

±0.01

2ndrun

17.953

1.163

5.818

Solution 2

1strun

17.953

1.161

5.809

2ndrun

17.920

1.160

5.806

Peak 4

Solution 1

1strun

19.253

1.196

5.925

5.92

±0.01

2ndrun

19.253

1.196

5.925

Solution 2

1strun

19.253

1.193

5.915

2ndrun

19.213

1.192

5.912

Peak 5

Solution 1

1strun

19.887

1.211

5.974

5.97

±0.01

2ndrun

19.887

1.211

5.974

Solution 2

1strun

19.887

1.208

5.964

2ndrun

19.847

1.207

5.961

Peak 6

Solution 1

1strun

20.813

1.232

6.042

6.04

±0.01

2ndrun

20.807

1.232

6.042

Solution 2

1strun

20.807

1.229

6.033

2ndrun

20.78

1.228

6.031

 

 

There were two more peaks to see on the test item chromatogram with retention times of 52.1 and 57.3 minutes (see Figure 3). These peaks were beyond the acceptability range of the Guideline, and represent less than 10 % of the test item (area %). They were not evaluated.

 

Conclusion

During this study, the partition coefficient (n-octanol/water) of the test item was determined using the HPLC method. The log Pow values based on six peaks representing more than 90 % of the test item ranged from 5.71 to 6.04.

Conclusions:
A partition coefficient range of 5.71 to 6.04 (at 20 °C) was determined for the test substance according to OECD 117.

Description of key information

Log Pow range: 5.71 to 6.04 at 20°C (OECD 117, HPLC Method)

Key value for chemical safety assessment

Log Kow (Log Pow):
6.04
at the temperature of:
20 °C

Additional information

The test item showed a chromatographic profile consisting of several peaks. The log Pow values based on six peaks representing more than 90 % of the test item ranged from 5.71 to 6.04.