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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:
from 2017-11-14 to 2017-11-24
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)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient - HPLC Method)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 830.7570 (Partition Coefficient, n-octanol / H2O, Estimation by Liquid Chromatography)
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:
1.91
Temp.:
25 °C
pH:
8.5
Key result
Type:
Pow
Partition coefficient:
81
Temp.:
25 °C
pH:
8.5
Details on results:
The three calibration series and three test item series were measured alternately. The partition coefficient Pow was determined based on a calibration curve using seven reference items. The capacity factors (k) were calculated from the dead time and retention times of the reference substances. The log k data of the reference substances were plotted against their log Pow values. The equation of the curve fitted to the calibration points is as follows:
log k = 0.408* log Pow - 0.706 (Rsq = 0.95)

Measured and calculated data for the test item

Retention time (min)

log k

log Pow

Pow

Repeatability

log unit

Calculated

Test item

5.35

0.082

1.93

85

0.064

5.35

0.082

1.93

85

5.33

0.079

1.92

84

5.33

0.079

1.92

84

5.19

0.058

1.87

74

5.18

0.056

1.87

74

Mean

5.29

0.073

1.91

81

-

Conf.int. (95%)

0.08

-

0.03

5.80

-

CV%

1.52

-

-

-

-

The determined log Pow refers to the ionized form of the test item. The determination of the log Pow of the non-ionized form is technically not possible using HPLC method and buffered solutions at pH 11.

The two isomers of the test item are structural isomers and it is chromatographically not possible to separate the two isomers. Therefore, the determined log Pow value is applicable for both isomers as only one peak in the chromatograms was evaluated.

A QSAR estimation of both isomers was performed with EPI Suite, KOWWIN model. The estimation is based on the non-ionised form of the isomers and the log Pow was estimated to be 0.97 for both isomers. It is lower than the determined log Pow value in this study due to different polarity of the non-ionised forms. The estimated log Pow values for both isomers are identical, as well as, the determined log Pow values. In conclusion, the log Pow of the test item is determined to be 1.91 at pH 8.5.

Quality criteria were met as values of log Pow derived from individual measurements fell within a range of 0.1 log units.

QSAR Estimation

Isomer 1 : SMILES: c1cccc(CNCC(N)C)c1

Estimated log Pow: 0.9729

Isomer 1 : SMILES: c1cccc(CNC(C)CN)c1

Estimated log Pow: 0.9729

Conclusions:
The partition coefficient of the test item was determined using high performance liquid chromatography HPLC. The log Pow was determined to be 1.91 at 25 °C and pH 8.5 and the Pow to be 81, respectively.
Executive summary:

A study was conducted in accordance with OECD TG 117, Regulation (EC) No 440/2008 method A.24 and EPA OPPTS 830.7570 to determine the partition coefficient of the test substance using the HPLC method. A solution of the test substance was prepared in acetonitrile and diluted with eluent to get a concentration of 200 µg/L. The three calibration series and three test item series were measured alternately. The partition coefficient Pow was determined based on a calibration curve using seven reference items. The capacity factors (k) were calculated from the dead time and retention times of the reference substances. The log k data of the reference substances were plotted against their log Pow values. The partition coefficient log Pow for the test item in its ionized form was determined to be 1.91 at pH 8.5. A QSAR estimation of the log Pow of the two isomers of the test item in their non-ionized forms was performed. A log Pow of 0.97 for both isomers was estimated. It is lower than the determined log Pow value due to different polarity of the non-ionized forms. The estimated log Pow values for both isomers are identical, as well as, the determined log Pow values. In conclusion, the log Pow of the test item is determined to be 1.91 at pH 8.5.

 

Description of key information

The partition coefficient of the test item was determined using high performance liquid chromatography HPLC. The log Pow was determined to be 1.91 at 25 °C and pH 8.5 and the Pow to be 81, respectively.

Key value for chemical safety assessment

Log Kow (Log Pow):
1.91
at the temperature of:
25 °C

Additional information

A study was conducted in accordance with OECD TG 117, Regulation (EC) No 440/2008 method A.24 and EPA OPPTS 830.7570 to determine the partition coefficient of the test substance using the HPLC method. A solution of the test substance was prepared in acetonitrile and diluted with eluent to get a concentration of 200 µg/L. The three calibration series and three test item series were measured alternately. The partition coefficient Pow was determined based on a calibration curve using seven reference items. The capacity factors (k) were calculated from the dead time and retention times of the reference substances. The log k data of the reference substances were plotted against their log Pow values. The partition coefficient log Pow for the test item in its ionized form was determined to be 1.91 at pH 8.5. A QSAR estimation of the log Pow of the two isomers of the test item in their non-ionized forms was performed. A log Pow of 0.97 for both isomers was estimated. It is lower than the determined log Pow value due to different polarity of the non-ionized forms. The estimated log Pow values for both isomers are identical, as well as, the determined log Pow values. In conclusion, the log Pow of the test item is determined to be 1.91 at pH 8.5.