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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-04-17 - 2012-05-09
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)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
>= 1.59 - <= 3.48
Temp.:
20 °C
pH:
11.5
Remarks on result:
other: The HPLC column temperature was 40°C. The results are considered to be applicable for 20°C.
Key result
Type:
log Pow
Partition coefficient:
2.17
Temp.:
20 °C
pH:
11.5
Remarks on result:
other: weighted mean log Pow (using the measured peak area for each calculated partition coefficient)
Details on results:
Four peaks were observed in the HLPC chromatogram of the test item. Individual log Pow values calculated: 1.59, 2.29, 2.97 and 3.48 with observed relative peak areas of 49.0%, 25.4%, 14.9% and 10.7%, respectively.
Conclusions:
The log Pow of the test item was determined to be in the range of 1.59 to 3.48 with a weighted mean log Pow (using the measured peak area for each calculated partition coefficient) of 2.17 at 20°C and pH 11.5, following the HPLC method.
Endpoint:
partition coefficient
Type of information:
other: Estimation
Adequacy of study:
supporting study
Study period:
No data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented estimation of the log P under GLP conditions.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Log P is estimated based on the use of empirically derived atomic or group fragment constants and structural factors which when summed for the whole molecule estimate the partition coefficient directly. Reference is made to the Handbook of Chemical Property Estimation methods, fourth edition by W.J. Lyman et al., 1990.
GLP compliance:
yes (incl. QA statement)
Type of method:
other: Estimation based on chemical structure
Partition coefficient type:
octanol-water
Type:
log Pow
Partition coefficient:
1.18
Remarks on result:
other: Log P is estimated, temperature and pH are not applicable
Details on results:
From the molecular structure, Jeffamine RFD-270 Amine contains a C6H10 cyclic fragment, a CH3 fragment, 4-C aliphatic fragments, 7 aliphatic-H fragments, an O-aliphatic fragment and 2 aliphatic-NH2 fragments. Thus fragment constants of value 3.50 (-C6H10 ring); 0.89 (-CH3 aliphatic), 0.20 (-C- aliphatic), 0.23 (-H-aliphatic), -1.82 (-O- aliphatic), and -1.54 (-NH2-aliphatic) are applied. The sum of the fragments in the molecule was therefore calculated as 1.90.
Also present in the molecule are 7 bonds between the fragments. Therefore, a bond factor of -0.72 applies.

From the sum of fragments and factors the partition coefficient was estimated by calculation as 1.18 log units.
Conclusions:
The estimated log P value for the test substance is 1.18.

Description of key information

The log Pow of the substance was determined in a GLP study according to OECD Guideline 117 and EC A.8 to be in the range of 1.59 to 3.48 at 20 °C and pH 11.5, following the HPLC method (Tarran, 2012).

Key value for chemical safety assessment

Log Kow (Log Pow):
2.17
at the temperature of:
20 °C

Additional information

The log Pow range represents four peaks observed in the HPLC chromatogram (column temperature: 40°C). Individual log Pow values calculated are: 1.59, 2.29, 2.97 and 3.48 with observed relative peak areas of 49.0%, 25.4%, 14.9% and 10.7%, respectively. Using the measured peak area for each calculated partition coefficient, the weighted mean Log Pow for the test substance is 2.17.

The results are also considered to be applicable at 20°C. The test was performed at pH 11.5 to ensure the substance is predominantly in its non-ionised form. This does not truly reflect physiological and environmental conditions (pH 5-9) at which pH the ionisable groups might be charged and the water solubility increased resulting in a lower octanol/water partition coefficient. In addition, the log Pow was estimated based on atomic or group fragment constants and structural factors to be 1.18 (Younis S, 2012).