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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study OECD 117, non-GLP. Study performed and documented equivalent to GLP standards. Study according to relevant guideline.
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)
Version / remarks:
(Directive 92/69/EEC, Official Journal L 383 A)
Deviations:
no
Principles of method if other than guideline:
The partition coefficient (P) is defined as the ratio of the equilibrium concentrations (c) of a dissolved substance in a two-phase system consisting of
two largely immiscible solvents. In the case n-octanol and water:
Pow = C n-octanol / C water
The partition coefficient therefore is the quotient of two concentrations and is usually given in the form of its logarithm to base 10 (log P).
For preliminary information the following calculated value was available (estimation software EPIWIN): log Pow = 2.21
As the HPLC method is applicable when the log Pow value falls within the range 0 to 6, that method was chosen for the determination of the partition
coefficient. HPLC is performed on analytical columns packed with a commercially available solid phase containing long hydrocarbon chains chemically bound onto silica. Chemicals injected onto such a column move along it at different rates because of the different degrees of partitioning between
the mobile phase and the hydrocarbon stationary phase. Mixtures of chemicals are eluted in order of their hydrophobicity, with water-soluble
chemicals eluted first and oil-soluble chemicals last, in proportion to their hydrocarbon-water partition coefficient. This enables the relationship
between the retention time on such a (reverse phase) column and the n-octanol / water partition coefficient to be established. The partition
coefficient is deduced from the capacity factor k', given by the expression
t(r) - t(0)
k'= -------------
t(0)
in which, t(r) = retention time of the test substance, and t(o) = average time a solvent molecule needs to pass through the column (dead time).

The test substance was dissolved in n-octanol and water at varying concentrations and analzyed by HPLC. The elution times were used to calculate
the capacity factor k', from which the partition coefficient was deduced. The linear regression of the log Pow of the reference substances against their log k' had a coefficient of determination of 0.9838 .
GLP compliance:
no
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
2.4
Remarks on result:
other: According to OECD 117 and EU test method A.8
Conclusions:
The partition coefficient n-octanol / water (Pow) of the test item was determined according to OECD guideline 117 and EU test method A.8 with the
HPLC method. The partition coefficient n-octanol / water (Pow) was reported to be 2.4.
Executive summary:

The partition coefficient n-octanol / water (Pow) of the test item was determined according to OECD guideline 117 and EU test method A.8 with the HPLC method. The partition coefficient n-octanol / water (Pow) was reported to be 2.4.

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Description of key information

The measured partition coefficient was determined to be log Pow: 2.4 at ambient temperature (according to OECD guideline 117 and EU method A.8). (Evonik Industries, 2010). This value is supported by the calculated logPow of 2.21 (estimation software EPIWIN (v4.00, subversion 1.68).

Key value for chemical safety assessment

Log Kow (Log Pow):
2.4
at the temperature of:
20 °C

Additional information