Tar, wood

Partition coefficient

Description of key information

As peaks 1, 2, 3, 8, 10, 11, 12, 13, 14 and 15 showed relative areas < 5 % (see table 9.2–
b in the study report), they were considered as minor peaks.
Although area is not necessarily correlated to absolute concentration if a UV detector is
used, it is assumed that the test item consists mainly of the peaks 4, 5, 6, 7 and 9. Using
the correlation log K / log POW, the log POW of the major components of test item Tar wood
was calculated as 0.239 ± 0.000 – 2.022 ± 0.000 (mean ± standard deviation). Due to the
fact that the calculated log POW of peak 4 lay outside the calibrated range, the log POW of
Tar wood should be stated as < 0.3 – 2.022 ± 0.000 (mean ± standard deviation).

Key value for chemical safety assessment

Log Kow (Log Pow):

2.022

at the temperature of:

25 °C

Additional information

This study was performed in order to estimate the distribution coefficient log POW of Tar

wood using HPLC.

The partition coefficient (POW) is defined as the ratio of the equilibrium concentrations of a

dissolved substance in a two-phase system consisting of two largely immiscible solvents

(n-octanol and water). The log POW is a key parameter in studies of the environmental fate

of chemical substances. A highly significant relationship between the POW of non-ionised

form of substances and their bioaccumulation in fish has been shown. It has also been

shown that POW is a useful parameter in the prediction of adsorption on soil and sediments

and for establishing quantitative structure-activity relationships for a wide range of biological

effects.

The HPLC method covers log POW in the range of 0 to 6. Reverse phase HPLC is performed

on analytical columns packed with a commercially available solid phase containing

long hydrocarbon chains (e.g. C8, C18) chemically bound onto silica.

A test item injected on such a column partitions between the mobile solvent phase and the

hydrocarbon stationary phase as it is transported along the column by the mobile phase.

The test items are retained in proportion to their hydrocarbon-water partition coefficient,

with hydrophilic chemicals eluted first and lipophilic chemicals last. The retention times of

the peaks of the test item are compared with retention times of reference substances with

known hydrocarbon-water partition coefficients.

Experimental data (retention times of peaks of the test item and of the reference items) are

used together with literature values for the log POW of the reference items to calculate the

log POW for the test item.

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 0.9721. This value was considered as sufficiently high to use the calibration function

for the determination of the log POW of the test item Tar wood.

As peaks 1, 2, 3, 8, 10, 11, 12, 13, 14 and 15 showed relative areas < 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 item Tar wood consists mainly of

the peaks 4, 5, 6, 7 and 9.

Due to the fact that the calculated log POW of peak 4 lay outside the calibrated range, the

log POW of Tar wood should be stated as < 0.3 – 2.022 ± 0.004 (mean ± standard deviation).

No observations were made which might cause doubts concerning the validity of the study

outcome.