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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2008-12-10 to 2008-12-18
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Radiolabelling:
no
Test temperature:
Room temperature, 22 ± 1 °C
Details on study design: HPLC method:
EQUIPMENT
- Type, material and dimension of analytical (guard) column: Reprosil-Pur CN Dr. Maisch, 4.6 mm i.D., 100mm length, perticle size 3 µm
- Detection system: Dionex, UVD 170S; Wavelength for evaluation: 210 nm

MOBILE PHASES
- Type: Mixture of 55% methanol and 45% water, both HPLC-grade, isocratic
- pH: 6.92
- Solutes for dissolving test and reference substances: The test item was dissolved and diluted in the eluent.

DETERMINATION OF DEAD TIME
- Method: by inert substances which are not retained by the column
- inert substance: Sodium nitrate

REFERENCE SUBSTANCES
- Identity: see table below

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: see table below
- Quantity of reference substances: see table below
- Intervals of calibration: each three times before and after the measurements of the test item

REPETITIONS
- Number of determinations: 6 repetitions for reference substances, 3 repetitions for test item
Key result
Type:
log Koc
Value:
>= 3.548 - <= 5.578 dimensionless
Details on results (HPLC method):
See section 'Any other information on results incl. tables'

Test item solution was measured on 18 Dec 2008. Eight peaks could be identified. The mean of their retention times are presented in the following table :


















































 Peak Mean retention time [min] Log Koc ± sd
 1 4.693 3.548 ± 0.019
 2 4.9953.676 ± 0.020
 3 9.342 4.887 ± 0.026
 4 10.120 5.036 ± 0.027
 5 10.683 5.136 ± 0.027
 6 11.507 5.272 ± 0.027
 7 12.220 5.382 ± 0.028
 8 13.614 5.578 ± 0.028

These values are the means ± standard deviations of three independent determinations.


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 Koc is very accurate, as calibration gave a coefficient of determination r2 = 0.9911.
As the test item is a mix of isomers, the chromatogram shows many peaks.
No observations were made which might give doubts concerning the validity of the study outcome.

Validity criteria fulfilled:
yes
Conclusions:
The logKoc values determined for the tested substance are in the range between 3.548 and 5.578
Executive summary:

The study was performed using a HPLC with a cyanopropyl chemical bound resin on a silica base column. Seven reference items with different retention times were used to produce a calibration curve, since retention time on cyanopropyl columns and Koc are correlated. The reference items were chosen on behalf of the retention time of the test item Dibenzyltoluene on the column.
First, a solution of the reference items was analysed three times with HPLC, then a solution of the test item (three times) and finally three more times the solution  with the references.
For each reference item, the capacity factor k' was calculated from the retention time of sodium nitrate and the retention time of the respective reference item. A calibration function was set up using the literature values for Koc of the reference items and the mean capacity factor of the six determinations. ln the graph Log k' versus Log Koc, linear regression was performed, giving r2 = 0.9911 and r = 0.9955. 
The chromatogram of the test item gave eight peaks. With the help of the calibrati on function log K versus log Koc, the corresponding log Koc values were determined as :


















































 Peak Mean retention time [min] Log Koc ± sd
 1 4.693 3.548 ± 0.019
 2 4.9953.676 ± 0.020
 3 9.342 4.887 ± 0.026
 4 10.120 5.036 ± 0.027
 5 10.683 5.136 ± 0.027
 6 11.507 5.272 ± 0.027
 7 12.220 5.382 ± 0.028
 8 13.614 5.578 ± 0.028

These values are the means ± standard deviations of three independent determinations.

Description of key information

Key value for chemical safety assessment

Koc at 20 °C:
3 532

Additional information

An OECD 121 study was conducted on Dibenzylbenzene, ar-methyl derivative. The log Koc was calculated to be between 3.548 and 5.578.

[LogKoc: 3.548]