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Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the physicochemical properties of the substance indicate that it can be expected to have a low potential for adsorption
the study does not need to be conducted because the substance and its relevant degradation products decompose rapidly
other:
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Information to support the waiver.
Qualifier:
according to
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Deviations:
yes
Principles of method if other than guideline:
During the preparation phase of the study problems in dissolving the test substance occurred as well as problems in detecting the test substance in an appropriate HPLC set up.
GLP compliance:
no
Type of method:
other: Information
Radiolabelling:
no

The test substance appeared not to dissolve in methanol which is the recommended solvent according to OECD 121 guideline. It was observed that the test substance did dissolve in other organic solvents, like acetonitrile and tetrahydrofuran. However no significant peak detection was observed when injecting these solutions into a HPLC set up. Moreover if other solvents than methanol would be used the theoretical log Kocvalues of the reference substances would be doubtful and as a result of this the outcome of the study would also be doubtful.

Based on the calculated value of 7.6 – 8.8 for log Kocof the test substance a retention time of about 3 – 4 hours was to be expected when injecting the test substance in the HPLC test set up for the Kocdetermination. Although this value is a calculated value it was an important indication that injecting of the test substance onto the HPLC column would most probably result in very broad peak detection and by that cause also a severe contamination of the column that could hardly be removed anymore.

The above described reasons mean that it was technically not possible to determine a Kocvalue using this HPLC reference method according to OECD 121.

The alternative OECD guideline 106 for determination of adsorption and desorption of the test substance will also not be possible to conduct. The value for water solubility of the test substance was calculated to be 0.025 µg/L and the detection limit of the analytical method for the determination of the test substance was defined in the report for water solubility to be 1 µg/L. In the test set up of this adsorption/desorption study it is necessary to analyze the test substance in an aqueous phase but due to the low water solubility in combination with the determined detection limit for the analytical method this will not be possible.

The overall conclusion must be that it is experimentally not possible to determine an adsorption coefficient for the test substance and thus only the calculated value can be used.


 

Validity criteria fulfilled:
not applicable
Conclusions:
It is experimentally not possible to determine an adsorption coefficient for dihexadecyl peroxodicarbonateand thus only the calculated value can be used.
Executive summary:

This study reveals the inpossibility to determine the partition coefficient experimentally. The outcome is used for waiving of the endpoint.

Description of key information

The endpoint is waived: The study is  technically not feasible. An estimated log Koc of 7.6  to 8.8 can be used.

Key value for chemical safety assessment

Additional information

See 26322-14-5, Adsorption on soil and sewage, Vos, 2011, SS: It is experimentally not possible to determine an adsorption coefficient for dihexadecyl peroxodicarbonate.

An estimated log Koc of 7.6 to 8.8 can be used.