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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
29.09.2011 - 07.10.2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study done under GLP following international guideline
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:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Radiolabelling:
no
Test temperature:
30 degrees celsius
Details on study design: HPLC method:
The Koc was determined by applying the HPLC method. This method was performed on an analytical column packed with a commercially available cyanopropyl solid phase containing lipophilic and polar moieties. A moderately polar stationary phase based on a silica matrix was used. While passing through the column along with the mobile phase the test substance interacted with the stationary phase. As a result of partitioning between the mobile phase and stationary phase the test substance was retarded. The dual composition of the stationary phase having polar and non-polar sites allowed for interaction of polar and non-polar groups of a molecule in a similar way as in the case for organic matter in soil or sewage sludge matrices. This enabled the relationship between the retention time on the column and the adsorption coefficient on organic matter to be established. The partition coefficient was deduced from the capacity factor k, given by the expression:
K = (tR – t0)/t0 = where tR was the retention time of the test substance, and t0 was the dead-time, i.e. the average time a solvent molecule needed to pass the column. Quantitative analytical methods were not required and only the determination of retention times was necessary.
Analytical monitoring:
no
Details on sampling:
not relevant
Details on matrix:
not relevant
Details on test conditions:
The test substance as well as the reference substances were measured in duplicate. All substances were measured at least once in separate runs and if possible also in mixtures of substances. For each reference substance a stock solution was prepared by weighing an exact amount of substance on an analytical balance and transferring it into a 25 mL measuring flask. The measuring flask was filled up to the mark with methanol. The reference solutions to be injected into the HPLC system were prepared by transferring 50 µL (100 µL for 2nd injection of 4,4’-DDT) of reference stock solution into HPLC vials and adding 950 µL (900 µL for 2nd injection of 4,4’-DDT) of mobile phase in order to dissolve the reference substances as close as possible to the ratio of methanol and water as used for the mobile phase.

For the test substance a stock solution was prepared by weighing an exact amount of substance (see Table 2 for details) on an analytical balance and transferring it into a 5 mL measuring flask. The measuring flask was filled up to the mark with methanol. This solution was transferred into a HPLC vial before analyzing. In the same way as described for the reference substances a stock solution and test solution of sodium nitrate was prepared; the only adaptation was the preparation of the stock solution in 50 mL of methanol.

Two mixtures of several reference substances were made by transferring 100 µL of the stock solution of the substances into a glass vessel and adding 2.7 mL of mobile phase in order to dissolve the mixtures as close as possible to the ratio of methanol and water as used for the mobile phase. The solutions were injected into the HPLC system as reference substances and test substance.

reference/test substances
Methylbenzoate
Aniline
1,2,3-Trichlorobenzene
Naphtalene
Phenantrene
4,4’-DDT
Sodium nitrate (dead time)
1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate)
Type:
log Koc
Value:
4.9
Temp.:
30 °C
Details on results (HPLC method):
Average net retention times (minutes

Methylbenzoate : 1.87
Aniline : 1.24
1,2,3-Trichlorobenzene : 3.64
Naphtalene : 3.69
Phenantrene : 9.09
4,4’-DDT : 20.03
Sodium nitrate (dead time) : 0
1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate): 14.35
Adsorption and desorption constants:
not applicable
Recovery of test material:
not applicable
Concentration of test substance at end of adsorption equilibration period:
not applicable
Concentration of test substance at end of desorption equilibration period:
not applicable
Details on results (Batch equilibrium method):
not applicable
Statistics:
Correlation between log Koc and logK
r2 = 0.944
std error = 0.378

Results of net retention times of reference and test substance

Substance

Lok Koc theor.

Ave net retention time (min)

Ave logK

Sodium nitrate (dead time)

 

0

 

Aniline

2.07

1.24

0.06

Methylbenzoate

1.80

1.87

0.24

 1,2,3-Trichlorobenzene

3.16

3.64

0.53

Naphtalene

2.75

3.69

0.53

Phenantrene

4.09

9.09

0.93

4,4’-DDT

5.63

20.03

1.27

1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate)

 

14.35

1.12

Validity criteria fulfilled:
yes
Remarks:
The individual results for log Koc of the reference substances as well as the test substance calculated using the information of the calibration plot of Log Koc versus Log k were within the range of ± 0.25 log units.
Conclusions:
The average measured log Koc value for 1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate) as calculated from the test was 4.9.
Executive summary:

The adsorption coefficient (Koc) of 1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate) was estimated using the High Performance Liquid Chromatography (HPLC) method. The Koc test was performed in accordance with the OECD guideline 121 without modification. The data on Koc can be used to predict the potential of the test substance to partition to soil, sediment or sewage sludge. The average measured log Koc value for 1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate) as calculated from the test was 4.9.

Description of key information

The average measured log Koc value for 1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate) as calculated from a OECD 121 test was 4.9.

Key value for chemical safety assessment

Koc at 20 °C:
79 433

Additional information

The adsorption coefficient (Koc) of 1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate) was estimated using the High Performance Liquid Chromatography (HPLC) method. The Koc test was performed in accordance with the OECD guideline 121 without modification. The data on Koc can be used to predict the potential of the test substance to partition to soil, sediment or sewage sludge. The average measured log Koc value for 1,1,4,4-tetramethylbutane-1,4-diyl bis(2-ethylperoxyhexanoate) as calculated from the test was 4.9.

[LogKoc: 4.9]