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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08 July 2010- 30 July 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study has been performed according to OECD and EC guidelines and according to GLP principles.
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
Qualifier:
according to guideline
Guideline:
EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Media:
other: soil-adsorption-reference data
Radiolabelling:
not specified
Details on study design: HPLC method:
Performance of the study
The principle of the test method is similar to that of the OECD guideline no. 117: "Partition coefficient (n-octanol/water), high performance liquid chromatography (HPLC) method". While passing through the column along with the mobile phase the test substance interacts with the stationary phase. As a result of partitioning between mobile and stationary phases, the test substance is retarded. The dual composition of a cyanopropyl stationary phase, having polar and non-polar sites allows for interaction of polar and non-polar groups of a molecule in a similar way as is the case for organic matter in soil or sewage sludge matrices. This enables the relationship between the retention time on the column and the Koc on organic matter to be established.

Solutions of one reference substance and the test substance were analysed. Based on the retention times of the compounds the Koc and log Koc values of the test substance were determined.

Analytical conditions
Instrument: Alliance Separation Module 2695 (Waters, Milford, MA, USA)
Detector: Dual λ Absorbance Detector 2487 (Waters)
Column: Hypersil BDS-CN, 150 mm x 4.6 mm i.d., dp = 5 µm (Thermo Fisher Scientific, Waltham, MA, USA)
Column temperature: 35°C +/- 1°C
Mobile phase:
A – 55/45 (v/v) methanol/water
B – methanol
Gradient:
0 min, 100%A, 0%B
8 min, 100%A, 0%B
9 min, 0%A, 100%B
15 min, 0%A, 100%B
16 min, 100%A, 0%B
23 min, 100%A, 0%B
Flow: 1 ml/min
Injection volume: 10 µl
UV detection: 210 nm

Preparation of the solutions
Reference substance solution: A stock solution of reference substance (2,4-DDT, 97.2%, Supelco, log Koc=5.63) at a concentration of approximately 1 g/l in methanol was used. The blank solution for the reference substance was methanol.
Test solution: A 1075 mg/l stock solution of the test substance was prepared in methanol. The test substance blank solution was methanol.

Injections
The reference substance and test substance solutions were injected in duplicate. Blank solutions were analysed by single injection.
Key result
Type:
log Koc
Value:
> 5.63
Temp.:
35 °C
Details on results (HPLC method):
Results
Calculation of pKa values
No pKa values for acidic and basic groups in the molecular structure of the test substance in the logarithm range of 1 – 14 were calculated.

Determination of the Koc
In the chromatogram of the test substance solution, one peak with a retention time of 11.7 minutes was observed. Under the same analytical conditions, the retention time of 2,4-DDT (log Koc = 5.63) was 5.0 minutes. Hence, it was concluded that the log Koc of the test substance was > 5.63 (Koc > 4.27 x 10E5).

Since a gradient to 100% methanol was required to elute the test substance from the analytical column, extrapolation of the Koc was not possible.
Validity criteria fulfilled:
yes
Conclusions:
The HPLC method using soil-adsorption-reference data was chosen for the determination of the adsorption coefficient of Decanoic acid, mixed esters with heptanoic acid, octanoic acid and trimethylolpropane.

The Koc and log Koc value of the test substance was > 5.63 (Koc > 4.27 x 10E5).

Description of key information

Determined in accordance with OECD Guideline 121.

Key value for chemical safety assessment

Koc at 20 °C:
426 579

Additional information

The adsorption/desorption coefficient Koc of the substance was determined to be > 426579 (log Koc > 5.63).

[LogKoc: 5.63]

[LogKoc: 5.63]

[LogKoc: 5.63]