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adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
16 Jan 2008 - 14 May 2008
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study has been performed according to OECD and EC guidelines and according to GLP principles.

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
according to guideline
EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method

Test material

Constituent 1
Details on test material:
- Name of test material (as cited in study report): S-500
- Physical state: yellow powder
- Lot/batch No.: MF1456-2345
- Expiration date of the lot/batch: 18 August 2011
- Storage condition of test material: At room temperature in the dark
- Stability under storage conditions: Stable

Study design

Test temperature:
Column temperature 35°C ± 1.0°C

HPLC method

Details on study design: HPLC method:
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.

According to the guidelines, the determination of the Koc for test substances that are ionized for at least 10% within pH 5.5 to 7.5 should be performed with both the ionized and non-ionized form. Therefore, the pKa values of the major components A and B of the test substance were calculated using the Perrin calculation method. Based on the calculations (no pKa values in the logarithm range 1-14), the HPLC analysis was performed at neutral pH.

- Apparatus: HPLC
- Type: Alliance Separation Module 2695 (Waters, Milford, MA, USA)
- Type, material and dimension of analytical (guard) column: Hypersil BDS-CN, 150 mm x 4.6 mm i.d.; dp = 5 µm (Thermo, San Jose, CA, USA)
- Detection system: Dual λ Absorbance Detector 2487; UV detection: 210 nm and 424 nm

- Type: A: 55/45 (v/v) methanol/water B: 100% methanol
Since it proved not possible to elute the test substance under isocratic conditions with a mobile phase of 55/45 (v/v) methanol/water as described in the guideline, a gradient was applied directly after the isocratic run in order to rinse the test substance off the column.

Time [minutes] %A %B

0 100 0
10 100 0
11 0 100
25 0 100
26 100 0
30 100 0

Flow 1 ml/min

Due to the limited solubility of the test substance in common organic solvents, microwave extraction as recommended by the sponsor was applied in attempts to dissolve the test substance. To 50 ml 99:1 (v/v) THF/HCl in a microwave teflon vessel 1.52 mg test substance was added and gently heated according to the following procedure:

Microwave oven: MARS 5Xpress Microwave Oven (CEM Corporation, Matthews, NC, USA)
Power: 100% (max 400 W)
Ramp: in 20 minutes from room temperature to target temperature
Temperature: 50ºC
Pressure: 800 psi
Duration: 10 minutes
Stirring: yes (fast)

After adjustment to room temperature, the solution was quantitatively transferred from the teflon vessels into a volumetric flask of 100 ml and filled up to the mark with 99:1 (v/v) THF/HCl.
Since the test substance could not be dissolved completely by microwave extraction and in order to get an estimate of the log Koc of the soluble components of the test substance, the solutions were filtrated over a 25 mm syringe filter with a 0.45 µm polypropylene membrane. This test solution was used undiluted.

The test substance blank solution was 99:1 (v/v) THF/HCl and treated similarly as the test solution, i.e. microwave extraction and filtration.

- Identity:
A stock solution of the reference substance at a concentration of 1160 mg/l in methanol was used. The reference substance solution was prepared by adding 50 µl of the stock solution to a 5 ml volumetric flask. The flask was filled up to the mark with 55/45 (v/v) methanol/water.

The blank solution for the reference substance was prepared by adding 50 µl methanol to a 5 ml volumetric flask. This flask was also filled up to the mark with mobile phase.

Reference substance: 2,4-DDT
Purity: 97.0%
Supplier: Supelco
log Koc # = 5.63

- Quantity of test substance introduced in the column: Injection volume 10 µl
- Quantity of reference substances: Injection volume 10 µl

- Number of determinations: The reference substance and test substance solutions were injected in duplicate. Blank solutions were analysed by single injection.

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.

Results and discussion

Adsorption coefficientopen allclose all
> 427 000
log Koc
> 5.63

Results: HPLC method

Details on results (HPLC method):
In the chromatogram of the test substance solution no test substance peak was observed during isocratic elution with 55/45 (v/v) methanol/water. Under the same analytical conditions, the retention time of 2,4-DDT (log Koc = 5.63) was 8.3 minutes. Yet, two test substance related peaks were observed at approximately 12.9 and 14.4 minutes, respectively, which is during the column rinse, i.e. under gradient conditions. Hence, it was concluded that the log Koc of all UV-visible components of the test substance was > 5.63 (Koc > 4.27 x 10^5).
Impurities with a peak area percentage of > 1% of the total peak area were not observed.

Applicant's summary and conclusion

Validity criteria fulfilled:
It was concluded that the log Koc of all UV-visible components of the test substance was > 5.63 (Koc > 4.27 x 10^5).