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Adsorption / desorption

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adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Version / remarks:
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Test temperature:
25 ± 0.5 °C
Details on study design: HPLC method:
- Apparatus: HPLC Ultimate3000
- Type:
- Type, material and dimension of analytical (guard) column: Dr. Maisch Reprosil Pur 120 CN (125x4.6 mm, S/N 50318, 2902 02) with precolumn Phenomenex Security Guard CN, 4x3 mm
- Detection system: UV Detector MWD-3000 (220 nm)

- Type: MeOH/H2O 55/45 (% v/v)
- Experiments with additives carried out on separate columns: yes / no
- pH: 5-6
- Solutes for dissolving test and reference substances:

- Method: by inert substances which are not retained by the column (Sodium Nitrate, NaNO3, CAS 7631-99-4)

- Identity: Acetanilide (CAS 103-84-4), Methylbenzoate (CAS 93-58-3), Naphthalene (CAS 91-20-3), 1,2,3-trichlorobenzene (CAS 87-61-1), Phenanthrene (CAS 85-01-8), DDT (CAS 50-29-3)

- Quantity of test substance introduced in the column: 10 µg
- Quantity of reference substances:
- Intervals of calibration:

- Number of determinations: 6 (reference substances), 3 (test substance)

- Calculation of capacity factors k':
- Calculation of retention times:
- Determination of the log K-oc value: log k’ = 0.2395 * logKOC – 0.1083
Key result
log Koc
> 5.63
25 °C
Details on results (HPLC method):
- Retention times of reference substances used for calibration: Acetanilide 2.700, Methylbenzoate 3.149, Naphthalene 4.476, 1,2,3-trichlorobenzene 5.283, Phenanthrene 7.583, DDT 20.574
- Details of fitted regression line (log k' vs. log Koc): log k’ = 0.2395 * logKOC – 0.1083 with a coefficient of determination r2 = 0.9900
- Average retention data for test substance: 33.001
Validity criteria fulfilled:
As the substance is not eluted within the isocratic part of the HPLC program, the log KOC of the test item is stated as > 5.63 (log KOC of DDT, reference item mix com-ponent with the highest log KOC).
Executive summary:

The study was performed using a HPLC with a cyanopropyl chemical bound resin on a silica base column. Six 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 N-(hydroxymethyl) stearamide based on the results of the pre-test.


A solvent blank followed by three injections of a solution of the reference items were analysed with HPLC, then three injections of a solution of the test item; and finally three injections of the solution with the reference items, in total ten runs.

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. In the graph log k’ versus log KOC, linear regression was performed, giving r2 = 0.9900.


The chromatogram of the test item gave one peak (mean RT = 33.001 min). The test item did not elute within the isocratic part of the method, therefore calculation of the log KOC of the test item N-(hydroxymethyl) was not possible.

The log KOC of the test item is stated as > 5.63 (reference item with the highest log KOC DDT with a log KOC of 5.63.

Description of key information

The key value is determined in a HPLC screening study. As the substance is not eluted within the isocratic range of the determination, the value is estimated to be > 5.63. For the assessment this value is used.

Key value for chemical safety assessment

Koc at 20 °C:
426 580

Additional information