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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The adsorption coefficient log Ko was determined to be 3.3 for soil and 3.4 for sewage sludge.

Key value for chemical safety assessment

Koc at 20 °C:
1 995

Additional information

The adsorption coefficient (KOC) on soil and on sewage sludge using high performance liquid chromatography (HPLC) was estimated according to OECD 121 (2001) and Council Regulation (EC) No. 440/2008, Method C.19 for the test item.

The test was performed temperature controlled, (22.7 °C, mean value) with a mobile phase consisting of 50 % acetonitrile and 50 % HPLC water. A 50mg/L sample of the test item Disperse Green GNA was analysed threefold via HPLC on a cyanopropyl (CN-) column with DAD‑detection.

Calibrations were performed using eight reference items for soil and seven for sewage sludge with known log KOC values (given by the guidelines). The reference items were measured twice, once before and once after the measurement (double injection of one replicate) of the test item. Void time of the HPLC-system was determined with sodium nitrate.


Two individual logKOCvalues for soil and for sewage sludge for the test item were derived under consideration of the first and second calibration. Finally, a mean value for soil and for sewage sludge was calculated from these individual log KOC values. Based on these data a log KOC of 3.3 for soil and a log KOC of 3.4 for sewage sludge were determined for the test item.


Test Item


logKOC, soil

logKOC,sewage sludge





3.3 ± 0.1
3.0  to 3.6 (95 % CI)

3.3 ± 0.1
3.0 to 3.6 (95 % CI)

3.4 ± 0.2
3.0 to 3.8 (95 % CI)

3.4 ± 0.2
3.0 to 3.8 (95 % CI)





KOC         : Adsorption coefficient      CI           : Confidence Interval



The adsorption coefficient log KOC for the test item was determined to be 3.3 for soil and 3.4 for sewage sludge.