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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The adsorption/desorption coefficient Koc of the test item was assessed using an HPLC method. The test item concentration was 4.3 mg/L mobile phase. The experimentally derived log Koc was 6.49 with pH 7.2 at 35°C.

Key value for chemical safety assessment

Other adsorption coefficients

Type:
other: log Koc
Value in L/kg:
6.49
at the temperature of:
35 °C

Additional information

The adsorption/ desorption coefficient Koc of the test item was assessed using an HPLC method according to OECD 121, adopted in 2001. HPLC analysis is performed on an analytical column packed with a commercially available cyanopropyl solid phase, based on a silica matrix, containing lipophilic and polar moieties. 15 µL of the test item solution (4.3 mg/L mobile phase) were injected onto the column. The test item moves along the column at different rates because of the different degrees of partitioning between the mobile phase and the stationary phase. This enables to establish the relationship between the retention time on the column and the adsorption coefficient on organic matter. The retention time of the oligomer n= 2 was determined in duplicate and the capacity factor k was calculated. The assay was performed with pH 7.2 at 35°C. 6 reference compounds were included. The adsorption coefficient is defined as the ratio between the concentration of the substance in the soil/ sludge and the concentration of the substance in the aqueous phase at the adsorption equilibrium. The estimated calculated logKoc was 6.5 at pH 7.2 (PCKOCWIN). This corresponds to a Koc = 3.23 x 10E06.The experimentally derived logKoc which was deduced from the capacity factor k' using a calibration plot of log k' versus log Koc of the reference compounds, was 6.49 at pH 7.2 and 35°C. This corresponds to a Koc = 3.1 x 10E06. Based on this result it is estimated that the test item is not free dissolved in water but adsorbs to organic material.