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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The adsorption coefficient from a comparable read-across substance was log Koc >5.63. 
QSAR estimates were also made on the two substance constituents typically present at the highest concentration. The predicted log Koc values were 8.7 and 10.02.

Key value for chemical safety assessment

Koc at 20 °C:
430 000

Additional information

Read-across study on EC No. 434 -430 -9 (EA-3098)

The estimation of the adsorption coefficient (Koc) in soil and on sewage sludge using HPLC was based on the following guidelines:

  • OECD 121 "Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using HPLC"EEC Directive 2001/59/EC
  • Method C.19 "Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using HPLC"

According to these guidelines, the estimation of the adsorption coefficient (Koc) for test substances that are ionised for at least 10% within pH 5.5 to 7.5, should be performed with both the ionised and non-ionised form. Based on calculated pKa values (16.28 and 16.88 for an acidic group and -0.48 and 0.12 for a basic group), it was decided to perform the HPLC method at neutral pH.

The adsorption coefficient (koc) of EA-3098 was determined to be >4.3 x 105(log koc >5.63) at 35°C.

QSAR data:

Estimates of the adsorption coefficients of the two substance constituents typically present at the highest concentration were obtained using the specialised predictive software PCKOCWIN, version 1.66 (from the EPI Suite program (v 3.20), developed by the US EPA). The software uses a first order molecular connectivity index (MCI) and a series of statistically derived fragment corrections.

The estimated results are given below:

Substance Constituent

Estimated log Koc

N,N'-[1,3-phenylenebis(methylene)]bis(12-hydroxyoctadecanamide) (CAS No. 128554-52-9)

8.7085

12-hydroxy-N-{3-[(stearoylamino)methyl]benzyl}octadecanamide (CAS No. 1262779-46-3)

10.0184

The predicted results confirm the experimental results obtained in the read-across substance.

The results indicate that the substance constituents may partition out of water into soil/sediment compartments and have potential to accumulate in the soil/sediment compartments.

[LogKoc: 5.63]