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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Three reliable studies (conducted according to guidelines and using GLP principals) are included on two different read-across substances, to assess the adsorption potential.

 

One study was carried out on fatty acids, C16-18 (even numbered) and C18 unsatd., reaction products with diethylene triamine, di-Me sulfate quaternized. This study assessed the adsorption coefficient using High Performance Liquid Chromatography method. This study included six reference chemicals, with the most strongly adsorping chemical being 2,4 -DDT. The test substance was not eluted from the column and therefore the sorption coefficient (Koc) was determined to be greater than the maximum reference item adsorption coefficient of, >427,000 (log Koc>5.63) at 25˚C. This value would indicate that the test substance will be adsorbed by organic carbon in soil. Based on the results, the test item can be regarded as immobile in soil. According to the statement in the guideline, however, the method may not work for surface-active substances and the results (test substance was not eluted from the column) confirm this statement.

 

The other two studies were carried out on Imidazolium compounds, 2-C17-unsatd.-alkyl-1-(2-C18-unsatd. amidoethyl)-4,5-dihydro-N-methyl, Me sul... / 931-745-8; oleic-acid based IQAC, DMS quaternised. One of the studies used the HPLC method to assess adsorption coefficient, however only the reference item 2,4 -DDT was included. It was found that the test item strongly interacted with the analytical column. Based on the results obtained it was concluded that the test substance has a Koc value of higher than the reference substance 2,4-DDT, which corresponds to a Koc and log Koc of > 427000 and > 5,63 at 35˚C, respectively. The other study was a batch equilibrium study in which the potential for adsorption and desorption was measured in five soils, including silts, sands and loams. The results demonstrated that the compound adsorbed to all tested soils with Koc values above 135000, which classifies the compound as immobile in soils according to McCall et al. During the desorption experiements, the test item showed a low desorption (0.05 to 0.7 %) during desorption kinetic experiments, thus, the expected desorption was too low for a reliable determination because the experimental error in the applied analytical methods would have been higher. Overall, this indicated that the adsorption was not reversible.

Overall, all of these studies indicate the test substance is highly adsorptive in soils and sediment and will be immobile. Once adsorbed, the test substance is unlikely to be re-mobilised. However, a cautionary note is added regarding the applicability of this method to surface active substances, such as these two read-across substances.

Key value for chemical safety assessment

Other adsorption coefficients

Type:
other: KOC
Value in L/kg:
427 000
at the temperature of:
25 °C

Other adsorption coefficients

Type:
other: Log KOC
Value in L/kg:
5.63
at the temperature of:
25 °C

Additional information

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