Formaldehyde, oligomeric reaction products with aniline

Adsorption / desorption

Description of key information

All the studies provide complementary information on the adsorption/desorption behaviour of MDA in various soils under aerobic and anaerobic conditions. 
MDA has been shown to irreversibly (i. e. covalently) bind with soils under normal aerobic condition. 

Key value for chemical safety assessment

Koc at 20 °C:

10 729

Additional information

Justification on read-across of data for the 4,4´-isomer of MDA for oligomeric MDA in the scope of REACH is documented in IUCLID and described in sections 4.1.2 of the CSR.

Experiments with radiolabelled 4,4'-MDA revealed that the substance forms covalent bonds with the organic fraction in soils. Initial sorption of MDA in silt loam was nearly completed by 4 hours under aerobic conditions. Under anaerobic conditions, sorption appeared to still be proceeding at 7 days. The K_OC values were determined to 4,848 l.kg^-1 after 8 hours and 7,041 l.kg^-1 after 7 days for aerobic conditions. The values for anaerobic conditions are 3,828 l.kg^-1 and 10,729 l.kg^-1 for 8 h and 7 d, respectively. Furthermore, surface adsorption or ion exchange processes were found with minerals without organic content. It should be kept in mind that the term "K_OC" generally describes the distribution of a substance between the pore water and the organic matter when the substance is physically bound; if chemisorption occurs the use of this term is not quite correct.

MDA has been shown to irreversibly (i.e. covalently) bind with soils under normal aerobic condition. This binding is suppressed under low redox conditions (i.e. anaerobic). This behaviour is consistent with the literature where aromatic amino groups are known to chemically react with aldehyde and keto groups as well as double bonds of quinoid systems typically found in humic substances present in soils. Under low redox conditions such groups / quinoid systems would not be available for reaction with the amino moiety.