H112323

Adsorption / desorption

Description of key information

In a HPLC screening study (OECD 221),  the adsorption coefficient for test substance was determined to be log Koc < 1 at 24°C. 
In an adsorption/desorption study (OECD 106),  ithe test substance H112323 was totally adsorbed onto Nebo soil, a silty clay loam, with no detectable evidence of subsequent desorption. With Kenny Hill soil, a sandy loam, up to 64% adsorption of Substance H112323 occurred, of which 25% of the adsorbed substance was desorbed.
The resulting adsorption coefficients for Substance H112323 ranged from 5.0 (2 hours) to 9.1 (16 hours) for the Kenny Hill soil, with a corresponding range in Koc values of 180 to 320. For the Nebo soil the values for Kd ranged from 250 (2 hours) to > 2600 (16 hours) giving Koc values of 15000 to >160000.

Key value for chemical safety assessment

Koc at 20 °C:

180

Additional information

The adsorption coefficient of the test substance was determined according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)). The sorption coefficient (Koc) is a measure for the adsorption of chemicals in the soil. In this test, the order of magnitude of the adsorption coefficient for test substance was determined to be log Koc < 1 at 24°C.

An adsorption/desorption study was conducted according to OECD test guideline 106 in compliance with GLP.

The adsorption characteristics of the test item H 112323 from a 0.01 M CaCl2 solution to Kenny Hill sandy loamy and Nebo silty clay loam test soils was studied. The adsorption coefficient for each soil (Kd) was derived and the adsorption coefficient calculated as a function of the organic carbon content of each soil (Koc), was also derived. For each soil sample from the 16 hour adsorption test for which adsorption was found to be >25%, the desorption was determined.

The results of the adsorption test show that when mixed with the Kenny Hill soil 50% adsotption of Substance H112323 occurs within 2 hours rising to 64% after 16 hours. For the Nebo soil 98% of Substance H112323 was adsorbed within 2 hours with virtually all the test substance having been adsorbed after 16 hours. The results also indicate that for the Nebo soil, equilibrium was established at 6 hours. Although for the Kenny Hill soil equilibrium may not have been fully established there was a difference of <10% between the means of the 6 and 16 hour soil extract analyses indicating that a plateau had been reached. It is also clear that the values of Ce would be unlikely to alter substantially with extended equilibrium. times.

The derived adsorption coefficients for Substance H112323 rise over time. For the Kenny Hill soIl the values for Kd ranged from 5.0 (2 hours) to 9.1 (16 hours) with a corresponding range in Koc values of 180 to 320. For the Nebo soil the values for Kd ranged from 250 (2 hours) to > 2600 (16 hours) giving Koc values of 15000 to >160000.

The desorption test results show that for the Kenny Hill soil 25% of the adsorbed test material was desorbed whilst for the Nebo soil no detectable desorption occurred.

In conclusion, Substance H112323 was totally adsorbed onto Nebo soil, a silty clay loam, with no detectable evidence of subsequent desorption. With Kenny Hill soil, a sandy loam, up to 64% adsorption of Substance H112323 occurred, of which 25% of the adsorbed substance was desorbed.

[LogKoc: 2.3]