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Adsorption / desorption

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Description of key information

The adsorption coefficient (Kd) of the substance was determined in a test according to OECD TG 121 (GLP, reliability 1). The log Kd was reported as -0.26. This corresponds to log Koc of 1.94.  

Key value for chemical safety assessment

Koc at 20 °C:

Additional information

The adsorption coefficient (Koc) of Sodium caprylimino dipropionate was estimated using the High Performance Liquid Chromatography (HPLC) method (OECD 121, GLP, reliability 1). The test was performed in duplicate using two buffer solutions of pH 3.0 and pH 7.4, reflecting different dissociation forms of the test substance (pKa is 4.51 and 8.17). The data on Koc can be used to predict the potential of the test substance to partition to soil, sediment or sewage sludge.

During the study two peaks for the test substance were detected at pH 7.4. Based on the information provided by the sponsor the peak with the lowest retention time (average net retention time of 0.12) was considered to be representative of the monopropionate whereas the peak with the highest retention time (average net retention time 0.87) was considered to be representative of the dipropionate. During the test at pH 3.0 only one peak was detected for the test substance.

As the first peak was outside the range of retention times of the reference compounds used for the calibration, log Koc has been reported as < 1.3 for the first peak (1.3 is the lowest value for log Koc among the reference compounds). This value is not used for further calculations as it was reported to be representative for the monopropionate. Log Koc is 1.94 as determined from the second peak. The latter value has been used as key value for further calculations because this value was considered to be representative of Sodium caprylimino dipropionate. It can be concluded that the Log Koc of Sodium caprylimino dipropionate is 1.94 at the environmentally relevant pH of 7.4. This value corresponds to Koc of 87.

Log Koc of 2.2 was determined at pH 3.0 (corresponding to Koc of 170).

[LogKoc: 1.94]