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Description of key information

Based on the results of a batch equilibrium experiment in which the adsorption of the substance to three different soils with varying properties was investigated, a key Koc value of 49.7 (geometric mean of three Koc values) was selected as key value for the CSA. This corresponds to a log Koc value of 1.7. Because pH was not monitored in the aqueous solution, the pH dependency of adsorption of this ionisable substance could not be evaluated. Therefore the study was scored as Klimisch 2.

Key value for chemical safety assessment

Koc at 20 °C:
49.7

Additional information

Based on a calculation of the pKa's and the results of the determination of the log Kow, it is clear that the test substance is ionized for at least 10% in the range pH 5.5 -7.5. Therefore both the ionized and the unionized form should be tested in appropriate buffer solutions. Since the highest pKa was calculated to be 9.9, the test substance must be tested both at a pH of > 10.9 (neutral form) and at a pH < 8.9 (ionized form). Due to the limited pH range of the cyanopropyl column required for the OECD 121 method, testing at pH > 10.9 is impossible. Testing at pH < 8.9 is in principle possible, but due to the very unfavorable interaction of the protonated form of the test substance with residual silanol groups of the stationary phase, test substance peak shape and retention time reproducibility will be extremely poor. Therefore, it is not possible to determine the partition constant according to the OECD 121 method (HPLC method).

Alternatively, a batch equilibrium test was performed (Environmental Testing Laboratory, 2012) according to a guideline similar toe OECD guideline 106. In this study, the adsorption of the substance was studied in three different Chinese soils with variable properties (pH, organic carbon, CEC, % clay). The log Koc values obtained in these soils range from 1.52 to 1.79. Although for this substance it would have been interesting to investigate pH dependency of adsorption, no information on this is obtained since pH was not monitored in the aqueous phase. Therefore, this study was scored as Klimisch 2.

As supporting information, several QSAR estimates can be used. The QSAR for nonhydrophobics reported by Sabljic and Güsten (1995) and reported in the TGD (2003) of the European Commission yields a log Koc of 2.06 (using a linear regression equation based on the log Kow). This value may be underestimated since the model may underestimate the log Koc of aliphatic amines by 1-2 log units. Therefore, the value should be used with caution. NOTOX Project 375637 presents another QSAR prediction (also based on log Kow), in which the final values were (worst case) corrected for the possible underestimation for aliphatic amines. The resulting values were log Koc = 2.8 and 3.2 for two components, respectively. Here too, these values should be used with caution. Therefore, both QSAR estimates represent supporting information.