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Partition coefficient

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Description of key information

The partition coefficient of the test substance is 3.4 (log Pow).

Key value for chemical safety assessment

Log Kow (Log Pow):
at the temperature of:
25 °C

Additional information

The registered substance is a surface active with a surface tension of 27 mN/m at 20C and 1000 mg/L. For surfactants,measurement of the Kow is challenging or in most cases infeasible (see REACH Guidance R.7.8.1.). The registrant has managed to measure the Kow under the conditions described in the end-point robust study summary with the slow-stirring method. Other conditions were found to be infeasible. The conditions used in the slow-stirring test are environmentally relevant (pH range to be considered is 4-9). Based on the pKa of 8.8, the registered substance does not exist exclusively in a neutral form within this environmentally relevant pH range.

The log Kow is regarded as an essential data point within the chemical safety assessment e.g. to estimate water solubility, adsorption/desorption and bioaccumulation in fish. For the registered substance measured values for water solubility (as Critical Micelle Concentration in IUCLID Chapter 4.8) and measured sorption constants (see IUCLID Chapter 5.4.1) are available. Therefore estimation of these parameters with help of Kow is not necessary. As the registered substance is a cationic surfactant measurement of the BCF in an OECD 305 test is not feasible as the cationic substance strongly sorbs to the negatively charged mucous of the fish. This statement is based on an attempt to measure the BCF fish for 1-Hexadecanammonium chloride which failed. The currently best method to estimate the BCF of a cationic substance is the ADME Model of Arnot and Gobas BCFBAF implemented in the US EPA EPIWIN Suite. This ADME model takes into account adsorption, distribution, metabolism and excretion of a substance and not only the distribution e.g. based on the log Kow alone.