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Physical & Chemical properties

Partition coefficient

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Description of key information

log Kow not used to predict the bioaccumulation potential of Quaternary ammonium compounds, di-C16-18 (even numbered)-alkyldimethyl, chlorides.

Key value for chemical safety assessment

Log Kow (Log Pow):
8.4
at the temperature of:
25 °C

Additional information

The partition coefficient for Quaternary ammonium compounds, di-C16-18 (even numbered) -alkyldimethyl, chlorides has been determined according to OECD 123 (slow-stirring method) and following GLP rules (Vos 2010). The log Kow for the 3 major components was calculated in the range 8.2 to 8.4 (pH7, 25°C). The slow-stirring method is considered to be the best to determine the Kow of surfactants, as indicated in the Chapter R.7A of the REACH guidance (Section R.7.1.8.3; Guidance on regulatory compliant Kow determination for surfactants). However, it is also indicated that this method is still not demonstrated to be perfect and that none of the experimental methods is very well suited for determining the Kow of surface active chemicals. Indeed, due to the physico-chemical properties of surfactants, specifically their tendency to either accumulate at the octanol/water interface or to coat the surfaces of the above-described HPLC adsorbent phase, the logKow of surfactants cannot be accurately measured for these substances. The difficulty to obtain a reliable result for cationic surfactants is confirmed with the variability of results from different methodologies. Indeed, in contrary to the results from Vos (2010), the study from Sánchez Leal, J. et al. (1994) determined a value of 3.8 for the log Kow of DODMAC (CAS 107-64-2). A value of 1.74 was obtained in an additional study using reverse-phase HPLC method (OECD 117 from Baroid Ltd). Therefore, the log Kow values of Quaternary ammonium compounds, di-C16-18 (even numbered) -alkyldimethyl, chlorides can not be used to predict the partitioning behaviour (sorption or bioaccumulation potential) of this compound, as indicated in the EU Risk Assessment DODMAC (EU, 2002). Instead of this, the available experimentally determined and higher tier sorption and BCF/BAF figures are used to predict the fate in the environment.