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Physical & Chemical properties

Water solubility

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Description of key information

Water solubility measurements for MCCP test materials are generally in the range of 4-10 µg/L (0.004-0.010 mg/L), with the exception of one reported of value of 27 µg/L (0.027 mg/L) for a radiolabelled test material of a C15 chlorinated paraffin, 51% chlorination by weight.   A recent OECD 105 guideline study (VU 2019) found a total solubility of 6.1 µg/L (0.0061 mg/L) ±29% (RSD), for a C14 chlorinated paraffin, 50% chlorination by weight using a column elution method with a levelling system at 19oC.  This study is unique among the water solubility studies for MCCP in that it evaluated the specific water solubility of congener groups within the test material. The analysis found that lower chlorinated congener groups were relatively more soluble up to C14H24Cl6(approximately 53% chlorine by weight) and then the relative solubility levels dropped dramatically with higher chlorinated congener groups. The study has been selected as the key study for this endpoint given the improved analytical methods employed in this study over earlier studies.

 

An early water solubility study of C15 chlorinated paraffin, 51% chlorination by weight was conducted by stirring 50 mg of the material, weighed on to a microscope slide, in 5 L water for 91 days. After allowing the solution to settle for 87 days to equilibrate, the concentration of test material was determined by a radiochemical method and by analysis of the parent compound by thin-layer chromatography. The water solubility determined by the two methods was 0.005 mg/L (parent compound) and 0.027 mg/L (radiochemical) at 20 oC.  Given that the radiolabelled test material results are outside the range of other studies, it’s possible this result represents both dissolved and undissolved fractions and therefore overstates the water solubility of MCCP.

 

Campbell and McConnell (1980) reported the solubility at 16-20oC of a C16 chlorinated paraffin (52% chlorinated) to be 0.010 mg/L and 0.004 mg/l in freshwater and seawater, respectively, based on radioactivity measurements. Few other details are available about the method used, but according to the RAR (EU, 2005) the results obtained are comparable with those reported by Madeley et al. (1983a).

Key value for chemical safety assessment

Water solubility:
0.006 mg/L
at the temperature of:
20 °C

Additional information