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Physical & Chemical properties

Partition coefficient

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Description of key information

Based on the complex and not totally defined composition of the substance and taking into account the tensio-active properties of the surfactant fraction and the fact that classical methods cannot be used, it is considered reasonable to assume a log Kow value of -1.

It is pragmatically assumed that the water solubility of the substance is 10 times higher than its n-octanol solubility, as the surfactant fraction of the substance is always under ionized form and in particular as a sodium salt form as manufactured.

A log Kow of -1 is supported by a calculated log Kow of –1.62 to -4.19 for the main part of the surfactant fraction.

Key value for chemical safety assessment

Log Kow (Log Pow):
-1
at the temperature of:
20 °C

Additional information

As the substance is an UVCB substance, containing numerous surface active constituents and NaCl, it is expected that NaCl and the different surfactant constituents will behave differently in water and in octanol. So the standard test methods are not appropriate to measure the log Kow. The only suitable method was considered to be the estimation method, as all other methods were assessed to be not adequate; review of available methods:

 

HPLC method:

-Not suitable for surfactants and for switterionic substances

Flask method:

-Not suitable for surface active substances

-Not suitable for substances with many constituents

-Quantitative determination of the substance concentration in water and octanol is not possible

Calculation method:

-Not suitable as calculations are not possible for all constituents

-Not suitable for substances with many constituents, leading to a broad range with limited use

-Not suitable for salts

-Unreliable as it was shown that different calculation methods gave different results

Slow stirring method:

-Not suitable for substances with many constituents

-Quantitative determination of the substance concentration in water and octanol is not possible

Estimation method:

The estimation method is another alternative method cited in the guidance: Guidance on information requirements and chemical safety assessment -Chapter R.7a: Endpoint specific guidance. The estimation method is based on a separate measurement of the solubility in water and in octanol followed by the ratio of these measurements to estimate the Kow: Kow = [n-octanol] / [water]. On the basis of the conducted solubility tests in water and in octanol with the substance it was shown that:

- The water solubility of the substance is extremely high. Visually it was determined that a solution of 1.02 kg/L in water results in a clear solution without undissolved material.

- The n-octanol solubility of the surfactant part of the substance is also extremely high (> 783 g surfactant part/L). The in n-octanol undissolved particles observed in the study most probably derive from sodium chloride. Visual it was determined that a solution of 1.08 g/L in n-octanol results in a solution with undissolved material.

Also with the estimation method it is concluded that it is technically not possible to determine a reliable estimate of the log Kow for this complex and variable substance.