Registration Dossier

Physical & Chemical properties

Partition coefficient

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Alkyl phosphate and stearyl amine salts (EC = 952-252-4) are mainly composed by primary alkylamines (CAS 90640-32-7, UVCB), Monoalkyl dihydrogenophosphate and Dialkyl hydrogenophosphate salts (CAS 39471-52-8, Multi-Constituent). This different chemical structures are constituted by variable chain lenght with C16 and C18.

 

For primary alkylamines, a weight of evidence is based on various studies. The highest log Pow value (4.33) is resulting for(Z)-Octadec-9-enylamine, and this value is used as the worst-case key value.

Phosphoric acid, octadecyl ester (CAS 39471-52-8) has a log Kow value less than 0.3 to 2.31 according to an TG OECD 117. to 2.31 according to an TG OECD 117. In a worst case approach, the environmental fate (e-fate) and ecotoxicity of the Alkyl phosphate and stearyl amine salts (EC = 952-252-4) was considered as driven by the properties of the alkylammonium part.

 

Moreover, it is of importance to note that a new study on the Alkyl phosphate and stearyl amine salts (EC = 952-252-4) will be performed (if technichally feasible) according the TG OECD 123 to reinforce this approach.

Key value for chemical safety assessment

Log Kow (Log Pow):
4
at the temperature of:
20 °C

Additional information

The registered substance is an Alkyl phosphate and stearyl amine salts (EC = 952-252-4). It is mainly composed by saturated primary alkylamines C16 -C18 (CAS 90640-32-7, UVCB), Monoalkyl dihydrogenophosphate and Dialkyl hydrogenophosphate salts (CAS 39471-52-8, Multi-Constituent). This different chemical structures are constituted by saturated and variable chain lenght with C16 and C18.

 

For primary alkylamines, a weight of evidence is based on various studies performed under technical guidelines OCDE. Alkylamines are difficult substances with regard to the determination of the partitioning coefficient n-octanol water: the compounds are strong bases (pKa 10.6), such that at neutral pH (pH 7) these compounds are ionised (primary ammonium ion) by 99.98%. The resulting primary ammonium derivative is surface active.

 

In the Chapter R.7A of the REACH guidance (Section R.7.1.8.3; Guidance on regulatory compliant Kow determination for surfactants), it is indicated that none of the experimental methods is very well suited for determining the Kow of surface active chemicals.

 

 The slow stirring method (OECD 123) seems to be the best in theory, but still not demonstrated to be perfect. 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 log Kow of surfactants cannot be accurately measured for these substances.

 

According to the REACH guidance Chapter R.7a v6 (July 2017), the ratio solubility in octanol / solubility in water is acceptable for such compounds. The present weight of evidence approach follows this recommendation. Given the equilibrium in water between the alkyl ammonium ion and the free amine, relevant for octanol solubility is the one determined from the free amine (uncharged).

 

To choose a relevant worst-case key value for risk assessment, the following table presents available experimentally determined water solubilities (CMCs) of alkylamine hydrochlorides, together with experimental values for octanol solubilities of their respective free amine. Resulting calculated partition coefficients n-octanol/water are given in the table:

 

Table 1: Resulting partition coefficient n-octanol water (Pow) calculated from water solubilities (alkyl amine hydrochlorides) and n-octanol solublities (free amines):

 

Substance name

Solubility in octanol (20°C) [g/L]

Reference

Solubility in water (25°C) (CMC) [g/L]

Reference

Pow

log Pow

Dodecylamine

539

Clariant, 2009j

3.5

Clariant, 2008e

154.00

2.19

Tetradecylamine

310

Clariant, 2009k

0.69

Clariant, 2009r

449.28

2.65

Hexadecylamine

148

Clariant, 2009i

0.063

Clariant, 2010v

2349.21

3.37

Octadecylamine

126

Clariant, 2009g

0.013

Clariant, 2010w

9692.31

3.99

(Z)-Octadec-9-enylamine

813

Clariant, 2009h

0.038

Clariant, 2009q

21394.74

4.33

 

As could be expected, a clear increasing trend for Pow becomes obvious with increasing carbohydrate chain length.

 

Regarding the other part of the salt, the Phosphoric acid, octadecyl ester (CAS = 39471-52-8), a log Kow value is available and was determined to be less than 0.3 to 2.31 according to an TG OECD 117. Therefore, Phosphoric acid, octadecyl ester are not considered as the worst case constituant for the registered substance.

 

Moreover, it is of importance to note that a new study on the Alkyl phosphate and stearyl amine salts (EC = 952-252-4) will be performed (if technichally feasible) according the TG OECD 123 to reinforce this approach.

 

The highest log Pow value (4.33) is resulting for(Z)-Octadec-9-enylamine, and this value is used as the worst-case key value.