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Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-10-09 - 2018-01-07 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - Shake Flask Method)

Version / remarks:

Method A.8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)

Version / remarks:

Method 107 of the OECD Guidelines for Testing of Chemicals, 27 July 1995

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

mass spectrometry

Key result

Type:

log Pow

Partition coefficient:

2.43

Temp.:

23 °C

pH:

>= 6.4 - <= 6.7

Remarks on result:

other: for the Amine, C12-14-tert-alkyl cation content

Key result

Type:

log Pow

Partition coefficient:

4.8

Temp.:

23 °C

pH:

>= 6.4 - <= 6.7

Remarks on result:

other: for the O,O-di-ethylhexyl hydrogen phosphorodithioate anion content

Conclusions:

The partition coefficient logPow was determined in a GLP guideline study according to OECD 107 and EU method A.8 without deviations on the registered substance itself. The method was considered suitable for the nature of the test item. Hence, there is no indication given that the results are not reliable.
The partition coefficient of salts is required within the environmentally relevant pH range of 5 to 9 at which the theoretical solubility is maximized in n-octanol and therefore the value of partition coefficient is maximized. As the quaternary amine retains a permanent cationic charge irrespective of pH, evaluation of the test system pH was therefore limited to the 2-ethylhexanoic acid content of the test item.
Estimated dissociation constant values for the test item were -0.12 for the thiol functional group of the O,O-di-ethylhexyl hydrogen phosphorodithioate anion and 10.7 for the amine functional group of the Amine, C12-14-tert-alkyl cation (Advanced Chemistry Development Inc., pKa, Algorithm Version v12.1.0.50374). The partition coefficient was therefore performed at an unadjusted, approximately neutral pH, with the actual aqueous phase pH range being 6.4 to 6.7. This was since both the anion and cation content of the test item would remain charged across the full environmentally relevant pH range of 5 to 9.
On analysis, a slightly lowered mass balance recovery was obtained for sample number 6. Whereas this did not evidently influence the calculated partition coefficient of the test item during quantification in positive polarity, when analysing in negative polarity, the resulting calculated partition coefficient value was identified as a statistically significant outlier (Grubbs’ Test, P = 0.05). This value has therefore been excluded from the calculation of the overall mean partition coefficient for the O,O-di-ethylhexyl hydrogen phosphorodithioate anion content of the test item.
All individual partition coefficient results were within ± 0.3 log units of the mean, thus satisfying the criteria specified in the guidelines.
So, the partition coefficient of the test item has been determined at an aqueous phase pH range of 6.4 to 6.7 and a test temperature of 23.0 ± 0.5 °C to logPow = 2.43 for the Amine, C12-14-tert-alkyl cation content, and to logPow = 4.80 for the O,O-di-ethylhexyl hydrogen phosphorodithioate anion content.

Executive summary:

Testing for the logPow of the test item was performed using a shake-flask method, designed to be compatible with Method A8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 107 of the OECD Guidelines for Testing of Chemicals, 27 July 1995, under GLP. At a test temperature of 23.0 ± 0.5 °C and an aqueous phase pH range of 6.4 to 6.7, results as summarized in the following table were obtained:

 

Table Partition Coefficient Summary

Component	Partition coefficient (Pow)	Log Pow
Amine, C12-14-tert-alkyl cation content	269	2.43
O,O-di-ethylhexyl hydrogen phosphorodithioate anion content	6.33 x 10E4	4.80

Description of key information

Partition coefficient: logPow = 2.43 for the Amine, C12-14-tert-alkyl cation content, and to logPow = 4.80 for the O,O-di-ethylhexyl hydrogen phosphorodithioate anion content at pH6.4 to 6.7 and a test temperature of 23.0 ± 0.5 °C (shake-flask method, OECD 107, GLP)

Key value for chemical safety assessment

Log Kow (Log Pow):

4.8

at the temperature of:

23 °C

Additional information

The given logPow of 4.8 does not depict the actual situation properly. The partition coefficient was determined for the cation and anion part separately, to logPow = 2.43 for the Amine, C12-14-tert-alkyl cation content, and to logPow = 4.80 for the O,O-di-ethylhexyl hydrogen phosphorodithioate anion content. As, due to limitations of this text field, only one value can be entered, the priority was set to the most critical one.