Tris(2-ethylhexyl) phosphate

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 April 2016 to 21 September 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted in accordance with international guidelines and in accordance with GLP. All relevant validity criteria were met.

Qualifier:

according to guideline

Guideline:

EU Method A.23 Partition Coefficient (1-Octanol/Water): Slow-Stirring Method

Version / remarks:

January 2014

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)

Version / remarks:

23 March 2006

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

slow-stirring method

Partition coefficient type:

octanol-water

Analytical method:

gas chromatography

mass spectrometry

Key result

Type:

log Pow

Partition coefficient:

> 6.26

Temp.:

25 °C

pH:

ca. 7

Details on results:

VALIDATION:
The linearity of the detector response with respect to concentration was assessed over relevant concentration ranges for each matrix analyzed during the determination of partition coefficient. In each case, the results were satisfactory with a correlation coefficient of at least 0.99 being obtained.
Recovery of analysis of the aqueous phase sample extraction procedure was assessed and proved adequate for the test. At a nominal concentration of 0.4 mg/L, a mean percentage recovery of 102 % was obtained (n = 5, range 96.2 to 109%, RSD = 5.09%).

DISCUSSION
The solubility of the test item in n-octanol was confirmed to be greater than a nominal concentration of 70 g/L. Therefore the nominal stock solution concentration of 40 g/L satisfied the guideline requirements of being below 70% saturation concentration in n-octanol and below 0.1 M.
No peak was detected for the test item on analysis of any of the aqueous phase samples. Therefore a limit value has been used for the aqueous phase concentrations to allow calculation of the partition coefficient results. This limit value originated from the lowest standard used within the aqueous linearity with the concentration factor of the samples applied, supplying a limit of 0.02 mg/L. The use of a limit value therefore gives a lower limit of Pow.

The sampling times, analyzed concentration (mg/L) of the respective phases, aqueous phase pH and resulting partition coefficient values (as log10 Pow) are shown in the following tables. The mean stock solution concentration on analysis was 4.09 x 10^4 mg/L.

Table 1. Vessel 1

Sample Number	Equilibration Time (hours)	Organic Phase Concentration (mg/L)	Aqueous Phase Concentration (mg/L)	Aqueous Phase pH	Log Pow
1	48.67	3.92E+04	<0.02	7.3	>6.29
2	72.50	3.87E+04	<0.02	6.9	>6.29
3	94.08	3.79E+04	<0.02	7.1	>6.28
4	99.25	4.16E+04	<0.02	7.3	>6.32
5	166.33	3.83E+04	<0.02	6.9	>6.28
6	171.42	4.09E+04	<0.02	7.0	>6.31
7	190.08	3.72E+04	<0.02	6.9	>6.27
8	195.25	3.69E+04	<0.02	6.7	>6.27
9	219.17	3.87E+04	<0.02	6.8	>6.29

Table 2. Vessel 2

Sample Number	Equilibration Time (hours)	Organic Phase Concentration (mg/L)	Aqueous Phase Concentration (mg/L)	Aqueous Phase pH	Log Pow
1	190.08	3.90E+04	<0.02	7.0	>6.29
2	195.25	3.97E+04	<0.02	6.8	>6.30
3	214.00	3.87E+04	<0.02	6.8	>6.29
4	219.17	3.89E+04	<0.02	7.0	>6.29

Table 3. Vessel 3

Sample Number	Equilibration Time (hours)	Organic Phase Concentration (mg/L)	Aqueous Phase Concentration (mg/L)	Aqueous Phase pH	Log Pow
1	190.08	3.90E+04	<0.02	6.9	>6.29
2	195.25	3.67E+04	<0.02	6.7	>6.26
3	214.00	3.88E+04	<0.02	6.8	>6.29
4	219.17	3.89E+04	<0.02	6.9	>6.29

Table 4. Validation of Analytical Method

Analysis	Matrix	Nominal Concentration Range (mg/L)	Correlation Coefficient (r)
Stock solution and organic phases	Acetonitrile: water saturated n-octanol (49:1 v/v)	300 to 1.25E+03	0.996
Aqueous Phases	Iso-octane	0.1 to 2.0	0.990

Conclusions:

The partition coefficient of the test item was determined as follows:
Log Pow = >6.26
Partition Coefficient (Pow) = >1.82E+06

Executive summary:

The partition coefficient (Pow) of the test item at 25.0 ± 0.5 °C was determined using a slow-stirring method designed to be compatible with Method A.23, 24 January 2014, and Method 123 of the OECD Guidelines for Testing of Chemicals, 23 March 2006.

Analysis in both phases were conducted with a GC-MS validated method. The test item could not be detected in the aqueous phase, therefore the result is expressed as a limit value. pH was measured as ca 7.

The partition coefficient of the test item was determined as follows:

Log Pow = >6.26

Partition Coefficient (Pow) = >1.82E+06

Description of key information

n-Octanol/Water Partition Coefficient = >1.82E+06 (Log Pow = >6.26) (25.0 °C, pH ca 7); OECD 123; Jein (2016)

Additional information

In a single key study, the partition coefficient (Pow) of the test item at 25.0°C was determined, under GLP, according to EU A.23 and OECD 123 guidelines, using a slow-stirring method. Three vessels were prepared, and both octanol and aqueous phases were analysed by GC-MS method. The pH of the aqueous phase was recorded.

The partition coefficient of the test item was determined as follows:

Log Pow = >6.26 (25°C, pH ca 7)

Partition Coefficient (Pow) = >1.82E+06

As the result is a limit value, it was not retained as key value for CSA (no > sign allowed).