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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:

2022-01-11 to 2022-04-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)

Version / remarks:

2004

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

-1.4

Temp.:

20 °C

Remarks on result:

other: Estimated log Pow < -1.4

Preliminary test

The preliminary test at room temperature showed, that the octanol solubility of the test item is between 58.7 and 176 g/L. The observations of the preliminary test are summarized in Table 1.

With the value of the water solubility estimated from the water solubility study (> 5232 g/L) and the estimated solubility in octanol from this preliminary test of 58.7 – 176 g/L, the partition coefficient was estimated to be between -2.0 and -1.5. For this range the partition coefficient can be calculated from the solubilities in both solvents. Thus, the flask method is used for the determination of the octanol solubility.

Table 1: Results of the preliminary test for the octanol solubility

Amount of test item [g]	Total volume of added octanol [mL]	Stirring time at RT [h:min]	Remark
6.08	5	0:45	Not dissolved
0.88	5	1:05	Not dissolved
	15	16:10	Dissolved

Main test (flask method)

For the main test three flasks were prepared with an amount of test item and 1-octanol, and one flask only with 1-octanol (4a, blank). After stirring and centrifugation the clear octanol phases were measured by means of UV/Vis spectrometry. The solution of each flask has been measured once. The results of these measurements are shown in Table 2. The values represented in the table are rounded values. The calculation was carried out with the original not rounded values.

Table 2: Results of the flask method

Flask	1a	2a	3a	4a
Measured value [mg/L]	20.9	19.1	21.8	0.00
Aliquot of the flask [mL]	0.1	0.1	0.1	0.1
Total volume after 1st dilution [mL]	50	50	50	50
Aliquot of the 1st dilution [mL]	0.15	0.15	0.15	0.15
Total volume after 2nd dilution [mL]	3	3	3	3
Octanol solubility [g/L]	209.1	190.5	218.2	0
Mean value of octanol solubility [g/L]	206.0			0
Standard deviation [g/L]	14.1			-
Relative standard deviation [%]	6.9			-

To verify the accuracy of the analytical method two freshly prepared standard solutions (prepared with the test item) were measured in between the samples of the flask method. The recovery rate of the measured standard solutions was in the range from 97.0 % to 98.7 %, which shows a good accuracy of the analytical method.

The water solubility of the test item was estimated in the water solubility study to be > 5232 g/L. Thus, the partition coefficient of the test item is estimated to be log Pow < -1.4.

Conclusions:

Due to the high water solubility of the test item, the octanol/water partition coefficient of the test item is estimated to be: log Pow = < -1.4.

Executive summary:

In a GLP study conducted according to EU Methods A.6. and A.8. and OECD Test Guidelines 105, 107 and 117 the partition coefficient at ambient temperature of the test item was determined using the shake flask method. The analytical method has been validated according to SANTE/2020/12830. 
Due to the test item's high water solubility ( > 5232 g/L), the octanol/water partition oefficient can be estimated to be: Log Pow ≤ -1.4.

Description of key information

In a GLP study conducted according to EU Methods A.6. and A.8. and OECD Test Guidelines 105, 107 and 117 the partition coefficient at ambient temperature of the test item was determined using the shake flask method. The analytical method has been validated according to SANTE/2020/12830. 
Due to the test item's high water solubility ( > 5232 g/L), the octanol/water partition oefficient can be estimated to be: Log Pow ≤ -1.4.

Key value for chemical safety assessment

Log Kow (Log Pow):

-1.4

at the temperature of:

20 °C