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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
14 May - 07 Jul 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Qualifier:
according to guideline
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient - Shake Flask Method)
GLP compliance:
yes (incl. QA statement)
Remarks:
Hess. Ministerium für Umwelt, Klimaschutz, Landwirtschaft und Verbraucherschutz, Wiesbaden, Germany
Type of method:
calculation method (fragments)
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
Storage conditions: room temperature
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
ca. -3.8
pH:
>= 7.2 - <= 8.7
Remarks on result:
other: 24.6 to 28.4 °C
Remarks:
calculated from water solubility and octanol solubility

Results

Preliminary tests

The first preliminary test at room temperature showed, that the octanol solubility of the test item seemed to be below 0.3 g/L. The observations of the first preliminary test are summarized in Table 2.

Table 2: First preliminary test for the octanol solubility

Amount of test item [mg]

Total volume of added octanol [mL]

Stirring time at RT [min]

Remark

460

20

65

not dissolved

70

80

not dissolved

69.7

20

55

not dissolved

60

25

not dissolved

15.4

50

1045

not dissolved

With the values of the water solubility estimated from the first preliminary test of endpoint ‘4.8. Water Solubility’(between 65 and 174 g/L) and the estimated solubility in octanol from this first preliminary test of <0.3 g/L, the partition coefficient can be estimated to be <-2.3.For this range the partition coefficient can be calculated from the solubilities in both solvents. Thus, the flask method is also used for the determination of the octanol solubility.

Due to the analytical problems, a further preliminary test with higher amounts of 1-octanol was performed:

Table 3: Second preliminary test for the octanol solubility

Amount of test item [mg]

Total volume of added water [mL]

Stirring time at RT [min]

Remark

4.3

10

60

not dissolved

20

30

not dissolved

30

40

not dissolved

40

30

not dissolved

50

70

not dissolved

60

35

not dissolved

70

35

not dissolved

80

30

not dissolved

90

30

not dissolved

100

930

not dissolved

110

30

not dissolved

120

30

not dissolved

130

30

not dissolved

According to the second preliminary test, the solubility of the dried solid test item in octanol could be estimated to be below 33.1 mg/L.

With a water solubility, estimated from the second preliminary test of the water solubility study, of 201.3 – 212.9 g/L and an octanol solubility, estimated from this second preliminary test, the log POWcan be estimated to be approx. -3.8.

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 the clear octanol phase of flask 1a was measured by means of HPLC.

The chromatogram of the test item in 1-octanol did not match the chromatograms of the calibration and validation, which were measured in study for the endpoint ‘4.8 Water Solubility’.

As described in the endpoint ‘4.8 Water Solubility’, the HPLC (with UV-detection) is not a suitable analytical method for the determination of the concentration of the test item in water. The HPLC is also not a suitable analytical method for the determination of the concentration of the test item in octanol.

Thus, the octanol solubility can only be estimated based on the preliminary tests to be below 33.1 mg/L.

From the estimated solubilities in water and 1-octanol, the partition coefficient can be calculatedby the following equation:

POW= c1-Octanol/ cwater

to be

log POW  approx. -3.8

Final Results

According to OECD Test Guidelines 105 (1995), 107 (1995) and 117 (2004) the partition coefficient at ambient temperature (24.6 to 28.4 °C) and a pH value of 7.2 to 8.7 of the dried solid test item ETA Lösung 181 / TRISODIUM EDTA SOLUTION 20% can be estimated to

log POW approx. -3.8

Description of key information

log Pow approx.: -3.8 at ambient temperature at pH value of 7.2 to 8.7 (OECD 105, 107 and 117)

Key value for chemical safety assessment

Log Kow (Log Pow):
-3.8
at the temperature of:
25 °C

Additional information

According to OECD Test Guidelines 105 (1995), 107 (1995) and 117 (2004) the partition coefficient at ambient temperature (24.6 to 28.4 °C) and a pH value of 7.2 to 8.7 of the test item can be estimated to log Pow approx. -3.8.

The HPLC (with UV-detection) is not a suitable analytical method for the determination of the concentration of the test item in water. The HPLC is also not a suitable analytical method for the determination of the concentration of the test item in octanol.

Thus, the octanol solubility can only be estimated based on the preliminary tests. From the estimated solubilities in water and 1-octanol, the partition coefficient has been calculated by the following equation: POW= c 1-Octanol / c water

In addition, a log D calculation (QSAR ,Sparc v4.6; EDTA) was performed at 25 °C.

Log D at pH 5: -11.835

Log D at pH 7: -16.297

Log D at pH 9: -20.37