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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:
26-08-2019 to 25-10-2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed under GLP. All relevant validity criteria were met.
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 830.7570 (Partition Coefficient, n-octanol / H2O, Estimation by Liquid Chromatography)
Deviations:
no
Qualifier:
according to
Guideline:
other: EU Method A.24
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
EU Method A.8 (Partition Coefficient - HPLC Method)
Deviations:
not specified
GLP compliance:
yes
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
>= 1.8 - <= 2.5
Temp.:
35 °C
pH:
7
Remarks on result:
other: range of log Pow; (n=3). Individual values were 1.8 (99% peak area), 2.0 (0.51% peak area), 2.5 (0.28% peak area)

HPLC method

The mean void time (t0) was determined to be 0.608 minutes.

The results of the HPLC method are given in the Table 3. The calibration curves of the log k of the reference substances as function of log Pow had a regression line represented by the equations:

Calibration: log Pow = a * log k + b

where correlation coefficient r = 0.995, a= 0.372, b = 0.892.

Table 2. Calibration data

Substance

Retention time (min)

log Pow

Pow

Peak area
(%)

tr,1

tr,2

mean

Formamide (t0)

0.608

0.608

0.608




2-Butanone

0.711

0.711


0.3



Benzylalcohol

0.792

0.793


1.1



Nitrobenzene

0.980

0.981


1.9



Toluene

1.570

1.572


2.7



1,4-Dichlorobenzene

2.049

2.052


3.4



Biphenyl

2.769

2.775


4.0



 

Table 3. Test item determination

Substance

Retention time (min)

log Pow

Pow

Peak area
(%)

tr,1

tr,2

mean

Test item – peak 1

0.973

0.974

0.974

1.8

6.4 +/- 101

99

Test item – peak 2

1.048

1.055

1.052

2.0

1.1 +/- 102

0.51

Test item – peak 3

1.292

1.295

1.294

2.5

3.5 +/- 102

0.28

Overall log10 Pow: ≥ 1.8 and ≤ 2.5

Conclusions:
The partition coefficient of the test item was determined to be log Pow = ≥ 1.8 and ≤ 2.5 for three constituent peaks at 35°C and ca. pH 7.00. The area of the test item peak corresponding to log Pow=1.8 was 99%.
Executive summary:

The n-octanol/water partition coefficient was determined using the HPLC method according to OECD TG 117, EPA OPPTS 830.7570 and EU Method A.24 in accordance with GLP. The test was performed with a concentration of 10 mg/L test item in methanol/water (pH 7.0, 75/25 v/v), injected at 5 µL with a mobile phase of 75% methanol : 25% water. Samples of the test item were analysed via UPLC on an UPLC HSS T3 column with UPLC TUV detector. Calibration was performed using six reference items with known log Pow values (given by the guidelines). The dead time of the HPLC system was determined with formamide. The dead time and the reference items were measured in duplicate. The test item was injected and measured in duplicate. Three individual partition coefficient values for each of the three chromatographic resolved test item signals were derived. A mean value was calculated from these individual log Pow values which were determined to be 1.8, 2.0 and 2.5 respectively. The partition coefficient of the test item was determined to be in the log Pow range: 1.8 to 2.5 at a mean temperature 35°C and approximately neutral pH. The peak signal corresponding to log Pow=1.8 had a peak area of 99%.

Description of key information

log Pow = ≥ 1.8 and ≤ 2.5 at 35 °C and pH 7.00, OECD TG 117 - HPLC Method, 2019

Key value for chemical safety assessment

Log Kow (Log Pow):
2.5
at the temperature of:
35 °C

Additional information

Key study : OECD TG 117, 2019 : The n-octanol/water partition coefficient was determined using the HPLC method according to OECD TG 117, EPA OPPTS 830.7570 and EU Method A.24 in accordance with GLP. The test was performed with a concentration of 10 mg/L test item in methanol/water (pH 7.0, 75/25 v/v), injected at 5 µL with a mobile phase of 75% methanol : 25% water. Samples of the test item were analysed via UPLC on an UPLC HSS T3 column with UPLC TUV detector. Calibration was performed using six reference items with known log Pow values (given by the guidelines). The dead time of the HPLC system was determined with formamide. The dead time and the reference items were measured in duplicate. The test item was injected and measured in duplicate. Three individual partition coefficient values for each of the three chromatographic resolved test item signals were derived. A mean value was calculated from these individual log Pow values which were determined to be 1.8, 2.0 and 2.5 respectively. The partition coefficient of the test item was determined to be in the log Pow range: 1.8 to 2.5 at a mean temperature 35°C and approximately neutral pH. The peak signal corresponding to log Pow=1.8 had a peak area of 99%.