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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:
27-03-2018 to 05-09-2018
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:
EU Method A.8 (Partition Coefficient)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
inspected: June 2016 ; signature: January 2017
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
photometric method
Type:
log Pow
Partition coefficient:
4.38
Temp.:
22.2 °C
pH:
ca. 7

HPLC method

The mean void time (t0) was determined to be 0.537 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 an regression line represented by the equations:

Calibration 1: log Pow = 2.9820 × log k + 0.8043 (r = 0.9861, n = 14 and r2 = 0.9930).

Calibration 2: log Pow = 2.9867 × log k + 0.7981 (r = 0.9861, n = 14 and r2 = 0.9930).

 

Table 2. Calibration data

Reference item

log POW

1st Calibration

2nd Calibration

tR1
[min]

k

log k

tR2
[min]

k

log k

Benzonitrile

1.6

  1.385

  1.58

0.198

  1.389

  1.59

0.200

Nitrobenzene

1.9

  1.815

  2.38

0.377

  1.820

  2.39

0.378

Toluene

2.7

  3.247

  5.05

0.703

  3.254

  5.06

0.704

Ethylbenzene

3.2

  4.411

  7.21

0.858

  4.419

  7.23

0.859

Isopropylbenzene

3.7

  5.787

  9.78

0.990

  5.796

  9.79

0.991

1,2,4-Trichlorobenzene

4.2

  7.816

13.6 

1.13 

  7.816

13.6 

1.13 

n-Butylbenzene

4.6

10.074

17.8 

1.25 

10.067

17.7 

1.25 

Dibenzyl

4.8

10.998

19.5 

1.29 

10.998

19.5 

1.29 

tR1: Retention time 1. Injection

tR2: Retention time 2. Injection

log k: Common logarithm of the Capacity factor reference item

log POW: Common logarithm of the Partition Coefficient (n-octanol / water)

 

Table 3. Test item determination

Test Item

tR
[min]

k

log k

log POW

1st Calibration

2nd Calibration

9.139

16.0

1.20

4.38 ± 0.07
4.20 to 4.56 (95 % CI)

4.38 ± 0.07
4.20 to 4.56 (95 % CI)

9.133

16.0

1.20

 

Mean

9.136

16.0

1.20

4.38

tR : Retention time

k : Capacity factor test item

POW : Partition Coefficient (n-octanol / water)

CI : Confidence Interval

Conclusions:
The partition coefficient of the test item was determined to be log Pow = 4.38 at 22.2 °C and ca. pH 7.0
Executive summary:

The n-octanol-water partition coefficient was determined using theHPLC method of OECD Method 117 and EU Method A.8 under GLP. The test was performed with a concentration of 100 mg test item/L in 75 % methanol : 35 % HPLC water. Samples of the test item were analysed via HPLC on a C18 column with diode array detection. Calibration was performed using eight reference items with known log Pow values (given by the guidelines). The reference items were measured twice, once before and once after the measurement of the test item, for which one replicate was double injected. The void time of the HPLC system was determined with sodium nitrate. Two individual log Pow values for each of the single chromatographic resolved test item signals were derived under consideration of the first and second calibration. Finally, a mean value was calculated from these individual log Pow values. The log Pow was 4.38 ± 0.07. The partition coefficient of the test item was determined to be log Pow = 4.38 at mean temperature 22.2 °C and approximately neutral pH.

Description of key information

Log Pow = 4.38 ± 0.07 at 22.2 °C and ca. pH 7.0, HPLC method, OECD TG 117, 2018

Key value for chemical safety assessment

Log Kow (Log Pow):
4.38
at the temperature of:
22.2 °C

Additional information

Key study : OECD TG 117, 2018 : The n-octanol-water partition coefficient was determined using theHPLC method of OECD Method 117 and EU Method A.8 under GLP. The test was performed with a concentration of 100 mg test item/L in 75 % methanol : 35 % HPLC water. Samples of the test item were analysed via HPLC on a C18 column with diode array detection. Calibration was performed using eight reference items with known log Pow values (given by the guidelines). The reference items were measured twice, once before and once after the measurement of the test item, for which one replicate was double injected. The void time of the HPLC system was determined with sodium nitrate. Two individual log Pow values for each of the single chromatographic resolved test item signals were derived under consideration of the first and second calibration. Finally, a mean value was calculated from these individual log Pow values. The log Pow was 4.38 ± 0.07. The partition coefficient of the test item was determined to be log Pow = 4.38 at mean temperature 22.2 °C and approximately neutral pH.