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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
disregarded due to major methodological deficiencies
Study period:
From 05/07/2011 to 06/07/2011
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: This study was performed according to OECD Guideline 117 with GLP statement. However it's known that the HPLC method is not accurate and overestimates results for "alkyl" substances due to reference substances which are "benzyl" substances.
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Remarks:
2011-03-02
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
5.55
Temp.:
55 °C
pH:
7.4
Remarks on result:
other: The result issued from the 3 determinations (log Pow at 5.550, 5.550 and 5.552) is in the guideline tolerance for repeatability (+/- 0.1 log units).
Details on results:
Injection 1: retention time = 6.31 min / log Pow = 5.550
Injection 2: retention time = 6.31 min / log Pow = 5.550
Injection 3: retention time = 6.32 min / log Pow = 5.552

Table 4.7/1: Results of the partition coefficient determination of the test item:

Products

Mean retention time (min)

Value of the capacity factor k’

Value of log k’

Value of log Pow

Formamide

0.55

-

-

-

Toluene

1.18

1.145454546

0.058977860

2.7

Ethylbenzene

1.54

1.800000000

0.255272505

3.2

Biphenyle

2.06

2.745454547

0.438614258

4.0

1,2,4-trichlorobenzene

2.38

3.327272725

0.522088400

4.2

Phenanthrene

2.67

3.854545451

0.585973171

4.5

Dibenzyle

3.50

5.363636358

0.729459326

4.8

Triphenylamine

6.87

11.49090910

1.060354389

5.7

DDT

11.80

20.45454546

1.310789833

6.2

Using the capacity factor k' and the partition coefficient log Pow of the reference items, the following calibration curve was obtained:

log Pow = 2.8436 log k' + 2.6489

r² = 0.9863

Conclusions:
The results issued from the 3 determinations with the test item is in the guideline tolerance for repeatability. The mean value of the log Pow is 5.55 (5.550, 5.550 and 5.552).
Executive summary:

This study was performed according to OECD Guideline 117 with GLP statement, to determine the partition coefficient of the test item by applying the HPLC method.

This methodology was chosen because the estimation of log Pow is 4.66 according to Kowwin v1.68 from the Episuite software. The test item is injected on a liquid chromatography system where a partition occurs between the stationary hydrocarbon phase of the column (Silica C18 100 A) and the eluent phase (methanol at 64% with water at 36%, in isocratic mode). Chemicals are retained according to their partition coefficient, hydrophilic ones being eluted first and hydrophobic ones last. Therefore a relation exists between the retention time and the partition coefficient of a chemical product. The determination of the HPLC retention times of the test item and of the analytical reference items (8 refence items) was made twice. The partition coefficient is given by the following equation: log Pow = m. log k' + b, where k' is the capacity factor of the chromatographic column (k' = (t.r-t.0)/t.0, where t.r is the retention time and t.0 is the dead volume time) and m/b the coefficients of the calibration curve. The dead time t.0 was measured by using unretained formamide. The next step is to plot a correlation log k versus log P for appropriate reference substances with log P values near the value expected for the test substance. The retention times are determined preferably on a recording integrator linked to the detection system. The corresponding logarithms of the capacity factors, log k', are plotted as a function of log P.

Using the capacity factor k' and the partition coefficient log Pow of the reference items, the following calibration curve was obtained: log Pow = 2.8436 log k' + 2.6489 with r² = 0.9863. The results issued from the 3 determinations with the test item is in the guideline tolerance for repeatability. The mean value of the log Pow is 5.55 (5.550, 5.550 and 5.552). The temperature during the measurement did not vary by more than +/- 1°C (55 +/- 0.5°C) and the pH of the mobile phase was 7.4 at this temperature.

Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
Run on 2013-03
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The partition coefficient of the test substance was evaluated with KOWWIN model v168 from EPI Suite v4.1, which fulfilled all OECD principles. Test substance is within the domain of the KOWWIN model based on the molecular weight and fragments present in the KOWWIN database.
Justification for type of information:
QSAR prediction
Principles of method if other than guideline:
KOWWIN (the Log Octanol-Water Partition Coefficient Program) estimates the logarithmic octanol-water partition coefficient (log P) of organic compounds.
GLP compliance:
no
Partition coefficient type:
octanol-water
Key result
Type:
log Pow
Partition coefficient:
4.66
Remarks on result:
other: estimated value

SMILES : O=C(OCC(CCCC)CC)OOC(C)(C)C

CHEM  : Carbonoperoxoic acid, oo-(1,1-dimethylethyl) o-(2-ethylhexyl) ester

MOL FOR: C13 H26 O4

MOL WT : 246.35

Log Kow  =  4.6600

-------+-----+--------------------------------------------+---------+--------

TYPE | NUM | LOGKOW FRAGMENT DESCRIPTION | COEFF | VALUE

-------+-----+--------------------------------------------+---------+--------

Frag | 5 | -CH3 [aliphatic carbon] | 0.5473 | 2.7365

Frag | 5 | -CH2- [aliphatic carbon] | 0.4911 | 2.4555

Frag | 1 | -CH [aliphatic carbon] | 0.3614 | 0.3614

Frag | 1 | -tert Carbon [3 or more carbon attach] | 0.2676 | 0.2676

Frag | 1 | -OC(=O)O- [carbonate,aliphatic attach] |-1.0900 | -1.0900

Frag | 1 | -O- [oxygen attach] |-0.3000**| -0.3000

Const | | Equation Constant | | 0.2290

-------+-----+--------------------------------------------+---------+--------

NOTE | | An estimated coefficient (**) used |

-------+-----+--------------------------------------------+---------+--------

Log Kow = 4.6600

Conclusions:
The Log Kow of the test substance was estimated as 4.66
Executive summary:

The partition coefficient of the test substance was evaluated with KOWWIN model v168 from EPI Suite v4.1, which fulfilled all OECD principles. Test substance is within the domain of the KOWWIN model based on the molecular weight and fragments present in the KOWWIN database.


The Log Kow of the test substance was estimated as 4.66

Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-09-20 to 2013-09-27
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP and guideline study
Qualifier:
according to
Guideline:
OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)
Deviations:
no
Principles of method if other than guideline:
Not Applicable
GLP compliance:
yes (incl. certificate)
Remarks:
07/18/2012
Type of method:
other: Slow-stirring method
Partition coefficient type:
octanol-water
Analytical method:
other: UPLC/MS
Key result
Type:
log Pow
Partition coefficient:
> 5.17 - < 5.21
Temp.:
25 °C
pH:
> 6.8 - < 6.89
Details on results:
The determinations show that for the partition coefficient of OO-t-BUTYL-O-(2-ETHYLHEXYL)MONOPEROXYCARBONATE, the log Pow mean value was 5.20. During the test, the temperature was 25°C and the pH value was 6.86.

Time, h

0

5

24

48

53

72

77

Mean values

Log Pow

Samples

 

Water A, mg/L

-

0.029

0.035

0.033

0.036

0.037

0.039

0.036

5.17

pH

-

7.54

-

6.70

6.76

7.19

-

6.88

1-octanol A, g/L

5.0

-

-

-

-

-

5.37

5.37

Water B, mg/L

-

0.028

0.036

0.033

0.035

0.035

0.037

0.035

5.23

pH

-

7.51

-

6.58

6.99

7.10

-

6.89

1-octanol B, g/L

5.0

-

-

-

-

-

6.00

6.00

Water C, mg/L

-

0.024

0.037

0.034

0.036

0.034

0.035

0.035

5.21

pH

-

7.37

-

6.56

6.72

7.13

-

6.80

1-octanol C, g/L

5.0

-

-

-

-

-

5.62

5.62

Log Pow (mean value) = 5.20

pH (mean value) = 6.86

Remarks: shadowed values were not used for calculation and no determination was performed when “-“ is indicated.

Water phase: DL = 0.0028 mg/L, QL = 0.0093 mg/L

1 -octanol phase: DL = 0.066 g/L, QL = 0.22 g/L

Conclusions:
The determinations show that for the partition coefficient of OO-t-BUTYL-O-(2-ETHYLHEXYL)MONOPEROXYCARBONATE, the log Pow mean value was 5.20. During the test, the temperature was 25°C and the pH value was 6.86.
Executive summary:

This study was performed according to the OECD 123 Guideline with GLP statement, to determine the partition coefficient of the test item by applying the slow-stirring method.

A previous analysis performed according to the OECD 117 Guideline (HPLC method) gave a Kow value of 5.5. However it is known that the HPLC method is not accurate and overestimates results for "alkyl" substances due to reference substances which are "benzyl" substances. Moreover, Kow estimated with Epiwin was lower (4.5). Therefore, the present test was performed in order to obtain more accurate results.

The principle of the test is to dilute the test item into water-saturated 1-octanol and add a 1-octanol saturated ultrapure water into a test vessel. Both phases are gently stirred until concentration equilibrium is achieved into both phases (i.e. test item concentrations in both phases do not change with time).

Here, the experiment was performed in triplicate. Initial concentration of the test item into 1-octanol was 5000 mg/L. Water/1-octanol ratio was 32.5. Equilibrium was reached after 24 hours, as shown by its stability into both phases until 77 hours. Item substance was analysed according to a UPLC/MS method validated for both water and 1 -octanol. The mean log Pow value was 5.20 for a mean pH value of 6.86 and a temperature of 25°C.

Description of key information

The partition coefficient of the test substance was determined with the slow-stirring method OECD 123 guideline (most suitable method for this type of compound). The log Kow is 5.20 at T=25 °C.

Key value for chemical safety assessment

Log Kow (Log Pow):
5.2
at the temperature of:
25 °C

Additional information

The partition coefficient OO-t-butyl-O-(2-ethylhexyl)monoperoxycarbonate was firstly evaluated in a study performed in accordance with OECD testing guideline 117 and GLP requirements. The partition coefficient was of 5.55 at 55°C. However it's known that the HPLC method is not accurate and overestimates results for "alkyl" substances due to reference substances which are "benzyl" substances.

Therefore it was decided to perform a new Kow determination according to OECD 123 guideline which is the most suitable methode for this type of compound. The Log Kow has been determined to be 5.20 at T=25°C.