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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:
August 05, 2016 - August 22, 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: Flask method
Principles of method if other than guideline:
The saturation concentration of the test item in n-octanol is determined by means of the flask method (based the European Commission Regulation (EC) No. 440/2008, A.6. water solubility and the OECD Guideline 105). For the final calculation of the partition coefficient the water solubility of the test item determined in project 20160175.03 is used.
The quantity of test item necessary to saturate the desired volume of n-octanol is estimated from the preliminary visual test (see chapter 4.5.1). About five times of the estimated solubility is weighed into each of three glass vessels fitted with glass stoppers. After adding a defined volume of n-octanol the batches are stirred at 30 °C in tightly closed flasks for different times (24 h, 48 h and 72 h). After equilibration (further stirring for 24 h at 20 °C) the suspensions are taken and prepared for the analytical determination.
GLP compliance:
no
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
analysis (not specified)
Key result
Type:
log Pow
Partition coefficient:
< -3.4
Temp.:
20 °C
Remarks on result:
other: pH not determined

 Individual results

Preliminary visual estimation of the n-octanol solubility

Defined amounts of the test item were stirred with increasing volumes of n-octanol at room temperature and visually checked for any undissolved parts.

Table1: Results of the preliminary visual estimation of the n-octanol solubility

Amount of test item

/ mg

Added volume of n-octanol

/ mL

Total volume of n-octanol

/ mL

Stirring time

/ h

Appearance of mixture

5.6

10

10

0.5

not dissolved

90

100

2

not dissolved

According to this preliminary test the solubility of the test item in n-octanol was below 56 mg/L (without correction for the purity).

Calculation of the partition coefficient log POW from the preliminary test

The estimated partition coefficient was calculated with the water solubility data determined in project 20160175.03 (cS > 456 g/L) and the data obtained above. It was calculated to be: log POW < -3.9.

Due to the calculations the partition coefficient was estimated based on the ratio of the solubilities in water and octanol. The octanol solubility was determined using the flask method.

Determination of the solubility in n-octanol: Flask method

The individual saturation solubility of the test item in n-octanol, based on the flask method described in the OECD guideline 105, was performed within this study. After that, the partition coefficient was estimated based on the ratio of the test item solubility in n-octanol and water (determined in project 20160175.03).

The flask method was performed as described. The data for the evaluation are given in Table 2.The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table2.


 

Table2: n-Octanol solubility experiments of the test item

Experiment

24 h experiment

48 h experiment

72 h experiment

blank

experiment (72 h)

Amount of test item / mg

31.5

28.7

28.7

--

Amount of octanol / mL

100

100

100

100

Stirring time at 30 °C / h

24

48

72

72

Measured concentration / mg Ni/kg

< 5

< 5

< 5

< 5

Calculated concentration of test item1)in sample/ mg/kg

< 161

< 161

< 161

< 161

n-Octanol solubility2)/ g/L

< 0.2

< 0.2

< 0.2

< 0.2

Remark:1) The nickel content of the test item was determined to 3.1 % (w/w).

             2) Calculated with the density of n-octanol: 0.817 kg/L (20 °C)

The n-octanol solubility of the test item at 20 °C was determined to be <0.2 g/L.

Calculation of the partition coefficient log POWfrom the individual solubilities

In the project 20160175.03 the water solubility of the test item at 20 °C was determined to be > 456 g/L. Within this project the n-octanol solubility of the test item at 20 °C was determined to be < 0.2 g/L.

The partition coefficient POWof the test item was determined to be:

log POW  < -3.4

Conclusions:
The partition coefficient (n-octanol/water) of the test item Reactive Blue 38 was estimated based on the ratio of the individual solubilities of the test item in water and n-octanol. It was found to be: log POW < -3.4

Executive summary:

The partition coefficient (n-octanol/water) of the test itemReactive Blue 38was estimated based on the ratio of the individual solubilities of the test item in water and n-octanol.

It was found to be:

log POW< -3.4

Description of key information

The objective of this study was the determination of the partition coefficient n-octanol/water of the test item according to:

EuropeanCommission Regulation (EC) No. 440/2008,

                           A.8. partition coefficient n-octanol/water

and OECD test guidelines

                           OECD 107 and OECD 117, partition coefficient n-octanol/water

Key value for chemical safety assessment

Log Kow (Log Pow):
-3.4
at the temperature of:
20 °C

Additional information

The partition coefficient (n-octanol/water) of the test itemReactive Blue 38was estimated based on the ratio of the individual solubilities of the test item in water and n-octanol.

It was found to be:

log POW< -3.4

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