Disodium [3-[(4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo]-4-hydroxy-5-nitrobenzenesulphonato(3-)][2-[(2-hydroxybenzylidene)amino]-4-nitrophenolato(2-)-N2,O1,O2]chromate(2-)

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April 13, 2018 - April 24, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD 105 flask method

Deviations:

not applicable

Principles of method if other than guideline:

OECD 105 flask method

GLP compliance:

no

Type of method:

flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

-1.6

Temp.:

20 °C

Remarks on result:

other: pH not determined

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.

Table4: 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
126.6	2	2	1	dissolved
452.5	2	2	1	not dissolved (not stirrable)
	1	3	67	not dissolved (stirrable)

According to this preliminary test the solubility of the test item in n-octanol was between 63 g/L and 151 g/L (without correction for the purity). Regarding the stirrability of the test runs a load of 150 g/L was used instead of the fivefold amount of the preliminary test.

Calculation of the partition coefficient log P_OW from the preliminary test

The partition coefficient P_OWmay be estimated from the saturation concentrations in n-octanol and water. The estimated partition coefficient was calculated with the water solubility data determined in project 20170181.04 (c_S = 507 g/L) and the data obtained above. It was calculated to be: log P_OW < -0.5.

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.The shake flask method was not applied due to the composition of the test item (salt content, mixture) and the HPLC method was not applicable due to the constitution of the test item (metal complex).

Determination of the solubility in n-octanol: Flask method

The individual saturation solubility of the test item in n-octanol 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. The flask method was performed as described above. The data for the evaluation are given in Table 5. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table 5.

 

Table5: n-Octanol solubility experiments of the test item

Experiment	24 h experiment	48 h experiment	72 h experiment	168 h experiment	blank experiment (72 h)
Amount of test item / mg	3.2716	3.4502	3.3593	3.3069	--
Amount of octanol / mL	20	20	20	20	20
Stirring time at 30 °C / h	24	48	72	168	72
Dilution factor	500	500	500	500	500
Measured concentration / mg/L	26.53 / 26.51	22.10 / 22.06	13.55 / 13.48	11.19 / 11.19	-- / --
Mean concentration / mg/L	26.52	22.08	13.51	11.19	--
n-Octanol solubility / mg/L	13.3	11 0	6.8	5 6	--

The n-octanol solubilities showed a decreasing tendency. As a conservative approach the highest value was stated. The n-octanol solubility of the test item at 20 °C was determined to be 13.3g/L.

1.1.4.Calculation of the partition coefficient log P_OWfrom the individual solubilities

In theproject 20170181.04the water solubility of the test item at 20 °C was determined to be 507 g/L. Within this project the n-octanol solubility of the test item at 20 °C was determined to be 13.3 g/L.

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

log P_OW= -1.6

Executive summary:

The partition coefficient (n-octanol/water) of the test item was estimated based on the ratio of the individual solubilities of the test item in water and n-octanol. The solubilities were determined according to the flask method. It was found to be without correction of the purity:

 

log P_OW = -1.6

Description of key information

The partition coefficient (n-octanol/water) of the test item was estimated based on the ratio of the individual solubilities of the test item in water and n-octanol. The solubilities were determined according to the flask method. It was found to be without correction of the purity:

 

log P_OW = -1.6

Key value for chemical safety assessment

Log Kow (Log Pow):

-1.6

at the temperature of:

20 °C