Disodium 2,2'-[(9,10-dihydro-5,8-dihydroxy-9,10-dioxo-1,4-anthrylene)diimino]bis[5-tert-butylbenzenesulphonate]

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January 29, 2018 - February 02, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD 105

Deviations:

not applicable

Principles of method if other than guideline:

OECD 105

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

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.

Table3: 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
8.7	2	2	1.5	not dissolved
	8	10	~3	not dissolved (slightly cloudy)
	90	100	~64	not dissolved (very little solid at bottom, not cloudy)

According to this preliminary test the solubility of the test item in n-octanol was below 87 mg/L (without correction for the purity).

Calculation of the partition coefficient log P_OW from the preliminary test

The partition coefficient P_OW may 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 20170174.04 (c_S > 0.96 g/L) andthe data obtained above. It was calculated to be: log P_OW = -1. 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 and the HPLC method were not applicable due to the large salt content of the test item.

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 Table4. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table4.

Table4: 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	1.2779	1.3101	1.2572	--
Amount of octanol / mL	50	50	50	50
Stirring time at 30 °C / h	24	48	72	72
Dilution factor	200	200	200	200
Measured concentration / mg/L	0.487 / 0.488	0.298 / 0.300	0.230 / 0.232	-- / --
Mean concentration / mg/L	0.488	0.299	0.231	--
n-Octanol solubility / mg/L	97.6	59.8	46.2	--

The solubility experiments showed a decreasing amount of the test item at increasing stirring time. This may result from instability of the test item in n-Octanol. Therefore, as a conservative approach the highest measured concentration was taken into account. Hence, the n-octanol solubility of the test item at 20 °C was determined to be ≥ 98 mg/L without correction of the purity.

 

Calculation of the partition coefficient log P_OW from the individual solubilities

In theproject 20170174.04the water solubility of the test item at 20 °C was determined to be c_S^water = 960 mg/L. Within this project the n-octanol solubility of the test item at 20 °C was determined to be c_S^n-Octanol ≥ 98 mg/L.

The partition coefficient P_OW of the test item was determined to be: 

log P_OW ≥- 1

Executive summary:

The partition coefficient (n-octanol/water) of the test item Acid Green 81 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.The shake flask method and the HPLC method were not applicable due to the large salt content of the test item.

It was found to be:

logP_OW ≥ -1

Description of key information

The partition coefficient (n-octanol/water) of the test item Acid Green 81 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.The shake flask method and the HPLC method were not applicable due to the large salt content of the test item.

It was found to be:

logP_OW  ≥ -1