Tetrasodium 4-amino-5-hydroxy-6-[[2-methoxy-5-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]azo]-3-[[4-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]azo]naphthalene-2,7-disulphonate

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 29, 2015 - May 08, 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient)

Deviations:

not applicable

Qualifier:

according to guideline

Guideline:

OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)

Deviations:

not applicable

Principles of method if other than guideline:

Estimation of the partition coefficient from the individual solubilities of the test item in water and n-octanol based on OECD 105 and A.6., flask method

GLP compliance:

no

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

estimation method (solubility ratio)

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

< -4.7

Temp.:

20 °C

pH:

>= 4.7 - <= 4.8

Details on results:

The partition coefficient (n-octanol/water) 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” described in the European Commission Regulation (EC) No. 440/2008, A.6. and in the OECD Guideline 105.
The partition coefficient log Pow of the test item at 20 °C was determined to be:
log POW = < - 4.7

 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.

Table 4: 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
3.4	10	10	1	undissolved
	90	100	~21	undissolved (slightly cloudy)
2.0	250	250	~21	undissolved (tiny particles, hardly detectable)

According to this preliminary test the solubility of the test item in n-octanol is at least below 34 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. Prior to the determination of the partition coefficient, the water solubility of the test item was determined by the flask method according to OECD 105 in the project 20150018.05. The estimated partition coefficient was calculated with the water solubility data determined in project 20150018.05 (c_S = 392 g/L) and the data obtained in the chapter above. It was calculated to be: log P_OW < -4.06.

Also the program KOWWIN (part of EPI Suite) was used for calculating the log P_OWof the test item. The calculated value was -4.05.

Because of this very negative preliminary estimated log P_ow neither the shake-flask method (OECD 107) nor the HPLC method (OECD 107) are applicable for the present test item.

For such test items, where it is technically not feasible (or good practice) to measure an octanol-water partition coefficient by OECD 107 of OECD 117, it is possible to obtain a ratio of the saturated water solubility (OECD 105) and the saturated octanol solubility (no guideline currently available but based on the principles of OECD 105).

 

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 20150018.05).

The flask method was performed as described above. The data for the evaluation are given in Table5. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table5.

Table5: n-Octanol solubilityexperimentsof the test item

Experiment	24 h experiment	48 h experiment	72 h experiment	blank experiment (72 h)
Amount of test item [mg]	19.1	19.2	17.8	--
Amount of octanol [mL]	100	100	100	100
Stirring time at 30 °C [h]	24	48	72	72
Aliquot of the flasks /mL]	10	10	10	10
Total volume of the aqueous phase used for the extraction [mL]	3	3	3	3
Concentration factor	0.3	0.3	0.3	0.3
Measured concentration [mg/L]	<0.027 / <0.027	<0.027 / <0.027	<0.027 / <0.027	-- / --
Mean concentration [mg/L]	<0.027	<0.027	<0.027	--
n-Octanol solubility [mg/L]	<0.008	<0.008	<0.008	--

The n-octanol solubility of the test item at 20 °C was determined to be < 0.008mg/L.

 

Calculation of the partition coefficient log P_OWfrom the individual solubilities

In the project 20150018.05 the water solubility of the test item at 20 °C was determined to be 392 g/L (± 4 g/L). Within this project the n-octanol solubility of the test item at 20 °C was determined to be < 0.008 mg/L.

The partition coefficient P_OW was estimated from the individual solubility in n-octanol and water. It was determined to be:         

log P_OW < -4.7

Conclusions:

The partition coefficient log Pow of the test item at 20 °C was determined to be  < - 4.7

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” described in the European Commission Regulation (EC) No. 440/2008, A.6. and in the OECD Guideline 105.

The partition coefficient log P_ow of the test item at 20 °C was determined to be:

                                                          log P_OW < - 4.7

Description of key information

The partition coefficient of the test item was determined  according to the European Commission Regulations (EC) No. 440/2008,
A.8. partition coefficient n-octanol/water and according to the OECD test guideline, OECD 107 (Individual solubilities based on OECD 105, flask method).

Key value for chemical safety assessment

Log Kow (Log Pow):

-4.7

at the temperature of:

20 °C

Additional information

The partition coefficient (n-octanol/water) 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” described in the EuropeanCommission Regulation (EC) No. 440/2008, A.6. and in the OECD Guideline 105.

The partition coefficient log P_owof the test item at 20 °C was determined to be:

                                                          log P_OW < - 4.7