Sodium 6-amino-5-[[2-[(ethylphenylamino)sulphonyl]phenyl]azo]-4-hydroxynaphthalene-2-sulphonate

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June from 07 to 13, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1995

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Type:

log Pow

Partition coefficient:

-0.6

Temp.:

26 °C

pH:

ca. 7.3

Details on results:

As 20 ml of the stock solution were added to each separating funnel, each funnel should contain 85.75 mg of the test item.
To verify the accuracy of the analytical method two fresh prepared standard solutions in double distilled water (prepared with the test item) were measured in between the samples of the shake-flask-method.

PRELIMINARY TEST
The preliminary test at room temperature showed that the octanol solubility of the test item was between 14.9 and 32.5 g/l.
The water solubility was determined to be within 28.2 and 63.5 g/l at 20 °C, while the solubility in octanol between 14.9 and 32.5 g/l; therefore, the the partition coefficient log Pow can be estimated to be between -0.63 and 0.06 .
For the determination of the log Pow in this range, the shake flask method is recommended.

Results of the shake-flask-method

separating funnel	total amount of test item in the separating funnel (mg)	recovery rate (%)	Pow	log Pow
1a	85.42	99.6	0.27	-0.6
1b	86.01	100.3	0.27	-0.6
2a	86.28	100.6	0.24	-0.6
2b	81.18	94.7	0.23	-0.6
3a	84.62	98.7	0.32	-0.5
3b	85.84	100.1	0.32	-0.5
mean value				-0.6
standard deviation				<0.1

Concentrations in the aqueous phases

separating funnel	pH values*	measured concentration (mg/l)	mean concentration** (mg/l)
1a	7.4	37.9 / 37.3	1881.1
1b	7.4	38.0 / 37.8	1893.5
2a	7.3	34.1 / 35.3	1733.6
2b	7.3	33.1 / 32.6	1644.8
3a	7.2	51.9 / 51.2	2578.0
3b	7.3	52.0 / 52.8	2620.5

*at temperatures of 25.4 – 26.5 °C

**under consideration of the dilution factor 50

Concentrations in the octanol phases

separating funnel	measured concentration (mg/l)	mean concentration* (mg/l)
1a	10.3 / 10.1	508.9
1b	10.4 / 10.1	513.6
2a	17.0 / 16.9	423.3
2b	15.4 / 15.4	384.8
3a	16.4 / 16.6	826.5
3b	16.7 / 16.7	835.8

*under consideration of the dilution factor 50 (1 and 3) and factor 25 (2)

PRELIMINARY TEST

Preliminary test for the octanol solubility

Total amount of added test item [mg]	Volume of octanol [ml]	Stirring time at RT [min]	Remark
88.74	20	35	dissolved
298.87		30	dissolved
650.04		55	non dissolved

Conclusions:

log Pow: -0.6 at ca 26 °C and pH ca 7.3

Executive summary:

The partition coefficient was determined according to the OECD guideline 107, shake-flask method. Based on preliminary test results, the shake-flask method was used for the main experiment.

After adding different amounts of stock solution, pre-saturated double distilled water and pre-saturated 1-octanol, the funnels were shaken and then the phases were allowed to separate in the funnels. For the analytical measurement by means of HPLC, centrifuged clear aqueous phases were diluted from 1 to 50 ml with double distilled water. The pH values of all water phases were measured.

During the main test, the log Pow was measured to be -0.6 at ca 26 °C and pH ca 7.3.

To verify the accuracy of the analytical method two fresh prepared standard solutions in double distilled water (prepared with the test item) were measured in between the samples of the shake-flask-method.

Conclusion

log Pow: -0.6 at ca 26 °C and pH ca 7.3

Description of key information

log Pow: -0.6 at ca 26 °C and pH ca 7.3

Key value for chemical safety assessment

Log Kow (Log Pow):

-0.6

at the temperature of:

26 °C

Additional information

Shake-flask method - OECD 107