2-naphthol

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04.06.2018 - 15.06.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

no

Type of method:

flask method

Key result

Water solubility:

0.6 g/L

Conc. based on:

test mat. (dissolved fraction)

Incubation duration:

>= 24 - <= 72 h

Temp.:

20 °C

pH:

>= 6.1 - <= 6.3

Preliminary Test

The preliminary test at room temperature showed, that the water solubility of the test item was between 0.1 and 1.1 g/L.

Table: Preliminary test for the water solubility

Amount of test item [mg]	Total volume of added water [mL]	Stirring time at RT [h]	Remark
110.28	0.1	--	not dissolved
	0.6	--	not dissolved
	1.6	--	not dissolved
	3.6	--	not dissolved
	13.6	--^1)	not dissolved
	100.0	--^1)	not dissolved
9.92	100.0	69	dissolved
4.66	250.0	69	dissolved
4.88	500.0	69	dissolved

¹⁾The mixtures were treated in an ultrasonic bath for 10 minutes.

The solubility of the test item in water at room temperature was estimated to be between 0.1 and 1.1 g/L. Due to this result, the flask method was performed.

Main Test (flask method)

For the main test three flasks were prepared with an amount of test item and water, and one flask only with water. After stirring and centrifugation the aqueous phases were diluted with acetonitrile and measured by means of HPLC. The solution of each flask has been measured twice. The values represented in the table are rounded values. The calculation was carried out with the original not rounded values.

Table: Results of the flask method

Flask	1a	2a	3a	4a
measured value [mg/L]	33.76 / 33.93	29.16 / 28.49	27.49 / 27.08	0 / 0
aliquot of the flask [mL]	0.5	0.5	0.5	1
total volume after dilution [mL]	10	10	10	1
water solubility [mg/L]	675.3 / 678.7	583.3 / 569.7	549.7 / 541.6	0 / 0
average water solubility [mg/L]	677.0	576.5	545.7	0
mean value of the water solubility [mg/L]	599.7			0
standard deviation [mg/L]	68.7			--
relative standard deviation [%]	11.5			--

To verify the accuracy of the analytical method prepared standard solutions (prepared with the test item) were measured in between the samples of the flask method.

Table: Measurement of a standard solution

Standard solution (nominal value [mg/L])	Measured value [mg/L]	Repeatability [%]
Ü-1 (31.68)	32.14	101.4
	31.74	100.2
Ü-2 (12.06)	12.73	105.6
	12.86	106.6

The recovery rate of the measured standard solutions was in the range from 100.2 % to 106.6 %, which shows a good accuracy of the analytical method.

Conclusions:

The water-solubility of 2-naphthol using the flask-method was determined to be 0.6 g/L.

Executive summary:

According to OECD Test Guideline 105 (1995) and Regulation EC No. 440/2008 Method A.6. the water solubility at 20 °C of the test item beta-Naphthol was determined to be:

c_S = 0.6 g/L, RSD = 11.5 %.

Description of key information

A study was performed to determine the water solubility of the test substance 2-naphthol using the flask-method.  The study was conducted in compliance with OECD Test Guideline 105 and Regulation EC NO. 44/2008 Method A.6.  It concluded that the water solubility of the test substance 2-naphthol was 0.6 g/L at 20 ^oC.

Key value for chemical safety assessment

Water solubility:

0.6 g/L

at the temperature of:

20 °C