2-[[4-[ethyl(2-hydroxyethyl)amino]phenyl]azo]-6-methoxy-3-methylbenzothiazolium chloride

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 13, 2016 - November 04, 2016

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:

46 g/L

Conc. based on:

test mat.

Loading of aqueous phase:

238 g/L

Incubation duration:

4 d

Temp.:

20 °C

pH:

3

Preliminary visual estimation of the water solubility

In a stepwise procedure, increasing volumes of demineralized water were added at room temperature to a defined amount of the test item. After each addition of an amount of water the mixture was treated with ultrasound for 10 minutes and visually checked for any undissolved particles.

Table 1: Results of the preliminary visual estimation of the water solubility

Amount of test item / mg	Added volume of demin. water / mL	Total volume / mL	Appearance of mixture
108.3	0.1	0.1	not dissolved
	0.4	0.5	Slurry, not dissolved
	0.5	1.0	Dark violet mixture, not dissolved
	1.0	2.0	Dark violet mixture, not dissolved
	8.0	10.0	Dark violet mixture, not dissolved
	90.0	100.0	Dark violet mixture, not dissolved

One additional preliminary test was carried out with specified amount of the test item and 100 mL demineralized water, respectively. After each addition of an amount of water, the mixture was stirred for at least 24 hours, and visually checked for any undissolved particles

Table 2: Results of the preliminary visual estimation of the water solubility

Amount of test item / mg	Total volume of dist. water / mL	Appearance of mixture
49.5	100	Dark violet, dissolved

The preliminary visual experiments showed that the water solubility of the test item is > 10 mg/L. According to the preliminary visual estimation in the main test the water solubility was determined by the flask method.

Determination of the water solubility with about 5 g/L and about 10 g/L test item in demin. water showed complete dissolution of the test item. Therefore trials with higher test item concentrations were necessary. Thus the stirrability of higher loaded aqueous mixtures had to be examined. It was found that a mixture of 10 g test item in 40 mL demin. water could be stirred in the water bath.

Flask method

The flask method was performed. The data for the evaluation are given in Table 3. After the equilibration time precipitate was observed in the flasks of the experiments excluding in the blank experiment.The water solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table 3.

Table 3: Water solubility experiments of the test item

Experiment	24 h experiment	48 h experiment	72 h experiment	Blank experiment (72 h)
Amount of test item / g	9.99	10.02	10.00	--
Amount of demineralized water / mL	42	42	42	42
Stirring time at 30 °C / h	24	48	72	72
pH at 22 °C	2.9	3.0	3.0	5.5
Aliquot of the flasks / mg	23.2	22.5	20.8	24.6
1^stDilution to 100 mL volume / g	91.2429	91.2645	91.4138	91.3484
Dilution factor	3933	4056	4395	3713
Measured concentration / mg/L	11.89 / 11.85	11.89 / 11.86	9.60 / 9.58	-- / --
Mean concentration / mg/L	11.9	11.9	9.6	--
Water solubility / g/L	46.70	48.17	42.14	--

The water solubility of the test item at 20 °C was determined to be 45.67 g/L (± 3.14 g/L).

Final results

The water solubility c_S of the test item Basic Blue 41 Chloride at a temperature of 20 °C was determined according to the flask method. It was found to be:

                                                                 c_S= 46 g/L(± 3 g/L)

Conclusions:

The water solubility of the test item a temperature of 20 °C was determined according to the flask method to be:         cS= 46 g/L(± 3 g/L)

Executive summary:

The water solubility of the test subtance was deteremined according to OECD 105 using preliminary visual estimation and flask method. For the preliminary visual estimation of the water solubility a mixture of water and test item ist prepared and assessed visually.

The approximate water solubility of the test item, resulting from the preliminary test, indicates which of the two methods (column elution method < 10 g/L; flask method > 10 g/L). Additionally, the results of the preliminary test provide information regarding the appropriate amount of test item to be used in the main test. As the preliminary visual estimation indicated a solubility above 10 g/L, the flask method was performed.

For the flask method , the quantity of test item necessary to saturate the desired volume of water is estimated from the preliminary test and about five times that quantity is weighed into each of three glass vessels fitted with glass stoppers. The batches including a blank flask without test item are stirred for different times at 30 °C (24 h experiment, 48 h experiment, 72 h experiment) in tightly closed flasks. After equilibration (further stirring for 24 h at 20 °C) the suspensions are taken and prepared for the analytical determination via HPLC. The pH values of the saturated solutions are determined.

The water solubility c_Sof the test item at a temperature of 20 °C was determined to be:         c_S= 46 g/L(± 3 g/L)

Description of key information

The water solubility of the test subtance was deteremined according to OECD 105 using preliminary visual estimation and flask method as the preliminary estimation indicated a solubility above 10 g/L. For the flask method, three batches of a measured amount of the test item and deionized water are stirred for 24, 48, and 72 hours at 30°C followed by equilibration (further stirring for 24 h at 20°C).After preparation the concentration of the test item was determined using HPLC.

The water solubility c_Sof the test item at a temperature of 20 °C was determined to be:         c_S= 46 g/L(± 3 g/L)

Key value for chemical safety assessment

Water solubility:

46 g/L

at the temperature of:

20 °C