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Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

experimental dates: 14-22 February 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to an internationally recognised method, with some adaptation as recommended by ECHA conducted according to scientific principles, and under GLP. The substance is considered to be adequately characterised, with isomers composition. Therefore full validation applies.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

27 July 1995

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

Commission Regulation (EC) No 440/2008 on test methods, Method A.6: “Water Solubility” (as amended by Regulation (EU) No 260/2014
An adaptation of the standard method will be performed taking into account the findings of Letinski, D.J., Connolly, M.J., Peterson, D.R. and Parkerton, T.F. (2002) “Slow-stir water solubility measurements of selected alcohols and diesters”, Chemosphere 48, 257-265.
The OECD guideline for the Testing of Chemicals No 123 “Partition Coefficient (1-Octanol/Water): Slow-Stirring Method”, 11 July 2006, was also considered.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed on 15 Nov. 2018

Type of method:

flask method

Remarks:

with slow-stirring adaptation

Specific details on test material used for the study:

Storage conditions of test material: Stored refrigerated (2-8°C) in aluminium bottle. An injection of nitrogen conditions gas is performed into the bottle after each sampling to keep the test item under nitrogen atmosphere during the storage period.

Key result

Water solubility:

40 mg/L

Conc. based on:

test mat.

Temp.:

20 °C

pH:

>= 5.8 - <= 6.61

Preliminary test

A preliminary test was carried out as a range finding test prior to the main test. The concentration range obtained gave an indication on the necessary analytical method sensitivity.

Increasing volumes of water were added at room temperature to 21.0 mg of the test sample in a 100 mL glass-stoppered measuring cylinder. After each addition of an amount of water, the mixture was shaken for 10 minutes and was visually checked for any undissolved parts of the sample.

The test item (21.0 mg) was not solubilized by a water volume of 100 mL after 24 h, corresponding to a solubility inferior to 0.2 g/L.

Ecotoxicity tests were recently performed on this test item (“Daphnia sp., Acute Immobilisation Test”: see LPL report D18-027; "Freshwater Alga and Cyanobacteria, Growth Inhibition Test»: see LPL report A18-027). Stock solutions of the test item were prepared in water with the slow-stirring method. Approximately 1 g of test item was carefully added directly to the surface of the test water
(~ 1 L). The mixing vessel was thereafter closed immediately. The mixing was initiated with the vortex in the centre extending maximally around 10 % vessel depth from the top to the bottom of the vessel. After about 24 hours of gentle stirring in the dark at room temperature, the contents of the vessel were allowed to stand undisturbed for at least 1 hour before sampling. Two stock solutions were prepared for each test, one for the range finding test and the other for the final test.

Even though it was obtained with a fixed equilibration time (24 h), at a non-controlled temperature (room temperature) and not in pure water (algae and daphnia test waters), a value of about 40 mg/L can be considered as an estimation of the test item water solubility. This is consistent with the estimation of 39.7 mg/L obtained by a (Q)SAR method (Kreatis, iSafeRat model, data provided by the study monitor).

It was observed, during this preliminary test and the ecotoxicity tests, that the test item is less dense than water.

Main test

Concentrations profiles

The following table presents the concentrations (in mg/L) obtained during the study for the vessel 1.

Sampling date (m/d/y)	Equilibration time (h)	Replicate 1	Replicate 2	Mean
02/14/2019 11:05	Preparation (t0)	---	---	---
02/15/2019 10:35	ca 24h	26.84	26.59	26.72
02/18/2019 14:45	ca 100h	38.25	38.49	38.37
02/19/2019 11:30	ca 120h	38.10	38.76	38.43
02/20/2019 11:10	ca 144h	38.41	38.11	38.26
02/21/2019 10:15	ca 167h	40.37	39.19	39.78

Sampling in vessels 2 and 3 occurred on 22 February at 10:30, after ca 167 h. The concentrations measured (in mg/L) for these two vessels were:

	Replicate 1	Replicate 2	Mean
Vessel 2	40.13	39.25	39.69
Vessel 3	40.46	40.76	40.61

 The pH values measured in the three systems were:

- 6.61 in vessel 1 and 6.49 in vessels 2 and 3 at the beginning of the experiment;

- 5.83 in vessel 1, 5.80 in vessel 2 and 5.99 in vessel 3 at the end of the experiment.

The pH controlled with the indicator strips for each specimen was 5 for all the samples taken from the three vessels.

The temperature variations were included in the range 19.8 °C - 20.2 °C.

Equilibrium demonstration

From the t-test, the equilibrium state can be declared for the vessel 1 between 18 February at 14:45 to 21 February at 10:15.

The maximum difference observed in the 5 last samples was 4%.

Since the two conditions were fulfilled, the equilibrium state was declared on 21 February at 10:15 for the vessel 1.

Water solubility calculation

The mean of the two samples at the equilibrium statedeclaration on 21 February at 10:15 was:

39.78 mg/L for vessel 1.

The means of the two other vessels, obtained for the same equilibration time, on 22 February at 10:30, were:

39.69 mg/L for vessel 2.

40.61 mg/L for vessel 3.

The maximum difference observed between these three determinations is 2 %, which proves that an acceptable repeatability is obtained (the OECD 105 acceptability criterion for the maximum difference between two tests by the column elution method is 30 % and 15 % for the shake flask method).

The ST 03 C 18 solubility in water is given by the mean of the values obtained for the three vessels: 40.0 +/- 0.4 mg/L.

Executive summary:

The water solubility of the test substance was measured under GLP according OECD 105 guideline, modified with slow-stirring adaptation from Lentinski et al (2002).

Three vessels were prepared, at 20°C. Quantification was performed with a validated HPLC-DAD method. The first vessel was used to determine the equilibration time. When achieved, test item concentration was determined in the other two vessels.

The water solubility was calculated as the average of the three vessels at the final sampling time: 40.0 mg/L (at 20°C and pH ca 6).

Description of key information

Considered as slightly soluble, with equilibrium reached at 96h.

pH of saturated solution: ca 6.

Key value for chemical safety assessment

Water solubility:

40 mg/L

at the temperature of:

20 °C

Additional information

A fully reliable experimental study, conducted according to a recognized OECD/EC method and under GLP, is available. Therefore, it is considered as a key study, and the result is retained as key value.