Tar bases, coal, lutidine fraction

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 start date: 12 January 2016, Experimental completion date: 16 February 2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995 (Flask method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

Commission Regulation (EC) No 440/2008, dated May 30, 2008

Deviations:

no

GLP compliance:

no

Remarks:

However, the study was performed in a test facility which has been certified to be in compliance with the principles of GLP.

Type of method:

flask method

Water solubility:

>= 501 g/L

Temp.:

20 °C

pH:

9.4

Remarks on result:

other: At this highest concentration used a light straw coloured solution, free from excess, undissolved test item resulted. Temperature ± 0.5 °C

Details on results:

Preliminary Estimation of Solubility
The actual concentrations, observations recorded and solution pH’s following equilibration of the preliminary estimation samples at 20.0 °C are shown in Table 3. The results indicated a solubility of at least 100 g/L of solution at 20.0 °C.

Definitive Visual Evaluation
The actual concentrations, observations recorded and solution pH’s following equilibration of the definitive visual evaluation samples at 20.0 °C are shown in Table 4. The results indicated a solubility of greater than 500 g/L of solution at 20.0 °C.

Table 1: Preliminary Estimation of Solubility – Sample Preparation

Sample Identity	Nominal Concentration [g/L]	Mass of Test Item [g]	Final Dilution Volume with High Purity Water [mL]	Actual Concentration [g/L]   ^[1]
1	0.100	0.1027^[2]	1000	0.103
2	1.00	0.2511	250	1.00
3	10	1.0000	100	10.0
4	100	2.5002	25	100
5	250	6.2537	25	250
6	500	12.5013	25	500

^[1]Based on the total combined volume of the test item and water, using a test item density value of 0.934 g/cm³ and a water density value of 1.000 g/cm³.

^[2] Dispensed as 110 µL of test item, and the weight calculated using a density value of 0.934 g/cm³, as the mass of the flask was too high for balances of the required accuracy.

Table 2: Visual Evaluation – Sample Preparation

Sample Identity	Nominal Concentration [g/L]	Mass of  Test Item [g]	Mass of High Purity Water [g]	Actual Concentration [g/L]^[1]
7	100	2.0110	17.8562	101
8	200	4.0146	15.7290	200
9	250	4.9992	14.6387	250
10	300	6.0037	13.6008	300
11	400	8.0038	11.4485	400
12	500	10.0122	9.2844	501

^[1] Based on the total combined volume of the test item and water, using a test item density value of 0.934 g/cm³ and a water density value of 1.000 g/cm³.

Table 3: Preliminary Estimation of Solubility – Observations and Solution pH Values

Sample Identity	Actual Concentration [g/L]	Observations	Solution pH
1	0.103	A clear, colourless solution, free from excess, undissolved test item.	7.4
2	1.00	A clear, colourless solution, free from excess, undissolved test item.	8.6
3	10.0	A clear, colourless solution, free from excess, undissolved test item.	9.5
4	100	A pale straw coloured solution, free from excess, undissolved test item.	10.0
5	250	A straw coloured solution, containing a slight excess of undissolved test item.	9.8
6	500	A straw coloured solution, containing a slight excess of undissolved test item.	10.1

Table 4: Visual Evaluation – Observations and Solution pH Values

Sample Identity	Actual Concentration [g/L]	Observations	Solution pH
7	101	A light straw coloured solution, free from excess, undissolved test item.	9.5
8	200	A light straw coloured solution, free from excess, undissolved test item.	9.6
9	250	A light straw coloured solution, free from excess, undissolved test item.	9.6
10	300	A light straw coloured solution, free from excess, undissolved test item.	9.7
11	400	A light straw coloured solution, free from excess, undissolved test item.	9.5
12	501	A light straw coloured solution, free from excess, undissolved test item.	9.4

Conclusions:

In a valid, reliable and conclusive study according to OECD TG 105 and Method A.6 (EC) No 440/2008, the water solubility of the test item was ≥ 501 g/L at 20 °C ± 0.5 °C.

Executive summary:

The water solubility of the test item was investigated in a non-GLP study using the flask method according to the OECD TG 105 (1995) and EU A.6 (Commission Regulation (EC) No 440/2008) protocols. The experiment is considered relevant, adequate and conclusive.

Based on the results from the preliminary estimation of solubility, mixtures of test item and high purity water of nominal 100, 200, 300, 400 as well as 500 g/L were prepared to evaluate these concentrations by visual inspection using an initial saturation period of 30 °C, as presented in the regulatory methods. After addition of the test item and high purity water to the flasks, they were shaken at 30 °C for a saturation period of 72 hours, the maximum time evaluated in the standard regulatory methods. After re-equilibration at 20.0 °C for a period of 24 hours, with occasional shaking by hand, the contents of the flasks were then visually observed for successful dissolution and the solution pH was recorded.

The contribution of individual components to the test item’s composition, as well as literature values of their dissociation constants have been evaluated. Based on recommendations provided by ECHA for the evaluation of the water solubility of mixtures (Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7a: Endpoint specific guidance, July 2015), the preliminary assessment of water solubility included the nominal loading rates of 100 mg/L and 1000 mg/L (equivalent to 0.100 g/L and 1.00 g/L). There was no evidence of loading rate dependent solubility characteristics at these two loading rates, with complete dissolution achieved for both relevant samples. Further samples were therefore prepared at higher nominal loading rates to provide an initial estimate of the saturation concentration of solubility for the test item. Aqueous sample solutions of test item up to a concentration of 100 g/L were identified as being readily soluble/miscible when mixed at ambient laboratory temperature and then equilibrated to 20.0 °C. When applying an initial saturation period at an elevated temperature, as instructed by the previously referenced regulatory methods, and then re-equilibrating at 20.0 °C, successful dissolution was achieved at a nominal concentration of 501 g/L. Based on the magnitude of solubility observed for the test item and the absence of any excess undissolved material in the definitive visual evaluation samples, the analysis of the sample solutions was considered inconsequential. On review of the dissociation constant information and the sample solution pH values sample, solutions at the higher concentrations evaluated represented the unionized, molecular form of the test item. As such, solubility would theoretically increase, due to ionization of the test item components, as the solution pH decreased into the environmentally relevant pH range of 5 to 9. As significant solubility had already been demonstrated for the molecular form, additional sample preparation was not considered necessary or relevant.

In conclusion the water solubility of the test substance was ≥ 501 g/L at 20 °C ± 0.5 °C.

Description of key information

In a valid, reliable and conclusive study according to OECD TG 105  and Method A.6 (EC) No 440/2008, the water solubility of the test item was ≥501 g/L at 20 °C ± 0.5 °C.

Additional information

The UVCB substance is a complex mixture mainly of dimethyl- and methylpyridines. The water solubility of the substance was determined to be at least 501 g/L at 20 °C and pH 9.4. The value of 501 g/L at 20 °C will be used in the chemical safety assessment of the substance.