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Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2018-06-26 to 2018-08-24
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
GLP compliance:
no
Type of method:
flask method
Water solubility:
0.23 g/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
0.991 g/L
Incubation duration:
8 d
Temp.:
21.5 °C
pH:
ca. 5
Water solubility:
0.78 g/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
5.02 g/L
Incubation duration:
8 d
Temp.:
21.5 °C
pH:
ca. 5

Preliminary Tests

The preliminary tests revealed that already relatively low amounts of the sample material were visually not soluble even in large amounts of water from a subjective point of view.

Results

Saturation in Flask 1:

An overview of the sampling of flask 1 together with the determined content of TC as well as the corresponding deviation compared to each previous measurement in the range of the equilibrium are summarised in Table 1 (clearly indicating the equilibration of saturation)

Table 1: Sampling dates and determined sample contents of flask 1

sampling no.

test duration [d]

TC [mg/L]

deviation from previous measurement [%]

1

0

234

-

2

1

444

-

3

2

447

-

4

3

449

-

5

6

437

-2.8

6

7

438

+0.2

7

8

440

+0.5

 

mean (4-7)

441.0

-

SD (4-7)

5.7

-

RSD (4 -7) [%]

1.3

-

Agitation of all flasks was stopped on the ninth day as the last four control points in flask 1 differed no more than 15 % and showed no upward tendency.

Examination of Flasks 2 - 7:

Final examination of flasks 2 to 7 was conducted after 24 hours of temperature equilibration (21.5 °C +- 0.3 °C). The final concentration data obtained from TC measurements are given in Table 2 together with the initial weigh-in for each flask, the measured pH values, the resulting applied loading and the final concentration of the sample in water. The determined carbon content in flask 7 (blank) remained unconsidered for final calculations as it was found to be negligibly low (no significant influence on the final results).

The loading is calculated by weight of test item / volume of water used (here: 50 mL). The final concentration values for the sample were calculated by consideration of the carbon content of the native sample material, which was found to be 77.6 %.

Table 2: Final examination of flasks 2 to 7

flask no.

initial weigh-in [mg]

applied loading [g/L]

pH value (approx.) [-]

resulting TC concentration [mg/L]

final concentration of sample in water [g/L]

2

49.54

0.991

5

182

0.23

3

99.64

1.993

5

325

0.42

4

154.09

3.082

5

441

0.57

5

201.24

4.025

5

528

0.68

6

250.99

5.020

5

603

0.78

7

-

0

5

4

-

 

 

 

 

mean (flask 2 -6)

0.54 (*1)

 

 

 

 

SD (flask 2- 6)

0.19 (*1)

 

 

 

 

RSD (flask 2 -6) [%]

37.9 (*1)

(*1) mean concentration, standard deviation SD and relative standard deviation RSD are only given in accordance to the guideline; these values appear to be meaningless upon the interpretation of the results

Conclusions:
Due to the test item's chemical composition (mixture of different components, each having different physico-chemical properties and thus different individual water solubilities) the water solubility is indicated as 13.37 % (w/w) of the sample material is soluble at 21.5 °C +- 0.3 °C (linear dependence of the water solubility of the sample on the applied loading).
Executive summary:

The water solubility of the test item was determined according to OECD 105 using the flask method. The water solubility of the test item was determined at 21.5 °C +- 0.3 °C and depends on the loading of the sample material in water within the examined loading range of 0.991 g/L to 5.020 g/L. In that range, sample concentrations of 0.23 g/L to 0.78 g/L were found. The dependency between solubility and loading was found to be linear in the examined range of loadings with a slope value of 0.1337. The chemical composition of the sample should be considered for interpreting such behavior: the sample consists of a mixture of different compounds, each having different physico-chemical properties and thus different individual water solubilities. As a result, the linear dependence of the water solubility of the sample on the applied loading may be interpreted as an indication that 13.37 % (w/w) of the sample material is soluble at 21.5 °C +- 0.3 °C.

Description of key information

The water solubility of the test item was determined at 21.5 °C +- 0.3 °C and depends on the loading of the sample material in water within the examined loading range of 0.997 g/L to 5.020 g/L. In that range, sample concentrations of 0.23 g/L to 0.78 g/L were found. The dependency between solubility and loading was found to be linear in the examined range of loadings with a slope value of 0.1337. The chemical composition of the sample should be considered for interpreting such behavior: the sample consists of a mixture of different compounds, each having different physico-chemical properties and thus different individual water solubilities. As a result, the linear dependence of the water solubility of the sample on the applied loading may be interpreted as an indication that 13.37 % (w/w) of the sample material is soluble at 21.5 °C +- 0.3 °C.

Key value for chemical safety assessment

Additional information