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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:
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:
column elution method
Key result
Water solubility:
0.123 mg/L
Conc. based on:
test mat.
Temp.:
20 °C
pH:
ca. 6.2
Remarks on result:
other:
Remarks:
determined by column elution method

Sample preparation.

After passing the columns, the concentration of the test item in 5 collected aqueous fractions was determined in duplicate by HPLC. For this purpose, the fractions were diluted from 0.5 ml to 1mL with acetonitrile. The eluates of the coating check were diluted from 1.0 mL to 10 mL with acetonitrile and again from 0.05 mL to 1.0 mL with acetonitrile / demineralized water 75:25 % (v/v).

 

Preliminary test

Three preliminary tests were carried out with specified amounts of the test item and 100 mL and 500 mL demineralized water, respectively. After each addition of an amount of water, the mixture was stirred for 24 hours, and visually checked for any undissolved particles.

 

Table: Results of the preliminary test

Amount of test item /mg

Total volume of demineralized water / mL

Appearance of mixture

12.0

100

Not dissolved

12.6

500

Not dissolved

4.9

500

Not dissolved

 

The solubility of the test item in water was found to be below 9.8 mg/l (without correction for the purity). According to the preliminary test the water solubility was determined by the column elution method in the main test.

 

Column elution method

103.4 mg of the test item were dissolved in 100 ml acetone. For charging the columns in each case 25 mL of the test item solution was added to about 3 g of sea sand and the mixtures were shaken. The solvent was then removed under reduced pressure using a rotary evaporator (40 °C, approx. 20 mbar). The dry residues were placed into the columns of the test apparatus, which have afterwards been filled with water (test temperature: 20 °C; water pH at 20 °C:5.4). After a swelling time of 2 h pumps were started to rinse the test item coated sand with demineralized water. At the end of the study it was confirmed that residual test item remained on the columns. The residual test item was eluted with 50 mL acetone. As blank value demineralized water was tested. No signal was detected in the range of the retention time of the test item. The concentration of the test item was quantified by HPLC.

 

Column 1:

Rotation period of the fraction collector:         90 min per fraction

Duration of sampling:                           about 51 h (34 fractions)

 

Table column elution method, column 1 (approx. 12.5 mL/h)

Fraction no

V / mL

pH

Water solubility / mg/l

25

18.0

6.3

0.123

26

18.0

6.3

0.116

27

18.0

6.3

0.128

28

18.0

6.2

0.130

29

18.0

6.2

0.123

 

The water solubility was found to be 0.124 mg/l.

 

Column 2:

Rotation period of the fraction collector:         45 min per fraction

Duration of sampling:                           about 51 h (68 fractions)

 

Table column elution method, column 2 (approx. 25.0 mL/h)

Fraction no

V / mL

pH

Water solubility /µg/L

50

16.5

6.2

0.127

51

16.5

6.2

0.130

52

16.5

6.3

0.122

53

16.5

6.2

0.120

54

16.5

6.3

0.112

 

The water solubility was found to be 0.122 mg/l.

 

In both columns the concentration of five consecutive fractions was constant within ± 30 %. No increasing or decreasing tendency was observed.

 

Table Coating check

 

Amount of test item

used for coating /mg

Measured concentration of

 test item in eluate /mg

Amount of test item

 eluated /mg

Column 12.5 mL/h

25.6

0.022 / 0.022

21.8

Column 25.0 mL/h

25.6

 0.020 / 0.020

20.1

 

The coating check was successful. Enough test item remained on the columns. The water solubility cs of the test item was 0.123 mg/L (mean value of the columns) in both columns.

Conclusions:
The water solubility cs of the test item at a temperature of 20°C was determined according to the column elution method. It was found to be 0.123 mg/L.
Executive summary:

The water solubility was determined according to OECD 105 using the column elution method. The preliminary test showed that the water solubility of the test item is < 10 mg/L. The column elution method showed a solubility: cs = 0.123 mg/L.

Description of key information

The water solubility cs of the test item at a temperature of 20°C was determined according to the column elution method. lt was found to be 0.123 mg/L.

Key value for chemical safety assessment

Water solubility:
0.123 mg/L
at the temperature of:
20 °C

Additional information

The water solubility was determined according to OECD 105 using the column elution method. The preliminary test showed that the water solubility of the test item is < 10 mg/L. The column elution method showed a solubility of 0.123 mg/L at 20 °C.