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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:
25.06. - 21.08.15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 105 (Water Solubility)
Qualifier:
according to
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
no
Type of method:
column elution method
Key result
Water solubility:
< 0.02 mg/L
Conc. based on:
test mat.
Loading of aqueous phase:
1 mg/L
Incubation duration:
48 h
Temp.:
20 °C
pH:
> 5.5 - < 5.7

Preliminary visual estimation of the water solubility

Three preliminary tests were carried out with specified amounts of the test item and 100 mL and 500 mL distilled 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. The solubility of the test item in water was found to be below 8.0 mg/L. According to the guideline the column elution method is the appropriate method for solubilities below 10 mg/L therefore this method was used for the main test.

 

Column elution method

99.8 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 (50 °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 23 °C: 5.5). After a swelling time of 2 h pumps were started to rinse the test item coated sand with distilled 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. The eluate was diluted from 0.1 mL to 10 mL with acetonitrile and again from 0.75 mL to 1.0 mL with dist. water. The concentration of the test item was quantified by HPLC. As blank value the used distilled water was tested by means of HPLC. No signal was detected in the range of the retention time of the test item.

 

Column 12.5 mL/h:

 

Rotation period of the fraction collector: 90 min per fraction

Duration of sampling: about 48 h (32 fractions)

 

Fraction no.

V

/mL

PH

water solubility / µg/L

23

20.0

5.5

< 19.7

24

20.0

5.6

< 19.7

25

20.0

5.6

< 19.7

26

20.0

5.6

< 19.7

27

19.5

5.6

< 19.7

 

Evaluation of the fractions 23 to 27: The water solubility was found to be below the quantification limit of 19.7 µg/L.

 

Column 25.0 mL/h:

Rotation period of the fraction collector: 45 min per fraction Duration of sampling: about 48 h (64 fractions)

 

 

Fraction no.

V

/mL

PH

water solubility / µg/L

50

18.5

5.7

< 19.7

51

18.5

5.6

< 19.7

52

18.5

5.7

< 19.7

53

18.5

5.7

< 19.7

54

18.0

5.6

< 19.7

 

Evaluation of the fractions 50 to 54:

The water solubility was found to be below the quantification limit of 19.7 µg/L.

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

 

The water solubility of the test item at a temperature of 20 °C was determined to be below the quantification limit of < 0.02 mg/L.

Conclusions:
The water solubility of the test item at a temperature of 20°C was determined to be below 0.02 mg/L.
Executive summary:

The water solubility was determined according to OECD 105 using the column elution method with HPLC analysis. 99.8 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 (50 °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 23 °C: 5.5). After a swelling time of 2 h pumps were started to rinse the test item coated sand with distilled water. The values for the water solubility were calculated from fractions 23 to 27 for the 12.5 mL/h column and from the fractions 50 to 54 for the 25.0 mL/h column. In both columns the concentration of five consecutive fractions was constant within ± 30 %. No increasing or decreasing tendency was observed. The water solubility was found to be below the quantification limit of 19.7 µg/L. Thus, the water solubility of the test item was determined to be below 0.02 mg/L at 20 °C.

Description of key information

The water solubility of the test item at a temperature of 20°C was determined to be below 0.02 mg/L (reference 4.8 -1).

Key value for chemical safety assessment

Additional information

The water solubility was determined according to OECD 105 using the column elution method with HPLC analysis. 99.8 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 (50 °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 23 °C: 5.5). After a swelling time of 2 h pumps were started to rinse the test item coated sand with distilled water. The values for the water solubility were calculated from fractions 23 to 27 for the 12.5 mL/h column and from the fractions 50 to 54 for the 25.0 mL/h column. In both columns the concentration of five consecutive fractions was constant within ± 30 %. No increasing or decreasing tendency was observed. The water solubility was found to be below the quantification limit of 19.7 µg/L. Thus, the water solubility of the test item was determined to be below 0.02 mg/L at 20 °C.