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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:
23-29 Feb 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 105 (Water Solubility)
GLP compliance:
yes (incl. certificate)
Remarks:
Rheinland-Pfalz Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Mainz, Germany
Type of method:
flask method
Key result
Water solubility:
0.25 mg/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
300 mg/L
Incubation duration:
>= 2 - <= 6 d
Temp.:
20 °C
pH:
>= 6 - <= 7

To determine the dependency of the water solubility on the amount of the test item added, four different loading rates were chosen. The following amounts were added to the flasks (volume of H2O: 800 mL in each flask):

Flask No.

Amount test item* [µL]

Resulting nominal concentration [mg/L]

1A

255

300

1B

255

300

1C

255

300

2

42.6

50

3

85.1

100

4

426

500

*Calculated from the density of the test item 0.94 g/cm³

Measurements during equilibration: data acquired during equilibration time (flask 1A-C, in duplicate)

Day

Temperature [°C]

pH*

Measured conc. [mg/L]

Conc. Test Item** [mg/L]

Conc. Test Item Mean [mg/L]

Difference to previous sample

1

20.1

6-7

8.03;7.88

0.198;0.195

0.197

-

2

20.2

6-7

9.63;9.75

0.238;0.241

0.240

+21.9%

3

20.5

6-7

10.10;9.96

0.250;0.246

0.248

+3.5%

5***

19.5

6-7

10.95;10.51

0.270;0.259

0.265

+6.7%

6

19.6

6-7

10.16;10.00

0.251;0.247

0.249

-5.9%

*measured using pH paper

**50-fold enrichment and 81% recovery rate from the medium was taken into account

*** the test item solution from the flask 1A (day 4) was not measured as an error occurred during the extraction of the solution

After the analysis of the sample on day 6, the plateau was considered as reached.

Measurements at plateau:

Flask

2

3

4

pH

6.53

6.23

6.36

Measured concentration test item [mg/L]

9.76;9.79

10.46;10.60

12.47;12.44

Enrichment factor

50

50

50

Recovery rate from medium [%]

81

81

81

Concentration test item mean [mg/L]

0.242

0.260

0.308

Nominal concentration test item [mg/L]

50

100

500

The measurements of the days 2-6 were included in the calculation of the mean as the plateau was not reached on day 1 (flask 1A).

Day

Flask

Concentration [mg/L]

2

1B

0.240

3

1C

0.248

5

1B

0.265

6

1C

0.249

6

2

0.242

6

3

0.260

6

4

0.308*

*The value was stated as an outlier and it was not used in the calculation of the mean.

Mean: 0.25 ± 0.01 mg/L (RSD = 4.0%).

Description of key information

0.25 mg/L at 20 °C, pH 6 -7

Key value for chemical safety assessment

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

Additional information

The water solubility of the substance trihexyl phosphate (CAS No. 2528-39-4) was determined using flask method according to OECD 105.