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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:
May - June 2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Version / remarks:
July 1995
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
flask method
Water solubility:
141.4 mg/L
Conc. based on:
test mat.
Loading of aqueous phase:
600 mg/L
Incubation duration:
7 d
Temp.:
19.5 °C
pH:
>= 6.28 - <= 6.44
Details on results:
The preliminary test which is described in the guideline was not performed as the solubility of the test item was estimated during validation of the analytical method as 113 mg/L (measured in a solution with concentration of the test item 10 g/L). For test items with the water solubility > 10 mg/L, the flask method was used.
For the test, 600 mg/L 1,3-Diiodopropane were used to prepare a saturated solution as the water solubility detected in the pre-test was 113 mg/L (in the guideline, fivefold saturation is proposed). Six flasks were prepared (1A – 1C and 2 – 4); the flasks 1A – 1C were used during an equilibration time.
The volume of the test item was calculated using the density of the test item 2.576 g/cm³ (taken from the material safety data sheet). Flask 1A was intended for the sampling point 24 h, flask 1B for the sampling point 48 h and flask 1C for the sampling point 72 h. A preincubation at 30 °C was not used to avoid an oversaturation of the solution.
Four vessels (flasks 1C (for the sampling point 72 h) and flasks 2 – 4) were set onto the stirrer immediately and stirring was started at 270 rpm. After 24 ±2 hours, flask 1B (for the sampling point 48 h) and after 48 ±2 hours, flask 1A (for the sampling point 24 h) were set on the stirrer and all flasks were stirred for further 24 ±2 hours at room temperature. Then, flasks 1A - C were taken from the stirrer and tempered at 20.0 ± 0.5 °C; samples were taken, prepared as described above (without centrifugation) and measured via GC/MSD. Due to an upward tendency in the three flasks, the test was prolonged; all flasks were further stirred at room temperature and sampled on days 4 – 7. As the concentration of the test item in the flasks 1A – 1C on days 4 – 7 lay in the range of 49.1 – 138.3 mg/L, the test item solution from the flask 1C was additionally centrifuged (10 min at 4500 rpm), extracted as described in chapter 6.7.5 and measured again on day 7. Due to a difference of less than 15 % in the concentrations on days 3 and 7 (flask 1C only) and no upward tendency on days 2, 3 and 7, the test was finished on day 7. The results from the flasks 1A – 1C on days 4 – 6 were not used in the calculation as the values lay far below 100 mg/L due to the volatility of the test item.
The final measurement was performed as determination from flasks 2 – 4. The test item solutions were centrifuged (10 min at 4500 rpm) before extraction procedure. None of the separated and/or centrifuged test solutions showed a Tyndall effect (i.e. a laser beam was not scattered when transmitted through the liquid).
After the analysis of the sample of day 7, the plateau was considered as reached after comparison of the values from days 3 (flask 1C) and day 7 (flask 1C). The results from the flasks 1A – 1C on days 4 – 6 were not used in the calculation as the values lay below 100 mg/L due to a volatility of the test item.
The results from the flasks 2 – 4 (unopened flasks) confirmed the concentration of the test item in the flask 1C on days 3 and 7. As the relative standard deviation was lower than 15 % taking into account the values from the flask 2 – 4 and 1C on days 3 and 7, these values were also used in the calculation of the mean.
The results are presented here:
Day 3, Flask 1C: 145.7 mg/L
Day 7, Flask 1C: 138.3
Day 7, Flask 2: 139.1
Day 7, Flask 3: 145.1
Day 7, Flask 4: 138.9
Mean at the plateau was 141.4 ± 3.7 mg/L.
Conclusions:
The water solubility of the test item was stated as 141.4 ±3.7 mg/L with a relative standard deviation of 2.6 %.
Executive summary:

The solubility of 1,3-Diiodopropane in water was determined using the shake flask method from the measured concentrations of the test item in the centrifuged test solutions. During the equilibration time, the concentration in the flasks 1A – 1C was in the range of 49.13 – 145.7 mg/L, whereby the concentration of the test item on day 5 was lower than on day 1. A reason for this behaviour could be the volatility of the test item. The flasks 1A – 1C were sampled several times while the flasks 2 – 4 were stirred tightly closed with low head space during the whole test. Therefore, flasks 2 – 4 were used for evaluation. As the relative standard deviation was lower than 15 % taking also into account the values from the flask 1C on days 3 and 7, these values were also used in the calculation of the mean.

The water solubility of the test item was stated as 141.4 ± 3.7 mg/L with a relative standard deviation of 2.6 %.

Description of key information

The water solubility of the test item was stated as 141.4 ±3.7 mg/L with a relative standard deviation of 2.6 %.

Key value for chemical safety assessment

Water solubility:
141.4 mg/L
at the temperature of:
19.5 °C

Additional information