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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:
2014-03-18 to 2014-06-11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP Guideline study
Qualifier:
according to
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
yes
Remarks:
The water solubility test was not shaken at 30°C and equilibrated at 20°C, but shaken directly at 20°C. The deviation had no impact on the study.
Qualifier:
according to
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
yes
Remarks:
see previous comment
GLP compliance:
yes (incl. certificate)
Type of method:
flask method
Water solubility:
0.036 g/L
Temp.:
20 °C
pH:
6.6
Remarks on result:
other: Total organic carbon based on nominal loading rate of 0.1 g/L
Water solubility:
0.002 g/L
Temp.:
20 °C
pH:
6.6
Remarks on result:
other: boron based on nominal loading rate of 0.1 g/L
Details on results:
Preliminary test
The preliminary estimate of water solubility was 4.25E-02 g/L at 20.0°C by TOC.
Definitive test
The correlations (r2) of the TC and IC calibration plots were all at least 0.9999.
As it was known that the test item was hydrolytically unstable it was decided to perform the test with reduced shaking periods and directly at 20°C as an elevated temperature of 30°C would hydrolyse the test item at a more rapid rate. The samples were prepared at a nominal loading rate of 100 mg/L to tie in with the upper concentration limit of ecotoxicological testing.
Due to the instability of the test item, a substance specific analytical method was not available. Therefore, the samples were analysed for total organic carbon and boron by ICP-MS. The boron analysis identified the concentration of the degradation product, boric acid, was in solution.
Based on the representative structure of the test item, boron accounts for 2.24% by mass. As the mean boron concentration was 2.43 mg/L, this would equate to 108 mg/L of the test item. The loading rates of the 3 samples ranged from 111 to 113 mg/L, so it can be clearly seen that all or nearly all the boron had dissolved when taking into account the test item might not be 100% of the representative structure and analytical inaccuracies.
The organic part of the test item, which after decomposition of the test item was 2-propyl-1-heptanol, had a mean concentration of 35.6 mg/L With this representing 97.76% of the test item by mass, it only equates to 36.4 mg/L of test item which is significantly lower than the sample loading rates. This shows that not all the organic part of the test item had dissolved in the water. Considering this with the boron results, the test item appeared to have decomposed because the results (corrected to test item concentration) would have been the same if decomposition had not occurred.
As the results were consistent for all samples and taking the above conclusion into account, the test item must have essentially all degraded within 1 hour at 20°C.
The preliminary test was performed at a higher nominal loading rate of 1000 mg/L, ten times higher that the definitive test. Even so, with a total organic carbon result of 42.5 mg/L it indicated that loading rate would have no significant effect (assuming enough organic components were available to reach saturation) and suggests saturation had been reached. Whereas, the boron concentration would be expected to mirror the loading rate concentration as the test item would hydrolyse and boric acid is highly water soluble.
An estimation of water solubility using WSKOW v 1.42 (US EPA) gave a low solubility of 2.8E-7 mg/L.

See attached document.

Conclusions:
Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L) The substance hydrolyses in water.
The water solubility of the test item at 20.0°C was determined to be 3.56E-02 g/L of the total organic cabon and 2.43E-03 g/L boron based on a nominal loading rate of 0.1 g/L. The water solubility of the test item could not be determined directly due to it being hydrolytically unstable in water.
Executive summary:

Guideline

EC Method A6 of Commission Directive 92/69/EEC and OECD Guideline No. 105; flask method.

Result

The water solubility of the test item at 20.0 °C was determined to be 3.56E-02 g/L of the total organic cabon and 2.43E-03 g/L boron based on a nominal loading rate of 0.1 g/L. The water solubility of the test item could not be determined directly due to it being hydrolytically unstable in water.

Description of key information

The water solubility of the test item at 20.0°C was determined to be 3.56E-02 g/L of the total organic carbon and 2.43E-03 g/L boron based on a nominal loading rate of 0.1 g/L. The water solubility of the test item could not be determined directly due to it being hydrolytically unstable in water.

Key value for chemical safety assessment

Water solubility:
0.036 g/L
at the temperature of:
20 °C

Additional information

The water solubility of the test item at 20.0°C was determined to be 3.56E-02 g/L of the total organic cabon and 2.43E-03 g/L boron based on a nominal loading rate of 0.1 g/L. The water solubility of the test item could not be determined directly due to it being hydrolytically unstable in water.