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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:
26 October 2013 - 29 October 2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see "Remark"
Remarks:
The determination of water solubility was performed using the slow stirring method adapted from OECD Guideline No 123. This study was considered as reliable with restrictions because not enough details on quantification of the substance were reported in the report.
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
other: adapted from OECD Guideline 123
Deviations:
no
Principles of method if other than guideline:
In a stirring vessel maintained at 20 +/-0.5°C, ultra-pure water covered by a thin layer of the test item (~2 mm thickness) is slowly stirred. The speed was adjusted so that a minimal vortex is formed. The aim of this method is to prevent the formation of emulsions when saturating water. That can occur with the shake flask method and lead to a solubility overestimation. The water solubility is given by the mass concentration in water when a plateau as a function of time is reached. A second experiment is performed in the same conditions
GLP compliance:
no
Type of method:
other: slow-stirring method
Key result
Water solubility:
ca. 2.24 mg/L
Temp.:
20 °C
pH:
>= 5 - <= 7
Remarks on result:
other: Mean of two solubility values obtained in two different experiments.
Details on results:
First experiment (mean of the five last samples) = 2.26 mg/L (The relative difference = 10.43% : less than 15% as required by the OECD 105 - flask method)
Second experiment (mean of the five last samples) = 2.21 mg/L (The relative difference = 6.73% : less than 15% as required by the OECD 105 - flask method)

Preliminary test

The 10 mg sample was not fully dissolved in 10 mL of water. Therefor the experiment was extended with 100 mL of water.

The approximate solubility determined by the preliminary test was lower than 100 mg/L.

First experiment

The concentrations obtained as a function of time during this first experiment are presented in graph 1 : "Concentrations observed- first experiment"

Measured pH :

-       at the beginning of the experiment : 7

-       at the end of the experiment : 5

The mean ± standard deviation of the five last samples is 2.26 ± 0.10 mg/L (The relative difference = 10.43% : less than 15% as required by the OECD 105 - flask method)

 

The maximum difference observed in the five last samples is

           2.42 - 2.18 = 0.24 mg/L

 

The mean of these two maximum values is

           (2.42 + 2.18) / 2 = 2.30 mg/L

 

The relative difference, corresponding to the ratio of the maximum difference and the mean of the two maximum values is

           0.24 / 2.3 = 10.43 %

 

Second experiment

The concentrations obtained as a function of time during this second experiment are presented in graph 2 : "Concentrations observed- second experiment".

Measured pH :

-       at the beginning of the experiment : 7

-       at the end of the experiment : 5

 

The mean ± standard deviation of the five last samples is 2.21 ± 0.06 mg/L (The relative difference = 6.73 % : less than 15% as required by the OECD 105 - flask method)

 

The maximum difference observed in the five last samples is

           2.30 – 2.15 = 0.15 mg/L

 

The mean of these two maximum values is

           (2.30 + 2.15) / 2 = 2.23 mg/L

 

The relative difference, corresponding to the ratio of the maximum difference and the mean of the two maximum values is

0.15 /2.23 = 6.73 %

 

Conclusions:
Interpretation of results (migrated information): slightly soluble (< 100 mg/L)
The mean of the two solubility values obtained in the two different experiments is (2.21 + 2.26) / 2 = 2.24 mg/L
The relative difference between the results of the two experiments is (2.26 – 2.21) / 2.24 = 2.23 %
The mean values obtained from two experiments did not differ by more than 30%, so these results are valid.
Executive summary:

The determination of the water solubility of DIMETHYLOCTADIENE was performed using the slow stirring method adapted from OECD 123 guideline.

Due to the physicochemical properties of the test item (stability, volatility, adsorption on glass), the samples were analyzed as soon as possible after sampling. This precaution is crucial in order to avoid underestimation and variations of the measured concentrations.

Two independent experiments were carried out. The concentration of the substance was regularly measured by HPLC / UV (High Performance Liquid Chromatography with UV detector). The water solubility was recorded when the concentration reached a plateau.

The water solubility of DIMETHYLOCTADIENE obtained by the slow-stirring method is 2.24 mg/L.

This value is the mean of two independent measurements.

Description of key information

A GLP study was conducted to determine the water solubility of dimethyloctadiene according to OECD Guideline 105 using column elution method. 
Under the test conditions, the water solubility of dimethyloctadiene at 20 °C (pH: 8.2) was measured to be ≤ 0.15 mg/L.

Key value for chemical safety assessment

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

Additional information

This experimental value was measured in a study performed according to OECD Guideline 105 with minor deviations.