Gum turpentine oil, consisting of the volatile fraction resulting from the distillation of oleoresin collected by tapping softwoods from pinacea derivatives (genus: pinus). It consists of terpenes, mainly monoterpenes such as alpha-pinene and beta-pinene.

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From June 03 to September 07, 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Key result

Water solubility:

25.5 mg/L

Temp.:

20 °C

pH:

6.6

Remarks on result:

other: loading rate = 1 g/L

Details on results:

Preliminary test
The content of the test substance dissolved in the water samples at the loading rates of 1 and 10 g/l are given in Table 1.
A factor 5.9 was observed in the contents of the water samples at the loading rates of 1 and 10 g/l. It indicated that the test sample at 1 g/l was not completely saturated with the water soluble fraction of the test substance. According to this, the maximum loading rate of 1000 g/l (1:1 w/v) and a 10-times lower loading rate of 100 g/l were applied in the main study.

Main study
The results for the samples at the loading rates of 100 g/l and 1:1 w/v taken at 24, 48 and 72 hours are given in Table 2 and Table 3.
The maximum difference (MD) of the concentrations determined in the 24, 48 and 72 hour test samples at the loading rate of 100 g/l was < 15%. According to the guidelines, the water solubility of the test substance is given as the mean value of the analysed concentrations.
At a ratio of 1:1 w/v, the 24-hour measurement was somewhat lower than the 48- and 72- hour measurements (maximum difference > 15%). According to the guidelines, the water solubility of the test substance was given as the mean value of the 48- and 72-hour measurements.
The TOC background of the blank water sample was maximum 4.5% compared to the lowest content of the test samples. It was considered not significantly affect the results of the test samples.

Table1       Preliminary test

Loading rate [g/l]	Stirring time [hours]	Analysed concentration [g/l]	Percentage to loading rate [%]	pH
1	66.4	0.0255	2.6	6.6
10	66.5	0.152	1.5	6.1

Table2       Main study - water solubility at a loading rate of 100 g/l

Loading rate [g/l]	Stirring time [hours]	Analysed concentration [g/l]	Mean [g/l]	Percentage to loading rate [%]	MD [%]	pH
100	24	0.573	0.580	0.58	9.4	3.9
100	48	0.556				3.8
100	72	0.612				3.7

 

Table3       Main study - water solubility at a loading rate of 1:1 w/v

Loading rate [g/l]	Stirring time [hours]	Analysed concentration [g/l]	Mean [g/l]	Percentage to loading rate [%]	MD [%]	pH
1000	24	2.33	2.76	0.28	8.4^1	3.3
1000	48	2.64				3.2
1000	72	2.88				3.2

¹Obtained with the samples at 48 and 72 hours.

Conclusions:

The water solubility of gum turpentine oil (UVCB substance) was tested at 20 °C using the flask method at two loading rates, in accordance with OECD guideline 105 and EU method A.6.
At a loading rate of 100 g/l the water solubility of the test substance was 0.580 g/l (0.58% compared to the loading rate) and the pH of the aqueous samples was 3.7 – 3.9.
At a loading rate of 1:1 w/v (maximum possible loading rate) the water solubility was 2.76 g/l (0.27% compared to the loading rate) and the pH of the samples was in the range 3.2 – 3.3.

Executive summary:

A study was performed according to OECD guideline 105 and EU method A.6 to measure the water solubility of gum turpentine oil.

The test item being an UVCB substance, the flask method at two loading rates was used.

The water solubility of the test substance at 20°C increased with the loading rate of the samples.

In the preliminary test, at a loading rate of 1 g/L, the water solubility was 25.5 mg/L: this value was chosen as representative for chemical safety assessment.

At a loading rate of 100 g/L the water solubility of the test substance was 0.580 g/L. It corresponds to a water solubility percentage compared to the loading rate of 0.58%. The pH of the aqueous samples was 3.7 – 3.9.

At the loading rate of 1:1 w/v (maximum possible loading rate) the water solubility was 2.76 g/l. The value is relatively high, but compared to the loading rate it corresponds to a percentage of 0.28%. The pH of the samples was in the range 3.2 - 3.3.

The results indicate that the water solubility of the test substance is most likely related to a small fraction of components with a relatively high water solubility. The major of the test substance was not soluble in water.

The results were obtained under GLP and without deviation, so they are considered as reliable without restriction.

Description of key information

The water solubility at 20°C of gum turpentine oil (UVCB substance) was determined to be: 
- 25.5 mg/L at a loading rate of 1 g/L (2.6 % compared to the loading rate),
- 152 mg/L at a loading rate of 10 g/L (1.5 % compared to the loading rate),
- 580 mg/L at a loading rate of 100 g/L (0.58 % compared to the loading rate),
- 2.76 g/L at a loading rate of 1000 g/L (0.276 % compared to the loading rate).

Key value for chemical safety assessment

Water solubility:

25.5 mg/L

at the temperature of:

20 °C

Additional information

The water solubility of GUM TURPENTINE OIL (UVCB substance) was tested using the flask method in accordance with OECD Guideline 105 and EU method A.6.

 

A preliminary test was conducted with the loading rates of 1 and 10 g/L. A factor 5.9 was observed in the contents of the water samples at the loading rates of 1 and 10 g/L. It indicated that the test sample at 1 g/L was not completely saturated with the water soluble fraction of the test substance. However, the analysed concentrations were 0.0255 and 0.152 g/L at 1 and 10 g/L, respectively.

 

The main test was conducted with loading rates of 100 and 1000 g/L.

At a loading rate of 100 g/L the water solubility of the substance was 0.580 g/L (0.58 % compared to the loading rate).

At a loading rate of 1:1 w/v (maximum possible loading rate) the water solubility was 2.76 g/L (0.28 % compared to the loading rate).

 

The results indicate that the water solubility of the test substance is most likely related to a small fraction of components with relatively high water solubility. The major of the test substance was not soluble in water.

 

The water solubility of the test substance increased with the loading rate of the samples.

 

Therefore, the solubility of GUM TURPENTINE OIL at a loading rate of 0.1 g/L is expected to be lower than 0.0255 g/L (solubility at 1 g/L).

 

- For the ecotoxicological studies, the OECD guidelines recommend to test the toxicity of a substance at a maximum concentration of 0.1 g/L.

- According to the exposure scenario, the direct contamination of water is unlikely and the predicted concentrations in the water compartment are unlikely to reach concentrations above 1 g/L (even with a solubility of 1 g/L).

Therefore, we can estimate that the solubilised fraction will be lower than 25.5 mg/L.

This value will be considered for the exposure assessment.