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Water solubility

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Description of key information

The water solubility was tested by a slow-stirring method adapted from OECD Guideline No. 123.
The water solubility at 20°C of terpinolene multiconstituent was determined to be 1.02 g/L at a loading rate of 34.3 g/L (3.4% of the loading rate).

Key value for chemical safety assessment

Water solubility:
1 015.6 mg/L
at the temperature of:
20 °C

Additional information

The water solubility of terpinolene multiconstituent was tested using a slow-stirring method (adapted from OECD Guideline No. 123).

The test was conducted with a loading rate of around 30 g/L. The quantity of each main constituent in water was measured at 20°C over time, between 0 and 166 hours. The main impurities were also quantified.

An initial decrease of the concentration of all the quantified compounds was observed probably due to the spontaneous formation of a microemulsion at the beginning of the experiment and to its decantation afterwards.

Between 66 and 92 h, a plateau was observed for all measured constituents/impurities of the substance. After 92 h the concentrations decreased; this observation may be explained by the instability of the compounds.  

The mean value and relative standard deviation from five consecutive measures between 66 and 92 h were calculated, in order to determine the concentration of each selected constituent/impurity of terpinolene multiconstituent in water.

 

Loading rate : 34.3 g/L

Compound

% in terpinolene multiconstituent

Limit concentration of each constituent in the mixture terpinolene multi + water (mg/L)

Measured mean concentration in water (mg/L)

RSD (%)

Maximal Deviation (%)

Alpha pinene

0.7

240

0.07

6.6

9.2

1,4 -Cineole

21.1

7237

557.41

5.3

14.6

Alpha terpinene

3

1029

Co-eluted

Co-eluted

 

Dipentene

17.6

6037

1.22

2.6

6.5

1,8 Cineole

14.7

5042

454.07

4.2

11.6

Gamma terpinene

3.4

1166

0.21

7.4

17.3

Terpinolene

31

10633

2.87

3.5

9.7

 

No compound reached its theoretical limit concentration, calculated from the loading rate and the concentration of the compound in the substance. However, for each compound, the calculated RSD is below 15% (as required by the OECD Guideline 105 - flask method, to determine whether a longer equilibration time is required or not) and the relative maximum difference, corresponding to the ratio of the maximum difference and the mean of the two maximum values, is below 30% (as required by OECD Guideline 105 – column elution, to determine when the equilibrium is established).

Therefore, the limit of solubility of each compound was considered to be reached under these experimental conditions.

Finally, the water solubility of terpinolene multiconstituent was calculated as the sum of the mean measured concentration of the main constituents/impurities of the substance, i.e terpinolene, 1,4-cineole, 1,8-cineole and dipentene.

WS = 1015.6 mg/L for a loading rate of 34.3 g/L at 20°C between 66 and 92 h.

 

This value accounts for the substance itself. It is used as key value for the chemical safety assessment.

 

Note: when data on pure constituent/impurity is available, it may be noted that the measured concentration of the compound in water is supported by the estimated concentration, calculated from the water solubility of the pure compound and its relative presence in terpinolene multiconstituent (see table below). This data is provided as supporting study.

 

Substance

Water solubility of pure constituent (mg/L) (obtained by slow stirring method),except for 1,8-cineole

% in terpinolene multiconstituent

Contribution of each compound = water solubility x % of compound in terpinolene multiconstituent (mg/L)

Measured mean concentration in water (mg/L)

Alpha pinene

3.2

0.7

0.02

0.07

1,4-cineole

N/A

21.1

N/A

557.41

Dipentene

5.69

17.6

1

1.22

1,8-cineole

3500

14.7

514

454.07

Gamma terpinene

3.23

3.4

0.11

0.21

Terpinolene

7.03

31

2.18

2.87

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