Quantity analysis by solvent extraction
Choice of the extraction solvent:
The ideal solvent needed to be non-miscible with water and as volatile as possible to limit the heating during its extraction so as not to denature the essential oils.
We chose to use diethyl ether whose boiling point is 34.6°C at atmospheric pressure
Protocol:
Solvent extraction
- Pour the 750 mL of floral water obtained in a separating funnel
- Add 100 mL of ether
- Shake for as long as overpressure occurs
- Extract the aqueous phase after decantation
- Recuperate the ethereal phase in an Erlenmeyer flask
- Reiterate the extraction with 100 mL of ether and the aqueous phase
Drying the ethereal phase:
- Add sufficient anhydrous magnesium sulfate to absorb all the water contained in the ethereal phase
- Filter the ethereal phase in a pre-weighed ground-necked round-bottom flask
Vaporization of the solvent:
- Using a rotary evaporator, vaporize the ether without overheating, just by lowering the pressure to 750 mbars to avoid the loss of any volatile substances that may be present in the oils
- Weigh the flask once all the ether has been vaporized
- Measure the density
Table 5: Results
Type of distillation |
Raw material (in g) |
Volume of water (en L) |
Volume of distillate (en L) |
Time (in min) |
Masse of oil obtained (en g) |
Density of the oil |
Refractive index |
Traditional |
500 g of rosemary |
2.5 L |
0.75 L |
30 |
6.9 |
0.91 |
1.467 |
Solar |
0.75 L |
60 |
7.1 |
0.91 |
1.467 |
Conclusion: The physical characteristics measured on the extracted oils from the two methods of distillation are very close or even non-differentiable. Furthermore, for the same quantities of plants used, and of distillate recuperated, the mass of oil extracted is approximately the same.