Are our floral waters comparable to those produced by the traditional method?


Having succeeded in distilling plants with solar energy, we wanted to check whether the perfumed waters obtained were of equivalent quality to those obtained by a traditional distillation.

During our trip in January, we performed several extractions with the same quantities of flowers and water each time. The only variable was the time total time of distillation, since the heat flow provided by a gas burner is greater.

 

Distillation on 21 January 2016 in Marrakech

m = 500g rosemary 

Vwater = 2.5 L of water

Vdistillate = 75 cL. 

 

Quantity analysis by solvent extraction

Écrit par Rohan NOWAK et Waldan GIRARD le . Publié dans Are our floral waters comparable to those produced by the traditional method?

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.

Quality analysis by gas chromatography

Écrit par Rohan NOWAK et Waldan GIRARD le . Publié dans Are our floral waters comparable to those produced by the traditional method?

The analysis of the oils we obtained was done using gas chromatography (GC)   

- Hydrogen was used as the carrier gas

- The stationary phase was a polymer with “low polarity” 

 

Fig. 8: Spectrum of the oils obtained using the traditional method

 

Fig. 9: Spectrum of the essential oils obtained by the solar method

Table 6: Analysis of both spectrums (main peaks, and therefore main components of the oils are in red):

 

Traditional distillation

Solar distillation

t (in min)

%

t (in min)

%

4.741

8.8

4.801

11.8

5.028

2.8

5.086

3.5

5.496

2.5

5.552

2.7

5.644

1.3

5.697

1.3

6.258

1.9

6.313

1.8

6.421

50.1

6.483

51.3

7.422

1.7

7.47

1.1

8.248

19.7

8.303

16.5

8.601

4.6

8.652

3.4

8.913

4.6

8.964

3.3

12.09

2.1

12.113

1.6

 

Conclusion: the composition of the essential oils obtained by the solar method and those obtained by traditional method is very similar. We could form hypotheses about the different chemical species that were present and which correspond to the different peaks in the spectrum. Gas chromatography works according to the retention times, which are themselves linked to the polarity and therefore to the boiling temperature of the chemical species: the lower the boiling temperature is, lower the retention time of that one chemical species will be.

So we made hypotheses concerning the species which corresponded to the 3 main peaks in the spectrums:

  1. othe 1st peak would correspond to alpha-pinene, a molecule which boils at 156°C and for which the expected the content of was 9 to 14% of the extracted oils.
  2. othe 2nd peak would correspond to eucalyptol which boils at 176°C and with an expected content of 38 to 55%
  3. othe 3rd peak would correspond to camphor which boils at 204°C and with an expected content of 5 to 15%

We obtained samples of camphor and eucalyptol for analysis in the laboratory. The results of the gas chromatography confirmed that these were indeed the molecules we identified from the GC spectrum of the rosemary distillate.

We can also notice the contents are coherent with the oil composition of rosemary found in Morocco (see Table 4)