(Sánchez-Camargo et al. 2019). It can effuse through solids like a gas and dissolve
materials like a liquid (CO 2 ), ethylene, ethane, propylene, propane, and nitrous oxide
are some examples of substances which can exist in the supercritical state. Comparatively CO 2 is best suitable for use as it is non-flammable, odourless, easily disposable, and available at low cost. Most importantly it has a lower critical point. SFE is a
technique of extracting the bioactive component from the sample using supercritical
fluid like CO 2 as the solvent (Yousefi et al. 2019). The Supercritical fluid used can
easily be removed by depressurizing the sample where the solvent will turn to a
gaseous state. Moreover, the risk of heating up the equipment is not there in case
of SFE.
8.3.5 Hydrodistillation
Hydrodistillation is a conventional method used to extract essential oils, flavonoids,
and other bioactive compounds from various plants. This method does not use
organic solvents for extraction. Water or stream is used for the extraction of
bioactive compounds from the plants. The basic steps involved in this extraction
method are cleaning and cutting of plants, followed by soaking in distilled water at
1:2.5 ratio. The contents are then transferred into a round bottom flask, which is
fitted to Clevenger apparatus and condenser. It is distilled for a period of six hours
(Solanki et al. 2019).
8.3.6 Soxhlet Extraction
Soxhlet extraction technique is usually employed for the removal of fats from the
sample using soxhlet apparatus (Azwanida 2015). The sample is kept in the thimble
and the thimble is attached to the soxhlet flask where the solvent is added and it is
connected to the condenser. When the apparatus is turned on, the solvent gets heated
where evaporation and condensation takes place. N-Hexane (69
C), petroleum ether
(40–80
C), and ethanol (78
C) are the common solvents used in this technique.
8.3.7 Solid Phase Extraction (SPE)
Solid phase extraction is a sensitive method used for concentrating and purifying
analytes from a solution by sorption onto a disposable solid phase (Płotka-Wasylka
et al. 2015; Andrade-Eiroa et al. 2016). It consists of two phases: a mobile phase and
a stationary phase. The mobile phase carries the molecules to be extracted. In normal
phase SPE, the stationary phase absorbs the non-polar molecules while the polar
molecules get eluded later. In reverse phase SPE, the stationary phase absorbs the
polar molecules eluding the non-polar molecules at the end.
176
L. Manickam et al.
materials like a liquid (CO 2 ), ethylene, ethane, propylene, propane, and nitrous oxide
are some examples of substances which can exist in the supercritical state. Comparatively CO 2 is best suitable for use as it is non-flammable, odourless, easily disposable, and available at low cost. Most importantly it has a lower critical point. SFE is a
technique of extracting the bioactive component from the sample using supercritical
fluid like CO 2 as the solvent (Yousefi et al. 2019). The Supercritical fluid used can
easily be removed by depressurizing the sample where the solvent will turn to a
gaseous state. Moreover, the risk of heating up the equipment is not there in case
of SFE.
8.3.5 Hydrodistillation
Hydrodistillation is a conventional method used to extract essential oils, flavonoids,
and other bioactive compounds from various plants. This method does not use
organic solvents for extraction. Water or stream is used for the extraction of
bioactive compounds from the plants. The basic steps involved in this extraction
method are cleaning and cutting of plants, followed by soaking in distilled water at
1:2.5 ratio. The contents are then transferred into a round bottom flask, which is
fitted to Clevenger apparatus and condenser. It is distilled for a period of six hours
(Solanki et al. 2019).
8.3.6 Soxhlet Extraction
Soxhlet extraction technique is usually employed for the removal of fats from the
sample using soxhlet apparatus (Azwanida 2015). The sample is kept in the thimble
and the thimble is attached to the soxhlet flask where the solvent is added and it is
connected to the condenser. When the apparatus is turned on, the solvent gets heated
where evaporation and condensation takes place. N-Hexane (69
C), petroleum ether
(40–80
C), and ethanol (78
C) are the common solvents used in this technique.
8.3.7 Solid Phase Extraction (SPE)
Solid phase extraction is a sensitive method used for concentrating and purifying
analytes from a solution by sorption onto a disposable solid phase (Płotka-Wasylka
et al. 2015; Andrade-Eiroa et al. 2016). It consists of two phases: a mobile phase and
a stationary phase. The mobile phase carries the molecules to be extracted. In normal
phase SPE, the stationary phase absorbs the non-polar molecules while the polar
molecules get eluded later. In reverse phase SPE, the stationary phase absorbs the
polar molecules eluding the non-polar molecules at the end.
176
L. Manickam et al.