Supercritical Fluid Extraction technology-basics and application for extraction of neutraceuticals from various sources,

Supercritical Fluid Extraction
Prepared By:
MOHAMMAD KHALID
(Assistant Professor)
Krishna Pharmacy College, Bijnor (UP)

content
Introduction
CONCEPT
PROPERTIES OF SCF
HISTORICAL BACKGROUND
SUPERCRITICAL FLUID EXTRACTION (SFE)
APPARATUS
COMPONENTS OF SFE
SFE WITH RECYCLING (TRAPPING SYSTEM)
CRITICAL PROPERTIES OF SELECTED SUBSTANCES
OBJECTIVES FOR COMMERCIALIZATION
MULTIPLE SOLUTES IN SFE
ADVANTAGES of Sfe
LIMITATIONS
PRECAUTIONS
APPLICATIONS
29 April 2020 Krishna Pharmacy College, Bijnor 2

Introduction
Supercritical Fluid Extraction (SFE) is a eco-friendly
alternative of extraction replacing organic solvents.
In SFE use of Supercritical fluids (SCF’s) like supercritical
CO2 as solvent is there.
SCF are increasingly replacing organic solvents because of
regulatory and environmental pressures on hydrocarbon
and ozone depleting emissions.
SCF helps in extraction of natural products of wide range
of polarities.

CONCEPT
Cagniard de la Tour discovered critical point (CP) in 1822.
CP of pure substances is defined as the highest temperature
and pressure at which the substances can exist in vapour-
liquid equilibrium.
At temperature and pressure above this point, a single
homogenous fluid is formed, which is known as SCF.
SCF is heavy like liquid but has penetration power like gas.
SCF’s are produced by heating a gas above its critical
temperature or compressing a liquid above its critical
pressure but in this molar volume remains same irrespective
of original form( liquid or gas).

PROPERTIES OF SCF
Physical and thermal properties of SCFs are in between pure
liquid and gas, hence can also be known as ‘Compressible
liquids’ or ‘dense gases’
Changes in properties are for a SCF are as follows:
Liquid like densities (100-1000 times greater than gases)
Diffusivities higher than liquids (10-3 and 10-4 cm2 /s)
Good solvating power – Reduction in surface tension
Low viscosity (10-100 times less than liquid)
Gas like compressibility properties Therefore they posses
high penetrating power

HISTORICAL BACKGROUND
Solvent properties of SCF were first
reported well over 100 years ago in 1879 by
Hannay and Hogarth, (measured solubility
of inorganic salts in supercritical ethanol)
Since 1980s and 1990s SCF has been used
in several industrial processes.

Carbon dioxide as SCF
Carbon dioxide: Most commonly used SCF
Low critical parameters (31.1°C, 73.8 bar)
Low cost
Low density
Low viscosity
Non-toxicity.
Abundant source
Eco friendly

Continue……
Supercritical fluid extraction is the process of separating one component from
another (the matrix) using supercritical fluids as the extracting solvent.
Steps: Introduction of feed into extractor (solid feed) or extractor in modified
column either co-currently or counter currently
Formation of mobile phase: mixing of solutes with supercritical fluid.
Exposure of mobile phase to pressures (50-500 atm) and temperatures (ambient to
300°C) near or above the critical point for enhancing the mobile phase solvating power.
Isolation of dissolved solute by precipitation
Eg. CO2 in vapour form is compressed into a liquid before becoming supercritical
and then extraction takes place.

APPARATUS
Simple diagram of supercritical extractor

diagram of supercritical extractor

COMPONENTS OF SFE
1. Fluid reservoir (gas cylinder in case of CO2 )
2. Pump – Reciprocating pump – Syringe pump
(pulse-free flow at large range of flow rates)
3. Extraction cell/column (stationary phase)
Usually stainless steel Chamber or vessel in
compartment
Capable of withstanding high pressure (300-600 atm)
[for solids]
Open tubular capillary columns or packed columns
[liquids]

Continue….
4. Restrictor
Maintaining pressure change inside the extraction
vessel Two types-
fixed (linear restrictor, tapered desire, integral
restrictor, ceramic frit restrictor, metal restrictor)
Variable (variable nozzle, back pressure regulator)
5. Collector (trapping system)
6. Detectors (flame ionization detector of gas
chromatography)

SFE WITH RECYCLING (TRAPPING SYSTEM)
Recycling of SFE can be done-
1. Reduction of pressure - SCF unable to dissolve the solute,
separation of sold under gravity and the gas at low pressure is
compressed back to the supercritical conditions.

Continue…
2. Reduction of temperature - solute drops and
recovery of solvent without recompression
3. Pumping SCF to expansion tank - where it
becomes gas resulting in very less solubility i.e.
separation of solute. Spent gases are then
recompressed and recycled. Heat exchangers are
used to maintain temperature and prevent
excessive cooling at throttling valve called as
Joule-Kelvin effect.

Continue….
Pumping SCF to expansion tank

CRITICAL PROPERTIES OF SELECTED
SUBSTANCES

MODES OF SFE
STATIC EXTRACTION
MODE (steady state)
DYNAMIC EXTRACTION
MODE (non-steady)
o Sample matrix is
soaked in a fixed
amount of
supercritical fluid
o Can be compared
to a teabag in a cup
of water.
o Supercritical fluid
continuously passes
through the sample
matrix
o Analogous to coffee
maker

Continue..
Sample Matrix Parameters that influence SFE:
– Particle size and shape
– Surface area and porosity
– Moisture content
– Changes in morphology
– Sample size – Extractables level
The parameters effect on solubility:
– The vapour pressure of the component
– Interaction with the supercritical fluid
– Temperature, pressure, density and additives

OBJECTIVES FOR COMMERCIALIZATION
Separation of multiple solutes (as solubility of
solute in supercritical solvent may be a function
of temperature and pressure)
Use of entrainers/modifiers an enhance versatility
and efficiency. Eg. CO2mixed with 1-10% of
methanol to solubilise more polar solutes.

MULTIPLE SOLUTES IN SFE
Separation of solutes is by using a two-stage
process. Method
First extraction: similar to single stage
(soluble-dissolved, less soluble- left)
Second extraction: dissolution of the
remaining solute in the solid in the solvent
will result in the isolation

Continue…..

ADVANTAGES of SFe
Elimination of organic solvents i.e. reduces the risk
of storage.
Rapid (due to fast back-diffusion of analytes in the
SCF reduces the extraction time since the complete
extraction step is performed in about 20 min)
Suitable for extraction and purification of
compounds having low volatility present in solid or
liquid
Susceptible to thermal degradation (low operating
conditions)

Continue…..
Complete separation of solvent from extract
and raffinate
Continuous process
Low handling cost
Solvent recovery is easy
Versatile and efficient (use of co-solvents
and co-solutes)

LIMITATIONS
Prolonged time (penetration of SCF into the interior
of a solid is rapid, but solute diffusion from the solid
into the SCF).
Modeling is inaccurate
Scale is not possible (due to absence of fundamental,
molecular-based model of solutes in SCF)
Expensive
Consistency & reproducibility may vary in
continuous production

PRECAUTIONS
Adequate contact time
(for penetration of solvent into solid particles
and diffusion of solute from inside the solid
particles to solvent)
Equilibrium should be achieved
(i.e. proper flow of solvent such that concentration
of dissolved solutes in the solvent phase will be
below the solubility of solute in solvent)

APPLICATIONS
Food science
Fat and oil samples in meat, egg, meals,
chocolate, dairy products, seeds and food snacks,
Natural products
Flavors & spices of ginger, eucalyptus, soyabean,
coffee, soybean, basil, lime peels, potato chips,
popcorn
By-products recovery
Fruit and vegetable waste

REFERENCES
Sairam, P., Ghosh, S., Jena, S., Rao, K.N.V. and Banji, D. (2012)
Supercritical Fluid Extraction (SFE)-An Overview Asian J. Res.
Pharm. Sci.; Vol. 2: Issue 3, Pg 112-120.
Das, S. supercritical fluid extraction, module 10. NPTEL.
Jonin, T.M., Adjadj, L. P and Rizvi, S.S. Food Engineering. Vol III.
Encyclopedia of Life Suport System (EOLSS).
Toledo , Supercritical fluid extraction. Chapter Extraction. Third
Edition. pp 528-531
https://www.slideshare.net/NandhuLal/super-critical-fluid-
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https://www.slideshare.net/jasminekaur144/supercritical-fluid-
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