This document provides an overview of supercritical fluid chromatography (SFC). It defines SFC as a form of normal phase chromatography that uses supercritical fluids like carbon dioxide as the mobile phase. The key advantages of SFC are that it can be used to analyze thermally labile compounds at lower temperatures than gas chromatography, and it has higher diffusion coefficients and lower viscosity than liquid chromatography. The document discusses the instrumentation, principles, advantages, disadvantages and applications of SFC.

1. Dr. BASAVARAJAIAH S. M.
Assistant Professor and Coordinator
P.G. Department of Chemistry
Vijaya College
Bangalore-560 004
Supercritical FluidChromatography

2. Introduction
Definition
Principle
Instrumentation
Advantages
Disadvantages
Applications
CONTENTS

3. Use of Super Critical Fluid Chromatography (SFC) Was First
Proposed in 1958 By J. Lovelock.
First Reported Use Was In 1962 by Klesper et.al., Who
Separated Thermally Liable Porphyrins.
Supercritical fluid chromatography (SFC) can be used on an
analytical scale.
It is a combination of High performance liquid chromatography
(HPLC) and Gas chromatography (GC).
The most significant difference from HPLC is the replacement of
most of the liquid mobile phase with a dense compressed gas,
almost always carbon dioxide (CO2).
INTRODUCTION

4. At high pressures such as greater than 80 bar, CO2 acts as a
solvent.
It is used for the analysis & purification of low moderate
molecular weight, thermally liable molecules.
It can be used with the universal flame ionization detector.
It is important to producing narrower peaks due to rapid
diffusion.
It is important for the chiral separations and analysis of high-
molecular weight hydrocarbons.
Supercritical fluids are suitable as a substitute for organic
solvents in a range of industrial and laboratory processes.

5. DEFINITION
Supercritical fluid chromatography (SFC) is a
form of normal phase chromatography that uses
a supercritical fluid such as carbon dioxide as the
mobile phase.

6. PRINCIPLE
It is combination of GC and HPLC, the Principle is based on
Adsorption and partition Chromatography.
The principle based on Triple point and Critical point.
The principle is based on Supercritical Fluid.
However SFC typically utilizes carbon dioxide as the mobile
phase; therefore the entire chromatographic flow path must be
pressurized.
Because the supercritical phase represents a state in which
liquid and gas properties converge.
Supercritical fluid chromatography is sometimes called
"convergence chromatography”.

7. IMPORTANT ERMINOLOGY
Critical Temperature – The Constant Temperature.
Critical Pressure – The Constant Pressure.
SFC Temperature - For every substance there is a
temperature above which it can no longer exist as a liquid no
matter how much pressure is applied.
SFC Pressure - For every substance there is a pressure
above which it can no longer exist as a liquid no matter how
high temperature is raised.
Triple Point – The point in which state of material was
changes at constant temperature and pressure.

9. SFC SOLVENTS
Carbon Dioxide and water are the most commonly used
supercritical fluids, being used for decaffeination and power
generation, respectively.
Many pressurized gases are actually supercritical fluids. For
example, nitrogen has a critical point of 126.2K (- 147 °C) and 3.4
MPa (34 bar). Therefore, nitrogen (or compressed air) in a gas
cylinder above this pressure is actually a supercritical fluid.
These are more often known as permanent gases. At room
temperature, they are well above their critical temperature, and
therefore behave as a gas, similar to CO2 at 400K above.
However, they cannot be liquified by pressure unless cooled below
their critical temperature.

11. Properties of Supercritical Fluid
There is no surface tension in a supercritical fluid, as there is no
liquid/gas phase boundary.
Solubility in a supercritical fluid tends to increase with density of
the fluid (at constant temperature).
Since density increases with pressure, solubility tends to
increase with pressure.
At constant density, solubility will increase with temperature.

12. Choice of SCFs solvent
Good solubilizing and penetrating property
Inert to the product
Easy separation from the product
Cheap
Low CP because of economic reasons

13. Advantages of SF’s
The solvating power of supercritical fluids is very similar to many
conventional organic solvents and much higher than in gases.
Diffusion coefficient and viscosity of supercritical fluids are about 5 to
50 times higher than in liquids.
High density of SCF able to dissolve large nonvolatile molecules. E.g.
CO2 dissolves, n-alkane (n=5-22), Polycyclic aromatic hydrocarbons.
Therefore CO2 is used for extraction of caffeine and nicotine.
Analyte can be easily recovered by allowing the solution to equilibrate
at relatively low temp.
Diffusivities of solute is higher.
Viscosity is lower so very useful for compound which have no
functional group, as detection method in HPLC fails.

14. Supercritical Fluid Chromatography
INSTRUMENTATION
Stationary phase
Mobile phase
Pumps
Injectors
Ovens
Columns
Detectors

16. STATIONARY PHASE
Both packed and open tubular columns are used.
Packed columns can provide more theoretical plates and
handle large volume than open tubular columns.
Because of low viscosity of super critical media.
The column length is 10 to 20 m. and inside the diameter
is 50 to 100 mm common in open tubular columns.
For difficult separation column 60 m (or) large have been used.
Packed column usually made up of stainless steel,10 to 25 cm.
More than 100,000 plates have been achieved in plate column.
Many of column coating used in LC have been applied to SFC
as well.
Typically their are polysiloxane chemically bounded wall of
capillary tubing .

17. The mobile phase is composed primarily of super critical carbon
dioxide, but since CO2 on its own is too non-polar to effectively
elute many analytes, co-solvents are added to modify the mobile
phase polarity.
Co-solvents are typically simple alcohols like methanol, ethanol
or isopropyl alcohol. Other solvents such as acetonitrile,
chloroform or ethyl acetate can be used as modifiers.
 Modify valves for analytes ,ethane, pentane, diethyl ether,
ammonia.
Pressure maintained is 72.9 atm, temperature is 35 ºc.
MOBILE PHASE

18. Here mainly flow control is necessary so syringe pumps are
used for capillary SFC for consistent pressure and for packed
columns for easier blending of the mobile phase or introduction of
modifier fluids reciprocating pumps are used.
PUMPS
In capillary SFC small sample should be quickly injected into
the column and so pneumatically driven valves are used.
For packed SFC a typical injection valve is commonly used.
INJECTORS

19. OVENS
Conventional GAS chromatography & liquid chromatography
ovens are used.
COLUMNS
Two types of analytical columns are used in SFC i.e. packed
and capillary.
Packed columns contain small deactivated substances to which
the stationary phase adheres.
These are conventionally stainless steel. Capillary columns are
open tubular columns made of fused silica which have small
internal diameter.

20. Flame ionization detectors and flame photometry detector,
liquid-phase detectors like refractive index detector, ultraviolet-
visible spectrophotometric detectors and light scattering detectors
have been employed for SFC.
DETECTORS

21. ADVANTAGES
SFC is emerging as a separation technique that is superior
to both gas chromatography and liquid chromatography
for analysis of thermal liable or non volatile compounds.
Low viscosity.
Lower operating temperature. High diffusion co efficient.
High resolution at low temperature.

22. DISADVANTAGES
SFC is pressure operating conditions. High-pressure vessels
are expensive and bulky.
Maintaining pressure in SFC is difficult.
Supercritical fluids are highly compressible and their
physical properties change with pressure.
Cleaning will be time consuming.

23. APPLICATIONS
SFC is used in industry primarily for separation of
chiral molecules.
SFC now commonly used for chiral separation and
purification in the pharmaceutical industry.
SFC technique has been applied to wide verity of materials,
including natural products, drugs, food and polymers etc.
In overall ranking of chromatographic techniques it can be
judges that SFC falls somewhere between HPLC and GC.
In field of pharmaceutical chemistry and bioanalytical
applications SFC gained its applications.