hi this is most helpful for those who study supercritical fluid chromatography. it explain very easily and briefly. all data taken from several books, google research and research articles.Supercritical fluid chromatography (SFC) is a form of normal phase chromatography that uses a supercritical fluid such as carbon dioxide as the mobile phase.[1][2] It is used for the analysis and purification of low to moderate molecular weight, thermally labile molecules and can also be used for the separation of chiral compounds. Principles are similar to those of high performance liquid chromatography (HPLC), 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.

2. MOBILE PHASE
EFFECT OF PRESSURE
STATIONARY PHASE
PUMP
INJECTOR
OVEN
RESTRICTOR
COLUMN
DETECTOR
 MICRROPROCESOR

4.  Part of the theory of separation in SFC is based
on the density of supercritical fluid which
correspond to solvating power .As the pressure
in the system is increases, the supercritical
fluid density increases and correspondingly its
solvating power increases. Therefore as the
density of the supercritical fluid mobile phase
is increased , components retained in the
column can be made to elute. This is similar to
temperature programming in GC or using a
solvent gradient in HPLC.
 Density @ Solvating power

7. MOBILE PHASE/CARIIER=SUPERCRITICAL FLUID
SUPERCRITICAL FLUID=Any substance at a
temperature and pressure above its critical point ,
where distinct liquid & gas phase do not exist.
It can diffuse through solid like a gas and dissolve
material like liquid.

8.  Supercritical temperature= For every substance
there is temperature above which it can no longer
exist as a liquid, no matter how much pressure is
applied.
 Supercritical pressure= For every substance there
is a pressure above which the substance no longer
exist as gas , no matter how high the temperature
is raised.
 Supercritical fluid=A supercritical fluid is a
material that can be liquid or gas used in state
above critical temperature or critical pressure
where gas or liquid can co exist.

9.  LIQUID LIKE DENSITY INCREASED
 GAS LIKE VISCOSITY DECREASED
 GAS LIKE COMPRESIBILITY
 DIFFUSIBILITY ARE HIGHER THEN LIQUID
 REDUCTION IN SURFACE TENSION

11.  CO2 (MOST USED IN SFC)
 N2O (Nitrous oxide)
 Ethylene
 Propylene
 n-heptane
 Ethanol
 Propane
 Ammonia
 H2O

13. ADVANTAGE:
 LOW CRITICAL PRESSURE (74 atm )
 LOW CRITICAL TEMPERATURE ( 31c )
 CO2 is relatively non-toxic , non-flammable.
 High purity (available)
 Low cost
 Easily removable from extract
 CO2 IS LOW POLAR (LOW DIPOLE)
 CO2 + one or More co-solvent =increase polarity

14.  CAN NOT EXTRACT THE POLAR SOLUTES
NITROUS OXIDE (N2O)
ADV:
 GOOD FOR EXTRACTION OF POLAR
SOLUTES=B/C N2O HAS PERMANENT DIPOLE
MOMENT.
 EXAMPLE=N2O is better then CO2 for extraction
of Polychlorinates , Dibenzodioxines from flyash
(solid fuel produce during combustion )

15.  AT CRITICAL CONDITION IT CAN BE EXPLOSIVE.
H2O
DISADV:
 HIGH CRITICCAL PRESSURE ( 220 atm )
 HIGH CRITICAL TEMPERATURE (374c)
 AT THESE CONDITION H2O BECOMES CORROSIVE
(destroy solid material by chemical rxn ).

16.  THRESHOLD PRESSURE: A particular pressure at
which miscibility of solute & solvent is occur is
called threshold pressure.
 Pressure at which solute reaches its maximum
solubility.
 Knowledge of physical properties of solutes.

17.  Role=to modified the properties of solvent.
 Example= Alcohols, cyclic ethers, aceto-nitrile
and chloroform or ethyl acetate.
 The adding of modifier fluid improves the
solvating power of SF and sometimes enhances
selectivity of the separation.

18.  There are number of possible fluid which may be
used in SFC as the mobile phase .Mostly CO2 is
used.
 The main disadvantage of CO2 is its in ability to
elute very polar or ionic compounds.
 This can be overcome by adding a small portion of
a second fluid improves the solvating power of
the supercritical fluid and sometimes enhances
selectivity of the separation.

19.  Same as those for GC and LC, with some modification
 Silica/Alumina
 Useful for non-polar compounds
 Lead to irreversible adsorption of some
polar solutes
 Widely used polar stationary phase
 Poly-siloxanes :- stable, flexible Si…O bond lead to
good diffusion.
 Polymehtylsiloxanea: increase efficiency in
separating closely related polar analytes.
 Cyanopropyl polysiloxanes:- useful for compound
with COOH

20.  Pressure change in SFC is effect the retention time
and retention factor .The density of supercritical fluid
which correspond to solvating power .As the pressure
in the system is increases, the supercritical fluid
density increases and correspondingly its solvating
power increases. Which in turn to shorten the elution
time.
 Improvement in chromatogram realized by pressure
programming.

23.  In contact to HPLC Pumping system, Pressure
rather than flow control is necessary.
 In general, The type of High-pressure pump used
in SFC is determined by the column type=
I. For Packed column:- Reciprocating pumps are
generally used.(reciprocating pumps are allow
to easier mixing of the mobile phase or
introduction of modifier fluid.)
II. For capillary column:- Syringe pumps are
mostly employed.(Provide consistent pressure
for a neat mobile phase)

30.  The injector is required for sample inject into column.
 For Packed column:- A conventional HPLC
injection system is adequate.
 For Capillary column:- The sample volume
depend on column diameters.
The small sample volume must be quickly
injected into the column.
Therefore pneumatically driven valves are
required.
INJECTOR VOLUME
 Capillary column:- Injection volume >90nL
 Greater volume effect resolution.
 Packed column:- Injection volume >1uL

32.  A Thermostated column oven is required for precise
temperature control of the mobile.
 Convention GC & LC ovens are generally used.

33. RESTRICTOR=BACK PRESSURE
 It is used to maintain the desired pressure in the
column and to convert the eluent from
supercritical fluid to a gas for transfer to the
detector.
 It keeps mobile phase supercritical throughout
separation and often must be heated to prevent
clogging( block).

34.  One or more microprocessor are used in SFC
instrument to control pumping pressure, oven
temperature and detector performance.

35.  Once the sample is injected into the supercritical
stream it is carried into the analytical column.
The column contains a highly viscous liquid
(called a stationary phase) into which the analytes
can be temporarily adsorbed and then released
based on their chemical nature . This temporary
retention cause some analytes to remain longer in
the column and is what allow separation of the
mixture. Different types of stationary phase are
available with varying compositions and
polarities.
 There are two types column are used in SFC:
 Packed column & capillary column

36.  Both packed and open tubular columns are used.
Packed columns can provide more theoretical
plates and handle large volume than open tubular
columns.
 Packed column usually made up of
stainless steel,10 to 25cm.
 More than 1,00,000 plates have been achieved in
packed column.

37.  Open column :The column length is 10 to 20m. and
inside the diameter is 50 to 100mm common in open
tubular columns.
 For difficult separation column 60m (or) large have
been used.
 Typicallytheir are poly-siloxane chemically bounded
wall of capillary column.
 More analysis time.
 Less sample capacities.

38.  A major advantage of SFC over HPLC is that flame
ionization detector of gas can be employed .Mass
spectrometer are also more adapted as detector for SFC
then HPLC.
 Both HPLC and GC detector are compatible for
SFC.[UV,FID,FLOURESENCE DETECTOR]
 Choice depend on upon:
I. Mobile composition
II. Column type
III. Flow rate