these sides discuss chromatography with special emphasis on gas chromatography fundamentals general principles comparison of different chromatographic techniques

2. Submitted to :- Dr. Ozair Alam
Submitted by:- Shameer
Course :- M .pharm (P.Analysis)
Year & sem:- 1 yr. & 1 sem.
Session :- 2020-2021

3. o Slight introduction to chromatography
o Gas chromatography
o Instrumentation
o Applications
o References

4. • Chromatography was first
developed by the Russian
botanist Michael Tswett in 1903
• In which he has separated
colored pigments of plant
(chlorophyll and xanthophyll) by
percolating the petroleum ether
extract through glass column
packed with finely divided
calcium carbonate
• The separated species appeared
as a color band on the column,
which in turn accounts for the
name

5. • The application of chromatography has
grown explosively in the last half centaury,
that just not only due to the development of
several technique in this field but also due to
the growing need by the scientist to study
the more complex mixtures
• Chromatography encompasses a diverse
and important group of methods that allow
the separation, identification and
determination of closely related components
of complex mixture many of these separation
of mixtures are impossible by other method
• Generally in all chromatographic method the
sample is dissolve in a mobile phase, which
can be a gas, liquid or a supercritical fluid.
This mobile phase is then forced through
an immiscible stationary phase, which is
fixed in a column or on a solid surface

6. The two phases are chosen in such a way that the components of the sample
distribute themselves between the two phases of varying degrees
The components that are strongly retained by the stationary phase moves slowly with
the flow direction of the mobile phase in comparison with the components that are
not, (the weakly held components travels rapidly with the mobile phase)
Flow of the mobile phase

7. There are different type for chromatography techniques on the basis of type of
stationary phase and mobile phase used

8. • Based on the principle of selection
Adsorption
chromatography
Partition chromatography
• Separation on the
basis of the affinity
• Stationary phase –
solid
• GSC,TLC,CC &
HPLC
• Separation on the
basis of partition
coefficient
• Stationary phase –
liquid
• GLC, Paper partition
chromatography ,
column
chromatography
No two compounds have the same
affinity for a combination of stationary
phase ,
mobile phase and other condition
No two components can have
the same partition coefficient for
a particular combination of
stationary phase, mobile phase
and other condition
* The stationary phase as such can not be a liquid , hence
a solid support is used over which a thin film or coating of
liquid is made which acts as stationary phase

9. Based on the mode of chromatography
Mode
Normal phase
chromatography
Reverse phase
chromatography
Normal phase
chromatography
Reverse phase
chromatography
• Stationary phase
is polar in nature
(silica gel) & the
mobile phase is
non polar in nature
Stationary phase is
non polar in nature
while the mobile
phase is polar in
nature
• The normal phase chromatography is not much advantageous in the field of
pharmaceutical as most of the drug are polar in nature
• The reverse phase chromatography has advantage (as most of the
pharmaceuticals preparation are polar in nature therefore they are not retained
for a longer time and hence are eluted faster

10. Normal phase Reverse phase
Stationary phase Polar Non-polar
Mobile phase Non-polar Polar
Compound eluted first and retained less Non-polar Polar
Compound eluted last and retained more Polar Non-polar
Example of stationary phase Silica gel ODS(C18),C8,C4 –
bonded phases
Comparison between normal phase and reverse phase chromatography

11. • Ion exchange chromatography :- an
ion exchange resin is used reversible
exchange of ions takes place between
similar charged ions and with that of
ion exchange resin
• Gel permeation chromatography :-
also known as gel filtration and size
exclusion chromatography. A gel is
used to separate the components of a
mixture according to their molecular
size
• Chiral chromatography :-in this type of

13. • In gas chromatography the components of a
polarized sample are separated as a consequence
of being partitioned between a mobile phase and a
liquid or a solid stationary phase held in a column
• In performing gas chromatographic separation, the
sample is vaporized and injected onto the head of a
chromatographic column.
• Elution is brought about by the flow of an inert
gaseous mobile phase.
• The separation of the component gets done on the
basis partition coefficient
• In comparison with most of the other type of
chromatography, here the mobile phase doesn’t
interact with the molecule of the analyte.
• The only function which is to be performed by the
mobile phase is just to act like the carrier for the
analyte through the column

14. Types of gas chromatography
Gas chromatography
(GC)
Gas-liquid
chromatography
(GLC)
Gas-solid
chromatography
(GSC)

15. Gas liquid
chromatography (GLC)
Gas solid
chromatography (GSC)
• GLC finds widespread use in
all field of science
• In this the analyte is
partitioned between a gaseous
mobile phase and a liquid
immobilized the surface of an
inert solid packing or on the
wall of a capillary tubing
• GSC is based on a solid
stationary phase in which
retention of the analyte occur
because of the physical
adsorption
• It has got limited application
because of semi-permanent
retention of active or polar
molecule and also serve
tailing of elution peaks.
*Tailing is a result of the non-linear nature of the adsorption process
*The concept of GLC was first suggested in 1914 by Martin & Synge
(who were also responsible for he development of liquid-liquid partition
chromatography

16. Carrier gas
tank
Flow
regulator
Sample
injection
chamber
Column Detector
Flow
meter
Data system
Display
Sampl
e
Oven
Thermostat

17. • The mobile phase gas in GC is called as
carrier gas
• Most common mobile phase helium gas
{although Argon, Hydrogen and
Nitrogen}
• These gases are available in
pressurized tank and it’s requires
pressure regulator, gauges, and flow
meter to have a control over the flow
rate {in addition the carrier gas system
is also fitted with molecular sieve to
remove impurities and water}
• Flow rates are normally controlled by a
two stage pressure regulator first at the
gas cylinder and some sort of pressure
regulator or flow regulator mounted in
the chromatograph {inlet pressure 10-50

18. • Generally it is assume that the flow rate will be
constant unless and until the inlet pressure remains
constant
• For the establishment of flow rate, rotometer at the
head of column can be used however this device is
not as accurate as simple soap-bubble meter
• Usually the flow meter is located at the end of the
column
• Many modern computer-controlled gas
chromatographs are equipped with electronic flow
meters that can be regulated to maintain the flow
rate at the desired level

19. • In order to achieve high column efficiency the sample
must be of suitable size an introduces as a ‘plug’ of
vapor {slow injection or oversize sample causes band
spreading and poor resolution}
• For this purpose micro-syringes are used to inject
liquid samples through a rubber or silicone diaphragm
or septum, into the heated sample port located at the
head of the column
• The sample port is kept at 50°C above the boiling point
of the least volatile component of the sample
• For ordinary packed analytical columns, sample size
ranges from few tenths of a microliters to 20µL.
• Capillary columns requires samples that are smaller by
factor of 100 or more
• Therefore a sample splitter is often needed to deliver a
small known fraction (1:50 to 1:500) of the injected
sample and rest of the sample will be wasted.

20. • Commercial gas chromatography
intended for use with capillary columns
incorporated with such splitters, they
also allow for split-less injection to
improve the sensitivity or for used with
packed columns
• Autoinjectors with automatic sampling
trays are available for most of the
higher gas chromatographs, that
substantially improves the precision of
the injected volume over the manual
one

21. General type of
column
Open tubular
(capillary)
Packed
• In earlier days vast majority od gas chromatographic analyses used packed columns
• But as per for the current applications packed columns have been replaced by the more
efficient Open tubular columns
• Packed chromatographic columns vary in length from 1m to 5m , while the capillary
Columns can have ranges from few meters to 100m
• The material of construction for column are usually silica or stainless steel, although
Teflon and glass can also be used for the purpose
• In order to get fitted into the oven for thermostatting they are usually formed as coils
having diameter ranges from 10 to 30 cm

22. • Column temperature is an important variable
that must be controlled to a few tenths of a
degree in order to get precise work, now that’s
the reason for the column being ordinarily
housed in a thermostatted oven
• The optimal column temperature depends
upon the boiling point of the sample and the
degree of separation required roughly a
temperature equal to or slightly above the
average boiling point resulting in a
reasonable elution time
(for a samples with a broad boiling range it is
often desirable to employ temperature
programming in which the column temperature is
increased either in a continuous or in steps as
the separation proceeds)

23. • In market there are dozens of detector available which
are incorporated with gas chromatography
• In some cases, gas chromatographs are coupled with
spectroscopic instruments like mass and infrared
spectrometers.
• Benefits of such system is that the spectral device not
only detects the appearance of the analyte as they elute
from the column but also helps to identify them
• Adequate sensitivity (10-8 to 10-15 g solute/s)
• Good solidity and reproducibility
• A linear response to solutes that extends over several
orders of magnitude.
• A temperature to at least 400 °C
• A short response time independent of flow rate
• High reliability and ease of use
• The detector should be nondestructive

24. Type Applicable sample Typical detection limit
Flame ionization Hydrocarbon 1 pg/s
Thermal conductivity Universal detector 500 pg/ml
Electron capture Halogenated compounds 5 fg/s
Mass spectrometer Tunable for any species 0.25 to 100 pg
Thermionic Nitrogen and phosphorous
compounds
0.1 pg/s (P), 1 pg/s (N)
Electrolytic conductivity Compounds congaing
halogens, sulphur, or
nitrogen
0.5 pg cl/s, 2 pg S/s, 4 pg
N/s
Photoionization Compounds ionized by UV
radiation
2 pg C/s
Fourier transform IR Organic compounds 0.2 to 40 ng

25. Name of the detector Advantage Disadvantage
Thermal conductivity detector • Applicable in most of the
compounds
• Good linearity
• Sample is not destroyed &
hence used at preparative scale
• Simple, easy to handle and in-
expansive
• Low sensitivity affected by
fluctuation in flow rate and
temperature
• Gives Relative response
• Cannot analyze the biological
sample
•
Flame ionization detector • The detector is extremely
sensitive and background noise
is low. Hence µg quantities of
the solute can be detected
• Stable and intensive to small
changes in the flow rate of
carrier gas and water vapor
• Responds to most of the organic
compounds
• Linearity is excellent
• Quite complex in handling
• Require expertise guidance and
supervision
Argon ionization detector (AID) • Responds to most of organic
compounds
• Very much sensitive
• Response is not absolute rather
it is relative
• Linearity is poor
• Sensitivity is affected by water
and is much reduced for
halogenated compounds
Electron capture detector (ECD) • high sensitivity
• selectivity toward analyte with
electronegative functional
groups
• nondestructive
• nonlinear response under some
circumstances
• limited response range

27. Wall-coated open tubular
(WCOT)
Support-coated open
tubular(SCOT).
WCOT are simply capillary
tubes coated with thin layer
of the stationary phase.
In SCOT the inner surface of
the capillary is lined with a thin
film (~30 µm) of a support
material
• Early WCOT column were constructed od stainless steel, aluminum, copper
or plastic
• Later glass column began to used
• The most widely used capillary columns are fused silica wall coated (FSWC)
open tubular columns

28. • The FSWC have much thinner wall then the glass columns.
• Tubes have got extra strength by an outside protective polyimide coating. Which is applied
when the capillary tubing is drawn. That results in columns having quite flexibility which in
turn give them ease for being bent in coil having diameters of few inches.
• Silica open tubular columns are available commercially and because they offer several
important advantages (physical strength, much lower reactivity towards the sample
components, and flexibility) for most of the applications, they have replaced the older type
WCOT glass columns.
• The most widely used silica open tubular columns have inside diameters of 0.32 and 0.25
mm.
• Megabore columns are one of the new in the market. They can tolerate the sample sizes
that are similar to those for packed columns they have significantly better performance
characteristics then those of packed columns but not as much as that of smaller-diameter
columns.

29. Types of
solid phase
Polarity Separation
characteristi
cs
Application Operational
temperature
range
(approx.)
Methyl silicone Non-polar Boiling point
order
Petroleum,
solvents, high
boiling point
compounds
-60 to 360°C
Phenylmethyl Slightly polar-
moderately
polar
Phenyl group
retain aromatic
compounds.
Perfumes,
environmental
compounds,
aromatic
compounds
-60 to 340°C
Cyanopropyl
phenol
Moderately
polar-strongly
polar
Effective at
separating
oxygen-
containing
compounds,
isomers, etc.
Agriculture
chemicals,
oxygen
containing
compounds
-20 to 280°C
trifluropropyl Moderately
polar-strong
polar
Specifically
retains
compounds that
contains
Halogen
containing
compounds,
polar
-20 to 340°C

30. • The modern glass columns are fabricated
from glass or metal tubing
• They are typically 2-3 m long and have
inner diameter of 2-4 mm
• These tubes are densely packed with
uniform, finely divided packing material,
or solid support, coated with thin layer
(0.05-1 µm) of the stationary liquid phase.
• The tubes are usually formed as coils
with diameters of roughly 15 cm to permit
convenient thermostatting in an oven

31. the packing or solid support in a packed
column holds the liquid stationary phase in
place so that as large a surface area as
possible is exposed to the mobile phase.
Ideal support
• Small, uniform spherical particles
• Good mechanical strength
• A specific area of at least 1( m)2*/g
• It should be inert (at elevated temperature)
• And be uniformly wetted by the liquid phase
(no material is yet available that meets all of
these criteria perfectly)
The earliest and the most widely used
packing's for GC were prepared via naturally
occurring diatomaceous earth

32. • The efficiency of a gas chromatographic column
increases rapidly with decreasing particle
diameter
• The pressure difference required to maintain an
acceptable flow rate of carrier gas varies
inversely as the square of the particle diameter
• The latter relationship has placed lower limits
on the size of particles used in GC because it is
not convenient to use pressure differences that
are grater than about 50 psi
• As a result the usual support particles are 60-80
mesh (250-170µm) or 80-100 mesh (170-
149µm)

33. Desirable properties of immobilized liquid phase in a gas liquid
chromatographic column include
• Low volatility (ideally the boiling point of the liquid should be at
least 100°C higher than the maximum operating temperature
fro the column)
• Thermal stability
• Chemical inertness
• Solvent characteristics such that K & α {retention factor &
selectivity factor}
The retention time for an analyte on a column depends on its
distribution constant, which in-turn is related to the chemical
nature of the stationary phase

34. Stationary
phase
Common
trade name
Maximum
temperature
°C
Common
application
Polydimethyl
siloxane
OV-1,SE-30 350 General-purpose
non polar phase,
hydrocarbons , poly-
nuclear aromatics,
steroids, PCBs
5% phenyl-
Polydimethyl
siloxane
OV-3,SE-52 350 Fatty acid methyl
esters, alkaloids,
drugs halogenated
compounds
50% phenyl-
Polydimethyl
siloxane
OV-17 250 drugs, steroids,
pesticides glycols
50% trifluropropyl-
ploydimethyl
siloxane
OV-210 200 Chlorinated
aromatics
,nitroaromatics, alkyl
substituted
benzenes
Polyethylene glycol Carbowax 20M 250 Free acids, alcohols,
ethers, essential

35. • Retention time
• Retention volume
• Separation factor
• Resolution
• Theoretical plate

36. G.C.
Separation
tool
Detection
tool
In this role GC methods are unsurpassed
when applied to complex organic, metal-organic
And biochemical systems made up of volatile
species or species that can be derivatised to
Yield volatile substances
In this GC plays role in the
completion of an analysis, in
this role retention time or
volumes are used for
qualitative identifications, and
peak height or peak area
provide quantitative information
For qualitative purposes GC is
much more limited than most
of the spectroscopic methods

37. • Checking for the purity/impurity
of the compound :- by comparing the
chromatogram of the standard and that of
the sample, the purity/impurity of the
compound can be reported. If additional
peaks are obtained then difference in
purity/impurities are present and hence the
compound is not pure/contain impurity .
From the percentage area of the peaks
obtained, the % purity/% impurity can also
be reported.
• Quantitative analysis
It can be determined by
different methods
▫ Direct comparison method
▫ calibration curve method
▫ Internal standard method
• Isolation and identification of
drugs or metabolites in urine,
plasma, serum, etc. can be
carried out.
• Isolation and identification of

38. A textbook of principle of instrumental analysis
A textbook of analysis by S. Ravi Sankar
Wikipedia
 www.shimadzu.com
Google for picture