1. Gas chromatography is a technique used to separate mixtures by partitioning components between a stationary and mobile liquid or gas phase. 2. It works by forcing a gaseous or volatile sample mixture through a column containing a solid or liquid stationary phase, which interacts differently with each component. This causes the components to elute from the column at different times. 3. Gas chromatography is useful for separating volatile organic compounds and finds applications in fields like drug analysis and purity testing due to its high resolution, sensitivity, speed, and ability to perform both qualitative and quantitative analysis.

1. Chromatography
(Gas Chromatography)
Presented By:-
Ruta Satoskar
&
Suman Muthu

2. THE CHROMATOGRAPHIC PROCESS - PARTITIONING
(gas or liquid)
MOBILE PHASE
STATIONARY
PHASE
Sample
out
Sample
in
(solid or heavy liquid coated onto a solid or
support system)

3. Original Chromatography Experiment
Later
Start: A glass
column is filled
with powdered
limestone
(CaCO3).
End: A series of
colored bands is
seen to form,
corresponding to
the different
pigments in the
original plant
extract. These
bands were later
determined to
be chlorophylls,
xanthophylls
and carotenoids.
An EtOH extract
of leaf pigments
is applied to the
top of the column.
EtOH is used to
flush the pigments
down the column.

4. Chromatography: (Greek = chroma “color”
and graphein “writing” ) Tswett named this new
technique chromatography based on the fact that it
separated the components of a solution by color.
Common Types of Chromatography
Tswett’s technique is based on Liquid
Chromatography. There are now several common
chromatographic methods. These include:
1. Paper Chromatography
2. Thin Layer Chromatography (TLC)
3. Liquid Chromatography (LC)
4. High Pressure Liquid Chromatography (HPLC)
5. Ion Chromatography
6. Gas Chromatography (GC)

5. How Does Chromatography Work?
In all chromatographic separations, the sample is
transported in a mobile phase. The mobile phase can
be a gas, a liquid, or a supercritical fluid.
The mobile phase is then forced through a stationary
phase held in a column or on a solid surface. The
stationary phase needs to be something that does not
react with the mobile phase or the sample.
The sample then has the opportunity to interact with
the stationary phase as it moves past it. Samples that
interact greatly, then appear to move more slowly.
Samples that interact weakly, then appear to move
more quickly. Because of this difference in rates, the
samples can then be separated into their
components.

6. Chromatography is based on a physical
equilibrium
that results when a solute is transferred between
the mobile and a stationary phase.
A
A
A
A
A
A
A
A
A
A
A
A
K = distribution
coefficient or
partition ratio
K =
C
S
C
M
Where CS is the molar
concentration of the
solute in the stationary
phase and CM is the
molar concentration in
the mobile phase.
Cross Section of Equilibrium in a column.
“A” are adsorbed to the stationary phase.
“A” are traveling in the mobile phase.

8. Gas Chromatography
• The father of
modern gas
chromatography is
Nobel Prize winner
John Porter Martin,
who also developed
the first liquid-gas
chromatograph.
(1950)

9. Gas Chromatography

10. B.D of G.C.

11. GAS CHROMATOGRAPHY
 Separation of gaseous & volatile substances
 Simple & efficient in regard to separation
GC consists of :-
•GSC (gas solid chromatography)
•GLC (gas liquid chromatography
Gas → M.P
Solid / Liquid → S.P
GSC not used because of limited no. of S.P
GSC principle is ADSORPTION
GLC principle is PARTITION

12. Sample to be separated is converted into
vapour
And mixed with gaseous M.P
Component more soluble in the S.P → travels slower
Component less soluble in the S.P → travels faster
Components are separated according to their
Partition Coefficient
Criteria for compounds to be analyzed by G.C
1.VOLATILITY.
2.THERMOSTABILITY.

13. How a Gas Chromatography
Machine Works
– First, a vaporized sample is injected onto
the chromatographic column.
– Second, the sample moves through the
column through the flow of inert gas.
– Third, the components are recorded as a
sequence of peaks as they leave the
column.

14. Chromatographic Separation
-Deals with both the stationary
phase and the mobile phase.
• Mobile – inert gas used as
carrier.
• Stationary – liquid coated on a
solid or a solid within a column.

15. Chromatographic Separation
• Chromatographic Separation
– In the mobile phase, components of the
sample are uniquely drawn to the
stationary phase and thus, enter this
phase at different times.
– The parts of the sample are separated
within the column.
–Compounds used at the stationary
phase reach the detector at unique
times and produce a series of peaks
along a time sequence.

16. Chromatographic Separation
A(continued)
– The peaks can then be read and
analyzed by a forensic scientist to
determine the exact components of
the mixture.
– Retention time is determined by each
component reaching the detector at a
characteristic time.

17. Chromatographic Analysis
– The number of components in a sample
is determined by the number of peaks.
– The amount of a given component in a
sample is determined by the area under
the peaks.
– The identity of components can be
determined by the given retention times.

18. Peaks and Data

19. GRAPHICAL ANALYSIS

20. PRACTICAL REQUIREMENTS
• Carrier gas
• Flow regulators & Flow meters
• Injection devices
• Columns
• Temperature control devices
• Detectors
• Recorders & Integrators

21. CARRIER GAS
» Hydrogen
• Better thermal conductivity
• Disadvantage: it reacts with unsaturated
compounds & inflammable
» Helium
• Excellent thermal conductivity
• It is expensive
» Nitrogen
• Reduced sensitivity
• It is inexpensive

22. Requirements of a carrier gas
 Inertness
 Suitable for the detector
 High purity
 Easily available
 Cheap
 Should not cause the risk of fire
 Should give best column
performance

23. ADVANTAGES OF G.C
1. Very high resolution power, complex
mixtures can be resolved into its
components by this method.
2. Very high sensitivity with TCD, detect down
to 100 ppm
3. It is a micro method, small sample size is
required
4. Fast analysis is possible, gas as moving
phase- rapid equilibrium
5. Relatively good precision & accuracy
6. Qualitative & quantitative analysis is
possible

24. Disadvantages of G.C.
• The samples analysed are limited to
those that are volatile or can be made
volatile.
• The samples must be thermally stable to
prevent degradation when heated.
• Cannot be used to prepare samples for
further analysis once separated.
• Problems can be encountered when
injecting the sample

25. Applications of G.C
• G.C is capable of separating, detecting &
partially characterizing the organic
compounds , particularly when present in
small quantities.
1, Qualitative analysis
Rt & RV are used for the identification &
separation
2, Checking the purity of a compound
Compare the chromatogram of the std. & that
of the sample

26. Applications of G.C
3, Quantitative analysis
It is necessary to measure the peak area
or peak height of each component
4, Used for analysis of drugs & their
metabolites.

27. The Next Generation in Gas
Chromatography