Presentation about Gas Chromatography (GC) mainly used in analytical techniques with brief description of its components. Used mainly in R&D in chemical industries.

1. Topic
GAS CHROMATOGRAPHY (GC)

2. Chromatography
• Chromatography is defined as the technique
for separating chemical substances that relies
on differences in partitioning behaviour
between a flowing mobile phase and a
stationary phase to separate the components
in a mixture.

3. GAS CHROMATOGRAPHY
• In gas chromatography, mixture is separated
into its constituents by moving gas phase
passes over liquid or solid stationary phase.
• If adsorption takes place in solid stationary
phase, it is referred as gas-solid
chromatography(GSC).
• If in partition process in liquid stationary
phase it is called gas- liquid chromatography
(GLC)

4. Basic Principle
• When gas or vapour is in contact with solid
adsorbent or liquid material, fixed amount of
gas is adsorbed in adsorbent or dissolved in
liquid.
• Remaining gas is detected and gives its
characteristic peak

5. GC INSTRUMENT DETAIL
It consists of
•Supply carrier-gas with pressure regulator
•Sample Injector port
•Stationary phase
•Thermal chamber
•Detector
•Amplifier and recorder (computer)

6. Brief description of GC components
 CARRIER GAS
• The carrier gas is mobile phase in GC.
• Carrier gas is the means to move constituents of a sample through
the column.
• The carrier gas like Helium , Nitrogen , Hydrogen , or its mixture is
supplied with high pressure of 1-4 atmosphere.
• The continuous flow rate is measured during the experiment.
• Usually Nitrogen or Helium is used as carrier gas as they are easily
available

7. Sample Inlets
• The chromatographic process begins with the sample introduced into
the column.
• It is injected by a micro syringe quickly into the heated metal through
self sealing silicon.
• It is introduced in such a way that it does not disrupt the flow (of
mobile phase) into the column.
• The injection step establishes the initial (and best possible) peak
width for GC measurement.
• Usually microliter syringe is used to penetrate plastic membrane.
• If liquid or solid , sample is volatilized and swept to the column
• Gas samples can be introduced into the column using gas-tight
syringes

8.  OVENS
• Liquids or solids must be converted to vapour state and maintained
as a vapour throughout the GC separation.
• Therefore most GCs are equipped with ovens to keep the column at
temperatures from 40 to 350°C.
• The gas mixture of vaporized sample and carrier gas enters the
stationary phase column.
• This column may be packed column , open tubular or capillary
column.

9. Inside Column
• In GSC , the column is packed with activated carbon, silica gel or
alumina.
• In GLC , it is packed with porous materials like glass beads , ground
fire-bricks , finely divided celite or certain types of polymers like
taxan GC , poropak , chromosorb, etc.
• Thermal chamber is heated the column at fixed temperature during
the experiment.
• Some compounds are absorbed or adsorbed by stationary phase.
• So , each component of the mixture is carried at different rates and
finally come out from column at different time.
• Thereafter it is detected and recorded

10. Detectors And Data Systems
Detectors
• Effluent from the column enters a detector where the composition of
carrier gas stream is characterized through chemical and physical
properties of molecules.
• The main types of detectors are
• Fame ionization detector (FID)
• Thermal conductivity detector (TCD)
• Electron capture detector (ECD)
• Photoionization detector (PID)
• Nitrogen-Phosphorus detector
• Atomic emission detector

11.  Data Systems
• Data systems are used to store and analyze the data obtained from
detectors.
• Signal from the detector amplifier is digitized and stored to disk
allowing enormous convenience in retrieving and replaying results.
• Today only electronic recording-integrators or microcomputers are
used as data systems.
• Softwares allows the result to be displayed in an automated manner.
• All data can be economically integrated into total instrument control
and management through computer (i.e. Data Systems).

12. THANK YOU