Gas chromatography is a technique that uses inert gas as the mobile phase to separate volatile compounds based on their partitioning behavior between the mobile and stationary phases. It can be used to separate, identify, and quantify mixtures. There are two main types - gas-solid chromatography which uses a solid stationary phase and gas-liquid chromatography which is more widely used and uses a liquid stationary phase coated on an inert solid support. Common carrier gases used are hydrogen, helium, and nitrogen. Gas chromatography has high resolution, sensitivity, and speed and can be used to analyze compounds in areas like toxicology, forensics, and environmental analysis.

1. GAS CHROMATOGRAPHY
BOBBY SOLANKI
M.Sc Chemistry
Sharda University
Greater Noida

2. CHROMATOGRAPHY
Chromatography is a technique for
separating mixtures into their components in
order to analyze, identify, purify, and/or
quantify the mixture or components.”

3. GAS CHROMATOGRAPHY
Gas chromatography is a type of column
chromatographic technique that can be used to
separate volatile compounds.
Mobile phase: inert gas:
Nitrogen, helium, hydrogen → carrier gas.
Stationary phase: liquid/solid.

4. TYPES OF GC
1. Gas-solid chromatography:
Here, the mobile phase is a gas while the
stationary phase is a solid.
It has limited use.
2. Gas-liquid chromatography:
The mobile phase is a gas while the stationary
phase is a liquid retained on the surface as an
inert solid by adsorption or chemical bonding.
This is widely used.

5. BASIC PRINCIPLE
. GLC : partition
chromatography
GSC: adsorption
chromatography

6. MOBILE PHASE:
• Carrier gas – main purpose of the gas in GC is to
move the solutes along the column, mobile phase is
often referred to as carrier gas.
• Common carrier gas: include He, Ar, H2, N2

7. CARRIER GAS
The carrier gas should :-
be chemically inert
be cheap and readily available
be of high quality
not cause any fire
give best possible results and suitable for the sample
to be analyzed and for the detector

8. CARRIER GAS
Hydrogen, Helium, Nitrogen are commonly
used.
1. Hydrogen:-
- Easily available
- Has low density
- But it reacts with unsaturated compounds
- It is inflammable and explosive in nature.

9. 2. Nitrogen :-
- Easily available
- It is least expensive
- But it reduce the peak broadening
3. Helium :-
- Most commonly used in GC.
- Have good thermal conductivity
- Low density
- But it is expensive

10. STATIONARY PHASE
Stationary phase in GC is the main factor determining
the selectivity and retention of solutes.
There are three types of stationary phases used in GC:
 Non-coated solid materials
 Liquids coated on solid supports
 Direct coating of liquid

11. 1. Non-coated solid materials:-
same material is used as both the stationary phase and
support material
e.g. activated charcoal , alumina, silica gel
2. Liquids coated on solid supports:-
stationary phase is some liquid coated on a solid
support.
e.g. inert solid is diatomaceous earth coated
with liquid like silicon polymer and ethylene
glycol.

12. 3. direct coating of liquid:-
e.g. silicon polymer and ethylene glycol
These are coated in the inner wall of the column.

13. Columns & its types
Packed column:
• Typically a stainless steel coil.
• 1-5 m total length and 5 mm inner diameter.
• Filled with the ststationary phase or a packing coated with the
ststationary phase

14. Capillary (open tubular) column
• Thin fused-silica.
• Typically 10-100 m in length and 250 mm inner diameter.
• ststationary phase coated on the inner surface of capillary
tubing.
• Provide much higher separation efficiency
• But more easily overloaded by too much sample.

15. • It is mainly of two types:
 Wall-coated columns - consist of a capillary tube whose
walls are coated with liquid stationary phase.
 Support-coated columns- the inner wall of the
capillary is lined with a thin layer of support material such
as diatomaceous earth, onto which the stationary phase has
been adsorbed. It is also known as PLOT (porous-layer open
tubular columns).
 SCOT columns are generally less efficient than WCOT
columns. Both types of capillary column are more efficient
than packed columns.

16. INSTRUMENTATION:
- Carrier gas
He (common), N2, H2,
- Sample injection port
micro syringe
- Columns
- Oven
- Recorder
- Detectors
 Thermal conductivity (TCD)
 Electron capture detector(ECD)
 Flame Ionization detector(FID)
 Flame photometric (FPD)

17. INSTRUMENTATION:

18. GC DETECTORS:
The following devices are common types of GC
detectors:
1. Thermal Conductivity Detector (TCD)
2. Flame Ionization Detector (FID)
3. Nitrogen-phosphorus Detector (NPD)
4. Electron Capture Detector (ECD)
 The choice of detector will depend on the
analyte and how the GC method is being
used.

19. 1.Thermal conductivitydetector:-
- It is also known as hot wire detector.
- It is made up of tungsten rhenium alloy
wire.
- It is also known as universal detector.
- And the sensitivity of this detector is
(10-9 ).
2.Flame ionization detector:-
- It is highly sensitive detector for organic
compound.
- And sensitivity is (10-11 )

20. 3. Electron capture detector:-
In which we use radioactive source i.e. 63Ni
- Highly sensitive
- And sensitivity (10-9 - 10-12 )
4. Flame photometric detector:-
It is also known as sulphur & phosphorus
detector
- Highly sensitive for sulphur and
phosphorus
- Sensitivity is 105 times greater that other
organic compounds.

21. APPLICATION OF GC
Separation & identification of lipids, carbohydrates &
proteins.
Measurement of drugs & other metabolites in
biological fluids.
Used for toxicological analysis of biological fluid by
using ECD detectors in GC.
Analysis of pesticides in soil, water, food.
Forensic analysis of blood and urine alcohol levels
GC can be used to identify nitro-compounds in trace
quantities.

22. ADVANTAGES OF GC
- Very high resolution power, complex mixtures can be
resolved into its components by this method.
- Very high sensitivity with TCD, detect down to 100 ppm
- It is a micro method, small sample size is required
- Fast analysis is possible, gas as moving phase-rapid
equilibrium.