This presentation gives a detailed explanation about GC with its types and applications. It gives the basic principle of working and instrumentation.

1. CHROMATOGRAPHY
By
G. ARTHI

2. CHROMATOGRAPHY
Chromatography – “color writing”
Coined by M. S. Tswett, a Russian botanist – studied the
coloring materials in plant life in 1903.
Definition - “A method of separation in which the
components to be separated are distributed B/W two
phases (stationary & mobile)”
Chromatography – a method used for separating organic &
inorganic compounds – can be analyzed & studied.
To determine unknown substances
Great physical method for observing mixtures &
solvents.

3. Basic principle
There is a mobile phase (moves) & a stationary phase
(doesn’t move).
Mobile phase moves through the stationary phase - takes
the compounds with it.
Different components of compound are absorbed at
different points in stationary phase.

4. PURPOSE OF CHROMATOGRAPHY
Chromatography - a method to separate two or more
compounds in a mixture based on the differences in
the property of each individual substance.
The properties include polarity, solubility, ionic
strength, and size.
One of the most useful analytical methods for
separation, identification, and quantitation of
chemical compounds.

5. Type of
Chromatography
Applications in the
Real World
Why & What is it
Liquid
Chromatography
Test water samples to
look for pollution
Used to analyze metal ions &
organic compounds in
solutions. Uses liquids which
may incorporate hydrophilic,
insoluble molecules.
Gas
chromatography
Detect bombs in
airports, to identify &
quantify
Used to analyze volatile gases.
Helium is used to move the
gaseous mixture through a
column of absorbent material.
Thin-Layer
Chromatography
Detecting pesticide or
insecticide in food,
forensics to analyze dye
composition of fibers.
Uses an absorbent material on
flat glass plates. Simple & rapid
method to check purity of
organic compound.
Paper
Chromatography
Separating amino acids
, antibiotics & anions,
RNA fingerprinting
Most common type. Uses
capillary action to pull solutes
up through paper & separate
solutes.

6. GAS CHROMATOGRAPHY

7. • Use to separate & analyze volatile substances in gas
phase that can be vaporized without decomposition.
• Mobile phase – carrier gas (inert gas – He or N2)
• Stationary phase – microscopic layer of liquid or
polymer on inert solid
• Does not utilize the mobile phase for interacting with
the analyte.
• Based on stationary phase it is of:
Gas-solid chromatography (GSC) – solid
adsorbent
Gas-liquid chromatography (GLC) – liquid on
inert support

8. PRINCIPLE
• Runs on the principle of partition chromatography
• Involves separation of components of sample under
test due to partition in b/w gaseous mobile &
stationary liquid phase.

9. INSTRUMENTATION
CARRIER
GAS SUPPLY
INJECTION
PORT
COLUMN DETECTOR
DATA
SYSTEM
TEMPERATURE CONTROLLED

10. FRONT VIEW OF GC

11. REAR VIEW OF GC

12. CARRIER GAS
 Highly pure (> 99.9%)
 Inert - no reaction with stationary phase
 Compatible with the detector since some detectors
require the use of a specific carrier gas.
 A cheap and available carrier gas is an advantage.
• The carrier gas pressure ranges from 10-15 psi
• Depending on the column dimensions, flow rates from 1-
150 mL/min are reported.
• Helium & Nitrogen are the most versatile and common
carrier gases in GC.

13. Sample to be
analyzed is loaded at the
injection port via a
calibrated syringe through
a rubber septum & into the
vaporization chamber.
Splitter – used to direct
excess sample to waste.
Vaporization chamber –
heated 50 deg C (above
lowest boiling pt of
sample) & mixed with
carrier gas to transport the
sample to column
INJECTOR PORT

14. •Components of sample are separated.
•Contains stationary phase
Two types:
• packed
• capillary (open tubular)
Packed Columns
Packed with finely divided particles
(<100-300mm dia), coated with
stationary phase with length 1.5-10m &
2-5mm internal dia.
Fabricated from glass, stainless steel,
copper, or other suitable tubes.
Stainless steel - most common tubing
used with internal diameters from 1-4
mm.
COLUMN

15. Capillary Columns
•Internal dia of few tenths of mm.
•Stationary phase coated on inner walls
of tubular column
•Small sample capacity, high
resolution, shorter analysis time &
greater sensitivity
WCOT – Wall-coated Open tubular
<1µm thick liquid coating on
inside of silica tube
SCOT – Support-coated Open
tubular
30µm thick liquid coated support on
inside of silica tube
FSOT – Fused silica Open tubular
much thinner walls
strength by polyimide coating
flexible & wound into coils

16. Stationary phase
Liquid Stationary Phases
characteristics:
• Low volatile
• High decomposition temperature
(thermally stable)
• Chemically inert (reversible
interactions with solvent)
• Chemically attached to support
(to prevent bleeding)
MATERIAL:
• Mostly of polysiloxane
material.
• Polymeric liquid – high
boiling point
• Prevents from evaporating
off the column during
experiment
Interaction:
Components with more
interaction – move slowly

17. DETECTOR
Choice of detector is determined by general class of compounds being
analyzed & sensitivity . It is of viz.,
•Non-selective – responds to all compounds except carrier gas
•Selective - responds to a range of compounds with a common physical
or chemical property
•Specific - responds to a single chemical compound
THERMAL CONDUCTIVITY
DETECTOR:
•Based on principle of thermal conductivity
that depends on composition of gas.
•This results in the change in temperature of
the filament that results in change in voltage
signal which is detected & is proportional to
concentration of gas.
•Simple, nondestructive, and universal but is
not very sensitive for organic compounds.

18. FLAME IONIZATION
DETECTION:
•Most sensitive detector & used for
analysis of petrol & kerosines.
•Two separate gas cylinders, one for
fuel (H2)and the other for O2 or air
are used for the ignition of the flame.
•Sample undergoes combustion in
flame – ions & free electrons are
formed – produce a current flow
between electrodes
•Current α ion formation which
depends on composition of separated
sample. Extremely important
advantage where volatile solutes
present in water matrix can be easily
analyzed without any pre-treatment.

19. ELECTRON CAPTURE
DETECTION:
•Exhibits high intensity for halogen
containing compounds
•wide applications in the detection of
pesticides and polychlorinated
biphenyls.
•The mechanism of sensing relies on the
fact that electro-negative atoms, like
halogens, will capture electrons from a ß
emitter (usually 63Ni).
•In absence of halogenated compounds,
a high current signal will be recorded
due to high ionization of the carrier gas.
•In presence of halogenated compounds
the signal will decrease due to capture
of electrons.

20. CHROMATOGRAM
Output of detector is sent to a recorder that plots, stores &
analyses the data.
Detector signals the presence of each component as it arrives
from the column.
It is a plot of intensity as a function of retention time
Also usual to have tiny quantity of air & gets coined out first
followed by 2 signals for compounds A & B.

21. RETENTION TIME
The time it takes for a certain compound to pass through the column or
for a given peak to appear after injection.
From graph below, it indicates that compound B had stronger interaction
with the column & retarded more than A.
QUALITATIVE ANALYSIS
Provides rapid & very effective method of finding a certain unknown
substance X to be A or B.
If retention time of X coincides with that of A, the unknown is identified
as compound A.
A typical GC scan for a mixture of two components, A &
B

22. QUANTITATIVE
ANALYSIS
The response of detector for a given component is measured by the
area under signal curve.
Imagine the curve to be an isosceles triangle, with peak height H, &
base width W, as below. Then area is approximately = area of
triangle.
We can compare signal areas for components A&B.
The ratios of areas therefore = ratio of their concentrations in the
mixture.

23. APPLICATIO
NS
PETROCHEMICAL
ENVIRONMENTAL
FOODS/FLAVORS
/FRAGRANCES
CHEMICAL/
INDUSTRIAL
PHARMACEUTICAL